View Filing Data

$ 116,334

$ 109,713

$ 231,201

$ 218,704

19,565

18,229

39,916

36,885

Third party management fees, labor reimbursement and leasing

410

101

906

1,591

3,153

2,872

6,389

6,014

Other

1,457

888

2,330

2,399

140,919

131,803

280,742

265,593

Expenses:

39,490

36,363

78,908

74,223

Third party management expenses

14,215

13,508

28,552

26,977

1,363

1,264

2,788

2,514

General and administrative expenses

49,300

47,476

98,846

95,350

7,335

6,079

13,886

12,129

111,703

104,690

222,980

211,193

Operating Income (Loss)

29,216

27,113

57,762

54,400

Other Income (Expense):

Interest expense — amortization of deferred financing costs

122

1,838

180

2,320

Interest expense

(30,437)

(32,981)

(61,351)

(67,125)

(1,183)

(1,261)

(2,344)

(2,572)

Interest expense — financing obligation

(211)

(196)

(429)

(378)

Equity in income of real estate ventures

1,508

838

3,043

882

Gain from remeasurement of investment in a real estate venture

7,847

Net gain (loss) on real estate venture transactions

3,683

Gains (Losses) on Sales of Investment Real Estate

(11)

Loss on early extinguishment of debt

(1,113)

(1,250)

(1,116)

(1,498)

Income (loss) from continuing operations

9,432

(5,910)

7,275

(13,982)

Discontinued operations:

Net gain (loss) on disposition of discontinued operations

2,535

780

5,275

(2,260)

^[1]

10,177

3,044

24,845

Total discontinued operations

(2,252)

12,712

3,824

30,120

Net income

7,180

6,802

11,099

16,138

Discontinued operations attributable to non-controlling interests, Basic

(232)

(51)

(551)

Net (income) loss attributable to non-controlling interests — LP units

(88)

201

(39)

386

Net (income) loss attributable to non-controlling interests

(62)

(31)

(90)

(165)

Net income attributable to Brandywine Realty Trust

7,118

6,771

11,009

15,973

Distribution to Preferred Shares

(1,725)

(3,049)

(3,450)

(5,047)

Redemption Premium

(2,090)

Amount allocated to unvested restricted shareholders

(85)

(95)

(193)

(191)

Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust

$ 5,308

$ 1,537

$ 7,366

$ 8,645

Basic income (loss) per Common Share:

$ 0.05

$ (0.08)

$ 0.02

$ (0.15)

Net income (loss) attributable to common shareholders/unitholders, Basic

(0.02)

0.09

0.03

0.21

0.03

0.01

0.05

0.06

Diluted income (loss) per Common Share:

0.05

(0.08)

0.02

(0.15)

Net income (loss) attributable to common shareholders/unitholders, Diluted

(0.02)

0.09

0.03

0.21

$ 0.03

$ 0.01

$ 0.05

$ 0.06

Weighted Average Number of Shares Outstanding, Basic

155,347,384

143,300,637

149,508,957

143,060,796

Weighted Average Number of Shares Outstanding, Diluted

156,691,201

143,300,637

150,666,245

143,060,796

Net income (loss) attributable to Brandywine Realty Trust

Loss from continuing operations

$ 9,344

$ (5,709)

$ 7,236

$ (13,596)

Income (loss) from discontinued operations

(2,226)

12,480

3,773

29,569

Net Income (Loss) attributable to Brandywine Realty Trust

7,118

6,771

11,009

15,973

BRANDYWINE OPERATING PARTNERSHIP, L.P.

Revenue:

116,334

109,713

231,201

218,704

19,565

18,229

39,916

36,885

Third party management fees, labor reimbursement and leasing

410

101

906

1,591

3,153

2,872

6,389

6,014

Other

1,457

888

2,330

2,399

140,919

131,803

280,742

265,593

Expenses:

39,490

36,363

78,908

74,223

Third party management expenses

14,215

13,508

28,552

26,977

1,363

1,264

2,788

2,514

General and administrative expenses

49,300

47,476

98,846

95,350

7,335

6,079

13,886

12,129

111,703

104,690

222,980

211,193

Operating Income (Loss)

29,216

27,113

57,762

54,400

Other Income (Expense):

Interest expense — amortization of deferred financing costs

122

1,838

180

2,320

Interest expense

(30,437)

(32,981)

(61,351)

(67,125)

(1,183)

(1,261)

(2,344)

(2,572)

Interest expense — financing obligation

(211)

(196)

(429)

(378)

Equity in income of real estate ventures

1,508

838

3,043

882

Gain from remeasurement of investment in a real estate venture

7,847

Net gain (loss) on real estate venture transactions

3,683

Gains (Losses) on Sales of Investment Real Estate

(11)

Loss on early extinguishment of debt

(1,113)

(1,250)

(1,116)

(1,498)

Income (loss) from continuing operations

9,432

(5,910)

7,275

(13,982)

Discontinued operations:

Net gain (loss) on disposition of discontinued operations

2,535

780

5,275

(2,260)

10,177

3,044

24,845

Total discontinued operations

(2,252)

12,712

3,824

30,120

Net income

7,180

6,802

11,099

16,138

Distribution to Preferred Shares

(1,725)

(3,049)

(3,450)

(5,047)

Redemption Premium

(2,090)

Amount allocated to unvested restricted shareholders

(85)

(95)

(193)

(191)

Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust

$ 5,370

$ 1,568

$ 7,456

$ 8,810

Basic income (loss) per Common Share:

$ 0.05

$ (0.08)

$ 0.02

$ (0.15)

Net income (loss) attributable to common shareholders/unitholders, Basic

(0.02)

0.09

0.03

0.21

0.03

0.01

0.05

0.06

Diluted income (loss) per Common Share:

0.05

(0.08)

0.02

(0.15)

Net income (loss) attributable to common shareholders/unitholders, Diluted

(0.02)

0.09

0.03

0.21

$ 0.03

$ 0.01

$ 0.05

$ 0.06

Weighted Average Number of Shares Outstanding, Basic

157,131,697

145,958,358

151,323,813

145,721,890

Weighted Average Number of Shares Outstanding, Diluted

158,475,514

145,958,358

152,481,101

145,721,890

Net income (loss) attributable to Brandywine Realty Trust

Loss from continuing operations

$ 9,432

$ (5,910)

$ 7,275

$ (13,982)

Income (loss) from discontinued operations

$ (2,252)

$ 12,712

$ 3,824

$ 30,120

[1]	The loss of $(2.3) million for the second quarter of 2013 includes $1.1 million of closing costs incurred to sell the properties.

Consolidated Statements of Beneficiaries' Equity - USD ($) $ in Thousands	Total	Series E Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Deferred Compensation, Share-based Payments [Member]	Common Stock In Grantor Trust [Member]	Cumulative Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Distributions [Member]	Noncontrolling Interest [Member]
Beginning Balance, shares at Dec. 31, 2011		4,300,000	142,690,755		292,646
Beginning Balance at Dec. 31, 2011	$ 1,889,696	$ 43	$ 1,424	$ 2,776,197	$ 5,631	$ (5,631)	$ 477,338	$ (6,079)	$ (1,392,332)	$ 33,105
Net income (loss)	16,138						15,973			165
Comprehensive Income (Loss)	(10,564)							(10,370)		(194)
Equity Issuance Costs	(610)			(610)
Stock Redeemed or Called During Period, Shares		(2,000,000)
Stock Redeemed or Called During Period, Value		$ (20)
Conversion of LP Units to Common Shares, shares			20,464
Conversion of LP Units to Common Shares	(228)			149			(45)			(332)
Bonus Share Issuance, Shares			35,703
Bonus Share Issuance	387			387
Vesting of Restricted Shares, Shares			280,851		9,036
Vesting of Restricted Shares	(1,292)		$ 3	(1,295)
Restricted Share Amortization	1,426			1,426
Vesting of Restricted Performance Units, Shares			249,797
Vesting of Restricted Performance Units	(1,329)		$ 3	(1,332)
Restricted Performance Units Amortization	1,205			1,205
Exercise of Stock Options, Shares			94,429
Exercise of Stock Options	275		$ 1	274
Stock Option Amortization	747			747
Share Issuance from/to Deferred Compensation Plan, Shares			(5,389)		(8,560)
Share Issuance from/to Deferred Compensation Plan	0				$ (195)	195
Trustee Fees Paid in Shares, Shares			1,336
Trustee Fees Paid in Shares, Value	15			15
Adjustments to Non-controlling Interest	13			392						(379)
Preferred Share distributions	(5,047)								(5,047)
Redemption Premium	(2,090)								(2,090)
Distributions declared ($0.15 per share)	(43,953)								(43,193)	(760)
Ending Balance, shares at Jun. 30, 2012		6,300,000	143,367,946		293,122
Ending Balance at Jun. 30, 2012	1,893,729	$ 63	$ 1,431	2,826,475	$ 5,436	(5,436)	493,266	(16,449)	(1,442,662)	31,605
Preferred Stock, Shares Issued		4,000,000
Preferred Stock, Value, Issued		$ 40
Preferred Stock, Including Additional Paid in Capital, Net of Discount	96,850			96,810
Additional Paid in Capital, Preferred Stock	(47,910)			(47,890)
Preferred Stock, Shares Issued		4,000,000
Preferred Stock, Value, Issued	40
Beginning Balance, shares at Dec. 31, 2012		4,000,000	143,538,733		290,745
Beginning Balance at Dec. 31, 2012	1,773,516	$ 40	$ 1,434	2,780,194	$ 5,352	(5,352)	479,734	(15,918)	(1,493,206)	21,238
Net income (loss)	11,099						11,011			88
Comprehensive Income (Loss)	11,451							11,317		134
Issuance of Common Shares of Beneficial Interest, Shares, New Issues			12,650,000
Issuance of Common Shares of Beneficial Interest, Value, New Issues	182,034		$ 127	181,907
Equity Issuance Costs	(380)			(380)
Conversion of LP Units to Common Shares, shares			81,998
Conversion of LP Units to Common Shares	0		$ 1	1,240						(1,241)
Bonus Share Issuance, Shares			27,918
Bonus Share Issuance	361			361
Vesting of Restricted Shares, Shares			147,495		7,050
Vesting of Restricted Shares	(902)		$ 2	(904)
Restricted Share Amortization	1,703			1,703
Vesting of Restricted Performance Units, Shares			26,067
Vesting of Restricted Performance Units	(160)			(160)
Restricted Performance Units Amortization	2,411			2,411
Restricted Share Forfeitures	$ 9						9
Exercise of Stock Options, Shares	166,620		166,620
Exercise of Stock Options	$ 1,761		$ 1	1,760
Stock Option Amortization	377			377
Share Issuance from/to Deferred Compensation Plan, Shares			22,404		17,958
Share Issuance from/to Deferred Compensation Plan	0				$ 164	(164)
Trustee Fees Paid in Shares, Shares			1,409
Trustee Fees Paid in Shares, Value	20			20
Adjustments to Non-controlling Interest	0			(739)						739
Preferred Share distributions	(3,450)								(3,450)
Redemption Premium	0
Distributions declared ($0.15 per share)	(45,781)								(45,240)	(541)
Ending Balance, shares at Jun. 30, 2013		4,000,000	156,662,644		315,753
Ending Balance at Jun. 30, 2013	1,934,069	$ 40	$ 1,565	$ 2,967,790	$ 5,516	$ (5,516)	$ 490,754	$ (4,601)	$ (1,541,896)	$ 20,417
Preferred Stock, Shares Issued		4,000,000
Preferred Stock, Value, Issued	$ 40

Consolidated Statements of Beneficiaries' Equity Consolidated Statements of Beneficiaries' Equity (Parantheticals) - $ / shares	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2013
Cumulative Distributions [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.15	$ 0.15
Noncontrolling Interest [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.15	$ 0.15

Consolidated Statements of Comprehensive Income Statement - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 7,180	$ 6,802	$ 11,099	$ 16,138
Comprehensive Income (Loss)
Unrealized gain (loss) on derivative financial instruments	9,491	(10,650)	11,283	(10,623)
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	66	76	168	124
Unrealized loss on available-for-sale securities	0	(65)	0	(65)
Total comprehensive income (loss)	9,557	(10,639)	11,451	(10,564)
Comprehensive income (loss)	16,737	(3,837)	22,550	5,574
Comprehensive (income) loss attributable to non-controlling interest	(169)	163	(221)	29
Comprehensive income (loss) attributable to Brandywine Realty Trust	16,568	(3,674)	22,329	5,603
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Net income	7,180	6,802	11,099	16,138
Comprehensive Income (Loss)
Unrealized gain (loss) on derivative financial instruments	9,491	(10,650)	11,283	(10,623)
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	66	76	168	124
Unrealized loss on available-for-sale securities	0	(65)	0	(65)
Total comprehensive income (loss)	9,557	(10,639)	11,451	(10,564)
Comprehensive income (loss) attributable to Brandywine Realty Trust	$ 16,737	$ (3,837)	$ 22,550	$ 5,574

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 11,099	$ 16,138
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	100,459	101,624
Amortization of deferred financing costs	2,344	2,572
Amortization of debt discount/(premium), net	748	745
Amortization of stock compensation costs	4,048	2,433
Shares used for employee taxes upon vesting of share awards	(1,061)	(2,234)
Straight-line rent income	(11,250)	(12,861)
Amortization of acquired above (below) market leases to rental revenue, net	(3,556)	(2,922)
Straight-line ground rent expense	894	949
Provision for doubtful accounts	997	962
Net gain on sale of interests in real estate	(3,044)	(24,834)
Net gain on real estate venture transactions	(3,683)	0
Gain from remeasurement of investment in a real estate venture	(7,847)	0
Loss on early extinguishment of debt	1,116	1,498
Real estate venture income in excess of distributions	(2,031)	(590)
Deferred financing obligation	(896)	(825)
Changes in assets and liabilities:
Accounts receivable	2,035	3,561
Other assets	6,589	5,260
Accounts payable and accrued expenses	(1,252)	(11,546)
Deferred income, gains and rent	608	(2,871)
Other liabilities	474	(1,438)
Net cash from operating activities	96,791	75,621
Cash flows from investing activities:
Acquisition of properties	(20,758)	(9,226)
Payments to acquire available-for-sale securities	0	(98,744)
Proceeds from Sale of Available-for-sale Securities	0	56,322
Sales of properties, net	145,931	120,957
Distribution of sales proceeds from real estate ventures	16,963	0
Proceeds from repayment of mortgage notes receivable	200	23,931
Capital expenditures for tenant improvements	(46,828)	(48,591)
Capital expenditures for redevelopments	(4,676)	(3,110)
Capital expenditures for developments	(72)	0
Reimbursement from real estate venture for pre-formation development costs	1,976	0
Advances for purchase of tenant assets, net of repayments	(693)	283
Investment in unconsolidated Real Estate Ventures	(12,568)	(18,617)
Cash distributions from unconsolidated real estate ventures	3,445	1,723
Leasing costs	(14,313)	(14,940)
Net cash from investing activities	68,607	9,988
Cash flows from financing activities:
Proceeds from Unsecured Term Loans	0	600,000
Proceeds from Credit Facility borrowings	186,000	21,500
Repayments of Credit Facility borrowings	(255,000)	(297,000)
Repayments of mortgage notes payable	(5,537)	(6,028)
Deferred financing obligation non-cash interest expense	466	468
Proceeds from Issuance of Common Stock	181,527	0
Proceeds from Issuance of Preferred Stock and Preference Stock	0	96,240
Redemption of preferred shares	0	(50,188)
Repayments of unsecured notes	(12,912)	(167,371)
Repayments of unsecured term loan	0	(37,500)
Net settlement of hedge transactions	0	(74)
Debt financing costs	(6)	(8,431)
Exercise of stock options	1,762	276
Distributions paid to shareholders	(46,745)	(47,059)
Distributions to noncontrolling interest	(554)	(797)
Net cash from financing activities	49,001	104,036
Increase in cash and cash equivalents	214,399	189,645
Cash and cash equivalents at beginning of period	1,549	410
Cash and cash equivalents at end of period	215,948	190,055
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the six months ended June 30, 2013 and 2012 of $1,305 and $1,207, respectively	67,844	69,480
Supplemental disclosure of non-cash activity:
Change in operating real estate related to a non-cash acquisition of an operating property	(21,649)	0
Change in intangible assets, net related to non-cash acquisition of an operating property	(3,517)	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	462	0
Change in investments in joint venture related to non-cash acquisition of property	13,040	0
Change in operating real estate related to non-cash adjustment to land	(4,386)	0
Change in investments in real estate ventures related to a contribution of land	6,058	0
Change in capital expenditures financed through accounts payable at period end	(1,227)	(1,735)
Change in capital expenditures financed through retention payable at period end	(348)	56
Change in unfunded tenant allowance	(244)	(1,144)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Net income	11,099	16,138
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	100,459	101,624
Amortization of deferred financing costs	2,344	2,572
Amortization of debt discount/(premium), net	748	745
Amortization of stock compensation costs	4,048	2,433
Shares used for employee taxes upon vesting of share awards	(1,061)	(2,234)
Straight-line rent income	(11,250)	(12,861)
Amortization of acquired above (below) market leases to rental revenue, net	(3,556)	(2,922)
Straight-line ground rent expense	894	949
Provision for doubtful accounts	997	962
Net gain on sale of interests in real estate	(3,044)	(24,834)
Net gain on real estate venture transactions	(3,683)	0
Gain from remeasurement of investment in a real estate venture	(7,847)	0
Loss on early extinguishment of debt	1,116	1,498
Real estate venture income in excess of distributions	(2,031)	(590)
Deferred financing obligation	(896)	(825)
Changes in assets and liabilities:
Accounts receivable	2,035	3,561
Other assets	6,589	5,260
Accounts payable and accrued expenses	(1,252)	(11,546)
Deferred income, gains and rent	608	(2,871)
Other liabilities	474	(1,438)
Net cash from operating activities	96,791	75,621
Cash flows from investing activities:
Acquisition of properties	(20,758)	(9,226)
Payments to acquire available-for-sale securities	0	(98,744)
Proceeds from Sale of Available-for-sale Securities	0	56,322
Sales of properties, net	145,931	120,957
Distribution of sales proceeds from real estate ventures	16,963	0
Proceeds from repayment of mortgage notes receivable	200	23,931
Capital expenditures for tenant improvements	(46,828)	(48,591)
Capital expenditures for redevelopments	(4,676)	(3,110)
Capital expenditures for developments	(72)	0
Reimbursement from real estate venture for pre-formation development costs	1,976	0
Advances for purchase of tenant assets, net of repayments	(693)	283
Investment in unconsolidated Real Estate Ventures	(12,568)	(18,617)
Cash distributions from unconsolidated real estate ventures	3,445	1,723
Leasing costs	(14,313)	(14,940)
Net cash from investing activities	68,607	9,988
Cash flows from financing activities:
Proceeds from Unsecured Term Loans	0	600,000
Proceeds from Credit Facility borrowings	186,000	21,500
Repayments of Credit Facility borrowings	(255,000)	(297,000)
Repayments of mortgage notes payable	(5,537)	(6,028)
Deferred financing obligation non-cash interest expense	466	468
Proceeds from Issuance of Common Stock	181,527	0
Proceeds from Issuance of Preferred Stock and Preference Stock	0	96,240
Redemption of preferred shares	0	(50,188)
Repayments of unsecured notes	(12,912)	(167,371)
Repayments of unsecured term loan	0	(37,500)
Net settlement of hedge transactions	0	(74)
Debt financing costs	(6)	(8,431)
Exercise of stock options	1,762	276
Distributions paid to shareholders	(47,299)	(47,856)
Net cash from financing activities	49,001	104,036
Increase in cash and cash equivalents	214,399	189,645
Cash and cash equivalents at beginning of period	1,549	410
Cash and cash equivalents at end of period	215,948	190,055
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the six months ended June 30, 2013 and 2012 of $1,305 and $1,207, respectively	67,844	69,480
Supplemental disclosure of non-cash activity:
Change in operating real estate related to a non-cash acquisition of an operating property	(21,649)	0
Change in intangible assets, net related to non-cash acquisition of an operating property	(3,517)	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	462	0
Change in investments in joint venture related to non-cash acquisition of property	13,040	0
Change in operating real estate related to non-cash adjustment to land	(4,386)	0
Change in investments in real estate ventures related to a contribution of land	6,058	0
Change in capital expenditures financed through accounts payable at period end	(1,227)	(1,735)
Change in capital expenditures financed through retention payable at period end	(348)	56
Change in unfunded tenant allowance	$ (244)	$ (1,144)

Consolidated Statements of Cash Flows Consolidated Statement of Cash Flows (Parentheticals) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Supplemental Cash Flow Information [Abstract]
Capitalized interest	$ 1,305	$ 1,207
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Supplemental Cash Flow Information [Abstract]
Capitalized interest	$ 1,305	$ 1,207

Organization of the Parent Company and The Operating Partnership	6 Months Ended
	Jun. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP [Text Block]	ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP The Parent Company is a self-administered and self-managed real estate investment trust (“REIT”) that provides leasing, property management, development, redevelopment, acquisition and other tenant-related services for a portfolio of office and industrial properties. The Parent Company owns its assets and conducts its operations through the Operating Partnership and subsidiaries of the Operating Partnership. The Parent Company is the sole general partner of the Operating Partnership and, as of June 30, 2013, owned a 98.8% interest in the Operating Partnership. The Parent Company’s common shares of beneficial interest are publicly traded on the New York Stock Exchange under the ticker symbol “BDN”. As of June 30, 2013, the Company owned 210 properties, consisting of 182 office properties, 19 industrial facilities, five mixed-use properties, one development property, two redevelopment properties and one re-entitlement property (collectively, the “Properties”) containing an aggregate of approximately 24.2 million net rentable square feet. In addition, as of June 30, 2013, the Company owned economic interests in 17 unconsolidated real estate ventures that contain approximately 6.2 million net rentable square feet (collectively, the “Real Estate Ventures”). As of June 30, 2013, the Company also owned 435 acres of undeveloped land, and held options to purchase approximately 51 additional acres of undeveloped land. As of June 30, 2013, the total potential development that these land parcels could support, under current zoning, entitlements or combination thereof, amounted to 6.2 million square feet. The Properties and the properties owned by the Real Estate Ventures are located in or near Philadelphia, Pennsylvania; Metropolitan Washington, D.C.; Southern New Jersey; Richmond, Virginia; Wilmington, Delaware; Austin, Texas and Oakland, Concord, and Carlsbad, California. The Company conducts its third-party real estate management services business primarily through wholly-owned management company subsidiaries. As of June 30, 2013, the management company subsidiaries were managing properties containing an aggregate of approximately 30.8 million net rentable square feet, of which approximately 24.2 million net rentable square feet related to Properties owned by the Company and approximately 6.6 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.

The entire disclosure for the organization, consolidation and basis of presentation of financial statements disclosure, and significant accounting policies of the reporting entity. May be provided in more than one note to the financial statements, as long as users are provided with an understanding of (1) the significant judgments and assumptions made by an enterprise in determining whether it must consolidate a VIE and/or disclose information about its involvement with a VIE, (2) the nature of restrictions on a consolidated VIE's assets reported by an enterprise in its statement of financial position, including the carrying amounts of such assets, (3) the nature of, and changes in, the risks associated with an enterprise's involvement with the VIE, and (4) how an enterprise's involvement with the VIE affects the enterprise's financial position, financial performance, and cash flows. Describes procedure if disclosures are provided in more than one note to the financial statements.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Text Block]

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2013

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments (consisting solely of normal recurring matters) for a fair statement of the financial position of the Company as of June 30, 2013, the results of its operations for the three and six-month periods ended June 30, 2013 and 2012 and its cash flows for the six-month periods ended June 30, 2013 and 2012 have been included. The results of operations for such interim periods are not necessarily indicative of the results for a full year. These consolidated financial statements should be read in conjunction with the Parent Company’s and the Operating Partnership’s consolidated financial statements and footnotes included in their combined 2012 Annual Report on Form 10-K filed with the SEC on February 26, 2013.

Reclassifications

Certain amounts have been reclassified in prior years to conform to the current year presentation. The reclassifications are primarily due to the treatment of sold properties as discontinued operations on the statement of operations for all periods presented.

Principles of Consolidation

When the Company obtains an economic interest in an entity, the Company evaluates the entity to determine if the entity is deemed a variable interest entity (“VIE”), and if the Company is deemed to be the primary beneficiary, in accordance with the accounting standard for the consolidation of variable interest entities. The accounting standard for the consolidation of VIEs requires the Company to qualitatively assess if the Company was the primary beneficiary of the VIEs based on whether the Company had (i) the power to direct those matters that most significantly impacted the activities of the VIE and (ii) the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. For entities determined to be VIEs, but for which the Company is not the primary beneficiary, the Company's maximum exposure to loss is the carrying amount of its investments, as the Company has not provided any guarantees other than the guarantee of debt of the Real Estate Venture known as PJP VII which was approximately $0.6 million at June 30, 2013 (see Note 4), as well as a guarantee of the Company's share of the debt and potential cost overruns associated with the Real Estate Venture known as "HSRE-Campus Crest IX, LLC" (referred to hereafter as the "Grove Venture").

When an entity is not deemed to be a VIE, the Company considers the provisions of the same accounting standard to determine whether a general partner, or the general partners as a group, controls a limited partnership or similar entity when the limited partners have certain rights. The Company consolidates (i) entities that are VIEs and of which the Company is deemed to be the primary beneficiary and (ii) entities that are non-VIEs and controlled by the Company and in which the limited partners neither have the ability to dissolve the entity or remove the Company without cause nor any substantive participating rights. Entities that the Company accounts for under the equity method (i.e., at cost, increased or decreased by the Company’s share of earnings or losses, plus contributions, less distributions) include (i) entities that are VIEs and of which the Company is not deemed to be the primary beneficiary, (ii) entities that are non-VIEs which the Company does not control, but over which the Company has the ability to exercise significant influence, and (iii) entities that are non-VIEs that the Company controls through its general partner status, but the limited partners in the entity have the substantive ability to dissolve the entity or remove the Company without cause or have substantive participating rights. The Company continuously assesses its determination of whether an entity is a VIE and who the primary beneficiary is, and whether or not the limited partners in an entity have substantive rights, more particularly if certain events occur that are likely to cause a change in the original determinations. The Company’s assessment includes a review of applicable documents such as, but not limited to, applicable partnership agreements, real estate venture agreements, LLC agreements, and management and leasing agreements to determine whether the Company has control to direct the business activities of the entities. The portion of the consolidated entities that is not owned by the Company is presented as non-controlling interest as of and during the periods consolidated. All intercompany accounts and transactions have been eliminated in consolidation.

On January 25, 2013, the Company formed the Grove Venture together with two unaffiliated members. Based upon the facts and circumstances at formation of the Grove Venture, the Company determined that the Grove Venture is a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the variable interest model under the accounting standard for consolidation in order to determine whether to consolidate the Grove Venture. Based upon each member's shared power over the Grove Venture activities under the operating agreement of the Grove Venture, and the Company's lack of exclusive control over the development and construction phases of the project, the Grove Venture is not consolidated by the Company and is accounted for under the equity method of accounting. For further information regarding the Grove Venture and its formation, please refer to Note 4.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates. Management makes significant estimates regarding revenue, valuation of real estate and related intangible assets and liabilities, impairment of long-lived assets, allowance for doubtful accounts and deferred costs.

Operating Properties

Operating properties are carried at historical cost less accumulated depreciation and impairment losses. The cost of operating properties reflects their purchase price or development cost. Acquisition related costs are expensed as incurred. Costs incurred for the renovation and betterment of an operating property are capitalized to the Company’s investment in that property. Ordinary repairs and maintenance are expensed as incurred; major replacements and betterments, which improve or extend the life of the asset, are capitalized and depreciated over their estimated useful lives. Fully-depreciated assets are removed from the accounts.

Purchase Price Allocation

The Company allocates the purchase price of properties to net tangible and identified intangible assets acquired based on fair values. Above-market and below-market in-place lease values for acquired properties are recorded based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) the Company’s estimate of the fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining non-cancelable term of the lease (including the below market fixed renewal period, if applicable). Capitalized above-market lease values are amortized as a reduction of rental income over the remaining non-cancelable terms of the respective leases. Capitalized below-market lease values are amortized as an increase to rental income over the remaining non-cancelable terms of the respective leases, including any below market fixed-rate renewal periods.

Other intangible assets also include amounts representing the value of tenant relationships and in-place leases based on the Company’s evaluation of the specific characteristics of each tenant’s lease and the Company’s overall relationship with the respective tenant. The Company generally estimates the cost to execute leases with terms similar to the remaining lease terms of the in-place leases, including leasing commissions, legal and other related expenses. This intangible asset is generally amortized to expense over the remaining term of the respective leases and any fixed-rate bargain renewal periods. Company estimates of value are made using methods similar to those used by independent appraisers or by using independent appraisals. Factors considered by the Company in this analysis include an estimate of the carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance and other operating expenses and estimates of lost rentals at market rates during the expected lease-up periods, which primarily range from three to twelve months. The Company also considers information obtained about each property as a result of its pre-acquisition due diligence, marketing and leasing activities in estimating the fair value of the tangible and intangible assets acquired. The Company also uses the information obtained as a result of its pre-acquisition due diligence as part of its consideration of the accounting standard governing asset retirement obligations, and, when necessary, will record a conditional asset retirement obligation as part of its purchase price.

Characteristics considered by the Company in allocating value to its tenant relationships include the nature and extent of the Company’s business relationship with the tenant, growth prospects for developing new business with the tenant, the tenant’s credit quality and expectations of lease renewals, among other factors. The value of tenant relationship intangibles is generally amortized over the remaining initial lease term and expected renewals, but in no event longer than the remaining depreciable life of the building. The value of in-place leases is generally amortized over the remaining non-cancelable term of the respective leases and any fixed-rate renewal periods.

In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, would be charged to expense and market rate adjustments (above or below) would be recorded to revenue.

Impairment or Disposal of Long-Lived Assets

The accounting standard for property, plant and equipment provides a single accounting model for long-lived assets classified as held-for-sale; defines the scope of businesses to be disposed of that qualify for reporting as discontinued operations; and affects the timing of recognizing losses on such operations.

The Company reviews long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The review of recoverability is based on an estimate of the future undiscounted cash flows (excluding interest charges) expected to result from the long-lived asset’s use and eventual disposition. These cash flows consider factors such as expected future operating income, trends and prospects, as well as the effects of leasing demand, competition and other factors. If impairment exists due to the inability to recover the carrying value of a long-lived asset, an impairment loss is recorded to the extent that the carrying value exceeds the estimated fair-value of the property. The Company is required to make subjective assessments as to whether there are impairments in the values of the investments in long-lived assets. These assessments have a direct impact on its net income because recording an impairment loss results in an immediate negative adjustment to net income. The evaluation of anticipated cash flows is highly subjective and is based in part on assumptions regarding future occupancy, rental rates and capital requirements that could differ materially from actual results in future periods. Although the Company’s strategy is generally to hold its properties over the long-term, the Company will selectively dispose of properties for strategic needs. If the Company’s strategy changes or market conditions otherwise dictate an earlier sale date, an impairment loss may be recognized to reduce the property to the lower of the carrying amount or fair value less costs to sell, and such loss could be material. If the Company determines that impairment has occurred and the assets are classified as held and used, the affected assets must be reduced to their fair-value.

Where properties have been identified as having a potential for sale, additional judgments are required related to the determination as to the appropriate period over which the undiscounted cash flows should include the operating cash flows and the amount included as the estimated residual value. Management determines the amounts to be included based on a probability weighted cash flow. This requires significant judgment. In some cases, the results of whether an impairment is indicated are sensitive to changes in assumptions input into the estimates, including the hold period until expected sale.

The Company determined during its impairment review for the three and six-month periods ended June 30, 2013 and 2012, that no impairment charges were necessary.

The Company is a party to a development agreement and related ground leases covering two adjacent parcels of land. On January 25, 2013, the Company contributed its rights under one of the ground leases and associated development rights to the Grove Venture (please refer to Note 4 for further information), and the Grove Venture commenced construction during the three months ended March 31, 2013. The Company has the right, on terms and conditions in the development agreement and ground lease, to commence development of the other parcel by December 31, 2015. If the Company determines that it will not be able to commence development of the other parcel by December 31, 2015, or if the Company determines that development is not in its best interest and is unable to extend the development period, then the Company will be required to write off all costs that it has incurred in preparing this remaining land parcel for development, amounting to $6.0 million as of June 30, 2013.

Investments in Unconsolidated Real Estate Ventures

The Company accounts for its investments in unconsolidated Real Estate Ventures under the equity method of accounting as it is not the primary beneficiary (for VIEs) and the Company exercises significant influence, but does not control these entities under the provisions of the entities’ governing agreements pursuant to the accounting standard for the consolidation of VIEs. When the Company determines that its investment in an unconsolidated Real Estate Venture does not constitute a VIE, the Company utilizes the voting interest model under the accounting standard for consolidation to determine whether to consolidate the venture.

Under the equity method, investments in unconsolidated Real Estate Ventures are recorded initially at cost, as investments in Real Estate Ventures, and subsequently adjusted for equity in earnings, cash contributions, less distributions and impairments. On a periodic basis, management also assesses whether there are any indicators that the value of the Company’s investments in unconsolidated Real Estate Ventures may be other than temporarily impaired. An investment is impaired only if the value of the investment, as estimated by management, is less than the carrying value of the investment and the decline is other than temporary. To the extent that an impairment has occurred, the loss shall be measured as the excess of the carrying amount of the investment over the fair value of the investment, as estimated by management. The determination as to whether an impairment exists requires significant management judgment about the fair value of its ownership interest. Fair value is determined through various valuation techniques, including but not limited to, discounted cash flow models, quoted market values and third party appraisals.

When the Company acquires an interest in or contributes assets to a Real Estate Venture project, the difference between the Company’s cost basis in the investment and the value of the Real Estate Venture or asset contributed is amortized over the life of the related assets, intangibles and liabilities and such adjustment is included in the Company’s share of equity in income of unconsolidated Real Estate Ventures. For purposes of cash flow presentation, distributions from unconsolidated Real Estate Ventures are presented as part of operating activities when they are considered as return on investments. Distributions in excess of the Company’s share in the cumulative unconsolidated Real Estate Ventures’ earnings are considered as return of investments and are presented as part of investing activities in accordance with the accounting standard for cash flow presentation.

Revenue Recognition

Rental revenue is recognized on the straight-line basis, which averages minimum rents over the terms of the leases from the later of the date of the commencement of the lease or the date of acquisition of the property subject to existing leases. The straight-line rent adjustment increased revenue by approximately $5.1 million and $10.0 million for the three and six-month periods ended June 30, 2013, and approximately $5.3 million and $11.6 million for the three and six-month periods ended June 30, 2012, respectively. Deferred rents on the balance sheet represent rental revenue received prior to their due dates and amounts paid by the tenant for certain improvements considered to be landlord assets that will remain as the Company’s property at the end of the tenant’s lease term. The amortization of the amounts paid by the tenant for such improvements is calculated on a straight-line basis over the term of the tenant’s lease and is a component of straight-line rental income and increased revenue by $0.6 million and $1.2 million for the three and six-month periods ended June 30, 2013, and by $0.6 million and $1.2 million for the three and six-month periods ended June 30, 2012, respectively. Lease incentives, which are included as reductions of rental revenue in the accompanying consolidated statements of operations, are recognized on a straight-line basis over the term of the lease. Lease incentives increased revenue by $0.1 million and decreased revenue by $0.3 million for the three and six-month periods ended June 30, 2013, and decreased revenue by $0.1 million and $0.5 million for the three and six-month periods ended June 30, 2012, respectively.

Leases also typically provide for tenant reimbursement of a portion of common area maintenance and other operating expenses to the extent that a tenant’s pro rata share of expenses exceeds a base year level set in the lease or to the extent that the tenant has a lease on a triple net basis. For certain leases, significant assumptions and judgments are made by the Company in determining the lease term such as when termination options are provided to the tenant. The lease term impacts the period over which minimum rents are determined and recorded and also considers the period over which lease related costs are amortized. Termination fees received from tenants, bankruptcy settlement fees, third party management fees, labor reimbursement and leasing income are recorded when earned.

Stock-Based Compensation Plans

The Parent Company maintains a shareholder-approved equity-incentive plan known as the Amended and Restated 1997 Long-Term Incentive Plan (the “1997 Plan”). The 1997 Plan is administered by the Compensation Committee of the Parent Company’s Board of Trustees. Under the 1997 Plan, the Compensation Committee is authorized to award equity and equity-based awards, including incentive stock options, non-qualified stock options, restricted shares and performance-based shares. As of June 30, 2013, 5,195,177 common shares remained available for future awards under the 1997 Plan (including 3,053,267 shares available solely for options and share appreciation rights). Through June 30, 2013, all options awarded under the 1997 Plan had a one to ten-year term.

The Company incurred stock-based compensation expense of $2.4 million and $4.7 million during the three and six-month periods ended June 30, 2013, of which $0.3 million and $0.8 million, respectively, were capitalized as part of the Company’s review of employee compensation costs eligible for capitalization. The Company incurred stock-based compensation expense of $1.9 million and $3.6 million during the three and six-month periods ended June 30, 2012, of which $0.5 million and $0.9 million, respectively, were capitalized as part of the Company’s review of employee compensation costs eligible for capitalization. The expensed amounts are included in general and administrative expense on the Company’s consolidated income statement in the respective periods.

Accounting for Derivative Instruments and Hedging Activities

The Company accounts for its derivative instruments and hedging activities in accordance with the accounting standard for derivative and hedging activities. The accounting standard requires the Company to measure every derivative instrument (including certain derivative instruments embedded in other contracts) at fair value and record them in the balance sheet as either an asset or liability. See disclosures below related to the accounting standard for fair value measurements and disclosures.

For derivatives designated as cash flow hedges, the effective portions of changes in the fair value of the derivative are reported in other comprehensive income while the ineffective portions are recognized in earnings.

The Company actively manages its ratio of fixed-to-floating rate debt. To manage its fixed and floating rate debt in a cost-effective manner, the Company, from time to time, enters into interest rate swap agreements as cash flow hedges, under which it agrees to exchange various combinations of fixed and/or variable interest rates based on agreed upon notional amounts.

Fair Value Measurements

The Company estimates the fair value of its derivatives and available-for-sale securities in accordance with the accounting standard for fair value measurements and disclosures. The accounting standard defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. It also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value. Financial assets and liabilities recorded on the Consolidated Balance Sheets are categorized based on the inputs to the valuation techniques as follows:


•	Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access;

•

Level 2 inputs are inputs other than quoted prices included in Level 1, that are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals; and


•	Level 3 inputs are unobservable inputs for the asset or liability, which is typically based on an entity’s own assumptions, as there is little, if any, related market activity or information.

In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability.

The following table sets forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis as of June 30, 2013 (in thousands):



	Fair Value Measurements at Reporting Date Using:
	June 30,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Unobservable Inputs
Description	2013		(Level 1)		(Level 2)		(Level 3)
Recurring
Assets:
Interest Rate Swaps	$	175	$	—	$	175	$	—
Liabilities:
Interest Rate Swaps	$	3,089	$	—	$	3,089	$	—

The following table sets forth the Company’s financial liabilities that were accounted for at fair value on a recurring basis as of December 31, 2012 (in thousands):



	Fair Value Measurements at Reporting Date Using:
	December 31,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Unobservable Inputs
Description	2012		(Level 1)		(Level 2)		(Level 3)
Recurring
Assets:
Interest Rate Swaps	—		—		—		—
Liabilities:
Interest Rate Swaps	$	14,210	$	—	$	14,210	$	—

We classify our interest rate swaps, shown above, within Level 2 as the valuation inputs are based on quoted prices and market observable data of similar instruments.

Non-financial assets and liabilities recorded at fair value on a non-recurring basis to which the Company would apply the accounting standard where a measurement was required under fair value would include:


•	Non-financial assets and liabilities initially measured at fair value in an acquisition or business combination that are not remeasured at least quarterly at fair value,


•	Long-lived assets measured at fair value due to an impairment in accordance with the accounting standard for the impairment or disposal of long-lived assets,


•	Equity and cost method investments measured at fair value due to an impairment in accordance with the accounting standard for investments,


•	Notes receivable adjusted for any impairment in its value in accordance with the accounting standard for loan receivables, and


•	Asset retirement obligations initially measured at fair value under the accounting standard for asset retirement obligations.

There were no items that were accounted for at fair value on a non-recurring basis for the six months ended June 30, 2013.

Notes Receivable

As of June 30, 2013 and December 31, 2012, notes receivable included a purchase money mortgage with a 20-year amortization period bearing interest at 8.5%, which was valued at $7.0 million and $7.2 million, respectively.

The Company periodically assesses the collectability of the notes receivable in accordance with the accounting standard for loan receivables. The Company's $7.0 million outstanding purchase money mortgage note mentioned above was extended to a buyer (the “Borrower”) of a parcel of land in Newtown, Pennsylvania who has since defaulted on the note. As a result, a forbearance agreement was entered into between the Company and the Borrower, outlining the repayment terms of the outstanding debt (including accrued interest), as well as the metrics for selling and settling on homes over an agreed period of time. The Company has determined that the loan modification represents a troubled debt restructuring due to the fact that the Borrower was considered to be in a financial difficulty when it defaulted on the two mortgage debts, and that a concession was granted in the form of the forbearance agreements. Recurring loan repayments to the Company are expected to begin during 2013, however, during the six months ended June 30, 2013, the Company received a payment from the Borrower of $0.2 million, which the Company applied against the principal of the remaining loan balance. Based on actual current sales to date, as well as cash flow projections provided by the Borrower, the Company believes that the total note will be fully paid during 2015. Given the current circumstances, the Company performs, on an ongoing basis, a collectability assessment of the note using the expected cash flow information provided by the Borrower. The Company has obtained documentation to support the assumptions used by the Borrower. Based on the results of its probability weighted cash flow analysis, the Company has determined that, as of June 30, 2013, the present value of the expected cash flows of the note receivable exceeded the outstanding balance of the note and therefore the note is recoverable as of June 30, 2013. It is still possible, however, that if the housing market deteriorates, the Borrower will not meet its sales targets, and would fail to repay the note, thereby causing a loan loss for the Company which could be material to the Company's consolidated results of operations.

Income Taxes

Parent Company

The Parent Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the “Code”). In order to continue to qualify as a REIT, the Parent Company is required to, among other things, distribute at least 90% of its annual REIT taxable income to its shareholders and meet certain tests regarding the nature of its income and assets. As a REIT, the Parent Company is not subject to federal and state income taxes with respect to the portion of its income that meets certain criteria and is distributed annually to its shareholders. Accordingly, no provision for federal and state income taxes is included in the accompanying consolidated financial statements with respect to the operations of the Parent Company. The Parent Company intends to continue to operate in a manner that allows it to meet the requirements for taxation as a REIT. If the Parent Company fails to qualify as a REIT in any taxable year, it will be subject to federal and state income taxes and may not be able to qualify as a REIT for the four subsequent tax years. The Parent Company is subject to certain local income taxes. Provision for such taxes has been included in general and administrative expenses in the Parent Company’s Consolidated Statements of Operations and Comprehensive Income.

The Parent Company has elected to treat several of its subsidiaries as taxable REIT subsidiaries (each a “TRS”). A TRS is subject to federal, state and local income tax. In general, a TRS may perform non-customary services for tenants, hold assets that the Parent Company, as a REIT, cannot hold directly and generally may engage in any real estate or non-real estate related business.

Operating Partnership

In general, the Operating Partnership is not subject to federal and state income taxes, and accordingly, no provision for income taxes has been made in the accompanying consolidated financial statements. The partners of the Operating Partnership are required to include their respective share of the Operating Partnership’s profits or losses in their respective tax returns. The Operating Partnership’s tax returns and the amount of allocable Partnership profits and losses are subject to examination by federal and state taxing authorities. If such examination results in changes to the Operating Partnership profits or losses, then the tax liability of the partners would be changed accordingly.

The Operating Partnership may elect to treat one or more of its subsidiaries as REITs under Sections 856 through 860 of the Code. Each subsidiary REIT has met the requirements for treatment as a REIT under Sections 856 through 860 of the Code, and, accordingly, no provision has been made for federal and state income taxes in the accompanying consolidated financial statements. If any subsidiary REIT fails to qualify as a REIT in any taxable year, that subsidiary REIT will be subject to federal and state income taxes and may not be able to qualify as a REIT for the four subsequent taxable years. Also, each subsidiary REIT may be subject to certain local income taxes.

The Operating Partnership has elected to treat several of its subsidiaries as taxable TRSs, which are subject to federal, state and local income tax.

Recent Accounting Pronouncements

In February 2013, the Financial Accounting Standards Board (FASB) issued an amendment to the accounting standard for the presentation of comprehensive income. This amendment requires an entity to provide information about the amounts reclassified out of accumulated other comprehensive income by component, and represents the culmination of the FASB's redeliberation on the reporting of such reclassification adjustments. In addition, an entity is required to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income, but only if the amount reclassified is required under U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. For other amounts that are not required under U.S. GAAP to be reclassified in their entirety to net income, an entity is required to cross-reference to other disclosures required under U.S. GAAP that provide additional detail about those amounts. This update is effective for fiscal years and interim periods beginning after December 15, 2012. The Company’s adoption of the accounting standard did not have a material impact on its consolidated financial position or results of operations as the update relates only to changes in financial statement presentation.

Real Estate Investments

6 Months Ended

Jun. 30, 2013

Real Estate [Abstract]

Real Estate Disclosure [Text Block]

As of June 30, 2013 and December 31, 2012, the gross carrying value of the Company’s Properties was as follows (in thousands):



	June 30, 2013		December 31, 2012
Land	$	665,416	$	662,107
Building and improvements	3,466,460		3,576,065
Tenant improvements	488,584		487,997
	$	4,620,460	$	4,726,169

Acquisitions

On June 19, 2013, the Company acquired the remaining ownership interest in the Real Estate Venture known as "Six Tower Bridge" that it did not already own. See Note 4 "Investments in Unconsolidated Real Estate Ventures" for further discussion.

On April 25, 2013, the Company exercised its purchase option under the long term ground lease agreement it held through its acquisition of Three Logan Square on August 5, 2010 and acquired the 1.8 acre land parcel underlying Three Logan Square in Philadelphia, Pennsylvania for $20.8 million. The Company has accounted for the transaction as an asset acquisition. A portion of the original purchase price of Three Logan Square was allocated to the below market ground lease intangible asset, and as the sum of the purchase price of the land and the $4.3 million remaining balance for the intangible asset approximates the fair value of the land as unencumbered by the ground lease. The remaining intangible asset balance was reclassified to land upon exercise of the purchase option. The Company funded the cost of the acquisition with available corporate funds and capitalized $0.1 million of acquisition related costs as part of the basis in the operating land.

Dispositions

On June 28, 2013, the Company sold 16870 West Bernardo Drive, a 67,909 net rentable square feet office property located in San Diego, California, for a sales price of $18.0 million. The property was 98.8% occupied as of the date of sale.

On June 28, 2013, the Company sold 100 Arrandale Boulevard, a 34,931 net rentable square feet office property located in Exton, Pennsylvania, for a sales price of $3.5 million. The property was vacant at the date of sale.

On June 19, 2013, the Company sold 1700 Paoli Pike, a 28,000 net rentable square feet office property located in Malvern, Pennsylvania, for a sales price of $2.7 million. The property was vacant at the date of sale.

On June 14, 2013, the Company sold Pacific View Plaza, a 51,695 net rentable square feet office property located in Carlsbad, California, for a sales price of $10.3 million. The property was 90.5% occupied as of the date of sale.

On February 25, 2013, the Company sold a portfolio of eight office properties containing 800,546 square feet in Lawrenceville, New Jersey for an aggregate sales price of $121.0 million. These properties, collectively known as "Princeton Pike Corporate Center," were 86.9% occupied as of the date of sale.

The sales of these properties are included in discontinued operations (see Note 10).

The entire disclosure for certain real estate investment financial statements, real estate investment trust operating support agreements, real estate owned, retail land sales, time share transactions, as well as other real estate related disclosures.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 970
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28)
-URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 11
-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 66
-Paragraph 4, 5, 37, 50, 59, 65, 95, 97
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 154
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 67
-Paragraph 4, 5, 6, 7
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 34
-Paragraph 9, 11, 12, 13, 14, 15, 21
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 57
-Paragraph 2
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 144
-Paragraph 7, 34
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher OTS
-Name Federal Regulation (FR)
-Number Title 12
-Section 563c.102
-Paragraph 10
-Subparagraph a, b
-Chapter V
-Subsection I
-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 10
-Subparagraph 4
-Article 9

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 28
-Article 12

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher OTS
-Name Federal Regulation (FR)
-Number Title 12
-Section 563c.102
-Paragraph 11
-Chapter V
-Subsection I
-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph c
-Subparagraph Schedule III
-Article 5

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Section A
-Paragraph 9
-Chapter 3
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 04-2
-Paragraph 41, 63, 64
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Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 75-2
-Paragraph 47, 51, 52
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Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 6
-Subparagraph a
-Article 5

Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-DEP
-Paragraph 2, 6, 9-11, 18, 20
-IssueDate 2006-05-01
-Chapter 11
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 01-6
-Paragraph 13
-Subparagraph f
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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 15
-Paragraph 28
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 21: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 46R
-Paragraph 23, 24
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Deferred Costs

6 Months Ended

Jun. 30, 2013

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block]

DEFERRED COSTS

As of June 30, 2013 and December 31, 2012, the Company’s deferred costs were comprised of the following (in thousands):



	June 30, 2013
	Total Cost		Accumulated Amortization			Deferred Costs, net
Leasing Costs	$	150,128	$	(58,085	)	$	92,043
Financing Costs	40,117		(12,243		)	27,874
Total	$	190,245	$	(70,328	)	$	119,917



	December 31, 2012
	Total Cost		Accumulated Amortization			Deferred Costs, net
Leasing Costs	$	150,331	$	(58,343	)	$	91,988
Financing Costs	40,246		(9,991		)	30,255
Total	$	190,577	$	(68,334	)	$	122,243

During the three and six-month periods ended June 30, 2013, the Company capitalized internal direct leasing costs of $1.6 million and $3.2 million, respectively, and $1.4 million and $2.7 million during the three and six-month periods ended June 30, 2012, respectively, in accordance with the accounting standard for the capitalization of leasing costs.

Investment in Unconsolidated Ventures

6 Months Ended

Jun. 30, 2013

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments and Joint Ventures Disclosure [Text Block]

INVESTMENT IN UNCONSOLIDATED VENTURES

As of June 30, 2013, the Company had an aggregate investment of approximately $176.9 million in 17 unconsolidated Real Estate Ventures. The Company formed or acquired interests in these ventures with unaffiliated third parties to develop or manage office properties or to acquire land in anticipation of possible development of office or residential properties. As of June 30, 2013, 12 of the Real Estate Ventures owned 50 office buildings that contain an aggregate of approximately 6.2 million net rentable square feet; three Real Estate Ventures owned 24 acres of undeveloped parcels of land; one Real Estate Venture owned a one-acre parcel of land under active development and one Real Estate Venture developed a hotel property that contains 137 rooms in Conshohocken, PA.

The Company accounts for its unconsolidated interests in its Real Estate Ventures using the equity method. The Company’s unconsolidated interests range from 20% to 65%, subject to specified priority allocations of distributable cash in certain of the Real Estate Ventures.

The amounts reflected in the following tables (except for the Company’s share of equity and income) are based on the historical financial information of the individual Real Estate Ventures. The Company does not record operating losses of the Real Estate Ventures in excess of its investment balance unless the Company is liable for the obligations of the Real Estate Venture or is otherwise committed to provide financial support to the Real Estate Venture.

The following is a summary of the financial position of the Real Estate Ventures as of June 30, 2013 and December 31, 2012 (in thousands):



	June 30, 2013		December 31, 2012
Net property	$	813,056	$	923,536
Other assets	165,854		174,677
Other liabilities	27,054		53,645
Debt	709,975		724,780
Equity	241,881		319,788
Company’s share of equity (Company’s basis) (a)	176,875		193,555

(a) Amounts reflect the effects of basis differences resulting from assets contributed to Real Estate Ventures, as well as certain costs at the Real Estate Venture level. Basis differences occur from the impairment of investments and upon the transfer of assets that were previously owned by the Company into a Real Estate Venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the Real Estate Venture level.

The following is a summary of results of operations of the Real Estate Ventures for the three and six-month periods ended June 30, 2013 and 2012 (in thousands):



	Three-month periods ended June 30,					Six-month periods ended June 30,
	2013			2012		2013			2012
Revenue	$	36,927		$	39,064	$	77,816		$	77,872
Operating expenses	17,205			16,349		35,472			33,066
Interest expense, net	9,173			9,975		18,944			20,867
Depreciation and amortization	10,979			11,649		23,885			23,120
Net income (loss)	(430		)	1,091		(485		)	819
Company’s share of income (Company’s basis)	1,508			838		3,043			882

Two and Six Tower Bridge Exchange Transaction

On June 19, 2013, the Company acquired the outside ownership interest in Six Tower Bridge real estate venture, through a nonmonetary exchange with an unaffiliated party for its ownership interest in the Two Tower Bridge real estate venture. The Company previously accounted for its noncontrolling interest in Six Tower Bridge using the equity method. As a result of this transaction the Company obtained control of the Six Tower Bridge property and the Company's existing equity interest was remeasured at fair value based on the fair value of the underlying property and the distribution provisions of the real estate venture agreement. Accordingly, during 2013, the Company recorded a gain of approximately $7.8 million which is reflected in "Gain on remeasurement of investment in real estate venture" on the accompanying statements of operations. Following the acquisition, the Class A office property in Conshohocken, PA is wholly owned by the Company with an unencumbered fair value of $24.5 million. The Company accounted for this acquisition as a business combination and allocated the fair value as follows: $14.8 million to building, $6.9 million to land, $3.3 million to intangible assets and $0.5 million to below market lease liabilities assumed.

As mentioned above, the Company exchanged its investment in Two Tower Bridge real estate venture in an nonmonetary transaction with an unaffiliated party to acquire the outside investor interest in the Six Tower Bridge real estate venture. The investment in Two Tower Bridge had a fair value of $3.6 million on the date of the exchange transaction based on the fair value of the venture's equity and the distribution provisions of the real estate venture agreement. Based on this fair value and the carrying value for the Company's investment of $(0.1) million, during 2013 the Company recognized a gain on exchange of interests in real estate ventures of $3.7 million.

Grove Venture

On January 25, 2013, the Company formed the Grove Venture, a joint venture among the Company and two unaffiliated parties: Campus Crest Properties, LLC ("Campus Crest") and HSRE-Campus Crest IXA, LLC ("HSRE"). The Grove Venture has commenced construction of a 33-story, 850-bed student housing tower located in the University City submarket of Philadelphia, Pennsylvania to be called The Grove at Cira Centre South (the "Grove"). Each of the Company and Campus Crest owns a 30% interest in the Grove Venture and HSRE owns a 40% interest. The Grove Venture is developing the project on a one-acre land parcel held under a long-term ground lease with a third party lessor. The Company contributed to the Grove Venture its tenancy rights under a long-term ground lease, together with associated development rights, at an agreed-upon value of $8.5 million. The total estimated project costs are $158.5 million, which will be financed through partner capital contributions totaling $60.7 million, with the remaining $97.8 million being financed through a construction facility by PNC Bank, Capital One, and First Niagara Bank. Construction has already commenced, with a targeted project completion in 2014.

The Company's historical cost basis in the development rights that it contributed to the Grove Venture at formation was $6.0 million, thus creating an initial $2.5 million basis difference between the Company's initial outside investment basis compared to its $8.5 million initial equity basis in the Grove Venture. As this basis difference is not related to a physical land parcel, but rather to development rights to construct the Grove, the Company will accrete the basis difference as a reduction of depreciation expense over the life of the Grove Venture's assets.

Based upon the facts and circumstances at Grove Venture formation, the Company determined that the Grove Venture is a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the variable interest model under the accounting standard for consolidation in order to determine whether to consolidate the Grove Venture. Based upon each member's shared power over the activities of the Grove Venture under the operating agreement of the Grove Venture, and the Company's lack of exclusive control over the development and construction phases of the project, the Grove Venture is not consolidated by the Company, and is accounted for under the equity method of accounting. Accordingly, the land parcel and associated development rights contributed by the Company to the Grove Venture were deconsolidated by the Company upon formation of the Grove Venture.

The Company, from time to time, also provides guarantees and indemnities, including environmental indemnities, in connection with construction and permanent financing both for its own account and on behalf of its Real Estate Ventures. As of June 30, 2013, the Company had guaranteed repayment of approximately $0.6 million of loans on behalf of a Real Estate Venture. In addition, in connection with the Company's development of the Grove project through the Grove Venture, each of the Company and Campus Crest has provided, in addition to customary non-recourse carve-out guarantees, a completion and cost overrun guaranty, as well as a payment guaranty, on the construction financing (with the Company's share of the payment guaranty being approximately $23.0 million).

BDN Beacon Venture

On March 26, 2013, the Company sold its entire 20% ownership interest in an unconsolidated real estate venture known as BDN Beacon Venture LLC (the "Beacon Venture"). The carrying amount of the Company's investment in the Beacon Venture amounted to $17.0 million at the sale date, with the Company's proceeds effectively matching the carrying amount.

The entire disclosure for equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group.

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

6 Months Ended

Jun. 30, 2013

Intangible Assets Disclosure [Text Block]

As of June 30, 2013, the Company’s annual amortization for its intangible assets/liabilities were as follows (in thousands, and assuming no early lease terminations):



	Assets		Liabilities
2013 (six months remaining)	$	8,044	$	3,840
2014	13,740		6,181
2015	11,063		4,016
2016	6,497		2,076
2017	5,206		1,547
Thereafter	15,369		12,795
Total	$	59,919	$	30,455

Debt Obligations

6 Months Ended

Jun. 30, 2013

Debt Disclosure [Abstract]

Debt Disclosure [Text Block]

DEBT OBLIGATIONS

The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at June 30, 2013 and December 31, 2012 (in thousands):



Property / Location	June 30, 2013			December 31, 2012			Effective Interest Rate			Maturity Date
MORTGAGE DEBT:
Tysons Corner	$	92,296		$	93,188		5.36	%	(a)	Aug-15
Two Logan Square	88,960			89,340			7.57	%		Apr-16
Fairview Eleven Tower	21,847			22,000			4.25	%		Jan-17
IRS Philadelphia Campus	194,083			197,111			7.00	%		Sep-30
Cira South Garage	41,218			42,303			7.12	%		Sep-30
Principal balance outstanding	438,404			443,942
Plus: fair market value premiums (discounts), net	(786		)	(968		)
Total mortgage indebtedness	$	437,618		$	442,974
UNSECURED DEBT:
Credit Facility	—			69,000			LIBOR + 1.50%			Feb-16
Three-Year Term Loan - Swapped to fixed	150,000			150,000			2.60	%		Feb-15
Four-Year Term Loan - Variable	100,000			100,000			LIBOR + 1.75%			Feb-16
Seven-Year Term Loan - Swapped to fixed	200,000			200,000			3.62	%		Feb-19
$250.0M 5.400% Guaranteed Notes due 2014	232,199			238,379			5.53	%		Nov-14
$250.0M 7.500% Guaranteed Notes due 2015	161,430			166,535			7.76	%		May-15
$250.0M 6.000% Guaranteed Notes due 2016	149,919			150,429			5.95	%		Apr-16
$300.0M 5.700% Guaranteed Notes due 2017	300,000			300,000			5.68	%		May-17
$325.0M 4.950% Guaranteed Notes due 2018	325,000			325,000			5.13	%		Apr-18
$250.0M 3.950% Guaranteed Notes due 2023	250,000			250,000			4.02	%		Feb-23
Indenture IA (Preferred Trust I)	27,062			27,062			2.75	%		Mar-35
Indenture IB (Preferred Trust I)	25,774			25,774			3.30	%		Apr-35
Indenture II (Preferred Trust II)	25,774			25,774			3.09	%		Jul-35
Principal balance outstanding	1,947,158			2,027,953
plus: original issue premium (discount), net	(5,031		)	(5,597		)
Total unsecured indebtedness	$	1,942,127		$	2,022,356
Total Debt Obligations	$	2,379,745		$	2,465,330


(a)	This loan was assumed upon acquisition of the property that secures the mortgage debt. The interest rate reflects the market rate at the time of acquisition.

During the six-month period ended June 30, 2013 and June 30, 2012, the Company’s weighted-average effective interest rate on its mortgage notes payable was 6.64% and 6.72%, respectively.

During the six months ended June 30, 2013, the Company repurchased $11.8 million of its outstanding unsecured notes in a series of transactions that are summarized in the following table (in thousands):




Notes	Repurchase Amount		Principal		Loss			Deferred Financing Amortization
2014 5.400% Notes	$	6,570	$	6,180	$	(401	)	$	7
2015 7.500% Notes	5,728		5,105		(652		)	15
2016 6.000% Notes	573		510		(63		)	1
	$	12,871	$	11,795	$	(1,116	)	$	23

The Parent Company unconditionally guarantees the unsecured debt obligations of the Operating Partnership (or is a co-borrower with the Operating Partnership) but does not by itself incur unsecured indebtedness. The Parent Company has no material assets other than its investment in the Operating Partnership.

The Company utilizes its unsecured revolving credit facility (the "Credit Facility") for general business purposes, including to fund costs of acquisitions, developments and redevelopments and repayment of other debt. The scheduled maturity date of the Credit Facility in place at June 30, 2013 is February 1, 2016. The per annum variable interest rate on balances outstanding under the Credit Facility is LIBOR plus 1.50%. The interest rate and facility fee are subject to adjustment upon a change in the Company’s unsecured debt ratings. As of June 30, 2013, the Company did not have any outstanding borrowings on its Credit Facility, with $0.9 million in letters of credit outstanding, leaving $599.1 million of unused availability under the Credit Facility. During each of the three and six-month periods ended June 30, 2013 and 2012, there were no weighted-average interest rates associated with the Credit Facility because there were no borrowings outstanding under the Credit Facility during either period.

The Company has the option to increase the amounts available to be advanced under the Credit Facility, the $150.0 million three-year term loan, and the $100.0 million four-year term loan by an aggregate of $200.0 million, subject to customary conditions and limitations, by obtaining additional commitments from the current lenders and other financial institutions. The Company also has the option to extend the maturity dates of each of the credit facilities, the $150.0 million three-year term loan and the $100.0 million four-year term loan by one year, subject to payment of an extension fee and other customary conditions and limitations. The Company may repay the $150.0 million three-year term loan and the $100.0 million four-year term loan at any time without penalty. The $200.0 million seven-year term loan is subject to a declining prepayment penalty (3.00% commencing one year after closing, 2.00% after two years, 1.00% after three years and without penalty thereafter).

The spread to LIBOR for LIBOR-based loans under the Credit Facility and term loans depends on the Company's unsecured senior debt credit rating. Based on the Company's current credit rating, the spread for such loans will be 150 basis points under the Credit Facility, 175 basis points under both the $150.0 million three-year term loan and the $100.0 million four-year term loan and 190 basis points under the $200.0 million seven-year term loan. At the Company's option, advances under the Credit Facility and term loans may also bear interest at a per annum floating rate equal to the higher of the prime rate or the federal funds rate plus 0.50% per annum. The Credit Facility contains a competitive bid option that allows banks that are part of the lender consortium to bid to make loans to the Company at a reduced rate. The Company executed hedging transactions that fix the rate on the $200.0 million seven-year term loan at a 3.623% average rate for its full term, and the rate on the $150.0 million three-year term loan at a 2.596% average rate for periods of three to four years. All hedges commenced on February 1, 2012 and the rates are inclusive of the LIBOR spread based on the Company's current investment grade rating. See Note 9 for details of the interest rate swaps entered into as of June 30, 2013.

The Credit Facility and term loans contain financial and operating covenants and restrictions. The Company was in compliance with all such restrictions and financial covenants as of June 30, 2013.

As of June 30, 2013, the Company’s aggregate scheduled principal payments on debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):



2013 (six months remaining)	$	5,700
2014	244,141
2015	411,463
2016	346,528
2017	330,323
Thereafter	1,047,407
Total principal payments	2,385,562
Net unamortized premiums/(discounts)	(5,817		)
Outstanding indebtedness	$	2,379,745

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

Fair Value Disclosures [Text Block]

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2013

Fair Value Disclosures [Abstract]

FAIR VALUE OF FINANCIAL INSTRUMENTS

The Company determined the fair values disclosed below using available market information and discounted cash flow analyses as of June 30, 2013 and December 31, 2012, respectively. The discount rate used in calculating fair value is the sum of the current risk free rate and the risk premium on the date of measurement of the instruments or obligations. Considerable judgment is necessary to interpret market data and to develop the related estimates of fair value. Accordingly, the estimates presented are not necessarily indicative of the amounts that the Company could realize upon disposition. The use of different estimates and valuation methodologies may have a material effect on the fair value amounts shown. The Company believes that the carrying amounts reflected in the consolidated balance sheets at June 30, 2013 and December 31, 2012 approximate the fair values for cash and cash equivalents, accounts receivable, other assets, accounts payable and accrued expenses.

The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands):



	June 30, 2013				December 31, 2012
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Mortgage notes payable	$	438,404	$	474,036	$	443,942	$	486,412
Unsecured notes payable	$	1,418,548	$	1,495,998	$	1,430,343	$	1,553,123
Variable rate debt	$	528,610	$	526,693	$	597,610	$	595,693
Notes receivable	$	7,026	$	7,080	$	7,226	$	7,783

The fair value of the Company's unsecured notes payable is categorized at a Level 2 basis (as provided by the accounting standard for Fair Value Measurements and Disclosures). This is because the Company valued these instruments using quoted market prices as of June 30, 2013 and December 31, 2012.

The fair value of the Company's mortgage notes payable, variable rate debt and notes receivable are all categorized at a Level 3 basis (as provided by the accounting standard for Fair Value Measurements and Disclosures). The fair value of the variable rate debt was estimated using a discounted cash flow analysis valuation on the borrowing rates currently available to the Company for loans with similar terms and maturities, as applicable. The fair value of the mortgage debt was determined by discounting the future contractual interest and principal payments by a blended market rate. The fair value of the notes receivable was determined by using the expected cash flows of the notes receivable, and discounting those cash flows using the market rate of interest for mortgage notes with a comparable level of risk. These financial instruments have been categorized as Level 3 because the Company considers the rates used in the valuation techniques to be unobservable inputs.

The only significant unobservable input in the discounted cash flow model is the discount rate. For the fair value of the Company's unsecured notes, the Company uses a discount rate based on the indicative new issue pricing provided by lenders. For the Company's mortgage loans, the Company uses an estimate based on its knowledge of the mortgage market. The weighted average discount rate for the combined variable rate debt and mortgage loans used as of June 30, 2013 was 4.657%. An increase in the discount rate used in the discounted cash flow model would result in a decrease to the fair value of the Company's long-term debt. Conversely, a decrease in the discount rate used in the discounted cash flow model would result in an increase to the fair value of the Company's long-term debt.

Disclosure about the fair value of financial instruments is based upon pertinent information available to management as of June 30, 2013 and December 31, 2012. Although management is not aware of any factors that would significantly affect the fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since June 30, 2013, and current estimates of fair value may differ from the amounts presented herein.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15B
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44A, 44B
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-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 17-22, 27, 28
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-Name Statement of Financial Accounting Standard (FAS)
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-Subparagraph a-d
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Derivative Instruments and Hedging Activities Disclosure [Abstract]

Risk Management and Use of Financial Instruments

6 Months Ended

Jun. 30, 2013

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS [Text Block]

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS

Risk Management

In the course of its ongoing business operations, the Company encounters economic risk. There are three main components of economic risk: interest rate risk, credit risk and market risk. The Company is subject to interest rate risk on its interest-bearing liabilities. Credit risk is primarily the risk of inability or unwillingness of tenants to make contractually required payments and of counterparties on derivatives contracts to fulfill their obligations. Market risk is the risk of declines in the value of Company properties due to changes in rental rates, interest rates, supply and demand of similar products and other market factors affecting the valuation of properties.

Risks and Uncertainties

Challenging economic conditions have reduced the volume of real estate transactions and created credit stresses on many businesses. Vacancy rates may increase through 2013 and possibly beyond as the current economic climate continues to negatively impact tenants. The current financial markets also have an adverse effect on the Company’s Real Estate Venture partners and contractual counter parties, including counter parties in derivative contracts.

The Company was in compliance with all financial covenants as of June 30, 2013. Management continuously monitors the Company’s compliance with and anticipated compliance with the covenants. Certain of the covenants restrict the Company’s ability to obtain alternative sources of capital. While the Company currently believes it will remain in compliance with its covenants, in the event of a continued slow-down or deterioration in the economy, the Company may not be able to remain in compliance with such covenants, in which case a default would result absent a lender waiver.

Derivative Financial Instruments

The following table summarizes the terms and fair values of the Company's derivative financial instruments as of June 30, 2013 and December 31, 2012. The notional amounts provide an indication of the extent of the Company's involvement in these instruments at that time, but do not represent exposure to credit, interest rate or market risks (amounts presented in thousands).



Hedge Product	Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
				06/30/2013		12/31/2012						06/30/2013			12/31/2012
Assets:
Swap	Interest Rate	Cash Flow	(a)	25,774		25,774		3.300	%	December 22, 2011	January 30, 2021	154			(1,262		)
Swap	Interest Rate	Cash Flow	(a)	25,774		25,774		3.090	%	January 6, 2012	October 30, 2019	21			(1,129		)
				$	51,548	$	51,548					$	175		$	(2,391	)
Liabilities:
Swap	Interest Rate	Cash Flow	(a)	$	200,000	$	200,000	3.623	%	December 6-13, 2011	February 1, 2019	$	(1,506	)	$	(8,859	)
Swap	Interest Rate	Cash Flow	(a)	77,000		77,000		2.703	%	December 9-13, 2011	February 1, 2016	(798		)	(1,343		)
Swap	Interest Rate	Cash Flow	(a)	50,000		50,000		2.470	%	December 13, 2011	February 1, 2015	(328		)	(458		)
Swap	Interest Rate	Cash Flow	(a)	23,000		23,000		2.513	%	December 7-12, 2011	May 1, 2015	(174		)	(245		)
Swap	Interest Rate	Cash Flow	(a)	27,062		27,062		2.750	%	December 21, 2011	September 30, 2017	(283		)	(914		)
				$	377,062	$	377,062					$	(3,089	)	$	(11,819	)

(a) Hedging unsecured variable rate debt.

The Company measures its derivative instruments at fair value and records them in the balance sheet as either an asset or liability. As of June 30, 2013, two interest rate swaps held an asset position and were included in other assets on the Company's consolidated balance sheets. The remaining swaps are included in other liabilities on the Company's consolidated balance sheets.

Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. The Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that its derivative valuations in their entirety are classified in Level 2 of the fair value hierarchy.

Concentration of Credit Risk

Concentrations of credit risk arise for the Company when multiple tenants of the Company are engaged in similar business activities, or are located in the same geographic region, or have similar economic features that impact in a similar manner their ability to meet contractual obligations, including those to the Company. The Company regularly monitors its tenant base to assess potential concentrations of credit risk. Management believes the current credit risk portfolio is reasonably well diversified and does not contain an unusual concentration of credit risk. No tenant accounted for 10% or more of the Company’s rents during the three and six-month periods ended June 30, 2013 and 2012. Conditions in the general economy and the global credit markets have had a significant adverse effect on numerous industries. The Company has tenants concentrated in various industries that may be experiencing adverse effects from the current economic conditions and the Company could be adversely affected if such tenants were to default under their leases.

The entire disclosure for the entity's entire derivative instruments and hedging activities. Describes an entity's risk management strategies, derivatives in hedging activities and non-hedging derivative instruments, the assets, obligations, liabilities, revenues and expenses arising therefrom, and the amounts of and methodologies and assumptions used in determining the amounts of such items.

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Reference 21: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 45
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Name Statement of Financial Accounting Standard (FAS)
-Number 133
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Discontinued Operations and Disposal Groups [Abstract]

Discontinued Operations

6 Months Ended

Jun. 30, 2013

DISCONTINUED OPERATIONS [Text Block]

For the three and six-month periods ended June 30, 2013, income from discontinued operations relates to the twelve properties sold by the Company during 2013. The following table summarizes the revenue and expense information for properties classified as discontinued operations for the three and six-month periods ended June 30, 2013 (in thousands):



	Three-month period ended June 30, 2013			Six-month period ended June 30, 2013
Revenue:
Rents	$	626		$	4,129
Tenant reimbursements	2			331
Other	9			123
Total revenue	637			4,583
Expenses:
Property operating expenses	274			1,586
Real estate taxes	79			504
Depreciation and amortization	278			1,715
Total operating expenses	631			3,805
Other income (expense):
Interest income	2			2
Income from discontinued operations before gain on sale of interests in real estate	8			780
Net gain (loss) on disposition of discontinued operations (a)	(2,260		)	3,044
Income from discontinued operations	$	(2,252	)	$	3,824

(a) The loss of $(2.3) million for the second quarter of 2013 includes $1.1 million of closing costs incurred to sell the properties.

For the three and six-month periods ended June 30, 2012, income from discontinued operations relates to the 26 properties sold by the Company from January 1, 2012 through June 30, 2013. The following table summarizes the revenue and expense information for properties classified as discontinued operations for the three and six-month periods ended June 30, 2012 (in thousands):



	Three-month period ended June 30, 2012		Six-month period ended June 30, 2012
Revenue:
Rents	$	7,322	$	16,680
Tenant reimbursements	719		1,486
Termination fees	—		7
Other	164		188
Total revenue	8,205		18,361
Expenses:
Property operating expenses	2,137		4,841
Real estate taxes	843		1,977
Depreciation and amortization	2,695		6,274
Total operating expenses	5,675		13,092
Other income (expense):
Interest income	5		6
Income from discontinued operations before gain on sale of interests in real estate	2,535		5,275
Net gain on disposition of discontinued operations	10,177		24,845
Income from discontinued operations	$	12,712	$	30,120

Discontinued operations have not been segregated in the consolidated statements of cash flows. Therefore, amounts for certain captions will not agree with respective data in the consolidated statements of operations.

The entire disclosure for the facts and circumstances leading to the completed or expected disposal, manner and timing of disposal, the gain (loss) recognized in the income statement and the income statement caption that includes that gain (loss), amounts of revenues and pretax profit or loss reported in discontinued operations, the segment in which the disposal group was reported, and the classification (whether sold or classified as held for sale) and carrying value of the assets and liabilities comprising the disposal group. Includes all disposal groups, including those classified as components of the entity (discontinued operations).

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-Name Statement of Financial Accounting Standard (FAS)
-Number 144
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Non Controlling Interests In the Parent Company	6 Months Ended
Non Controlling Interests In the Parent Company	Jun. 30, 2013
Noncontrolling Interest [Abstract]
NON-CONTROLLING INTERESTS IN THE PARENT COMPANY [Text Block]	NON-CONTROLLING INTERESTS IN THE PARENT COMPANY Non-controlling interests in the Parent Company’s financial statements relate to redeemable common limited partnership interests in the Operating Partnership held by parties other than the Parent Company. As of June 30, 2013 and December 31, 2012, the aggregate book value of the non-controlling interests associated with the redeemable common limited partnership interests in the accompanying consolidated balance sheet of the Parent Company was $20.4 million and $21.2 million, respectively. The Parent Company believes that the aggregate settlement value of these interests (based on the number of units outstanding and the closing price of the common shares on the balance sheet date) was approximately $23.8 million and $22.5 million, respectively, as of June 30, 2013 and December 31, 2012.

The entire disclosure for noncontrolling interest in consolidated subsidiaries, which could include the name of the subsidiary, the ownership percentage held by the parent, the ownership percentage held by the noncontrolling owners, the amount of the noncontrolling interest, the location of this amount on the balance sheet (when not reported separately), an explanation of the increase or decrease in the amount of the noncontrolling interest, the noncontrolling interest share of the net Income or Loss of the subsidiary, the location of this amount on the income statement (when not reported separately), the nature of the noncontrolling interest such as background information and terms, the amount of the noncontrolling interest represented by preferred stock, a description of the preferred stock, and the dividend requirements of the preferred stock.

Beneficiaries Equity of the Parent Company

6 Months Ended

Jun. 30, 2013

BENEFICIARIES' EQUITY OF THE PARENT COMPANY [Text Block]

BENEFICIARIES’ EQUITY OF THE PARENT COMPANY

Earnings per Share (EPS)

The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding):



	Three month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	9,432		$	9,432		$	(5,910	)	$	(5,910	)
Net income (loss) from continuing operations attributable to non-controlling interests	(88		)	(88		)	201			201
Amount allocable to unvested restricted shareholders	(85		)	(85		)	(95		)	(95		)
Preferred share dividends	(1,725		)	(1,725		)	(3,049		)	(3,049		)
Preferred share redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common shareholders	7,534			7,534			(10,943		)	(10,943		)
Income (Loss) from discontinued operations	(2,252		)	(2,252		)	12,712			12,712
Discontinued operations attributable to non-controlling interests	26			26			(232		)	(232		)
Discontinued operations attributable to common shareholders	(2,226		)	(2,226		)	12,480			12,480
Net income attributable to common shareholders	$	5,308		$	5,308		$	1,537		$	1,537
Denominator
Weighted-average shares outstanding	155,347,384			155,347,384			143,300,637			143,300,637
Contingent securities/Share based compensation	—			1,343,817			—			—
Total weighted-average shares outstanding	155,347,384			156,691,201			143,300,637			143,300,637
Earnings per Common Share:
Income (Loss) from continuing operations attributable to common shareholders	$	0.05		$	0.05		$	(0.08	)	$	(0.08	)
Discontinued operations attributable to common shareholders	(0.02		)	(0.02		)	0.09			0.09
Net income attributable to common shareholders	$	0.03		$	0.03		$	0.01		$	0.01




	Six month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	7,275		$	7,275		$	(13,982	)	$	(13,982	)
Net income (loss) from continuing operations attributable to non-controlling interests	(39		)	(39		)	386			386
Amount allocable to unvested restricted shareholders	(193		)	(193		)	(191		)	(191		)
Preferred share dividends	(3,450		)	(3,450		)	(5,047		)	(5,047		)
Preferred share redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common shareholders	3,593			3,593			(20,924		)	(20,924		)
Income from discontinued operations	3,824			3,824			30,120			30,120
Discontinued operations attributable to non-controlling interests	(51		)	(51		)	(551		)	(551		)
Discontinued operations attributable to common shareholders	3,773			3,773			29,569			29,569
Net income (loss) attributable to common shareholders	$	7,366		$	7,366		$	8,645		$	8,645
Denominator
Weighted-average shares outstanding	149,508,957			149,508,957			143,060,796			143,060,796
Contingent securities/Share based compensation	—			1,157,288			—			—
Total weighted-average shares outstanding	149,508,957			150,666,245			143,060,796			143,060,796
Earnings per Common Share:
Income (Loss) from continuing operations attributable to common shareholders	$	0.02		$	0.02		$	(0.15	)	$	(0.15	)
Discontinued operations attributable to common shareholders	0.03			0.03			0.21			0.21
Net income (loss) attributable to common shareholders	$	0.05		$	0.05		$	0.06		$	0.06

Redeemable common limited partnership units totaling 1,763,739 and 2,657,721 as of June 30, 2013 and 2012, respectively, were excluded from the diluted earnings per share computations because their effect would have been anti-dilutive.

The contingent securities/share based compensation impact is calculated using the treasury stock method and relates to employee awards settled in shares of the Parent Company. The effect of these securities is anti-dilutive for periods that the Parent Company incurs a net loss from continuing operations available to common shareholders and therefore is excluded from the dilutive earnings per share calculation in such periods.

Unvested restricted shares are considered participating securities which require the use of the two-class method for the computation of basic and diluted earnings per share. For the six months ended June 30, 2013 and 2012, earnings representing nonforfeitable dividends as noted in the table above were allocated to the unvested restricted shares issued to the Company’s executives and other employees under the 1997 Plan.

Common and Preferred Shares

On April 10, 2013, the Parent Company closed a public offering of 12,650,000 common shares, inclusive of 1,650,000 common shares issued upon exercise by the underwriters of the option granted to them to purchase additional shares. The Parent Company contributed the net proceeds from the sale of shares, amounting to $181.7 million after deducting underwriting discounts and commissions and other offering expenses, to the Operating Partnership in exchange for partnership units of the Operating Partnership. The Operating Partnership continues to use the net proceeds for working capital, capital expenditures and other general corporate purposes, which may include acquisitions, developments and the repayment, repurchase and refinancing of debt.

On May 30, 2013, the Parent Company declared a distribution of $0.15 per common share, totaling $23.8 million, which was paid on July 19, 2013 to shareholders of record as of July 5, 2013. On May 30, 2013, the Parent Company declared distributions on its Series E Preferred Shares to holders of record as of June 30, 2013. These shares are entitled to a preferential return of 6.90% per annum on the $25.00 per share liquidation preference. Distributions paid on July 15, 2013 to holders of Series E Preferred Shares totaled $1.7 million.

In March 2010, the Parent Company commenced a continuous equity offering program (the “Offering Program”), that provided for the Parent Company's sale, from time to time until March 10, 2013, of up to an aggregate of 15,000,000 common shares in amounts and at times determined by the Parent Company. The Parent Company determined to sell shares under the Offering Program based on a variety of factors, including the trading price of its common shares, overall market conditions and the Parent Company's needs for and assessment of alternative sources of capital. Under the Offering Program, the Parent Company engaged sales agents, who received compensation of up to 2% of the gross sales price per share sold. From January 1, 2013 through the expiration of the Offering Program, as well as during the six-month period ended June 30, 2013, the Parent Company did not sell any shares under the Offering Program. From the inception of the Offering Program in March 2010 through its expiration, the Parent Company sold an aggregate of 6,421,553 common shares under the Offering Program at an average sales price of $12.50 per share. The Parent Company contributed the net proceeds from the sale of its shares to the Operating Partnership in exchange for the issuance of 6,421,553 common partnership units to the Parent Company. The Operating Partnership used the net proceeds contributed to it by the Parent Company to repay balances on credit facilities and for general corporate purposes.

Common Share Repurchases

The Parent Company maintains a share repurchase program under which it may repurchase its common shares from time to time in accordance with limits set by the Board of Trustees.

The Parent Company did not repurchase any shares under the share repurchase program during the six-month period ended June 30, 2013. As of June 30, 2013, the Parent Company may purchase an additional 0.5 million shares under the current program limits.

Repurchases may be made from time to time in the open market or in privately negotiated transactions, subject to market conditions and compliance with legal requirements. The share repurchase program does not contain any time limitation and does not obligate the Parent Company to repurchase any shares. The Parent Company may discontinue the program at any time.

Partners Equity of the Operating Partnership

6 Months Ended

Jun. 30, 2013

Partners Equity of Operating Partnership [Text Block]

PARTNERS’ EQUITY OF THE OPERATING PARTNERSHIP

Earnings per Common Partnership Unit

The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding):



	Three month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	9,432		$	9,432		$	(5,910	)	$	(5,910	)
Amount allocable to unvested restricted unitholders	(85		)	(85		)	(95		)	(95		)
Preferred unit dividends	(1,725		)	(1,725		)	(3,049		)	(3,049		)
Preferred unit redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common unitholders	7,622			7,622			(11,144		)	(11,144		)
Discontinued operations attributable to common unitholders	(2,252		)	(2,252		)	12,712			12,712
Net income attributable to common unitholders	$	5,370		$	5,370		$	1,568		$	1,568
Denominator
Weighted-average units outstanding	157,131,697			157,131,697			145,958,358			145,958,358
Contingent securities/Share based compensation	—			1,343,817			—			—
Total weighted-average units outstanding	157,131,697			158,475,514			145,958,358			145,958,358
Earnings per Common Partnership Unit:
Income (Loss) from continuing operations attributable to common unitholders	$	0.05		$	0.05		$	(0.08	)	$	(0.08	)
Discontinued operations attributable to common unitholders	(0.02		)	(0.02		)	0.09			0.09
Net income attributable to common unitholders	$	0.03		$	0.03		$	0.01		$	0.01




	Six-month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	7,275		$	7,275		$	(13,982	)	$	(13,982	)
Amount allocable to unvested restricted unitholders	(193		)	(193		)	(191		)	(191		)
Preferred unit dividends	(3,450		)	(3,450		)	(5,047		)	(5,047		)
Preferred unit redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common unitholders	3,632			3,632			(21,310		)	(21,310		)
Discontinued operations attributable to common unitholders	3,824			3,824			30,120			30,120
Net income attributable to common unitholders	$	7,456		$	7,456		$	8,810		$	8,810
Denominator
Weighted-average units outstanding	151,323,813			151,323,813			145,721,890			145,721,890
Contingent securities/Share based compensation	—			1,157,288			—			—
Total weighted-average units outstanding	151,323,813			152,481,101			145,721,890			145,721,890
Earnings per Common Partnership Unit:
Income (Loss) from continuing operations attributable to common unitholders	$	0.02		$	0.02		$	(0.15	)	$	(0.15	)
Discontinued operations attributable to common unitholders	0.03			0.03			0.21			0.21
Net income attributable to common unitholders	$	0.05		$	0.05		$	0.06		$	0.06

Unvested restricted units are considered participating securities which require the use of the two-class method for the computation of basic and diluted earnings per share. For the six months ended June 30, 2013 and 2012, earnings representing nonforfeitable dividends as noted in the table above were allocated to the unvested restricted units.

Common Partnership Units and Preferred Mirror Units

On April 10, 2013, the Parent Company closed a public offering of 12,650,000 common shares, inclusive of 1,650,000 common shares issued upon exercise by the underwriters of the option granted to them to purchase additional shares. The Company contributed the net proceeds from the sale of shares, amounting to $181.7 million after deducting underwriting discounts and commissions and other offering expenses, to the Operating Partnership in exchange for partnership units of the Operating Partnership. The Operating Partnership continues to use the net proceeds for working capital, capital expenditures and other general corporate purposes, which may include acquisitions, developments and the repayment, repurchase and refinancing of debt.

On May 30, 2013, the Operating Partnership declared a distribution of $0.15 per common partnership unit, totaling $23.8 million, which was paid on July 19, 2013 to unitholders of record as of July 5, 2013.

On May 30, 2013, the Operating Partnership declared distributions on its Series E-Linked Preferred Mirror Units to holders of record as of June 30, 2013. These units are entitled to a preferential return of 6.90% per annum on the $25.00 per unit liquidation preference. Distributions paid on July 15, 2013 to holders of Series E-Linked Preferred Mirror Units totaled $1.7 million.

From January 1, 2013 through expiration of the Offering Program on March 10, 2013, the Parent Company did not sell any shares under the Offering Program and, accordingly, the Operating Partnership did not issue any common partnership units to the Parent Company in connection with the Offering Program during this time. From the inception of the Offering Program in March 2010 through expiration of the Offering Program in March 2013, the Parent Company sold an aggregate of 6,421,553 common shares under the Offering Program at an average sales price of $12.50 per share. The Operating Partnership used the net proceeds contributed to it by the Parent Company to repay balances on credit facilities and for general corporate purposes.

Common Unit Repurchases

The Parent Company did not repurchase any shares under its share repurchase program during the six-month period ended June 30, 2013 and accordingly, during the six-month period ended June 30, 2012, the Operating Partnership did not repurchase any units in connection with the Parent Company’s share repurchase program.

Share Based and Deferred Compensation

6 Months Ended

Jun. 30, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

SHARE BASED AND DEFERRED COMPENSATION

Stock Options

At June 30, 2013, options exercisable for 2,868,838 common shares were outstanding under the Parent Company's shareholder approved equity incentive plan. There were 184,429 options unvested as of June 30, 2013 and $0.3 million of unrecognized compensation expense associated with these options to be recognized over a weighted average term of 0.7 years. During the three and six-month periods ended June 30, 2013 the Company recognized compensation expense related to unvested options of $0.2 million and $0.4 million, of which a nominal amount and $0.1 million, respectively, were capitalized. During the three and six-month periods ended June 30, 2012 the Company recognized compensation expense related to unvested options of $0.4 million and $0.7 million, of which $0.1 million and $0.2 million, respectively, were capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation.

Option activity as of June 30, 2013 and changes during the six months ended June 30, 2013 were as follows:



	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2013	3,337,549		$	14.50	7.20	$	—
Granted	—		—		—	—
Exercised	(166,620	)	$	10.26	—	—
Canceled	(117,662	)	$	18.61
Outstanding at June 30, 2013	3,053,267		$	15.35	5.68	$	—
Vested/Exerciseable at June 30, 2013	2,868,838		$	15.58	5.56	$	—

Restricted Share Awards

As of June 30, 2013, 563,713 restricted shares were outstanding under the 1997 Plan and vest over three to seven years from the initial grant date. At June 30, 2013, approximately $3.3 million of compensation expense remained to be recognized and is expected to be recognized over a weighted average remaining vesting period of 1.6 years. The Company recognized compensation expense related to outstanding restricted shares of $0.9 million and $1.8 million during the three and six-month periods ended June 30, 2013, of which $0.1 million and $0.3 million, respectively, were capitalized as part of the Company’s policies for capitalizing eligible portions of employee compensation. The Company recognized compensation expense related to outstanding restricted shares of $0.8 million and $1.5 million during the three and six-month periods ended June 30, 2012, of which $0.2 million and $0.3 million, respectively, were capitalized. The expensed amounts are included in general and administrative expense on the Company’s consolidated statement of operations in the respective periods.

The following table summarizes the Company’s restricted share activity for the six months ended June 30, 2013:



	Shares		Weighted Average Grant Date Fair value
Non-vested at January 1, 2013	597,708		$	9.46
Granted	182,576		13.13
Vested	(208,306	)	13.13
Forfeited	(8,265	)	11.41
Non-vested at June 30, 2013	563,713		$	12.56

On February 25, 2013, the Compensation Committee of the Company’s Board of Trustees awarded 157,208 restricted shares to the Company’s executives. The restricted shares will cliff vest after three years from the grant date. The vesting of the restricted shares is also subject to acceleration upon a change in control or if the recipient of the award were to die, become disabled or retire in a qualifying retirement. In the case of two of the Company's executives who have employment agreements with the Company, the vesting of the restricted shares is also subject to acceleration if either executive were to be terminated without cause or resign for good reason. Qualifying retirement means the recipient’s voluntary termination of employment after reaching at least age 57 and accumulating at least 15 years of service with the Company. In accordance with the accounting standard for stock-based compensation, the Company amortizes stock-based compensation costs through the qualifying retirement dates for those executives who meet the conditions for qualifying retirement during the scheduled vesting period.

Restricted Performance Share Units Plan

On each of February 25, 2013, March 1, 2012 and March 2, 2011, the Compensation Committee of the Parent Company’s Board of Trustees awarded an aggregate of 231,093, 242,122, and 113,256 share-based awards, respectively, to its executives. These awards are referred to as Restricted Performance Share Units, or RPSUs. The RPSUs represent the right to earn common shares. The number of common shares, if any, deliverable to award recipients depends on the Company’s performance based on its total return to shareholders during the three-year measurement period that commenced on January 1, 2013 (in the case of the February 25, 2013 awards), January 1, 2012 (in the case of the March 1, 2012 awards), and January 1, 2011 (in the case of the March 2, 2011 awards), and that ends on December 31, 2015, December 31, 2014 or December 31, 2013 (as applicable) or, if earlier, the date of a change of control. In the case of the awards made on February 25, 2013 and March 1, 2012, our performance is compared to the shareholder return of REITs within an index over the measurement period for 50% of the RPSUs awarded on that date, with the remaining 50% being compared to the total shareholder return of REITs within our proxy peer group over such period. In the case of the awards made on March 2, 2011, our performance is compared to the total shareholder return of REITs within an index over the performance period. The vesting of RPSUs is contingent upon the continued employment of the participants through the performance periods (with exceptions for death, disability and qualifying retirement). Dividends are deemed credited to the performance units accounts and are applied to “acquire” additional RPSUs for the account of the unit holder at the price per common share on the dividend payment date. If earned, RPSUs will be settled in common shares in an amount that reflects both the number of RPSUs in the holder’s account at the end of the applicable measurement period and the Company’s total return to shareholders during the applicable three year measurement period relative to the total shareholder returns of the REITs within the index or peer group, as applicable.

On the date of each grant, the RPSUs were valued using a Monte Carlo simulation. The fair values of the 2013, 2012 and 2011 awards on the grant dates were $4.1 million, $4.2 million and $2.0 million, respectively. The fair values of each award are being amortized over the three-year cliff vesting period. The vesting of RPSUs is subject to acceleration upon a change in control or if the recipient of the award were to die, become disabled or retire in a qualifying retirement prior to the vesting date. In the case of two of the Company's executives who have employment agreements with the Company, the vesting of the restricted shares is also subject to acceleration if either executive were to be terminated without cause or resign for good reason. Qualifying retirement means the recipient’s voluntary termination of employment after reaching age 57 and accumulating at least 15 years of service with the Company. In accordance with the accounting standard for stock-based compensation, the Company amortizes stock-based compensation costs through the qualifying retirement date for those executives who meet the conditions for qualifying retirement.

For the three and six-month periods ended June 30, 2013, the Company recognized total compensation expense for the 2013, 2012 and 2011 awards of $1.3 million and $2.5 million, of which $0.2 million and $0.4 million, respectively, were capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the three and six-month periods ended June 30, 2012, the Company recognized total compensation expense for the 2012, 2011 and 2010 awards of $0.7 million and $1.3 million, of which $0.2 million and $0.4 million, respectively, were capitalized.

A total of 372,102 common shares vested on December 31, 2012 (the end of the three-year measurement period for the linked RPSUs) and were delivered to holders of the RPSUs on March 1, 2013 in settlement of the RPSUs. Holders of these RPSUs also received cash dividend equivalents to the cash dividends paid on common shares on February 8, 2013.

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 50
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6406099&loc=d3e25284-112666

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5444-113901

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph 64, 65, A240
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 93-6
-Paragraph 53
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Tax Credit Transactions	6 Months Ended
Tax Credit Transactions	Jun. 30, 2013
Income Tax Disclosure [Abstract]
TAX CREDIT TRANSACTIONS	TAX CREDIT TRANSACTIONS Historic Tax Credit Transaction On November 17, 2008, the Company closed a transaction with US Bancorp (“USB”) related to the historic rehabilitation of the IRS Philadelphia Campus, a 862,692 square foot office building that is 100% leased to the IRS. On August 27, 2010, the Company completed the development of the IRS Philadelphia Campus and the IRS lease commenced. In connection with this completed development project, USB contributed to the Company $64.1 million of total project costs. In exchange for its contributions to the development of the IRS Philadelphia Campus, USB is entitled to substantially all of the benefits derived from the tax rehabilitation credits available under section 47 of the Internal Revenue Code. USB does not have a material interest in the underlying economics of the property. This transaction includes a put/call provision whereby the Company may be obligated or entitled to repurchase USB’s interest in the IRS Philadelphia Campus. The Company believes the put will be exercised and the amount attributed to that puttable non-controlling interest obligation is included in other liabilities and is being accreted to the expected fixed put price. Based on the contractual arrangements that obligate the Company to deliver tax benefits and provide other guarantees to USB and that entitle the Company through fee arrangements to receive substantially all available cash flow from the IRS Philadelphia Campus, the Company concluded that the IRS Philadelphia Campus should be consolidated. The Company also concluded that capital contributions received from USB, in substance, are consideration that the Company receives in exchange for its obligation to deliver tax credits and other tax benefits to USB. These receipts other than the amounts allocated to the put obligation will be recognized as revenue in the consolidated financial statements beginning when the obligation to USB is relieved which occurs upon delivery of the expected tax benefits net of any associated costs. The tax credit is subject to 20% recapture per year beginning one year after the completion of the IRS Philadelphia Campus. The total USB contributions presented within the Company’s consolidated balance sheet amounted to $39.1 million as of both June 30, 2013 and December 31, 2012. The contributions were recorded net of the amount allocated to non-controlling interest as described above of $2.7 million at the end of the period ended June 30, 2013 and $2.6 million at December 31, 2012, with the remaining balance being presented within deferred income. Beginning in September 2011 to September 2015, the Company recognized and will recognize, on an annual basis, the cash received as revenue net of allocated expenses over the five year credit recapture period as defined in the Internal Revenue Code within other income (expense) in its consolidated statements of operations. Direct and incremental costs incurred in structuring the transaction are deferred and will be recognized as expense in the consolidated financial statements upon the recognition of the related revenue as discussed above. The deferred cost at both June 30, 2013 and December 31, 2012 is $1.6 million, and is included in other assets in the Company’s consolidated balance sheet. Amounts included in interest expense related to the accretion of the non-controlling interest liability and the 2% return expected to be paid to USB on its non-controlling interest aggregate to $0.3 million and $0.7 million for the three and six-month periods ended June 30, 2013, respectively, and and $0.3 million and $0.7 million for the three and six-month periods ended June 30, 2012, respectively. New Markets Tax Credit Transaction On December 30, 2008, the Company entered into a transaction with USB related to the Cira South Garage in Philadelphia, Pennsylvania and expects to receive a net benefit of $7.8 million under a qualified New Markets Tax Credit Program (“NMTC”). The NMTC was provided for in the Community Renewal Tax Relief Act of 2000 (the “Act”) and is intended to induce investment capital in under-served and impoverished areas of the United States. The Act permits taxpayers (whether companies or individuals) to claim credits against their Federal income taxes for up to 39% of qualified investments in qualified, active low-income businesses or ventures. USB contributed $13.3 million to the development of the Cira South Garage and as such it is entitled to substantially all of the benefits derived from the tax credit, but it does not have a material interest in the underlying economics of the Cira South Garage. This transaction also includes a put/call provision whereby the Company may be obligated or entitled to repurchase USB’s interest. The Company believes the put will be exercised and an amount attributed to that obligation is included in other liabilities and is being accreted to the expected fixed put price. This put price is insignificant. Based on the contractual arrangements that obligate the Company to deliver tax benefits and provide various other guarantees to USB, the Company concluded that the investment entities established to facilitate the NMTC transaction should be consolidated. The USB contribution of $13.3 million is included in deferred income on the Company’s consolidated balance sheets at each of June 30, 2013 and December 31, 2012. The USB contribution other than the amount allocated to the put obligation will be recognized as income in the consolidated financial statements when the tax benefits are delivered without risk of recapture to the tax credit investors and the Company’s obligation is relieved. The Company anticipates that it will recognize the net cash received as revenue within other income/expense in the year ended December 31, 2015. The NMTC is subject to 100% recapture for a period of seven years as provided in the Internal Revenue Code. The Company expects that the put/call provision will be exercised in 2017. Direct and incremental costs incurred in structuring the transaction are deferred and will be recognized as expense in the consolidated financial statements upon the recognition of the related revenue as discussed above. The deferred cost at each of June 30, 2013 and December 31, 2012 is $5.3 million, and is included in other assets in the Company’s consolidated balance sheet.

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319

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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 136, 172
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

Reference 8: http://www.xbrl.org/2003/role/presentationRef
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Segment Reporting Disclosure [Text Block]

Segment Information

6 Months Ended

Jun. 30, 2013

Segment Reporting [Abstract]

SEGMENT INFORMATION

As of June 30, 2013, the Company was managing its portfolio within seven geographic segments: (1) Pennsylvania, (2) Philadelphia Central Business District (CBD), (3) Metropolitan Washington D.C., (4) New Jersey/Delaware, (5) Richmond, Virginia, (6) Austin, Texas and (7) California. The Pennsylvania segment includes properties in Chester, Delaware, and Montgomery counties in the Philadelphia suburbs. The Philadelphia CBD segment includes properties located in the City of Philadelphia in Pennsylvania. The Metropolitan Washington, D.C. segment includes properties in Northern Virginia and southern Maryland. The New Jersey/Delaware segment includes properties in Burlington, Camden and Mercer counties in New Jersey and in New Castle county in the state of Delaware. The Richmond, Virginia segment includes properties primarily in Albemarle, Chesterfield, Goochland and Henrico counties and one property in Durham, North Carolina. The Austin, Texas segment includes properties in Austin. The California segment includes properties in Oakland, Concord, and Carlsbad, California. The corporate group is responsible for cash and investment management, development of certain real estate properties during the construction period, and certain other general support functions. Land held for development and construction in progress are transferred to operating properties by region upon completion of the associated construction or project.

Segment information is as follows (in thousands):



	Pennsylvania Suburbs		Philadelphia CBD		Metropolitan, D.C.		New Jersey/Delaware		Richmond, Virginia		Austin, Texas		California		Corporate			Total
As of June 30, 2013:
Real estate investments, at cost:
Operating properties	$	1,198,731	$	1,023,619	$	1,199,885	$	408,940	$	310,229	$	286,808	$	192,248	$	—		$	4,620,460
Construction-in-progress															51,260			51,260
Land inventory															94,444			94,444
As of December 31, 2012:
Real estate investments, at cost:
Operating properties	$	1,178,730	$	988,590	$	1,193,200	$	546,644	$	309,923	$	285,346	$	223,736	$	—		$	4,726,169
Construction-in-progress															48,950			48,950
Land inventory															102,439			102,439
For the three-months ended June 30, 2013:
Total revenue	$	37,276	$	36,142	$	28,783	$	15,676	$	8,954	$	9,871	$	4,536	$	(319	)	$	140,919
Property operating expenses, real estate taxes and third party management expenses	13,151		13,587		10,774		7,245		3,599		4,208		2,339		165			55,068
Net operating income	$	24,125	$	22,555	$	18,009	$	8,431	$	5,355	$	5,663	$	2,197	$	(484	)	$	85,851
For the three-months ended June 30, 2012:
Total revenue	$	36,784	$	31,911	$	26,967	$	15,284	$	8,903	$	8,188	$	4,210	$	(444	)	$	131,803
Property operating expenses, real estate taxes and third party management expenses	12,640		11,962		10,451		7,083		3,470		3,611		2,249		(331		)	51,135
Net operating income	$	24,144	$	19,949	$	16,516	$	8,201	$	5,433	$	4,577	$	1,961	$	(113	)	$	80,668
For the six-months ended June 30, 2013:
Total revenue	$	75,461	$	72,067	$	56,567	$	31,278	$	17,719	$	19,129	$	9,142	$	(621	)	$	280,742
Property operating expenses, real estate taxes and third party management expenses	27,050		27,121		21,536		14,653		7,282		8,165		4,498		(57		)	110,248
Net operating income	$	48,411	$	44,946	$	35,031	$	16,625	$	10,437	$	10,964	$	4,644	$	(564	)	$	170,494
For the six-months ended June 30, 2012:
Total revenue	$	74,736	$	65,062	$	53,403	$	31,013	$	17,937	$	15,682	$	8,586	$	(826	)	$	265,593
Property operating expenses, real estate taxes and third party management expenses	25,902		24,648		20,518		14,912		7,112		7,009		4,384		(771		)	103,714
Net operating income	$	48,834	$	40,414	$	32,885	$	16,101	$	10,825	$	8,673	$	4,202	$	(55	)	$	161,879

Net operating income (“NOI”)is defined as total revenue less property operating expenses, real estate taxes and third party management expenses. Segment NOI includes revenue, real estate taxes and property operating expenses directly related to operation and management of the properties owned and managed within the respective geographical region. Segment NOI excludes property level depreciation and amortization, revenue and expenses directly associated with third party real estate management services, expenses associated with corporate administrative support services, and inter-company eliminations. NOI also does not reflect general and administrative expenses, interest expenses, real estate impairment losses, depreciation and amortization costs, capital expenditures and leasing costs. Trends in development and construction activities that could materially impact the Company’s results from operations are also not reflected in NOI. All companies may not calculate NOI in the same manner. NOI is the measure that is used by the Company to evaluate the operating performance of its real estate assets by segment. The Company also believes that NOI provides useful information to investors regarding the Company's financial condition and results of operations because it reflects only those income and expenses recorded at the property level. The Company believes that net income, as defined by GAAP, is the most appropriate earnings measure. Below is a reconciliation of consolidated NOI to consolidated net income, as defined by GAAP:



	Three-month periods ended June 30,						Six-month periods ended June 30,
	2013			2012			2013			2012
	(amounts in thousands)						(amounts in thousands)
Consolidated net operating income	$	85,851		$	80,668		$	170,494		$	161,879
Less:
Interest expense	(30,437		)	(32,981		)	(61,351		)	(67,125		)
Deferred financing costs	(1,183		)	(1,261		)	(2,344		)	(2,572		)
Depreciation and amortization	(49,300		)	(47,476		)	(98,846		)	(95,350		)
General and administrative expenses	(7,335		)	(6,079		)	(13,886		)	(12,129		)
Plus:
Interest income	122			1,838			180			2,320
Interest expense - financing obligation	(211		)	(196		)	(429		)	(378		)
Equity in income of real estate ventures	1,508			838			3,043			882
Gain from remeasurement of investment in a real estate venture	7,847			—			7,847			—
Net gain (loss) on real estate venture transactions	3,683			(11		)	3,683			(11		)
Loss on early extinguishment of debt	(1,113		)	(1,250		)	(1,116		)	(1,498		)
Income (loss) from continuing operations	9,432			(5,910		)	7,275			(13,982		)
Income from discontinued operations	(2,252		)	12,712			3,824			30,120
Net income	$	7,180		$	6,802		$	11,099		$	16,138

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 131
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

6 Months Ended

Jun. 30, 2013

COMMITMENTS AND CONTINGENCIES [Text Block]

COMMITMENTS AND CONTINGENCIES

Legal Proceedings

The Company is involved from time to time in litigation on various matters, including disputes with tenants and disputes arising out of agreements to purchase or sell properties. Given the nature of the Company’s business activities, these lawsuits are considered routine to the conduct of its business. The result of any particular lawsuit cannot be predicted, because of the very nature of litigation, the litigation process and its adversarial nature, and the jury system. The Company does not expect that the liabilities, if any, that may ultimately result from such legal actions will have a material adverse effect on the consolidated financial position, results of operations or cash flows of the Company.

Environmental

As an owner of real estate, the Company is subject to various environmental laws of federal, state, and local governments. The Company’s compliance with existing laws has not had a material adverse effect on its financial condition and results of operations, and the Company does not believe it will have a material adverse effect in the future. However, the Company cannot predict the impact of unforeseen environmental contingencies or new or changed laws or regulations on its current Properties or on properties that the Company may acquire.

Ground Rent

Future minimum rental payments under the terms of all non-cancelable ground leases under which the Company is the lessee are expensed on a straight-line basis regardless of when payments are due. The Company’s ground leases have remaining lease terms ranging from 16 to 90 years. Minimum future rental payments on non-cancelable leases at June 30, 2013 are as follows (in thousands):



2013 (six months remaining)	$	1,099
2014	2,288
2015	2,288
2016	2,288
2017	2,288
Thereafter	280,519

One of the land leases for a property provides for contingent rent participation by the lessor in certain capital transactions and net operating cash flows of the property after certain returns are achieved by the Company. Such amounts, if any, will be reflected as contingent rent when incurred. The leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate taxes. The above schedule of future minimum rental payments does not include any contingent rent amounts or any reimbursed expenses.

The Company acquired ground tenancy rights under a long term ground lease agreement related to its acquisition of 3020 Market Street in Philadelphia, Pennsylvania on August 12, 2011. The annual rental payments under this ground lease is equal to a percentage of the NOI generated by the property. The Company has not included the amounts in the table above since such amounts are not fixed or determinable.

Other Commitments or Contingencies

As part of the Company’s September 2004 acquisition of a portfolio of properties from The Rubenstein Company (which the Company refers to as the "TRC acquisition"), the Company acquired its interest in Two Logan Square, a 708,844 square foot office building in Philadelphia, primarily through its ownership of a second and third mortgage secured by this property. This property is consolidated, as the borrower is a variable interest entity and the Company, through its ownership of the second and third mortgages, is the primary beneficiary. The Company currently does not expect to take title to Two Logan Square until, at the earliest, September 2019. If the Company takes fee title to Two Logan Square upon a foreclosure of its mortgage, the Company has agreed to pay an unaffiliated third party that holds a residual interest in the fee owner of this property an amount equal to $2.9 million. On the TRC acquisition date, the Company recorded a liability of $0.7 million and this amount will accrete up to $2.9 million through September 2019. As of June 30, 2013, the Company had a balance of $1.6 million for this liability in its consolidated balance sheet.

The Company was audited by the Internal Revenue Service (the “IRS”) for its 2004 tax year. The audit concerned the tax treatment of the TRC acquisition in September 2004 in which the Company acquired a portfolio of properties through the acquisition of a limited partnership. On December 17, 2010, the Company received notice that the IRS proposed an adjustment to the allocation of recourse liabilities allocated to the contributor of the properties. The Company appealed the proposed adjustment and during the second quarter of 2013, the IRS finalized a settlement agreement which will not result in a material liability to the Company. The contributor of partnership interests in the 2004 transaction has agreed not to assert a claim against the Company for federal income tax purposes under the tax protection agreement entered into as part of the transaction.

As part of the Company’s 2006 merger with Prentiss Properties Trust ("Prentiss"), the 2004 TRC acquisition and several of our other transactions, the Company agreed not to sell certain of the properties it acquired in transactions that would trigger taxable income to the former owners. In the case of the TRC acquisition, the Company agreed not to sell acquired properties in non-exempt transactions for periods up to 15 years from the date of the TRC acquisition as follows at June 30, 2013: One Rodney Square and 130/150/170 Radnor Financial Center (January, 2015); and One Logan Square, Two Logan Square and Radnor Corporate Center (January, 2020). In the Prentiss acquisition, the Company assumed the obligation of Prentiss not to sell Concord Airport Plaza before March, 2018. The Company’s agreements generally provide that it may dispose of the subject properties only in transactions that qualify as tax-free exchanges under Section 1031 of the Internal Revenue Code or in other tax deferred transactions. If the Company were to sell a restricted property before expiration of the restricted period in a non-exempt transaction, the Company may be required to make significant payments to the parties who sold the applicable property on account of tax liabilities attributed to them.

As part of the Company’s acquisition of properties from time to time in tax-deferred transactions, the Company has agreed to provide certain of the prior owners of the acquired properties with the right to guarantee the Company’s indebtedness. If the Company were to seek to repay the indebtedness guaranteed by the prior owner before the expiration of the applicable agreement, the Company would be required to provide the prior owner an opportunity to guaranty qualifying replacement debt. These debt maintenance agreements may limit the Company’s ability to refinance indebtedness on terms favorable to the Company.

The Company invests in its properties and regularly incurs capital expenditures in the ordinary course to maintain the properties. The Company believes that such expenditures enhance its competitiveness. The Company also enters into construction, utility and service contracts in the ordinary course of business which may extend beyond one year. These contracts typically provide for cancellation with insignificant or no cancellation penalties.

During 2008, in connection with the development of the IRS Philadelphia Campus and the Cira South Garage, the Company entered into a historic tax credit and a new market tax credit arrangement, respectively. The Company is required to be in compliance with various laws, regulations and contractual provisions that apply to its historic and new market tax credit arrangements. Non-compliance with applicable requirements could result in projected tax benefits not being realized and require a refund to USB or reduction of investor capital contributions, which are reported as deferred income in the Company’s consolidated balance sheet, until such time as its obligation to deliver tax benefits is relieved. The compliance periods for the tax credit arrangements run through 2015. The Company does not anticipate that any material refunds or reductions of investor capital contributions will be required in connection with these arrangements.

The entire disclosure for commitments and contingencies.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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-Name FASB Interpretation (FIN)
-Number 14
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Use of Estimates, Policy [Policy Text Block]

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2013
Subsequent Events [Abstract]
Subsequent Events [Text Block]	SUBSEQUENT EVENTS The Company has evaluated subsequent events through the date the financial statements were issued.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2013

Accounting Policies [Abstract]

Use of Estimates

Investment, Policy [Policy Text Block]

Investments in Unconsolidated Real Estate Ventures

Consolidation, Policy [Policy Text Block]

Principles of Consolidation

Property, Plant and Equipment, Policy [Policy Text Block]

Operating Properties

Business Combinations and Other Purchase of Business Transactions, Policy [Policy Text Block]

Purchase Price Allocation

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

Impairment or Disposal of Long-Lived Assets

The Company determined during its impairment review for the three and six-month periods ended June 30, 2013 and 2012, that no impairment charges were necessary.

Revenue Recognition, Policy [Policy Text Block]

Revenue Recognition

Stock-Based Compensation Plans

Derivatives, Policy [Policy Text Block]

Accounting for Derivative Instruments and Hedging Activities

Fair Value of Financial Instruments, Policy [Policy Text Block]

Fair Value Measurements


•	Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access;

•


•	Level 3 inputs are unobservable inputs for the asset or liability, which is typically based on an entity’s own assumptions, as there is little, if any, related market activity or information.

The following table sets forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis as of June 30, 2013 (in thousands):



	Fair Value Measurements at Reporting Date Using:
	June 30,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Unobservable Inputs
Description	2013		(Level 1)		(Level 2)		(Level 3)
Recurring
Assets:
Interest Rate Swaps	$	175	$	—	$	175	$	—
Liabilities:
Interest Rate Swaps	$	3,089	$	—	$	3,089	$	—

The following table sets forth the Company’s financial liabilities that were accounted for at fair value on a recurring basis as of December 31, 2012 (in thousands):



	Fair Value Measurements at Reporting Date Using:
	December 31,		Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Unobservable Inputs
Description	2012		(Level 1)		(Level 2)		(Level 3)
Recurring
Assets:
Interest Rate Swaps	—		—		—		—
Liabilities:
Interest Rate Swaps	$	14,210	$	—	$	14,210	$	—

We classify our interest rate swaps, shown above, within Level 2 as the valuation inputs are based on quoted prices and market observable data of similar instruments.


•	Non-financial assets and liabilities initially measured at fair value in an acquisition or business combination that are not remeasured at least quarterly at fair value,


•	Long-lived assets measured at fair value due to an impairment in accordance with the accounting standard for the impairment or disposal of long-lived assets,


•	Equity and cost method investments measured at fair value due to an impairment in accordance with the accounting standard for investments,


•	Notes receivable adjusted for any impairment in its value in accordance with the accounting standard for loan receivables, and


•	Asset retirement obligations initially measured at fair value under the accounting standard for asset retirement obligations.

There were no items that were accounted for at fair value on a non-recurring basis for the six months ended June 30, 2013.

Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]

Notes Receivable

Income Tax, Policy [Policy Text Block]

Income Taxes

Parent Company

Operating Partnership

The Operating Partnership has elected to treat several of its subsidiaries as taxable TRSs, which are subject to federal, state and local income tax.

Recent Accounting Pronouncement [Policy Text Block]

Recent Accounting Pronouncements

Real Estate Investments Real Estate Investments (Tables)

6 Months Ended

Jun. 30, 2013

Real Estate [Abstract]

Gross Carrying Value Of Company's Properties [Table Text Block]

As of June 30, 2013 and December 31, 2012, the gross carrying value of the Company’s Properties was as follows (in thousands):



	June 30, 2013		December 31, 2012
Land	$	665,416	$	662,107
Building and improvements	3,466,460		3,576,065
Tenant improvements	488,584		487,997
	$	4,620,460	$	4,726,169

Deferred Costs Deferred Costs (Tables)

6 Months Ended

Jun. 30, 2013

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Components Of Deferred Costs Net [Table Text Block]

As of June 30, 2013 and December 31, 2012, the Company’s deferred costs were comprised of the following (in thousands):



	June 30, 2013
	Total Cost		Accumulated Amortization			Deferred Costs, net
Leasing Costs	$	150,128	$	(58,085	)	$	92,043
Financing Costs	40,117		(12,243		)	27,874
Total	$	190,245	$	(70,328	)	$	119,917



	December 31, 2012
	Total Cost		Accumulated Amortization			Deferred Costs, net
Leasing Costs	$	150,331	$	(58,343	)	$	91,988
Financing Costs	40,246		(9,991		)	30,255
Total	$	190,577	$	(68,334	)	$	122,243

Investment in Unconsolidated Ventures Investment in Unconsolidated Ventures (Tables)

6 Months Ended

Jun. 30, 2013

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investment Summarized Financial Information [Table Text Block]

The following is a summary of the financial position of the Real Estate Ventures as of June 30, 2013 and December 31, 2012 (in thousands):



	June 30, 2013		December 31, 2012
Net property	$	813,056	$	923,536
Other assets	165,854		174,677
Other liabilities	27,054		53,645
Debt	709,975		724,780
Equity	241,881		319,788
Company’s share of equity (Company’s basis) (a)	176,875		193,555

Summary of results of operations of unconsolidated Real Estate Venture [Table Text Block]

The following is a summary of results of operations of the Real Estate Ventures for the three and six-month periods ended June 30, 2013 and 2012 (in thousands):



	Three-month periods ended June 30,					Six-month periods ended June 30,
	2013			2012		2013			2012
Revenue	$	36,927		$	39,064	$	77,816		$	77,872
Operating expenses	17,205			16,349		35,472			33,066
Interest expense, net	9,173			9,975		18,944			20,867
Depreciation and amortization	10,979			11,649		23,885			23,120
Net income (loss)	(430		)	1,091		(485		)	819
Company’s share of income (Company’s basis)	1,508			838		3,043			882

Intangible Assets Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2013

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets [Table Text Block]

As of June 30, 2013 and December 31, 2012, the Company’s intangible assets were comprised of the following (in thousands):



	June 30, 2013
	Total Cost		Accumulated Amortization			Intangible assets, net
In-place lease value	$	84,944	$	(43,027	)	$	41,917
Tenant relationship value	48,939		(32,360		)	16,579
Above market leases acquired	3,139		(1,716		)	1,423
Total	$	137,022	$	(77,103	)	$	59,919
Below market leases acquired	$	77,004	$	(46,549	)	$	30,455



	December 31, 2012
	Total Cost		Accumulated Amortization			Intangible assets, net
In-place lease value	$	87,909	$	(42,894	)	$	45,015
Tenant relationship value	56,137		(37,389		)	18,748
Above market leases acquired	8,565		(1,708		)	6,857
Total	$	152,611	$	(81,991	)	$	70,620
Below market leases acquired	$	77,083	$	(43,224	)	$	33,859

Annual Amortization For Its Intangible Assets Liabilities [Table Text Block]

As of June 30, 2013, the Company’s annual amortization for its intangible assets/liabilities were as follows (in thousands, and assuming no early lease terminations):



	Assets		Liabilities
2013 (six months remaining)	$	8,044	$	3,840
2014	13,740		6,181
2015	11,063		4,016
2016	6,497		2,076
2017	5,206		1,547
Thereafter	15,369		12,795
Total	$	59,919	$	30,455

Debt Obligations Debt Obligations (Tables)

6 Months Ended

Jun. 30, 2013

Debt Disclosure [Abstract]

Consolidated Debt Obligations [Table Text Block]

The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at June 30, 2013 and December 31, 2012 (in thousands):



Property / Location	June 30, 2013			December 31, 2012			Effective Interest Rate			Maturity Date
MORTGAGE DEBT:
Tysons Corner	$	92,296		$	93,188		5.36	%	(a)	Aug-15
Two Logan Square	88,960			89,340			7.57	%		Apr-16
Fairview Eleven Tower	21,847			22,000			4.25	%		Jan-17
IRS Philadelphia Campus	194,083			197,111			7.00	%		Sep-30
Cira South Garage	41,218			42,303			7.12	%		Sep-30
Principal balance outstanding	438,404			443,942
Plus: fair market value premiums (discounts), net	(786		)	(968		)
Total mortgage indebtedness	$	437,618		$	442,974
UNSECURED DEBT:
Credit Facility	—			69,000			LIBOR + 1.50%			Feb-16
Three-Year Term Loan - Swapped to fixed	150,000			150,000			2.60	%		Feb-15
Four-Year Term Loan - Variable	100,000			100,000			LIBOR + 1.75%			Feb-16
Seven-Year Term Loan - Swapped to fixed	200,000			200,000			3.62	%		Feb-19
$250.0M 5.400% Guaranteed Notes due 2014	232,199			238,379			5.53	%		Nov-14
$250.0M 7.500% Guaranteed Notes due 2015	161,430			166,535			7.76	%		May-15
$250.0M 6.000% Guaranteed Notes due 2016	149,919			150,429			5.95	%		Apr-16
$300.0M 5.700% Guaranteed Notes due 2017	300,000			300,000			5.68	%		May-17
$325.0M 4.950% Guaranteed Notes due 2018	325,000			325,000			5.13	%		Apr-18
$250.0M 3.950% Guaranteed Notes due 2023	250,000			250,000			4.02	%		Feb-23
Indenture IA (Preferred Trust I)	27,062			27,062			2.75	%		Mar-35
Indenture IB (Preferred Trust I)	25,774			25,774			3.30	%		Apr-35
Indenture II (Preferred Trust II)	25,774			25,774			3.09	%		Jul-35
Principal balance outstanding	1,947,158			2,027,953
plus: original issue premium (discount), net	(5,031		)	(5,597		)
Total unsecured indebtedness	$	1,942,127		$	2,022,356
Total Debt Obligations	$	2,379,745		$	2,465,330

Summary Of Debt Repurchases [Table Text Block]




Notes	Repurchase Amount		Principal		Loss			Deferred Financing Amortization
2014 5.400% Notes	$	6,570	$	6,180	$	(401	)	$	7
2015 7.500% Notes	5,728		5,105		(652		)	15
2016 6.000% Notes	573		510		(63		)	1
	$	12,871	$	11,795	$	(1,116	)	$	23

Schedule of Extinguishment of Debt [Table Text Block]

As of June 30, 2013, the Company’s aggregate scheduled principal payments on debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):



2013 (six months remaining)	$	5,700
2014	244,141
2015	411,463
2016	346,528
2017	330,323
Thereafter	1,047,407
Total principal payments	2,385,562
Net unamortized premiums/(discounts)	(5,817		)
Outstanding indebtedness	$	2,379,745

Fair Value of Financial Instruments Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2013

Fair Value Disclosures [Abstract]

Schedule Of Financial Instruments With Fair Values Different From Their Carrying Amount [Table Text Block]

The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands):



	June 30, 2013				December 31, 2012
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Mortgage notes payable	$	438,404	$	474,036	$	443,942	$	486,412
Unsecured notes payable	$	1,418,548	$	1,495,998	$	1,430,343	$	1,553,123
Variable rate debt	$	528,610	$	526,693	$	597,610	$	595,693
Notes receivable	$	7,026	$	7,080	$	7,226	$	7,783

Risk Management and Use of Financial Instruments Risk Management and Use of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2013

Derivatives, Fair Value [Line Items]

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]



Hedge Product	Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
				06/30/2013		12/31/2012						06/30/2013			12/31/2012
Assets:
Swap	Interest Rate	Cash Flow	(a)	25,774		25,774		3.300	%	December 22, 2011	January 30, 2021	154			(1,262		)
Swap	Interest Rate	Cash Flow	(a)	25,774		25,774		3.090	%	January 6, 2012	October 30, 2019	21			(1,129		)
				$	51,548	$	51,548					$	175		$	(2,391	)
Liabilities:
Swap	Interest Rate	Cash Flow	(a)	$	200,000	$	200,000	3.623	%	December 6-13, 2011	February 1, 2019	$	(1,506	)	$	(8,859	)
Swap	Interest Rate	Cash Flow	(a)	77,000		77,000		2.703	%	December 9-13, 2011	February 1, 2016	(798		)	(1,343		)
Swap	Interest Rate	Cash Flow	(a)	50,000		50,000		2.470	%	December 13, 2011	February 1, 2015	(328		)	(458		)
Swap	Interest Rate	Cash Flow	(a)	23,000		23,000		2.513	%	December 7-12, 2011	May 1, 2015	(174		)	(245		)
Swap	Interest Rate	Cash Flow	(a)	27,062		27,062		2.750	%	December 21, 2011	September 30, 2017	(283		)	(914		)
				$	377,062	$	377,062					$	(3,089	)	$	(11,819	)

Discontinued Operations Discontinued Operations (Tables)

6 Months Ended

Jun. 30, 2013

Discontinued Operations and Disposal Groups [Abstract]

Revenue And Expense Information For Property Classified As Discontinued Operations [Table Text Block]



	Three-month period ended June 30, 2013			Six-month period ended June 30, 2013
Revenue:
Rents	$	626		$	4,129
Tenant reimbursements	2			331
Other	9			123
Total revenue	637			4,583
Expenses:
Property operating expenses	274			1,586
Real estate taxes	79			504
Depreciation and amortization	278			1,715
Total operating expenses	631			3,805
Other income (expense):
Interest income	2			2
Income from discontinued operations before gain on sale of interests in real estate	8			780
Net gain (loss) on disposition of discontinued operations (a)	(2,260		)	3,044
Income from discontinued operations	$	(2,252	)	$	3,824

(a) The loss of $(2.3) million for the second quarter of 2013 includes $1.1 million of closing costs incurred to sell the properties.



	Three-month period ended June 30, 2012		Six-month period ended June 30, 2012
Revenue:
Rents	$	7,322	$	16,680
Tenant reimbursements	719		1,486
Termination fees	—		7
Other	164		188
Total revenue	8,205		18,361
Expenses:
Property operating expenses	2,137		4,841
Real estate taxes	843		1,977
Depreciation and amortization	2,695		6,274
Total operating expenses	5,675		13,092
Other income (expense):
Interest income	5		6
Income from discontinued operations before gain on sale of interests in real estate	2,535		5,275
Net gain on disposition of discontinued operations	10,177		24,845
Income from discontinued operations	$	12,712	$	30,120

Beneficiaries Equity of the Parent Company Beneficiaries Equity of the Parent Company (Tables)

6 Months Ended

Jun. 30, 2013

Earnings Per Share (EPS), Basic and Diluted

Earnings per Share (EPS)



	Three month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	9,432		$	9,432		$	(5,910	)	$	(5,910	)
Net income (loss) from continuing operations attributable to non-controlling interests	(88		)	(88		)	201			201
Amount allocable to unvested restricted shareholders	(85		)	(85		)	(95		)	(95		)
Preferred share dividends	(1,725		)	(1,725		)	(3,049		)	(3,049		)
Preferred share redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common shareholders	7,534			7,534			(10,943		)	(10,943		)
Income (Loss) from discontinued operations	(2,252		)	(2,252		)	12,712			12,712
Discontinued operations attributable to non-controlling interests	26			26			(232		)	(232		)
Discontinued operations attributable to common shareholders	(2,226		)	(2,226		)	12,480			12,480
Net income attributable to common shareholders	$	5,308		$	5,308		$	1,537		$	1,537
Denominator
Weighted-average shares outstanding	155,347,384			155,347,384			143,300,637			143,300,637
Contingent securities/Share based compensation	—			1,343,817			—			—
Total weighted-average shares outstanding	155,347,384			156,691,201			143,300,637			143,300,637
Earnings per Common Share:
Income (Loss) from continuing operations attributable to common shareholders	$	0.05		$	0.05		$	(0.08	)	$	(0.08	)
Discontinued operations attributable to common shareholders	(0.02		)	(0.02		)	0.09			0.09
Net income attributable to common shareholders	$	0.03		$	0.03		$	0.01		$	0.01




	Six month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	7,275		$	7,275		$	(13,982	)	$	(13,982	)
Net income (loss) from continuing operations attributable to non-controlling interests	(39		)	(39		)	386			386
Amount allocable to unvested restricted shareholders	(193		)	(193		)	(191		)	(191		)
Preferred share dividends	(3,450		)	(3,450		)	(5,047		)	(5,047		)
Preferred share redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common shareholders	3,593			3,593			(20,924		)	(20,924		)
Income from discontinued operations	3,824			3,824			30,120			30,120
Discontinued operations attributable to non-controlling interests	(51		)	(51		)	(551		)	(551		)
Discontinued operations attributable to common shareholders	3,773			3,773			29,569			29,569
Net income (loss) attributable to common shareholders	$	7,366		$	7,366		$	8,645		$	8,645
Denominator
Weighted-average shares outstanding	149,508,957			149,508,957			143,060,796			143,060,796
Contingent securities/Share based compensation	—			1,157,288			—			—
Total weighted-average shares outstanding	149,508,957			150,666,245			143,060,796			143,060,796
Earnings per Common Share:
Income (Loss) from continuing operations attributable to common shareholders	$	0.02		$	0.02		$	(0.15	)	$	(0.15	)
Discontinued operations attributable to common shareholders	0.03			0.03			0.21			0.21
Net income (loss) attributable to common shareholders	$	0.05		$	0.05		$	0.06		$	0.06

Partners Equity of the Operating Partnership Partners Equity of the Operating Partnership (Tables)

6 Months Ended

Jun. 30, 2013

Earnings Per Common Partnership Unit [Table Text Block]

Earnings per Common Partnership Unit



	Three month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	9,432		$	9,432		$	(5,910	)	$	(5,910	)
Amount allocable to unvested restricted unitholders	(85		)	(85		)	(95		)	(95		)
Preferred unit dividends	(1,725		)	(1,725		)	(3,049		)	(3,049		)
Preferred unit redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common unitholders	7,622			7,622			(11,144		)	(11,144		)
Discontinued operations attributable to common unitholders	(2,252		)	(2,252		)	12,712			12,712
Net income attributable to common unitholders	$	5,370		$	5,370		$	1,568		$	1,568
Denominator
Weighted-average units outstanding	157,131,697			157,131,697			145,958,358			145,958,358
Contingent securities/Share based compensation	—			1,343,817			—			—
Total weighted-average units outstanding	157,131,697			158,475,514			145,958,358			145,958,358
Earnings per Common Partnership Unit:
Income (Loss) from continuing operations attributable to common unitholders	$	0.05		$	0.05		$	(0.08	)	$	(0.08	)
Discontinued operations attributable to common unitholders	(0.02		)	(0.02		)	0.09			0.09
Net income attributable to common unitholders	$	0.03		$	0.03		$	0.01		$	0.01




	Six-month periods ended June 30,
	2013						2012
	Basic			Diluted			Basic			Diluted
Numerator
Income (Loss) from continuing operations	$	7,275		$	7,275		$	(13,982	)	$	(13,982	)
Amount allocable to unvested restricted unitholders	(193		)	(193		)	(191		)	(191		)
Preferred unit dividends	(3,450		)	(3,450		)	(5,047		)	(5,047		)
Preferred unit redemption charge	—			—			(2,090		)	(2,090		)
Income (Loss) from continuing operations available to common unitholders	3,632			3,632			(21,310		)	(21,310		)
Discontinued operations attributable to common unitholders	3,824			3,824			30,120			30,120
Net income attributable to common unitholders	$	7,456		$	7,456		$	8,810		$	8,810
Denominator
Weighted-average units outstanding	151,323,813			151,323,813			145,721,890			145,721,890
Contingent securities/Share based compensation	—			1,157,288			—			—
Total weighted-average units outstanding	151,323,813			152,481,101			145,721,890			145,721,890
Earnings per Common Partnership Unit:
Income (Loss) from continuing operations attributable to common unitholders	$	0.02		$	0.02		$	(0.15	)	$	(0.15	)
Discontinued operations attributable to common unitholders	0.03			0.03			0.21			0.21
Net income attributable to common unitholders	$	0.05		$	0.05		$	0.06		$	0.06

Share Based and Deferred Compensation Share Based and Deferred Compensation (Tables)

6 Months Ended

Jun. 30, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Options Activity [Table Text Block]

Option activity as of June 30, 2013 and changes during the six months ended June 30, 2013 were as follows:



	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at January 1, 2013	3,337,549		$	14.50	7.20	$	—
Granted	—		—		—	—
Exercised	(166,620	)	$	10.26	—	—
Canceled	(117,662	)	$	18.61
Outstanding at June 30, 2013	3,053,267		$	15.35	5.68	$	—
Vested/Exerciseable at June 30, 2013	2,868,838		$	15.58	5.56	$	—

Company's Restricted Share Activity [Table Text Block]

The following table summarizes the Company’s restricted share activity for the six months ended June 30, 2013:



	Shares		Weighted Average Grant Date Fair value
Non-vested at January 1, 2013	597,708		$	9.46
Granted	182,576		13.13
Vested	(208,306	)	13.13
Forfeited	(8,265	)	11.41
Non-vested at June 30, 2013	563,713		$	12.56

Segment Information Segment Information (Tables)

6 Months Ended

Jun. 30, 2013

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment [Table Text Block]

Segment information is as follows (in thousands):



	Pennsylvania Suburbs		Philadelphia CBD		Metropolitan, D.C.		New Jersey/Delaware		Richmond, Virginia		Austin, Texas		California		Corporate			Total
As of June 30, 2013:
Real estate investments, at cost:
Operating properties	$	1,198,731	$	1,023,619	$	1,199,885	$	408,940	$	310,229	$	286,808	$	192,248	$	—		$	4,620,460
Construction-in-progress															51,260			51,260
Land inventory															94,444			94,444
As of December 31, 2012:
Real estate investments, at cost:
Operating properties	$	1,178,730	$	988,590	$	1,193,200	$	546,644	$	309,923	$	285,346	$	223,736	$	—		$	4,726,169
Construction-in-progress															48,950			48,950
Land inventory															102,439			102,439
For the three-months ended June 30, 2013:
Total revenue	$	37,276	$	36,142	$	28,783	$	15,676	$	8,954	$	9,871	$	4,536	$	(319	)	$	140,919
Property operating expenses, real estate taxes and third party management expenses	13,151		13,587		10,774		7,245		3,599		4,208		2,339		165			55,068
Net operating income	$	24,125	$	22,555	$	18,009	$	8,431	$	5,355	$	5,663	$	2,197	$	(484	)	$	85,851
For the three-months ended June 30, 2012:
Total revenue	$	36,784	$	31,911	$	26,967	$	15,284	$	8,903	$	8,188	$	4,210	$	(444	)	$	131,803
Property operating expenses, real estate taxes and third party management expenses	12,640		11,962		10,451		7,083		3,470		3,611		2,249		(331		)	51,135
Net operating income	$	24,144	$	19,949	$	16,516	$	8,201	$	5,433	$	4,577	$	1,961	$	(113	)	$	80,668
For the six-months ended June 30, 2013:
Total revenue	$	75,461	$	72,067	$	56,567	$	31,278	$	17,719	$	19,129	$	9,142	$	(621	)	$	280,742
Property operating expenses, real estate taxes and third party management expenses	27,050		27,121		21,536		14,653		7,282		8,165		4,498		(57		)	110,248
Net operating income	$	48,411	$	44,946	$	35,031	$	16,625	$	10,437	$	10,964	$	4,644	$	(564	)	$	170,494
For the six-months ended June 30, 2012:
Total revenue	$	74,736	$	65,062	$	53,403	$	31,013	$	17,937	$	15,682	$	8,586	$	(826	)	$	265,593
Property operating expenses, real estate taxes and third party management expenses	25,902		24,648		20,518		14,912		7,112		7,009		4,384		(771		)	103,714
Net operating income	$	48,834	$	40,414	$	32,885	$	16,101	$	10,825	$	8,673	$	4,202	$	(55	)	$	161,879

Reconciliation Of Consolidated Net Operating Income [Table Text Block]



	Three-month periods ended June 30,						Six-month periods ended June 30,
	2013			2012			2013			2012
	(amounts in thousands)						(amounts in thousands)
Consolidated net operating income	$	85,851		$	80,668		$	170,494		$	161,879
Less:
Interest expense	(30,437		)	(32,981		)	(61,351		)	(67,125		)
Deferred financing costs	(1,183		)	(1,261		)	(2,344		)	(2,572		)
Depreciation and amortization	(49,300		)	(47,476		)	(98,846		)	(95,350		)
General and administrative expenses	(7,335		)	(6,079		)	(13,886		)	(12,129		)
Plus:
Interest income	122			1,838			180			2,320
Interest expense - financing obligation	(211		)	(196		)	(429		)	(378		)
Equity in income of real estate ventures	1,508			838			3,043			882
Gain from remeasurement of investment in a real estate venture	7,847			—			7,847			—
Net gain (loss) on real estate venture transactions	3,683			(11		)	3,683			(11		)
Loss on early extinguishment of debt	(1,113		)	(1,250		)	(1,116		)	(1,498		)
Income (loss) from continuing operations	9,432			(5,910		)	7,275			(13,982		)
Income from discontinued operations	(2,252		)	12,712			3,824			30,120
Net income	$	7,180		$	6,802		$	11,099		$	16,138

Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2013

Operating Leases Future Minimum Payments Due [Table Text Block]

Ground Rent



2013 (six months remaining)	$	1,099
2014	2,288
2015	2,288
2016	2,288
2017	2,288
Thereafter	280,519

Organization of the Parent Company and The Operating Partnership Organization of the Parent Company and The Operating Partnership (Details) ft² in Millions	Jun. 30, 2013 a ft² Properties Real_Estate_Investments
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the Operating Partnership	98.80%
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet \| ft²	24.2
Area Owned By Company Of Undeveloped Parcels Of Land \| a	435
Area Of Additional Undeveloped Parcels Of Land With Option to Purchase \| a	51
Total potential development capacity \| ft²	6.2
Unconsolidated Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet \| ft²	6.2
Number Of Unconsolidated Real Estate Ventures \| Real_Estate_Investments	17
Wholly-owned Management Company Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet \| ft²	30.8
Third Parties and Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Net rentable square feet \| ft²	6.6
Total Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	210
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	182
Industrial Facilities [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	19
Mixed Use Properties [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	5
Development Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	1
Redevelopment Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	2
Re-entitlement Property [Member]
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of properties with ownership interest	1

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Summary of Significant Accounting Policies [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Minimum			1 year
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Maximum			10 years
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Revenue Increased By Straight Line Rent Adjustment	$ 5,100	$ 5,300	$ 10,000	$ 11,600
Increase In Revenue Due To Amortization Of Deferred Rent	600	600	1,200	1,200
Decrease (Increase) In Revenue Due To Lease Incentives	(100)	100	300	500
Guarantor Obligations, Current Carrying Value	600		600
Development costs for land	$ 6,000		$ 6,000
Increase In Shares Due To Amendments In Plan Shares Solely Available For Options And Share Appreciation Rights	3,053,267		3,053,267
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	5,195,177		5,195,177
Options Awarded Term			one to ten-year
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 300	500	$ 800	900
Allocated Share-based Compensation Expense	2,400	1,900	4,700	3,600
Notes receivable	7,026		7,026		$ 7,226
Interest income	122	$ 1,838	180	$ 2,320
Purchase money mortgage [Member] \| Twenty Year Amortization Period [Member]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Notes receivable	7,000		7,000		$ 7,200
OneTimePaymentReceivedFromBorrowerUnderDefault [Line Items]	$ 200		$ 200
Notes Receivable Amortization Period, Years			20 years		20 years
Mortgage Loans on Real Estate, Interest Rate			8.50%
Purchase money mortgage [Member] \| Notes Receivable Due Two Thousand Sixteen [Member]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Notes Receivable Amortization Period, Years			7 years		7 years

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Fair Value Measurements) (Details) - Fair Value, Measurements, Recurring [Member] - Interest Rate Swap [Member] - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 175	$ 0
Liabilities, Fair Value Disclosure	3,089	14,210
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	175
Liabilities, Fair Value Disclosure	3,089	14,210
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	$ 0	$ 0

Real Estate Investments Gross Carrying Value of Company's Properties (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Property, Plant and Equipment, Gross [Abstract]
Land	$ 665,416	$ 662,107
Buildings and Improvements, Gross	3,466,460	3,576,065
Leasehold Improvements, Gross	488,584	487,997
Real Estate Investment Property, at Cost	$ 4,620,460	$ 4,726,169

Real Estate Investments Acquisitions and Dispositions (Details) $ in Thousands		6 Months Ended
	Apr. 25, 2013 USD ($) a	Jun. 30, 2013 USD ($)	Jun. 30, 2012 USD ($)	Jun. 28, 2013 USD ($) ft²	Jun. 19, 2013 USD ($) ft²	Jun. 14, 2013 USD ($) ft²	Feb. 25, 2013 USD ($) ft² Properties
Significant Acquisitions and Disposals [Line Items]
Adjustment to Record Land Acquisition to Fair Value		$ (4,386)	$ 0
The Bluffs [Member]
Significant Acquisitions and Disposals [Line Items]
Net Rentable Space Sold \| ft²				67,909
Sale Consideration Of Sold Property				$ 18,000
Lease percentage of sold property				98.80%
100 Applebrook [Member]
Significant Acquisitions and Disposals [Line Items]
Net Rentable Space Sold \| ft²					28,000
Sale Consideration Of Sold Property					$ 2,700
100 Arrandale Boulevard [Member]
Significant Acquisitions and Disposals [Line Items]
Net Rentable Space Sold \| ft²				34,931
Sale Consideration Of Sold Property				$ 3,500
Pacific View Plaza [Member]
Significant Acquisitions and Disposals [Line Items]
Net Rentable Space Sold \| ft²						51,695
Sale Consideration Of Sold Property						$ 10,300
Lease percentage of sold property						90.50%
Princeton Pike Corporate Center [Member]
Significant Acquisitions and Disposals [Line Items]
Number of real estate properties sold \| Properties							8
Net Rentable Space Sold \| ft²							800,546
Sale Consideration Of Sold Property							$ 121,000
Lease percentage of sold property							86.90%
Three Logan Square [Member]
Significant Acquisitions and Disposals [Line Items]
Area of land acquired \| a	0
Business Acquisition, Cost of Acquired Entity, Purchase Price	$ 20,800
Adjustment to Record Land Acquisition to Fair Value	4,300
Business Acquisition, Cost of Acquired Entity, Transaction Costs	$ 100

Deferred Costs Deferred Costs (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Components of Deferred Costs Net [Abstract]
Leasing Costs, Total Cost	$ 150,128	$ 150,331
Financing Costs, Total Cost	40,117	40,246
Total Cost	190,245	190,577
Leasing Costs, Accumulated Amortization	(58,085)	(58,343)
Financing Costs, Accumulated Amortization	(12,243)	(9,991)
Total, Accumulated Amortization	70,328	68,334
Leasing, Deferred Costs, Net	92,043	91,988
Financing Costs, Deferred Costs, Net	27,874	30,255
Deferred Costs, Net	$ 119,917	$ 122,243

Investment in Unconsolidated Ventures Investment in Unconsolidated Ventures (Narrative) (Details) $ in Thousands, ft² in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2013 USD ($) a ft² Buildings Real_Estate_Ventures Room	Jun. 30, 2012 USD ($)	Jun. 30, 2013 USD ($) a ft² Buildings Real_Estate_Ventures Room	Jun. 30, 2012 USD ($)	Jun. 19, 2013 USD ($)	Mar. 26, 2013 USD ($) Rate	Jan. 25, 2013 USD ($) a Storey beds	Dec. 31, 2012 USD ($)
Schedule of Equity Method Investments [Line Items]
Gain from remeasurement of investment in a real estate venture	$ 7,847	$ 0	$ 7,847	$ 0
Company's share of equity (Company's Basis)	176,875		176,875					$ 193,555
Net gain (loss) on real estate venture transactions	$ 3,683		$ 3,683	0
Number of unconsolidated investments in Real Estate Ventures \| Real_Estate_Ventures	17		17
Number of real estate ventures that owns buildings \| Real_Estate_Ventures	12		12
Number of office buildings in Real Estate Ventures \| Buildings	50		50
Aggregate Approximate Area Of Office Buildings \| ft²	6.2		6.2
Number of real estate ventures that owns undeveloped land \| Real_Estate_Ventures	3		3
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land \| a	24		24
Payments to Acquire Equity Method Investments			$ 12,568	$ 18,617
Number of real estate ventures that owns land under development \| Real_Estate_Ventures	1		1
Area Owned By Real Estate Venture in Parcels Of Land Under Development \| a	1		1
Number of real estate ventures developed hotel property \| Real_Estate_Ventures	1		1
Number Of Rooms Contain In One Real Estate Venture Developed As Hotel Property \| Room	137		137
Minimum Percentage Of Unconsolidated Equity Method Investment Ownership			20.00%
Maximum Percentage Of Unconsolidated Equity Method Investment Ownership			65.00%
Guarantor Obligations, Current Carrying Value	$ 600		$ 600
Two Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Company's share of equity (Company's Basis)					$ (100)
Investments, Fair Value Disclosure					3,600
Six Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Gain from remeasurement of investment in a real estate venture			7,800
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net					24,500
Business Acquisition Purchase Price Allocation Building					14,800
Business Acquisition, Purchase Price Allocation, Land					6,900
Business Acquisition Purchase Price Allocation Intangible Assets					3,300
Business Acquisition Purchase Price Allocated To Market Lease Liabilities					$ 500
BDN Beacon Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company's share of equity (Company's Basis)						$ 17,000
Equity Method Investment, Ownership Percentage \| Rate						20.00%
The Grove at Cira Centre South [Member]
Schedule of Equity Method Investments [Line Items]
Number of floors of a building \| Storey							33
Student housing bed capacity \| beds							850
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land \| a							1
Equity Method Investment, Underlying Equity in Net Assets							$ 8,500
Equity Method Investment, Budgeted Total Project Cost	158,500		158,500
Payments to Acquire Equity Method Investments			60,700
Construction Loan	97,800		97,800
Equity Method Investment, Aggregate Cost							6,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity							$ 2,500
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 23,000		$ 23,000
The Grove at Cira Centre South [Member] \| Brandywine Realty Trust [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage							30.00%
The Grove at Cira Centre South [Member] \| Campus Crest Properties, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage							30.00%
The Grove at Cira Centre South [Member] \| HSRE, LLC [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage							40.00%

Deferred Costs Deferred Costs (Details Textuals) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Deferred Costs (Textuals) [Abstract]
Capitalized Internal Direct Leasing Costs	$ 1.6	$ 1.4	$ 3.2	$ 2.7

Investment in Unconsolidated Ventures Investment in Unconsolidated Ventures (Summary of Results of Operations of Unconsolidated Ventures) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Schedule of Equity Method Investments [Line Items]
Company's share of income (Company's basis)	$ 1,508	$ 838	$ 3,043	$ 882
Unconsolidated Real Estate Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Revenue	36,927	39,064	77,816	77,872
Operating expenses	17,205	16,349	35,472	33,066
Interest expense, net	9,173	9,975	18,944	20,867
Depreciation and amortization	10,979	11,649	23,885	23,120
Net income (loss)	(430)	1,091	(485)	819
Company's share of income (Company's basis)	$ 1,508	$ 838	$ 3,043	$ 882

The amount of net income (loss) reported by an equity method investment of the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14064-108612

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(g))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33912-111571

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph bb
-Article 1

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph f
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 20
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph w
-Article 1

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph g
-Subparagraph 1, 2
-Article 4

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.12)
-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 9
-Article 5

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 19
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 6
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 11
-Article 7

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Investment in Unconsolidated Ventures Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Company's share of equity (Company's Basis)	$ 176,875	$ 193,555
Unconsolidated Real Estate Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Net property	813,056	923,536
Other assets	165,854	174,677
Other liabilities	27,054	53,645
Debt	709,975	724,780
Equity	241,881	319,788
Company's share of equity (Company's Basis)	$ 176,875	$ 193,555

Intangible Assets Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Intangible Assets [Line Items]
Total Cost	$ 137,022	$ 152,611
Accumulated Amortization	(77,103)	(81,991)
Intangible Assets, net	59,919	70,620
In-place lease value
Intangible Assets [Line Items]
Total Cost	84,944	87,909
Accumulated Amortization	(43,027)	(42,894)
Intangible Assets, net	41,917	45,015
Tenant relationship value
Intangible Assets [Line Items]
Total Cost	48,939	56,137
Accumulated Amortization	(32,360)	(37,389)
Intangible Assets, net	16,579	18,748
Above market leases acquired
Intangible Assets [Line Items]
Total Cost	3,139	8,565
Accumulated Amortization	(1,716)	(1,708)
Intangible Assets, net	1,423	6,857
Below market leases acquired
Intangible Assets [Line Items]
Total Cost	77,004	77,083
Accumulated Amortization	(46,549)	(43,224)
Intangible Assets, net	$ 30,455	$ 33,859

Intangible Assets Annual Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Annual amortization of intangible assets and liabilities
Intangible Assets, net	$ 59,919	$ 70,620
Assets [Member]
Annual amortization of intangible assets and liabilities
2013	8,044
2014	13,740
2015	11,063
2016	6,497
2017	5,206
Thereafter	15,369
Intangible Assets, net	59,919
Liabilities [Member]
Annual amortization of intangible assets and liabilities
2013	3,840
2014	6,181
2015	4,016
2016	2,076
2017	1,547
Thereafter	12,795
Intangible Assets, net	$ 30,455

Debt Obligations Debt Obligations (Consolidated Debt Obligations Outstanding) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Net unamortized premiums/(discounts)	$ (5,817)
Total mortgage indebtedness	437,618	$ 442,974
Total Debt Obligations	2,379,745	2,465,330
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	438,404	443,942
Net unamortized premiums/(discounts)	(786)	(968)
Total mortgage indebtedness	437,618	442,974
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	1,947,158	2,027,953
Net unamortized premiums/(discounts)	(5,031)	(5,597)
Total unsecured indebtedness	1,942,127	2,022,356
Unsecured Debt [Member] \| Credit Facility
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 0	69,000
Debt Instrument Interest Rates Effective Percentage	LIBOR + 1.50%
Debt Instrument Maturity Dates	Feb-16
Unsecured Debt [Member] \| Three Year Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 150,000	150,000
Debt Instrument, Interest Rate, Effective Percentage	2.60%
Debt Instrument Maturity Dates	Feb-15
Unsecured Debt [Member] \| Four-Year Term Loan - Variable [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 100,000	100,000
Debt Instrument Interest Rates Effective Percentage	LIBOR + 1.75%
Debt Instrument Maturity Dates	Feb-16
Unsecured Debt [Member] \| Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 200,000	200,000
Debt Instrument, Interest Rate, Effective Percentage	3.62%
Debt Instrument Maturity Dates	Feb-19
Unsecured Debt [Member] \| $250.0M 5.400% Guaranteed Notes due 2014
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 232,199	238,379
Debt Instrument, Interest Rate, Effective Percentage	5.53%
Debt Instrument Maturity Dates	Nov-14
Unsecured Debt [Member] \| $250.0M 7.500% Guaranteed Notes due 2015
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 161,430	166,535
Debt Instrument, Interest Rate, Effective Percentage	7.76%
Debt Instrument Maturity Dates	May-15
Unsecured Debt [Member] \| $250.0M 6.000% Guaranteed Notes due 2016
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 149,919	150,429
Debt Instrument, Interest Rate, Effective Percentage	5.95%
Debt Instrument Maturity Dates	Apr-16
Unsecured Debt [Member] \| $300.0M 5.700% Guaranteed Notes due 2017
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 300,000	300,000
Debt Instrument, Interest Rate, Effective Percentage	5.68%
Debt Instrument Maturity Dates	May-17
Unsecured Debt [Member] \| $325.0M 4.950% Guaranteed Notes due 2018
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 325,000	325,000
Debt Instrument, Interest Rate, Effective Percentage	5.13%
Debt Instrument Maturity Dates	Apr-18
Unsecured Debt [Member] \| $250.0M 3.950% Guaranteed Notes due 2023
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 250,000	250,000
Debt Instrument, Interest Rate, Effective Percentage	4.02%
Debt Instrument Maturity Dates	Feb-23
Unsecured Debt [Member] \| Indenture IA (Preferred Trust I) [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 27,062	27,062
Debt Instrument, Interest Rate, Effective Percentage	2.75%
Debt Instrument Maturity Dates	Mar-35
Unsecured Debt [Member] \| Indenture IB (Preferred Trust I) [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 25,774	25,774
Debt Instrument, Interest Rate, Effective Percentage	3.30%
Debt Instrument Maturity Dates	Apr-35
Unsecured Debt [Member] \| Indenture II (Preferred Trust II) [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 25,774	25,774
Debt Instrument, Interest Rate, Effective Percentage	3.09%
Debt Instrument Maturity Dates	Jul-35
Tysons Corner [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 92,296	93,188
Debt Instrument, Interest Rate, Effective Percentage	5.36%
Debt Instrument Maturity Dates	Aug-15
Two Logan Square [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 88,960	89,340
Debt Instrument, Interest Rate, Effective Percentage	7.57%
Debt Instrument Maturity Dates	Apr-16
Fairview Eleven Tower [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 21,847	22,000
Debt Instrument, Interest Rate, Effective Percentage	4.25%
Debt Instrument Maturity Dates	Jan-17
IRS Philadelphia Campus [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 194,083	197,111
Debt Instrument, Interest Rate, Effective Percentage	7.00%
Debt Instrument Maturity Dates	Sep-30
Cira South Garage [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 41,218	$ 42,303
Debt Instrument, Interest Rate, Effective Percentage	7.12%
Debt Instrument Maturity Dates	Sep-30

Debt Obligations Debt Obligations (Outstanding Unsecured Notes in Series of Transactions) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2013 USD ($)
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	$ 12,871
Extinguishment of Debt, Amount	11,795
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	1,116
Write off of Deferred Debt Issuance Cost	23
Senior notes 5.400 Percent due 2014 [Member]
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	6,570
Extinguishment of Debt, Amount	6,180
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	401
Write off of Deferred Debt Issuance Cost	7
Senior Notes Due2015 [Member]
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	5,728
Extinguishment of Debt, Amount	5,105
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	652
Write off of Deferred Debt Issuance Cost	15
Senior Notes Due2016 [Member]
Extinguishment of Debt [Line Items]
Early Repayment of Senior Debt	573
Extinguishment of Debt, Amount	510
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	63
Write off of Deferred Debt Issuance Cost	$ 1

Debt Obligations Debt Obligations (Aggregate Scheduled Principal Payments of Debt Obligation, Excluding Amortization of Discounts and Premiums) (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Extinguishment of Debt [Line Items]
2013	$ 5,700
2014	244,141
2015	411,463
2016	346,528
2017	330,323
Thereafter	1,047,407
Total principal payments	2,385,562
Net unamortized premiums/(discounts)	(5,817)
Total Debt Obligations	$ 2,379,745	$ 2,465,330

Debt Obligations Debt Obligations (Details Textuals) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Debt Instrument [Line Items]
Unsecured credit facility	$ 0		$ 69,000
Repayments of Unsecured Debt	$ 0	$ 37,500
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate	6.64%	6.72%
Unsecured Debt [Member] \| Three Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150,000
Derivative, Average Fixed Interest Rate	2.596%
Notional Amount of Interest Rate Cash Flow Hedge Derivatives	$ 150,000
Unsecured Debt [Member] \| Letter of Credit [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	900
Unsecured Debt [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	599,100
Line of Credit Facility, Option for Additional Borrowing Capacity subject to customary conditions and limitations	200,000
Unsecured Debt [Member] \| Four Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	100,000
Unsecured Debt [Member] \| Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 200,000
Declining prepayment penalty in Year One	3.00%
Declining prepayment penalty in Year Two	2.00%
Declining prepayment penalty in Year Three	1.00%
Derivative, Average Fixed Interest Rate	3.623%

Debt Obligations Debt Obligations (Details Textuals 2) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2013 USD ($)
Unsecured Debt [Member] \| $250.0M 5.400% Guaranteed Notes due 2014
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250.0
Debt Instrument, Interest Rate, Stated Percentage	5.40%
Unsecured Debt [Member] \| $250.0M 7.500% Guaranteed Notes due 2015
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250.0
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Unsecured Debt [Member] \| $250.0M 6.000% Guaranteed Notes due 2016
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250.0
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Unsecured Debt [Member] \| $300.0M 5.700% Guaranteed Notes due 2017
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300.0
Debt Instrument, Interest Rate, Stated Percentage	5.70%
Unsecured Debt [Member] \| $325.0M 4.950% Guaranteed Notes due 2018
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 325.0
Debt Instrument, Interest Rate, Stated Percentage	4.95%
Unsecured Debt [Member] \| $250.0M 3.950% Guaranteed Notes due 2023
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250.0
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Unsecured Debt [Member] \| Three Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150.0
Debt Instrument Term	3 years
Option to Extend Term Loan	1 year
Debt Instrument, Basis Spread on Variable Rate	1.75%
Unsecured Debt [Member] \| Four-Year Term Loan - Variable [Member]
Debt Instrument [Line Items]
Debt Instrument Term	4 years
Option to Extend Term Loan	1 year
Debt Instrument, Basis Spread on Variable Rate	1.75%
Unsecured Debt [Member] \| Three and Four Year Term Loan [Member]
Debt Instrument [Line Items]
Derivative, Lower Remaining Maturity Range	3 years
Derivative, Higher Remaining Maturity Range	4 years
Unsecured Debt [Member] \| Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 200.0
Debt Instrument Term	7 years
Debt Instrument, Basis Spread on Variable Rate	1.90%
Senior notes 5.400 Percent due 2014 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.40%
Senior Notes Due2015 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.50%

Fair Value of Financial Instruments Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Company's estimates of fair value differ from the carrying amounts
Mortgage notes payable, Carrying Amount	$ 438,404	$ 443,942
Mortgage notes payable, Fair Value	474,036	486,412
Unsecured Notes Payable, Carrying Amount	1,418,548	1,430,343
Unsecured Notes Payable, Fair Value	1,495,998	1,553,123
Variable Rate Debt, Carrying Amount	528,610	597,610
Variable Rate Debt, Fair Value	526,693	595,693
Notes Receivable, Carrying Amount	7,026	7,226
Notes Receivable, Fair Value	$ 7,080	$ 7,783

Fair Value of Financial Instruments Fair Value of Financial Instruments (Details Textuals) (Details)	Jun. 30, 2013
Fair Value Disclosures [Abstract]
Weighted Average Fair Value Interest Rate on Debt	4.657%

Risk Management and Use of Financial Instruments Risk Management and Use of Financial Instruments (Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2013	Dec. 31, 2012
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 51,548	$ 51,548
Derivative, Fair Value, Net	175	(2,391)
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	377,062	377,062
Derivative, Fair Value, Net	(3,089)	(11,819)
3.300% Interest Rate Swap Maturing January 30, 2021 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 25,774	25,774
Derivative, Fixed Interest Rate	3.30%
Derivative, Fair Value, Net	$ 154	(1,262)
3.090% Interest Rate Swap Maturing October 30, 2019 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 25,774	25,774
Derivative, Fixed Interest Rate	3.09%
Derivative, Fair Value, Net	$ 21	(1,129)
3.623% Interest Rate Swap Maturing February 1, 2019 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 200,000	200,000
Derivative, Fixed Interest Rate	3.623%
Derivative, Fair Value, Net	$ (1,506)	(8,859)
2.703% Interest Rate Swap Maturing February 1, 2016 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 77,000	77,000
Derivative, Fixed Interest Rate	2.703%
Derivative, Fair Value, Net	$ (798)	(1,343)
2.470% Interest Rate Swap Maturing February 1, 2015 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 50,000	50,000
Derivative, Fixed Interest Rate	2.47%
Derivative, Fair Value, Net	$ (328)	(458)
2.513% Interest Rate Swap Maturing May 1, 2015 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 23,000	23,000
Derivative, Fixed Interest Rate	2.513%
Derivative, Fair Value, Net	$ (174)	(245)
2.750% Interest Rate Swap Maturing September 30, 2017 [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swap [Member] \| Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 27,062	27,062
Derivative, Fixed Interest Rate	2.75%
Derivative, Fair Value, Net	$ (283)	$ (914)

Discontinued Operations Discontinued Operations (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2013

Jun. 30, 2012

Jun. 30, 2013

Jun. 30, 2012

Revenue:

$ 116,334

$ 109,713

$ 231,201

$ 218,704

19,565

18,229

39,916

36,885

Other Real Estate Revenue

410

101

906

1,591

1,457

888

2,330

2,399

140,919

131,803

280,742

265,593

Expenses:

39,490

36,363

78,908

74,223

14,215

13,508

28,552

26,977

49,300

47,476

98,846

95,350

111,703

104,690

222,980

211,193

Income from discontinued operations before gain on sale of interests in real estate

122

1,838

180

2,320

2,535

780

5,275

Net gain on disposition of discontinued operations

(2,260)

^[1]

10,177

3,044

24,845

Discontinued Operations, Disposal Closing Costs

(2,252)

12,712

3,824

30,120

^[1]

1,100

Discontinued Operations [Member]

Revenue:

626

7,322

4,129

16,680

719

331

1,486

Other Real Estate Revenue

164

123

188

637

8,205

4,583

18,361

Expenses:

274

2,137

1,586

4,841

843

504

1,977

278

2,695

1,715

6,274

631

5,675

3,805

13,092

Income from discontinued operations before gain on sale of interests in real estate

2,535

780

5,275

Net gain on disposition of discontinued operations

10,177

3,044

24,845

$ (2,252)

$ 12,712

$ 3,824

$ 30,120

[1]	The loss of $(2.3) million for the second quarter of 2013 includes $1.1 million of closing costs incurred to sell the properties.

Discontinued Operations Discontinued Operations (Details Textuals) (Details) - Properties	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold	12	26

Non Controlling Interests In the Parent Company Non Controlling Interests In the Parent Company (Details) - USD ($) $ in Millions	Jun. 30, 2013	Dec. 31, 2012
Noncontrolling Interest [Abstract]
Aggregate amount related to non-controlling interests classified within equity	$ 20.4	$ 21.2
Settlement Value Of Non Controlling Interest In Operating Partnership	$ 23.8	$ 22.5

Beneficiaries Equity of the Parent Company Beneficiaries Equity of the Parent Company (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator
Income (Loss) from Continuing Operations, Basic	$ 9,432	$ (5,910)	$ 7,275	$ (13,982)
Income (Loss) From Continuing Operations, Diluted	9,432	(5,910)	7,275	(13,982)
Net Income (Loss) From Continuing Operations Attributable to Non controlling interests, Basic	(88)	201	(39)	386
Net Income (Loss) From Continuing Operations Attributable To Non Controlling Interests, Diluted	(88)	201	(39)	386
Amount allocated to unvested restricted shareholders/unitholders, Basic	(85)	(95)	(193)	(191)
Amount allocated to unvested restricted shareholders/unitholders, Diluted	(85)	(95)	(193)	(191)
Preferred share/unit dividends, Basic	(1,725)	(3,049)	(3,450)	(5,047)
Preferred share/unit dividends, Diluted	(1,725)	(3,049)	(3,450)	(5,047)
Redemption Premium	0	(2,090)	0	(2,090)
Redemption Premium, Diluted	0	(2,090)	0	(2,090)
Income (Loss) from Continuing Operations Available to Common Shareholders/unitholders, Basic	7,534	(10,943)	3,593	(20,924)
Income (Loss) from Continuing Operations Available to Common Shareholders/unitholders, Diluted	7,534	(10,943)	3,593	(20,924)
Income (Loss) from Discontinued Operations	(2,252)	12,712	3,824	30,120
Income (Loss) From Discontinued Operations, Diluted	(2,252)	12,712	3,824	30,120
Discontinued operations attributable to non-controlling interests, Basic	26	(232)	(51)	(551)
Discontinued Operations Attributable to Noncontrolling Interests- Diluted	26	(232)	(51)	(551)
Discontinued operations attributable to common shareholders, Basic	(2,226)	12,480	3,773	29,569
Discontinued operations attributable to common shareholders, Diluted	(2,226)	12,480	3,773	29,569
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	5,308	1,537	7,366	8,645
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	$ 5,308	$ 1,537	$ 7,366	$ 8,645
Denominator
Weighted Average Number of Shares Outstanding, Basic	155,347,384	143,300,637	149,508,957	143,060,796
Contingent securities/Share based compensation	1,343,817	0	1,157,288	0
Weighted Average Number of Shares Outstanding, Diluted	156,691,201	143,300,637	150,666,245	143,060,796
Earnings per common share from continuing operations Abstract
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$ 0.05	$ (0.08)	$ 0.02	$ (0.15)
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	0.05	(0.08)	0.02	(0.15)
Discontinued Operations attributable to common shareholders/unitholders, Basic	(0.02)	0.09	0.03	0.21
Discontinued Operations attributable to common shareholders/unitholders, Diluted	(0.02)	0.09	0.03	0.21
Net income (loss) attributable to common shareholders/unitholders, Basic	0.03	0.01	0.05	0.06
Net income (loss) attributable to common shareholders/unitholders, Diluted	$ 0.03	$ 0.01	$ 0.05	$ 0.06

Beneficiaries Equity of the Parent Company Beneficiaries Equity of the Parent Company (Details Textuals) (Details) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended		12 Months Ended	36 Months Ended
	Jul. 15, 2013	Apr. 10, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Mar. 10, 2013	May 30, 2013
Class of Stock [Line Items]
Common stock issued subsequent to balance sheet date, New issues		12,650,000
Additional shares granted under option to purchase in public offering		1,650,000
Proceeds from Issuance of Common Stock		$ 181,700	$ 181,527	$ 0
Distributions payable			25,587		$ 23,652
Dividends, Preferred Stock, Cash			$ 3,450	5,047
Additional shares Expected to be purchased under program			500,000
Class A Units [Member]
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			1,763,739		2,657,721
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage			6.90%
Preferred Stock, Liquidation Preference Per Share			$ 25.00
Dividends, Preferred Stock, Cash	$ 1,700
Dividend Declared [Member]
Class of Stock [Line Items]
Distribution Declared Per Common Partnership Unit							$ 0.15
Dividend Paid [Member]
Class of Stock [Line Items]
Distributions payable							$ 23,800
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Proceeds from Issuance of Common Stock			$ 181,527	$ 0
Distribution Declared Per Common Partnership Unit							$ 0.15
Distributions payable			$ 25,587		$ 23,652		$ 23,800
Preferred Stock, Shares Issued			4,000,000		4,000,000
Preferred Stock, Dividend Rate, Percentage			6.90%		6.90%
BRANDYWINE OPERATING PARTNERSHIP, L.P. \| Offering Program [Member]
Class of Stock [Line Items]
Shares Authorized For Equity Offering Program						15,000,000
Maximum percentage of Gross sale price per share compensation to sales agents						2.00%
Number Of Shares Sold By Company						6,421,553
Average Sales Price Per Share						$ 12.50

Partners Equity of the Operating Partnership Partners Equity of the Operating Partnership (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator
Income (Loss) from Continuing Operations, Basic	$ 9,432	$ (5,910)	$ 7,275	$ (13,982)
Income (Loss) From Continuing Operations, Diluted	9,432	(5,910)	7,275	(13,982)
Amount allocated to unvested restricted shareholders/unitholders, Basic	(85)	(95)	(193)	(191)
Amount allocated to unvested restricted shareholders/unitholders, Diluted	(85)	(95)	(193)	(191)
Preferred share/unit dividends, Basic	(1,725)	(3,049)	(3,450)	(5,047)
Preferred share/unit dividends, Diluted	(1,725)	(3,049)	(3,450)	(5,047)
Redemption Premium	0	(2,090)	0	(2,090)
Redemption Premium, Diluted	0	(2,090)	0	(2,090)
Income (Loss) from Discontinued Operations	(2,252)	12,712	3,824	30,120
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	5,308	1,537	7,366	8,645
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	$ 5,308	$ 1,537	$ 7,366	$ 8,645
Denominator
Weighted-average units outstanding, Basic	155,347,384	143,300,637	149,508,957	143,060,796
Contingent securities/Share based compensation	1,343,817	0	1,157,288	0
Weighted Average Number of Shares Outstanding, Diluted	156,691,201	143,300,637	150,666,245	143,060,796
Earnings per Common Partnership Unit [Abstract]
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$ 0.05	$ (0.08)	$ 0.02	$ (0.15)
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	0.05	(0.08)	0.02	(0.15)
Discontinued Operations attributable to common shareholders/unitholders, Basic	(0.02)	0.09	0.03	0.21
Discontinued Operations attributable to common shareholders/unitholders, Diluted	(0.02)	0.09	0.03	0.21
Net income (loss) attributable to common shareholders/unitholders, Basic	0.03	0.01	0.05	0.06
Net income (loss) attributable to common shareholders/unitholders, Diluted	$ 0.03	$ 0.01	$ 0.05	$ 0.06
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Income (Loss) from Continuing Operations, Basic	$ 9,432	$ (5,910)	$ 7,275	$ (13,982)
Income (Loss) From Continuing Operations, Diluted	9,432	(5,910)	7,275	(13,982)
Amount allocated to unvested restricted shareholders/unitholders, Basic	(85)	(95)	(193)	(191)
Amount allocated to unvested restricted shareholders/unitholders, Diluted	(85)	(95)	(193)	(191)
Preferred share/unit dividends, Basic	(1,725)	(3,049)	(3,450)	(5,047)
Preferred share/unit dividends, Diluted	(1,725)	(3,049)	(3,450)	(5,047)
Redemption Premium	0	(2,090)	0	(2,090)
Redemption Premium, Diluted	0	(2,090)	0	(2,090)
Income (Loss) from continuing operations available to common unitholders, Basic	7,622	(11,144)	3,632	(21,310)
Income (Loss) from continuing operations available to common unitholders, Diluted	7,622	(11,144)	3,632	(21,310)
Income (Loss) from Discontinued Operations	(2,252)	12,712	3,824	30,120
Income (Loss) From Discontinued Operations, Diluted	(2,252)	12,712	3,824	30,120
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	5,370	1,568	7,456	8,810
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	$ 5,370	$ 1,568	$ 7,456	$ 8,810
Denominator
Weighted-average units outstanding, Basic	157,131,697	145,958,358	151,323,813	145,721,890
Contingent securities/Share based compensation	1,343,817	0	1,157,288	0
Weighted Average Number of Shares Outstanding, Diluted	158,475,514	145,958,358	152,481,101	145,721,890
Earnings per Common Partnership Unit [Abstract]
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$ 0.05	$ (0.08)	$ 0.02	$ (0.15)
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	0.05	(0.08)	0.02	(0.15)
Discontinued Operations attributable to common shareholders/unitholders, Basic	(0.02)	0.09	0.03	0.21
Discontinued Operations attributable to common shareholders/unitholders, Diluted	(0.02)	0.09	0.03	0.21
Net income (loss) attributable to common shareholders/unitholders, Basic	0.03	0.01	0.05	0.06
Net income (loss) attributable to common shareholders/unitholders, Diluted	$ 0.03	$ 0.01	$ 0.05	$ 0.06

Partners Equity of the Operating Partnership (Details Textuals) (Details) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended		12 Months Ended	36 Months Ended
	Jul. 15, 2013	Apr. 10, 2013	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Mar. 10, 2013	May 30, 2013
Earnings per Common Partnership Unit [Line Items]
Common stock issued subsequent to balance sheet date, New issues		12,650,000
Additional shares granted under option to purchase in public offering		1,650,000
Proceeds from Issuance of Common Stock		$ 181,700	$ 181,527	$ 0
Distributions payable			25,587		$ 23,652
Dividends, Preferred Stock, Cash			3,450	5,047
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Proceeds from Issuance of Common Stock			181,527	$ 0
Distribution Declared Per Common Partnership Unit							$ 0.15
Distributions payable			$ 25,587		$ 23,652		$ 23,800
Preferred Stock, Dividend Rate, Percentage			6.90%		6.90%
6.90% Series E-linked Preferred Units [Member] \| BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Preferred Stock, Dividend Rate, Percentage			6.90%
Preferred Stock, Liquidation Preference Per Share			$ 25.00
Dividends, Preferred Stock, Cash	$ 1,700
Offering Program [Member] \| BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Number Of Shares Sold By Company						6,421,553
Average Sales Price Per Share						$ 12.50

Share Based and Deferred Compensation Share Based and Deferred Compensation (Option Activity) (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	5 years 8 months 6 days	7 years 2 months 13 days
Share Based Compensation Arrangement By Share Based Payment Award Option Activity [Abstract]
Outstanding at the beginning of year, shares	3,337,549
Outstanding at beginning of year, Weighted Average Exercise Price	$ 14.50
Outstanding at beginning of year, Aggregate Intrinsic Value	$ 0
Granted, shares	0
Granted, Weighted Average Grant Date Fair Value	$ 0.00
Exercised in Period, Shares	(166,620)
Exercises in Period, Weighted Average Grant Date Fair Value	$ 10.26
Forfeited, shares	(117,662)
Forfeited, Weighted Average Grant Date Fair Value	$ 18.61
Outstanding at the end of year, shares	3,053,267.000	3,337,549
Outstanding at end of year, Weighted Average Exercise Price	$ 15.35	$ 14.50
Outstanding at end of year, Aggregate Intrinsic Value	$ 0	$ 0
Vested/Exerciseable, shares	2,868,838
Vested/Exerciseable at end of period, Weigted Average Exercise Price	$ 15.58
Vested/Exerciseable at end of period, Weighted Average Remaining Contractual Term (in years)	5 years 6 months 23 days
Vested/Exercisable at end of year, Aggregate Intrinsic Value	$ 0
Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award Option Activity [Abstract]
Vested/Exerciseable, shares	2,868,838

Share Based and Deferred Compensation Share Based and Deferred Compensation (Restricted Share Activity) (Details) - Restricted Stock [Member]	6 Months Ended
	Jun. 30, 2013 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested at January 1, 2013, shares \| shares	597,708
Non-vested at January 1, 2013, Weighted Average Grant Date Fair Value \| $ / shares	$ 9.46
Granted, Shares \| shares	182,576
Granted, Weighted Average Grant Date Fair Value \| $ / shares	$ 13.13
Vested, shares \| shares	(208,306)
Vested, Weighted Average Grant Date Fair Value \| $ / shares	$ 13.13
Forfeited, shares \| shares	(8,265)
Forfeited, Weighted Average Grant Date Fair Value \| $ / shares	$ 11.41
Non-vested at June 30, 2013, shares \| shares	563,713
Non-vested at June 30, 2013, Weighted Average Grant Date Fair Value \| $ / shares	$ 12.56

Share Based and Deferred Compensation Share Based and Deferred Compensation (Details Textuals) (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2013 USD ($) Employees shares	Jun. 30, 2012 USD ($)	Jun. 30, 2013 USD ($) Age Employees shares	Jun. 30, 2012 USD ($)	Jun. 30, 2011 USD ($)	Feb. 25, 2013 shares	Dec. 31, 2012 shares	Mar. 01, 2012 shares	Mar. 02, 2011 shares	Apr. 02, 2009 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Minimum			1 year
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Maximum			10 years
Vested/Exerciseable, shares \| shares	2,868,838		2,868,838
Allocated Share-based Compensation Expense	$ 2.4	$ 1.9	$ 4.7	$ 3.6
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 0.3	0.5	$ 0.8	$ 0.9
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested/Exerciseable, shares \| shares	2,868,838		2,868,838
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition				8 months 13 days
Share Based Compensation Arrangement By Share Based Payment Stock Options Nonvested Number \| shares	184,429		184,429
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 0.3		$ 0.3
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 0.2	0.4	0.4	$ 0.7
Share-based Compensation Arrangement by Share-based Payment Award, Recognized compensation expense awards		0.1	$ 0.1	0.2
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Voluntary Termination Of Employment Terms			after reaching age 57 and accumulating at least 15 years of service with the Company
Accumulated Service Period For Voluntary Termination			15 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Minimum			3 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Maximum			7 years
Share-based Compensation Arrangement by Share-based Payment Award, Cliff Vesting After Grant Date, Minimum			3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number \| shares	563,713		563,713				597,708
Share Based Compensation Arrangement By Share Based Payment Award VestingPeriod1			three to seven years from the initial grant date
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition			1 year 7 months 6 days
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 3.3		$ 3.3
Allocated Share-based Compensation Expense	0.9	0.8	1.8	1.5
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 0.1	0.2	$ 0.3	0.3
Restricted Performance Share Units Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Voluntary Termination Of Employment Terms			after reaching age 57 and accumulating at least 15 years of service with the Company
Accumulated Service Period For Voluntary Termination			15 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years
Maximum Percentage Of Participants Base Units			200.00%
Number of executives with employment agreements \| Employees	2		2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value			$ 4.1	4.2	$ 2.0
Age Limit Of Voluntary Termination Of Employment \| Age			57
Allocated Share-based Compensation Expense	$ 1.3	0.7	$ 2.5	1.3
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$ 0.2	$ 0.2	$ 0.4	$ 0.4
Share-based Compensation Arrangement by Share-based Payment Award, shares are delivered \| shares										372,102
Executive Officer [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized \| shares						157,208
Number of executives with employment agreements \| Employees	2		2
Executive Officer [Member] \| Restricted Performance Share Units Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized \| shares						231,093		242,122	113,256

Tax Credit Transactions Tax Credit Transactions (Details)
$ in Thousands

3 Months Ended

6 Months Ended

12 Months Ended

Jun. 30, 2013

USD ($)

Jun. 30, 2012

USD ($)

Jun. 30, 2013

USD ($)

Jun. 30, 2012

USD ($)

Dec. 31, 2012

USD ($)

Aug. 27, 2010

USD ($)

Nov. 17, 2008

ft²

Segment Reporting Disclosure [Text Block]

$ 119,917

$ 122,243

SEGMENT INFORMATION

Segment information is as follows (in thousands):



	Pennsylvania Suburbs		Philadelphia CBD		Metropolitan, D.C.		New Jersey/Delaware		Richmond, Virginia		Austin, Texas		California		Corporate			Total
As of June 30, 2013:
Real estate investments, at cost:
Operating properties	$	1,198,731	$	1,023,619	$	1,199,885	$	408,940	$	310,229	$	286,808	$	192,248	$	—		$	4,620,460
Construction-in-progress															51,260			51,260
Land inventory															94,444			94,444
As of December 31, 2012:
Real estate investments, at cost:
Operating properties	$	1,178,730	$	988,590	$	1,193,200	$	546,644	$	309,923	$	285,346	$	223,736	$	—		$	4,726,169
Construction-in-progress															48,950			48,950
Land inventory															102,439			102,439
For the three-months ended June 30, 2013:
Total revenue	$	37,276	$	36,142	$	28,783	$	15,676	$	8,954	$	9,871	$	4,536	$	(319	)	$	140,919
Property operating expenses, real estate taxes and third party management expenses	13,151		13,587		10,774		7,245		3,599		4,208		2,339		165			55,068
Net operating income	$	24,125	$	22,555	$	18,009	$	8,431	$	5,355	$	5,663	$	2,197	$	(484	)	$	85,851
For the three-months ended June 30, 2012:
Total revenue	$	36,784	$	31,911	$	26,967	$	15,284	$	8,903	$	8,188	$	4,210	$	(444	)	$	131,803
Property operating expenses, real estate taxes and third party management expenses	12,640		11,962		10,451		7,083		3,470		3,611		2,249		(331		)	51,135
Net operating income	$	24,144	$	19,949	$	16,516	$	8,201	$	5,433	$	4,577	$	1,961	$	(113	)	$	80,668
For the six-months ended June 30, 2013:
Total revenue	$	75,461	$	72,067	$	56,567	$	31,278	$	17,719	$	19,129	$	9,142	$	(621	)	$	280,742
Property operating expenses, real estate taxes and third party management expenses	27,050		27,121		21,536		14,653		7,282		8,165		4,498		(57		)	110,248
Net operating income	$	48,411	$	44,946	$	35,031	$	16,625	$	10,437	$	10,964	$	4,644	$	(564	)	$	170,494
For the six-months ended June 30, 2012:
Total revenue	$	74,736	$	65,062	$	53,403	$	31,013	$	17,937	$	15,682	$	8,586	$	(826	)	$	265,593
Property operating expenses, real estate taxes and third party management expenses	25,902		24,648		20,518		14,912		7,112		7,009		4,384		(771		)	103,714
Net operating income	$	48,834	$	40,414	$	32,885	$	16,101	$	10,825	$	8,673	$	4,202	$	(55	)	$	161,879



	Three-month periods ended June 30,						Six-month periods ended June 30,
	2013			2012			2013			2012
	(amounts in thousands)						(amounts in thousands)
Consolidated net operating income	$	85,851		$	80,668		$	170,494		$	161,879
Less:
Interest expense	(30,437		)	(32,981		)	(61,351		)	(67,125		)
Deferred financing costs	(1,183		)	(1,261		)	(2,344		)	(2,572		)
Depreciation and amortization	(49,300		)	(47,476		)	(98,846		)	(95,350		)
General and administrative expenses	(7,335		)	(6,079		)	(13,886		)	(12,129		)
Plus:
Interest income	122			1,838			180			2,320
Interest expense - financing obligation	(211		)	(196		)	(429		)	(378		)
Equity in income of real estate ventures	1,508			838			3,043			882
Gain from remeasurement of investment in a real estate venture	7,847			—			7,847			—
Net gain (loss) on real estate venture transactions	3,683			(11		)	3,683			(11		)
Loss on early extinguishment of debt	(1,113		)	(1,250		)	(1,116		)	(1,498		)
Income (loss) from continuing operations	9,432			(5,910		)	7,275			(13,982		)
Income from discontinued operations	(2,252		)	12,712			3,824			30,120
Net income	$	7,180		$	6,802		$	11,099		$	16,138

Historic Tax Credit Transaction [Member]

Area Of Irs Campus Building | ft²

862,692

Percentage Of Building Leased To Irs

100.00%

Percentage Of Tax Credit Recapture

20.00%

Contribution allocated in non controlling interest

2,700

$ 2,700

2,600

Recognition Of Cash Received As Revenue Net Of Allocated Expenses

over the five year credit recapture period as defined in the Internal Revenue Code

Accretion Of Non Controlling Interest Liability

300

$ 300

$ 700

Rate Of Return On Noncontrolling Interest

1,600

$ 1,600

2.00%

Recognition Of Cash Received As Revenue Net Of Allocated Expenses, Period Credit Recapture in Years

5 years

New Markets Tax Credit Transaction [Member]

Tax Credit Carryforward, Description

100% recapture for a period of seven years as provided in the Internal Revenue Code

Percentage Of Tax Credit Recapture

100.00%

Expected benefit from qualified program

$ 7,800

Percentage Of Qualified Investments

39.00%

Limit on tax credit claims under the Community Renewal Tax Relief

5,300

$ 5,300

up to 39% of qualified investments in qualified, active low-income businesses or ventures

Recognition Of Cash Received As Revenue Net Of Allocated Expenses, Period Credit Recapture in Years

7 years

U S B [Member] | Historic Tax Credit Transaction [Member]

Agreed contribution in project cost

$ 64,100

Deferred Revenue

39,100

$ 39,100

U S B [Member] | New Markets Tax Credit Transaction [Member]

Deferred Revenue

$ 13,300

13,300

$ 5,300

Segment Information Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Real Estate Investments At Cost [Abstract]
Rental properties	$ 4,620,460		$ 4,620,460		$ 4,726,169
Construction-in-progress	51,260		51,260		48,950
Land inventory	94,444		94,444		102,439
Total revenue	140,919	$ 131,803	280,742	$ 265,593
Property operating expenses	(55,068)	(51,135)	(110,248)	(103,714)
Gross Profit	85,851	80,668	170,494	161,879
Pennsylvania [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	1,198,731		1,198,731		1,178,730
Total revenue	37,276	36,784	75,461	74,736
Property operating expenses	(13,151)	(12,640)	(27,050)	(25,902)
Gross Profit	24,125	24,144	48,411	48,834
Philadelphia CBD [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	1,023,619		1,023,619		988,590
Total revenue	36,142	31,911	72,067	65,062
Property operating expenses	(13,587)	(11,962)	(27,121)	(24,648)
Gross Profit	22,555	19,949	44,946	40,414
Metropolitan Dc [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	1,199,885		1,199,885		1,193,200
Total revenue	28,783	26,967	56,567	53,403
Property operating expenses	(10,774)	(10,451)	(21,536)	(20,518)
Gross Profit	18,009	16,516	35,031	32,885
New Jersey/ Delaware [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	408,940		408,940		546,644
Total revenue	15,676	15,284	31,278	31,013
Property operating expenses	(7,245)	(7,083)	(14,653)	(14,912)
Gross Profit	8,431	8,201	16,625	16,101
Richmond, Virginia [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	310,229		310,229		309,923
Total revenue	8,954	8,903	17,719	17,937
Property operating expenses	(3,599)	(3,470)	(7,282)	(7,112)
Gross Profit	5,355	5,433	10,437	10,825
Austin, Texas [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	286,808		286,808		285,346
Total revenue	9,871	8,188	19,129	15,682
Property operating expenses	(4,208)	(3,611)	(8,165)	(7,009)
Gross Profit	5,663	4,577	10,964	8,673
CALIFORNIA
Real Estate Investments At Cost [Abstract]
Rental properties	192,248		192,248		223,736
Total revenue	4,536	4,210	9,142	8,586
Property operating expenses	(2,339)	(2,249)	(4,498)	(4,384)
Gross Profit	2,197	1,961	4,644	4,202
Corporate [Member]
Real Estate Investments At Cost [Abstract]
Rental properties	0		0		0
Construction-in-progress	51,260		51,260		48,950
Land inventory	94,444		94,444		$ 102,439
Total revenue	(319)	(444)	(621)	(826)
Property operating expenses	(165)	331	57	771
Gross Profit	$ (484)	$ (113)	$ (564)	$ (55)

Segment Information Segment Information (Reconciliation of Consolidated Net Operating Income) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2013 USD ($)	Jun. 30, 2012 USD ($)	Jun. 30, 2013 USD ($) Reportable_Segments	Jun. 30, 2012 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Consolidated net operating income	$ 85,851	$ 80,668	$ 170,494	$ 161,879
Less:
Interest expense	(30,437)	(32,981)	(61,351)	(67,125)
Interest expense — amortization of deferred financing costs	(1,183)	(1,261)	(2,344)	(2,572)
Depreciation and amortization	(49,300)	(47,476)	(98,846)	(95,350)
General and administrative expenses	7,335	6,079	13,886	12,129
Plus:
Interest income	122	1,838	180	2,320
Interest expense — financing obligation	(211)	(196)	(429)	(378)
Equity in income of real estate ventures	1,508	838	3,043	882
Gain from remeasurement of investment in a real estate venture	7,847	0	7,847	0
Net gain (loss) on real estate venture transactions	3,683		3,683	0
Gains (Losses) on Sales of Investment Real Estate		(11)		(11)
Loss on early extinguishment of debt	(1,113)	(1,250)	(1,116)	(1,498)
Income (loss) from continuing operations	9,432	(5,910)	7,275	(13,982)
Income (Loss) from Discontinued Operations	(2,252)	12,712	3,824	30,120
Net income (loss)	$ 7,180	$ 6,802	$ 11,099	$ 16,138
Number of Reportable Segments \| Reportable_Segments			7

Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions	6 Months Ended
	Jun. 30, 2013 USD ($) ft² yr
Long-term Purchase Commitment [Line Items]
Minimum remaining lease period \| yr	16
Maximum remaining lease period \| yr	90
Leased Area Of Building \| ft²	708,844
If the Company takes fee title to Two Logan Square upon a foreclosure of its mortgage, the Company has agreed to pay an unaffiliated third party that holds a residual interest in the fee owner of this property	$ 2.9
Business Acquisition, Cost of Acquired Entity, Liabilities Incurred	0.7
Balance Portion Of Acquisition Related Liability	$ 1.6

Fair Value of the liabilities incurred by the acquirer to former owners of the acquiree, including the fair value of any contingent consideration. If liabilities transferred as consideration remain within the combined entity after the business combination (for example, because the assets or liabilities were transferred to the acquiree rather than to its former owners), and the acquirer therefore retains control of them; in that situation, the acquirer measures those liabilities at their carrying amounts immediately before the acquisition date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6405-128476

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 68
-Subparagraph f(3)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141
-Paragraph 51
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 39, 40, 41
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.