Brandywine Operating Partnership 10-K 19 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 17, 2015	Jun. 30, 2014
Entity Registrant Name	BRANDYWINE REALTY TRUST
Entity Central Index Key	790816
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$2,416,656,732
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		179,699,423
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Entity Registrant Name	BRANDYWINE OPERATING PARTNERSHIP, L.P.
Entity Central Index Key	1060386
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Rents	$483,682	$461,387	$437,560
Tenant reimbursements	84,879	79,087	77,060
Termination fees	8,000	4,497	3,233
Third party management fees, labor reimbursement and leasing	17,200	13,053	12,116
Other	3,221	4,186	5,710
Total revenue	596,982	562,210	535,679
Operating Expenses:
Property operating expenses	177,330	160,406	152,319
Real estate taxes	51,844	55,612	53,402
Third party management expenses	6,791	5,751	5,127
Depreciation and amortization	208,569	197,021	188,382
General and administrative expenses	26,779	27,628	25,413
Total operating expenses	471,313	446,418	424,643
Operating income	125,669	115,792	111,036
Other Income (Expense):
Interest Income	3,974	1,044	3,008
Historic tax credit transaction income	11,853	11,853	11,840
Interest expense	-124,329	-121,937	-132,939
Interest expense - amortization of deferred financing costs	-5,148	-4,676	-6,208
Interest expense — financing obligation	-1,144	-972	-850
Recognized hedge activity	-828	0	-2,985
Equity in income (loss) of real estate ventures	-790	3,664	2,741
Net gain from remeasurement of investments in real estate ventures	4,901	0	0
Net gain (loss) on sale of undepreciated real estate	1,184	-137	0
Net gain (loss) on sale of undepreciated real estate	458	6,866	0
Net gain (loss) on real estate venture transactions	-417	29,604	-950
Loss on early extinguishment of debt	-7,594	-2,119	-22,002
Provision for impairment on assets held for sale	-1,765	0	0
Income (loss) from continuing operations	6,024	38,982	-37,309
Discontinued operations:
Income from discontinued operations	18	825	9,064
Net gain (loss) on disposition of discontinued operations	900	3,382	34,774
Total discontinued operations	918	4,207	43,838
Net income (loss)	6,942	43,189	6,529
Net income from discontinued operations attributable to non-controlling interests - LP units	-10	-55	-797
Net loss attributable to non-controlling interests	44	0	0
Net (income) loss attributable to non-controlling interests — LP units	-1	-357	863
Net (income) loss attributable to non-controlling interest - partner's share of consolidated real estate ventures	33	-412	66
Distribution to Preferred Units	-6,900	-6,900	-10,405
Preferred share/unit redemption charge	0	0	-4,052
Amount allocated to unvested restricted shareholders	-349	-363	-376
Net income (loss) attributable to Common Shareholders/Unitholders	-274	35,514	-8,238
Net income (loss)	6,975	42,777	6,595
Basic income (loss) per Common Share/Unit:
Continuing operations (in dollars per share)	($0.01)	$0.20	($0.36)
Discontinued operations (in dollars per share)	$0.01	$0.03	$0.30
Basic income (loss) per Common Share (in dollars per share)	$0	$0.23	($0.06)
Diluted income (loss) per Common Share/Unit:
Continuing operations (in dollars per share)	($0.01)	$0.20	($0.36)
Discontinued operations (in dollars per share)	$0.01	$0.03	$0.30
Diluted income (loss) per Common Share/Unit (in dollars per share)	$0	$0.23	($0.06)
Basic weighted average shares outstanding (in shares)	166,202,649	153,140,458	143,257,097
Diluted weighted average shares outstanding (in shares)	166,202,649	154,414,311	143,257,097
Net income (loss)
Income (loss) from continuing operations	6,067	38,625	-36,446
Income (loss) from discontinued operations	908	4,152	43,041
Net income (loss)	6,975	42,777	6,595
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue:
Rents	483,682	461,387	437,560
Tenant reimbursements	84,879	79,087	77,060
Termination fees	8,000	4,497	3,233
Third party management fees, labor reimbursement and leasing	17,200	13,053	12,116
Other	3,221	4,186	5,710
Total revenue	596,982	562,210	535,679
Operating Expenses:
Property operating expenses	177,330	160,406	152,319
Real estate taxes	51,844	55,612	53,402
Third party management expenses	6,791	5,751	5,127
Depreciation and amortization	208,569	197,021	188,382
General and administrative expenses	26,779	27,628	25,413
Total operating expenses	471,313	446,418	424,643
Operating income	125,669	115,792	111,036
Other Income (Expense):
Interest Income	3,974	1,044	3,008
Historic tax credit transaction income	11,853	11,853	11,840
Interest expense	-124,329	-121,937	-132,939
Interest expense - amortization of deferred financing costs	-5,148	-4,676	-6,208
Interest expense — financing obligation	-1,144	-972	-850
Recognized hedge activity	-828	0	-2,985
Equity in income (loss) of real estate ventures	-790	3,664	2,741
Net gain from remeasurement of investments in real estate ventures	4,901	0	0
Net gain (loss) on sale of undepreciated real estate	1,184	-137	0
Net gain (loss) on sale of undepreciated real estate	458	6,866	0
Net gain (loss) on real estate venture transactions	-417	29,604	-950
Loss on early extinguishment of debt	-7,594	-2,119	-22,002
Provision for impairment on assets held for sale	-1,765	0	0
Income (loss) from continuing operations	6,024	38,982	-37,309
Discontinued operations:
Income from discontinued operations	18	825	9,064
Net gain (loss) on disposition of discontinued operations	900	3,382	34,774
Total discontinued operations	918	4,207	43,838
Net income (loss)	6,942	43,189	6,529
Net loss attributable to non-controlling interests	44	0	0
Distribution to Preferred Units	-6,900	-6,900	-10,405
Preferred share/unit redemption charge	0	0	-4,052
Amount allocated to unvested restricted shareholders	-349	-363	-376
Net income (loss) attributable to Common Shareholders/Unitholders	-263	35,926	-8,304
Net income (loss)	6,942	43,189	6,529
Basic income (loss) per Common Share/Unit:
Continuing operations (in dollars per share)	($0.01)	$0.20	($0.36)
Discontinued operations (in dollars per share)	$0.01	$0.03	$0.30
Basic income (loss) per Common Share (in dollars per share)	$0	$0.23	($0.06)
Diluted income (loss) per Common Share/Unit:
Continuing operations (in dollars per share)	($0.01)	$0.20	($0.36)
Discontinued operations (in dollars per share)	$0.01	$0.03	$0.30
Diluted income (loss) per Common Share/Unit (in dollars per share)	$0	$0.23	($0.06)
Basic weighted average shares outstanding (in shares)	167,942,246	154,929,545	145,883,217
Diluted weighted average shares outstanding (in shares)	167,942,246	156,203,398	145,883,217
Net income (loss)
Income (loss) from continuing operations	6,024	38,982	-37,309
Income (loss) from discontinued operations	918	4,207	43,838
Net income (loss)	$6,942	$43,189	$6,529

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Real estate investments:
Operating properties	$4,603,692	$4,669,289
Accumulated depreciation	-1,067,829	-983,808
Operating real estate investments, net	3,535,863	3,685,481
Construction-in-progress	201,360	74,174
Land inventory	90,603	93,351
Total real estate investments, net	3,827,826	3,853,006
Cash and cash equivalents	257,502	263,207
Accounts receivable, net	18,757	17,389
Accrued rent receivable, net	134,051	126,295
Assets held for sale, net	18,295	0
Investment in real estate ventures, at equity	225,004	180,512
Deferred costs, net	125,224	122,954
Intangible assets, net	99,403	132,329
Notes receivable	88,000	7,026
Other assets	65,111	62,377
Total assets	4,859,173	4,765,095
LIABILITIES AND BENEFICIARIES' EQUITY
Mortgage notes payable	654,590	670,151
Unsecured term loans	200,000	450,000
Unsecured senior notes, net of discounts	1,596,718	1,475,230
Accounts payable and accrued expenses	96,046	83,693
Distributions payable	28,871	25,584
Deferred income, gains and rent	59,452	71,635
Acquired lease intangibles, net	26,010	34,444
Other liabilities	37,558	32,923
Liabilities related to assets held for sale, net	602	0
Total liabilities	2,699,847	2,843,660
Commitments and contingencies (Note 20)
Brandywine Realty Trust's equity:
6.90% Series E Preferred Shares/Units; issued and outstanding- 4,000,000 in 2014 and 2013	40	40
Common Shares of Brandywine Realty Trust’s beneficial interest, $0.01 par value; 400,000,000 and 200,000,000 shares authorized in 2014 and 2013, respectively; 179,293,160 and 156,731,993 issued and outstanding in 2014 and 2013, respectively	1,793	1,566
Additional paid-in capital	3,314,693	2,971,596
Deferred compensation payable in common shares	6,219	5,407
Common shares in grantor trust, 384,386 in 2014 and 312,280 in 2013	-6,219	-5,407
Cumulative earnings	529,487	522,528
Accumulated other comprehensive loss	-4,607	-2,995
Cumulative distributions	-1,700,579	-1,592,515
Total equity, excluding non-controlling interests	2,140,827	1,900,220
Non-controlling interests	18,499	21,215
Total equity	2,159,326	1,921,435
Total liabilities and equity	4,859,173	4,765,095
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real estate investments:
Operating properties	4,603,692	4,669,289
Accumulated depreciation	-1,067,829	-983,808
Operating real estate investments, net	3,535,863	3,685,481
Construction-in-progress	201,360	74,174
Land inventory	90,603	93,351
Total real estate investments, net	3,827,826	3,853,006
Cash and cash equivalents	257,502	263,207
Accounts receivable, net	18,757	17,389
Accrued rent receivable, net	134,051	126,295
Assets held for sale, net	18,295	0
Investment in real estate ventures, at equity	225,004	180,512
Deferred costs, net	125,224	122,954
Intangible assets, net	99,403	132,329
Notes receivable	88,000	7,026
Other assets	65,111	62,377
Total assets	4,859,173	4,765,095
LIABILITIES AND BENEFICIARIES' EQUITY
Mortgage notes payable	654,590	670,151
Unsecured term loans	200,000	450,000
Unsecured senior notes, net of discounts	1,596,718	1,475,230
Accounts payable and accrued expenses	96,046	83,693
Distributions payable	28,871	25,584
Deferred income, gains and rent	59,452	71,635
Acquired lease intangibles, net	26,010	34,444
Other liabilities	37,558	32,923
Liabilities related to assets held for sale, net	602	0
Total liabilities	2,699,847	2,843,660
Commitments and contingencies (Note 20)
Redeemable limited partnership units at redemption value;
Redeemable limited partnership units at redemption value; 1,535,102 and 1,763,739 issued and outstanding in 2014 and 2013, respectively	24,571	26,486
Brandywine Realty Trust's equity:
6.90% Series E Preferred Shares/Units; issued and outstanding- 4,000,000 in 2014 and 2013	96,850	96,850
General Partnership Capital, 179,293,160 and 156,731,993 units issued and outstanding in 2014 and 2013, respectively	2,041,902	1,800,530
Accumulated other comprehensive loss	-5,007	-3,377
Total equity, excluding non-controlling interests	2,133,745	1,894,003
Non-controlling interests	1,010	946
Total equity	2,134,755	1,894,949
Total liabilities and equity	4,859,173	4,765,095
Series E-linked Preferred Stock [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Brandywine Realty Trust's equity:
Total equity	96,850	96,850
Noncontrolling Interest [Member]
Brandywine Realty Trust's equity:
Total equity	18,499	21,215
Noncontrolling Interest [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Brandywine Realty Trust's equity:
Total equity	$1,010	$946

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Preferred Stock, Value, Issued	$40	$40
Brandywine Realty Trust's equity:
Preferred shares, shares authorized	20,000,000	20,000,000
Preferred shares, dividend rate (as a percent)	6.90%	6.90%
Preferred shares, par value (in dollars per share)	$0.01	$0.01
Preferred shares, shares issued	4,000,000	4,000,000
Preferred shares, shares outstanding	4,000,000	4,000,000
Common shares in grantor trust	$0.01	$0.01
Common shares of Brandywine Realty Trust's beneficial interest, shares authorized	400,000,000	200,000,000
Common shares of Brandywine Realty Trust's beneficial interest, shares issued	179,293,160	156,731,993
Common shares of Brandywine Realty Trust's beneficial interest, shares outstanding	179,293,160	156,731,993
Common shares in grantor trust	384,386	312,280
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Preferred Stock, Value, Issued	$96,850	$96,850
Brandywine Realty Trust's equity:
Preferred shares, dividend rate (as a percent)	6.90%	6.90%
Preferred shares, shares issued	4,000,000	4,000,000
Preferred shares, shares outstanding	4,000,000	4,000,000
Redeemable Limited Partnership, units issued	1,535,102	1,763,739
Redeemable Limited Partnership, units outstanding	1,535,102	1,763,739
General Partners' Capital account, units issued	179,293,160	156,731,993
General Partners' Capital account, units outstanding	179,293,160	156,731,993

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income (loss)	$6,942	$43,189	$6,529
Comprehensive income (loss):
Unrealized gain (loss) on derivative financial instruments	-1,190	12,789	-7,338
Loss on settlement of interest rate swaps	-828	0	-2,985
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	388	286	297
Total comprehensive income (loss)	-1,630	13,075	-10,026
Comprehensive (income) loss attributable to non-controlling interest	51	-564	261
Comprehensive income (loss)	5,312	56,264	-3,497
Comprehensive income (loss) attributable to Brandywine Realty Trust	5,363	55,700	-3,236
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Net income (loss)	6,942	43,189	6,529
Comprehensive income (loss):
Unrealized gain (loss) on derivative financial instruments	-1,190	12,789	-7,338
Loss on settlement of interest rate swaps	-828	0	-2,985
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	388	286	297
Total comprehensive income (loss)	-1,630	13,075	-10,026
Comprehensive (income) loss attributable to non-controlling interest	44	0	0
Comprehensive income (loss)	$5,356	$56,264	($3,497)

Consolidated_Statements_of_Ben

Consolidated Statements of Beneficiaries' Equity (USD $)	Total	Preferred Stock [Member]	Common Stock	Deferred Compensation Payable in Common Shares	Common Shares in Grantor Trust	Additional Paid-in Capital	Cumulative Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Distributions	Non-Controlling Interests	Subsidiaries [Member]	Subsidiaries [Member]	Subsidiaries [Member]	Subsidiaries [Member]	Subsidiaries [Member]	Subsidiaries [Member]
In Thousands, except Share data												Accumulated Other Comprehensive Income (Loss)	Non-Controlling Interests	Series D Preferred Stock [Member]	Total partners equity [Member]	Series E-linked Preferred Stock [Member]
Beginning Balance at Dec. 31, 2011	$1,889,696	$43	$1,424	$5,631	($5,631)	$2,776,197	$477,338	($6,079)	($1,392,332)	$33,105		($6,426)		$47,912	$1,851,326	$0
Beginning Balance, shares at Dec. 31, 2011		4,300,000	142,690,755	292,646										2,000,000		0
Net income (loss)	6,529						6,595			-66	6,529				6,529
Comprehensive income (loss)	-10,026							-9,839		-187	-10,026	-10,026			-10,026
Issuance of Common Shares of Beneficial Interest, shares		4,000,000														4,000,000
Issuance of Common Shares of Beneficial Interest	96,850	40				96,810									96,850	96,850
Preferred share issuance costs	-613					-613									-613
Redemption of preferred shares	-103,448	-43				-103,405								-47,912	-103,450
Conversion of LP Units to Common Shares	-167		1			149	-49			-268					-49
Stock Issued During Period, Shares, Other			35,703
Conversion of LP Units to Common Shares, shares			20,464
Redemption of preferred shares, Shares		-4,300,000												-2,000,000
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			797,375	9,036
Conversion of LP units to cash	-9,741						-4,185			-5,556					-9,741
Share Issuance from/to Deferred Compensation Plan, shares			-5,564	-10,937
Share Issuance from/to Deferred Compensation Plan	0			-279	279
Bonus share issuance	387					387									387
Share-based compensation activity	6,432		9			6,388	35								6,432
Adjustment to Non-controlling Interest	0					4,281				-4,281
Preferred Share distributions	-10,405								-10,405						-10,405
Preferred share/unit redemption charge	-4,052								-4,052		-4,052				-4,052
Distributions declared ($0.60) per share in each of 2014, 2013, and 2012	-87,926								-86,417	-1,509
Ending Balance at Dec. 31, 2012	1,773,516	40	1,434	5,352	-5,352	2,780,194	479,734	-15,918	-1,493,206	21,238		-16,452	0	0	1,746,739	96,850
Ending Balance, shares at Dec. 31, 2012		4,000,000	143,538,733	290,745										0		4,000,000
Net income (loss)	43,189						42,777			412	43,189				43,189
Comprehensive income (loss)	13,075							12,923		152	13,075	13,075			13,075
Issuance of Common Shares of Beneficial Interest, shares			12,650,000
Issuance of Common Shares of Beneficial Interest	182,034		127			181,907
Preferred share issuance costs	-744					-744
Noncontrolling Interest, Increase from Business Combination	946									946			946		946
Conversion of LP Units to Common Shares	0		1			1,239				-1,240					1,240
Stock Issued During Period, Shares, Other			27,918
Conversion of LP Units to Common Shares, shares			81,998
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			438,356	34,117
Share Issuance from/to Deferred Compensation Plan, shares			-5,012	-12,583
Share Issuance from/to Deferred Compensation Plan	0			55	-55
Bonus share issuance	361					361									361
Share-based compensation activity	9,438		4			9,417	17								9,437
Adjustment to Non-controlling Interest	0					-778				778
Preferred Share distributions	-6,900								-6,900						-6,900
Preferred share/unit redemption charge	0										0
Distributions declared ($0.60) per share in each of 2014, 2013, and 2012	-93,480								-92,409	-1,071
Ending Balance at Dec. 31, 2013	1,921,435	40	1,566	5,407	-5,407	2,971,596	522,528	-2,995	-1,592,515	21,215	1,894,949	-3,377	946	0	1,894,949	96,850
Ending Balance, shares at Dec. 31, 2013		4,000,000	156,731,993	312,279										0		4,000,000
Net income (loss)	6,942						6,975			-33	6,942		-44		6,898
Comprehensive income (loss)	-1,630							-1,612		-18	-1,630	-1,630			-1,630
Issuance of Common Shares of Beneficial Interest, shares	21,850,000		21,850,000
Issuance of Common Shares of Beneficial Interest	335,398		219			335,179
Preferred share issuance costs	-495					-495
Conversion of LP Units to Common Shares	0		2			3,612				-3,614					3,614
Conversion of LP Units to Common Shares, shares			228,536
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures			403,902
Share Issuance from/to Deferred Compensation Plan, shares			80,152	72,257
Share Issuance from/to Deferred Compensation Plan	-90			812	-812	-90
Share Choice Plan Issuance Shares	0		-1,423
Share-based compensation activity	6,847		6			6,857	-16								6,847
Adjustment to Non-controlling Interest	0					-1,966				1,966
Preferred Share distributions	-6,900								-6,900						-6,900
Preferred share/unit redemption charge	0										0
Distributions declared ($0.60) per share in each of 2014, 2013, and 2012	-102,181								-101,164	-1,017
Ending Balance at Dec. 31, 2014	$2,159,326	$40	$1,793	$6,219	($6,219)	$3,314,693	$529,487	($4,607)	($1,700,579)	$18,499	$2,134,755	($5,007)	$1,010	$0	$2,134,755	$96,850
Ending Balance, shares at Dec. 31, 2014		4,000,000	179,293,160	384,536										0		4,000,000

Consolidated_Statements_of_Ben1

Consolidated Statements of Beneficiaries' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Distributions Declared, Per Share	$0.60	$0.60
Cumulative Distributions
Distributions Declared, Per Share	$0.60	$0.60
Non-Controlling Interests
Distributions Declared, Per Share	$0.60	$0.60

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income (loss)	$6,942	$43,189	$6,529
Adjustments to reconcile net income (loss) to net cash from operating activities:
Depreciation and amortization	208,569	198,731	198,579
Amortization of deferred financing costs	5,148	4,676	6,208
Amortization of debt discount/(premium), net	-531	2,480	1,760
Amortization of stock compensation costs	4,137	6,998	5,685
Shares used for employee taxes upon vesting of share awards	-1,177	-1,062	-2,493
Recognized hedge activity	828	0	2,985
Straight-line rent income	-16,046	-20,136	-23,566
Amortization of above (below) Market Leases, Net	-6,377	-7,170	-6,084
Straight-line ground rent expense	89	1,509	1,897
Provision for doubtful accounts	1,763	2,467	2,198
Net gain on sale of interests in real estate	-6,085	-29,166	-34,774
Loss on real estate venture formation	0	0	950
Net gain on real estate venture transactions	417	-3,683	0
Net gain from remeasurement of investments in real estate ventures	-458	-6,866	0
Loss on early extinguishment of debt	7,594	2,119	22,002
Provision for impairment on assets held for sale	1,765	0	0
Historic tax credit transaction income	-11,853	-11,853	-11,840
Real estate venture income in excess of distributions	1,954	-2,014	-1,517
Deferred financing obligation	-1,147	-974	-1,803
Changes in assets and liabilities:
Accounts receivable	-2,869	-4,048	262
Other assets	-4,111	5,440	4,244
Accounts payable and accrued expenses	962	-526	-8,355
Deferred income, gains and rent	2,436	3,758	-2,167
Other liabilities	-2,951	-385	-1,590
Net cash from operating activities	188,999	183,484	159,110
Cash flows from investing activities:
Acquisition of properties	-18,443	-161,604	-77,555
Investments in available-for-sale securities	0	0	-105,250
Proceeds from the sale of available-for-sale securities	0	0	105,250
Sales of properties, net	118,855	423,480	170,918
Net proceeds from the contribution of land to an unconsolidated real estate venture	8,212	0	0
Distribution of sales proceeds of real estate ventures	0	16,963	0
Proceeds from repayment of mortgage notes receivable	7,026	200	23,364
Capital expenditures for tenant improvements	-131,077	-109,357	-86,986
Capital expenditures for redevelopments	-19,245	-6,265	-11,964
Capital expenditures for developments	-86,608	-5,490	-162
Reimbursement from real estate venture pre-formation development costs	0	1,976	0
Advances for purchase of tenant assets, net of repayments	-540	-127	270
Loan proceeds from an unconsolidated real estate venture	0	0	566
Loan provided to unconsolidated real estate venture	-88,000	0	0
Investment in unconsolidated real estate venture	-46,098	-33,069	-65,354
Increase (Decrease) in escrow cash	283	1,902	-1,827
Cash distributions from unconsolidated Real Estate Ventures in excess of cumulative equity income	9,767	7,496	5,109
Leasing costs	-24,917	-31,397	-31,243
Net cash from (used in) investing activities	-270,785	104,708	-74,864
Cash flows from financing activities:
Proceeds from unsecured term loans	0	0	600,000
Proceeds from Credit Facility borrowings	0	186,000	90,500
Repayments of Credit Facility borrowings	0	-255,000	-297,000
Repayments of mortgage notes payable	-13,441	-11,268	-68,513
Proceeds from unsecured notes	496,459	0	248,183
Deferred financing obligation interest expense	0	0	935
Net proceeds from issuance of common stock	335,016	181,527	0
Net proceeds from issuance of preferred shares	0	0	96,237
Redemption of preferred units	0	0	-108,536
Redemption of partnership units	0	0	-9,676
Redemption of unsecured notes	-383,768	-31,369	-338,097
Repayments of unsecured term loan	-250,828	0	-190,485
Debt financing costs	-3,705	-355	-10,128
Exercise of stock options	2,143	2,381	976
Distributions paid to shareholders/unitholders	-104,731	-97,367	-96,030
Distributions to noncontrolling interest	-1,064	-1,083	-1,473
Net cash from (used in) financing activities	76,081	-26,534	-83,107
Increase (decrease) in cash and cash equivalents	-5,705	261,658	1,139
Cash and cash equivalents at beginning of period	263,207	1,549	410
Cash and cash equivalents at end of period	257,502	263,207	1,549
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the years ended December 31, 2014, 2013, and 2012 of $6,802, $3,137 and $2,560, respectively	129,160	118,714	137,823
Supplemental disclosure of non-cash activity:
Change in operating real estate related to a non-cash acquisition of an operating property			0
Change in operating real estate related to a non-cash acquisition of an operating property	0	-21,649
Change in intangible assets, net related to non-cash acquisition of an operating property	0	-3,517	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	0	462	0
Change in investments in joint venture related to non-cash acquisition of property	0	13,040	0
Change in investments in joint venture related to non-cash disposition of property	-5,897	-17,628	0
Change in operating real estate related to non-cash adjustment to land	0	7,752	0
Change in receivable from settlement of acquisitions	619	0	0
Change in mortgage notes payable related to acquisition of an operating property	0	238,082	0
Change in investments in joint venture related to a contribution of land at period end	-1,182	-6,058	-15,222
Change in investments in joint venture related to a contribution of services	0	0	-711
Change in capital expenditures financed through accounts payable at period end	7,336	11,703	7,059
Change in capital expenditures financed through retention payable at period end	6,164	-204	566
Change in unfunded tenant allowance	-955	-969	-1,089
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Cash flows from operating activities:
Net income (loss)	6,942	43,189	6,529
Adjustments to reconcile net income (loss) to net cash from operating activities:
Depreciation and amortization	208,569	198,731	198,579
Amortization of deferred financing costs	5,148	4,676	6,208
Amortization of debt discount/(premium), net	-531	2,480	1,760
Amortization of stock compensation costs	4,137	6,998	5,685
Shares used for employee taxes upon vesting of share awards	-1,177	-1,062	-2,493
Recognized hedge activity	828	0	2,985
Straight-line rent income	-16,046	-20,136	-23,566
Amortization of above (below) Market Leases, Net	-6,377	-7,170	-6,084
Straight-line ground rent expense	89	1,509	1,897
Provision for doubtful accounts	1,763	2,467	2,198
Net gain on sale of interests in real estate	-6,085	-29,166	-34,774
Loss on real estate venture formation	0	0	950
Net gain from remeasurement of investments in real estate ventures	-458	-6,866	0
Net gain (loss) on real estate venture transactions	417	-3,683	0
Loss on early extinguishment of debt	7,594	2,119	22,002
Provision for impairment on assets held for sale	1,765	0	0
Historic tax credit transaction income	-11,853	-11,853	-11,840
Real estate venture income in excess of distributions	1,954	-2,014	-1,517
Cumulative interest accretion of repayments of unsecured notes	0	0	0
Contributions from historic tax credit transaction, net of deferred costs	0	0	0
Deferred financing obligation	-1,147	-974	-1,803
Changes in assets and liabilities:
Accounts receivable	-2,869	-4,048	262
Other assets	-4,111	5,440	4,244
Accounts payable and accrued expenses	962	-526	-8,355
Deferred income, gains and rent	2,436	3,758	-2,167
Other liabilities	-2,951	-385	-1,590
Net cash from operating activities	188,999	183,484	159,110
Cash flows from investing activities:
Acquisition of properties	-18,443	-161,604	-77,555
Investments in available-for-sale securities	0	0	-105,250
Proceeds from the sale of available-for-sale securities	0	0	105,250
Sales of properties, net	118,855	423,480	170,918
Net proceeds from the contribution of land to an unconsolidated real estate venture	8,212	0	0
Distribution of sales proceeds of real estate ventures	0	16,963
Proceeds from repayment of mortgage notes receivable	7,026	200	23,364
Capital expenditures for tenant improvements	-131,077	-109,357	-86,986
Capital expenditures for redevelopments	-19,245	-6,265	-11,964
Capital expenditures for developments	-86,608	-5,490	-162
Reimbursement from real estate venture pre-formation development costs	0	1,976
Advances for purchase of tenant assets, net of repayments	-540	-127	270
Loan proceeds from an unconsolidated real estate venture	0	0	566
Loan provided to unconsolidated real estate venture	-88,000	0	0
Investment in unconsolidated real estate venture	-46,098	-33,069	-65,354
Increase (Decrease) in escrow cash	283	1,902	-1,827
Cash distributions from unconsolidated Real Estate Ventures in excess of cumulative equity income	9,767	7,496	5,109
Leasing costs	-24,917	-31,397	-31,243
Net cash from (used in) investing activities	-270,785	104,708	-74,864
Cash flows from financing activities:
Proceeds from unsecured term loans	0	0	600,000
Proceeds from Credit Facility borrowings	0	186,000	90,500
Repayments of Credit Facility borrowings	0	-255,000	-297,000
Repayments of mortgage notes payable	-13,441	-11,268	-68,513
Proceeds from unsecured notes	496,459	0	248,183
Deferred financing obligation interest expense	0	0	935
Net proceeds from issuance of common stock	335,016	181,527	0
Net proceeds from issuance of preferred shares	0	0	96,237
Redemption of preferred units	0	0	-108,536
Redemption of partnership units	0	0	-9,676
Redemption of unsecured notes	-383,768	-31,369	-338,097
Repayments of unsecured term loan	-250,828	0	-190,485
Debt financing costs	-3,705	-355	-10,128
Exercise of stock options	2,143	2,381	976
Distributions paid to shareholders/unitholders	-105,795	-98,450	-97,503
Net cash from (used in) financing activities	76,081	-26,534	-83,107
Increase (decrease) in cash and cash equivalents	-5,705	261,658	1,139
Cash and cash equivalents at beginning of period	263,207	1,549	410
Cash and cash equivalents at end of period	257,502	263,207	1,549
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the years ended December 31, 2014, 2013, and 2012 of $6,802, $3,137 and $2,560, respectively	129,160	118,714	137,823
Supplemental disclosure of non-cash activity:
Change in operating real estate related to a non-cash acquisition of an operating property	0	-21,649	0
Change in intangible assets, net related to non-cash acquisition of an operating property	0	-3,517
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	0	462
Change in investments in joint venture related to non-cash acquisition of property	0	13,040
Change in investments in joint venture related to non-cash disposition of property	-5,897	-17,628
Change in operating real estate related to non-cash adjustment to land	0	7,752
Change in receivable from settlement of acquisitions	619	0	0
Change in mortgage notes payable related to acquisition of an operating property	0	238,082	0
Change in investments in joint venture related to a contribution of land at period end	-1,182	-6,058	-15,222
Change in investments in joint venture related to a contribution of services	0	0	-711
Change in capital expenditures financed through accounts payable at period end	7,336	11,703	7,059
Change in capital expenditures financed through retention payable at period end	6,164	-204	566
Change in unfunded tenant allowance	($955)	($969)	($1,089)

Consolidated_Statements_of_Cas1

Consolidated Statements of Cash Flows (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental disclosure:
Capitalized interest	$6,802	$3,137	$2,560
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Supplemental disclosure:
Capitalized interest	$6,802	$3,137	$2,560

Consolidated_Statement_of_Part

Consolidated Statement of Partners' Equity (USD $)	Total	BRANDYWINE OPERATING PARTNERSHIP, L.P.	Series E Preferred Stock [Member]	Series E-linked Preferred Stock [Member]	General Partner [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Noncontrolling Interest [Member]	Total partners equity [Member]
In Thousands, except Share data			BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P.		BRANDYWINE OPERATING PARTNERSHIP, L.P.		BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P.
Beginning Balance at Dec. 31, 2011	$1,889,696		$55,538	$0	$1,754,302	($6,079)	($6,426)	$33,105		$1,851,326
Beginning Balance, shares at Dec. 31, 2011			2,300,000	0	142,690,755
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	6,529	6,529			6,529			-66		6,529
Comprehensive income (loss)	-10,026	-10,026				-9,839	-10,026	-187		-10,026
Deferred Compensation Obligation Shares					-5,564
Deferred Compensation Obligation										0
Stock Issued During Period, Shares, New Issues				4,000,000
Stock Issued During Period, Value, New Issues	96,850			96,850						96,850
Preferred share issuance costs	-613				-613					-613
Redemption of preferred shares, Value	-103,448		-55,538							-103,450
Redemption of preferred shares, Shares			-2,300,000
Share-based compensation activity	6,432				6,432					6,432
Stock Issued During Period, Shares, Other					35,703
Bonus share issuance	387				387					387
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures					797,375
Stock Issued During Period, Value, Conversion of Units	-167				-49			-268		-49
Stock Issued During Period, Shares, Conversion of Units					20,464
Conversion of LP units to cash	-9,741				-9,741			-5,556		-9,741
Adjustment of Redeemable Partnership Units to Liquidation Value at Period End					9,968					9,968
Dividends, Preferred Stock, Cash	-10,405				-10,405					-10,405
Preferred share/unit redemption charge	-4,052	-4,052			-4,052					-4,052
Partners' Capital Account, Distributions					-86,417					-86,417
Ending Balance at Dec. 31, 2012	1,773,516		0	96,850	1,666,341	-15,918	-16,452	21,238	0	1,746,739
Ending Balance, shares at Dec. 31, 2012			0	4,000,000	143,538,733
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	43,189	43,189			43,189			412		43,189
Comprehensive income (loss)	13,075	13,075				12,923	13,075	152		13,075
Deferred Compensation Obligation Shares					-5,012
Deferred Compensation Obligation										0
Stock Issued During Period, Value, New Issues	182,034
Issuance of LP Units					181,289					181,289
Issuance of LP Units Shares					12,650,000
Preferred Stock, Shares Issued	4,000,000	4,000,000
Preferred share issuance costs	-744
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	946							946	946	946
Share-based compensation activity	9,438				9,437					9,437
Stock Issued During Period, Shares, Other					27,918
Bonus share issuance	361				361					361
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures					438,356
Stock Issued During Period, Value, Conversion of Units	0				1,240			-1,240		1,240
Stock Issued During Period, Shares, Conversion of Units					81,998
Adjustment of Redeemable Partnership Units to Liquidation Value at Period End					-778					-778
Adjustments to Additional Paid in Capital, Increase in Carrying Amount of Redeemable Preferred Stock					-1,240					-1,240
Dividends, Preferred Stock, Cash	-6,900				-6,900					-6,900
Preferred share/unit redemption charge	0	0
Partners' Capital Account, Distributions					-92,409					-92,409
Ending Balance at Dec. 31, 2013	1,921,435	1,894,949	0	96,850	1,800,530	-2,995	-3,377	21,215	946	1,894,949
Ending Balance, shares at Dec. 31, 2013			0	4,000,000	156,731,993
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	6,942	6,942			6,942			-33	-44	6,898
Comprehensive income (loss)	-1,630	-1,630				-1,612	-1,630	-18		-1,630
Deferred Compensation Obligation Shares					80,152
Deferred Compensation Obligation					-90					-90
Stock Issued During Period, Shares, New Issues	21,850,000
Stock Issued During Period, Value, New Issues	335,398
Issuance of LP Units					334,903					334,903
Issuance of LP Units Shares					21,850,000
Preferred Stock, Shares Issued	4,000,000	4,000,000
Preferred share issuance costs	-495
Share-based compensation activity	6,847				6,847					6,847
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures					403,902
Stock Issued During Period, Value, Conversion of Units	0				3,614			-3,614		3,614
Stock Issued During Period, Shares, Conversion of Units					228,536
Share Choice Plan Issuance Shares	0				-1,423
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	184,116
Adjustment of Redeemable Partnership Units to Liquidation Value at Period End					942					942
adjustment to non controlling interest					-108				108
Adjustments to Additional Paid in Capital, Increase in Carrying Amount of Redeemable Preferred Stock					-3,614					-3,614
Dividends, Preferred Stock, Cash	-6,900				-6,900					-6,900
Preferred share/unit redemption charge	0	0
Partners' Capital Account, Distributions					-101,164					-101,164
Ending Balance at Dec. 31, 2014	$2,159,326	$2,134,755	$0	$96,850	$2,041,902	($4,607)	($5,007)	$18,499	$1,010	$2,134,755
Ending Balance, shares at Dec. 31, 2014			0	4,000,000	179,293,160

Organization_of_The_Parent_Com

Organization of The Parent Company and The Operating Partnership	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP	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 December 31, 2014, owned a 99.0% 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 December 31, 2014, the Company owned 200 properties, consisting of 167 office properties, 20 industrial facilities, five mixed-use properties, one retail property (193 core properties), three development properties, two properties classified as held for sale, one redevelopment property and one re-entitlement property (collectively, the “Properties”) containing an aggregate of approximately 25.1 million net rentable square feet. In addition, as of December 31, 2014, the Company owned economic interests in 17 unconsolidated real estate ventures that contain approximately 6.7 million net rentable square feet (collectively, the “Real Estate Ventures”). As of December 31, 2014, the Company also owned 415 acres of undeveloped land, and held options to purchase approximately 63 additional acres of undeveloped land. As of December 31, 2014, the total potential development that these land parcels could support, under current zoning, entitlements or combination thereof, amounted to an estimated 6.0 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. In addition to managing properties that the Company owns, as of December 31, 2014, the Company was managing approximately 8.9 million net rentable square feet of office and industrial properties for third parties and Real Estate Ventures.
	All references to building square footage, acres, occupancy percentage and the number of buildings are unaudited.
	The Company conducts its third-party real estate management services business primarily through six management companies (collectively, the “Management Companies”): Brandywine Realty Services Corporation (“BRSCO”), BTRS, Inc. (“BTRS”), Brandywine Properties I Limited, Inc. (“BPI”), BDN Brokerage, LLC (“BBL”), Brandywine Properties Management, L.P. (“BPM”) and Brandywine Brokerage Services, LLC (“BBS”). Each of BRSCO, BTRS and BPI is a taxable REIT subsidiary. As of December 31, 2014, the Operating Partnership owns, directly and indirectly, 100% of each of BRSCO, BTRS, BPI, BBL, BPM and BBS. As of December 31, 2014, the Management Companies were managing properties containing an aggregate of approximately 33.9 million net rentable square feet, of which approximately 25.0 million net rentable square feet related to Properties owned by the Company and approximately 8.9 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Reclassifications
	Reclassifications are related to the treatment of sold properties as discontinued operations on the statement of operations for all periods presented. See Recent Accounting Pronouncements below for revisions to the accounting guidance for discontinued operations.
	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 of December 31, 2014, the Company has provided guarantees on behalf of certain real estate ventures, consisting of (i) a $24.7 million payment guaranty on the construction loan for the project being undertaken by evo at Cira; (ii) a $3.2 million payment guarantee on the construction loan for a project being undertaken by TB-BDN Plymouth Apartments; and (iii) a $0.5 million payment guarantee on a loan provided to PJP VII.
	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/managing member, or the general partners/managing members as a group, controls a limited partnership or similar entity when the limited partners/non-managing members 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 for which the Company maintains an ownership interest through its general partner/managing member status, but the limited partners/non-managing members in the entity have the substantive ability to dissolve the entity or remove the Company without cause or have substantive participating rights.  Currently there are no real estate ventures that a limited partner/non-managing member has the unilateral right to dissolve. 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/non-managing members 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, LLC and other real estate venture 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.
	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 costs related to business combinations are expensed as incurred, whereas the costs related to asset acquisitions are capitalized 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 considered to be business combinations 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 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 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 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 four 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. Though the Company considers the value of tenant relationships, the amounts are determined on a tenant-specific basis. On certain of our acquisitions this intangible has been deemed immaterial. In these instances no related intangible value is assigned.
	In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) are recorded to revenue.
	Depreciation and Amortization
	The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements (5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset, 1 to 16 years, or (ii) the lease term).
	Construction in Progress
	Project costs directly associated with the development and construction of a real estate project are capitalized as construction in progress. Construction in progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. Internal direct costs are capitalized to projects in which qualifying expenditures are being incurred. Internal direct construction costs totaling $5.2 million in 2014, $3.7 million in 2013, $4.7 million in 2012 and interest totaling $4.8 million in 2014, $2.6 million in 2013, and $2.6 million in 2012 were capitalized related to development of certain properties and land holdings. The increase in capitalized costs is due to the development activity. See Item 1., "Business - Developments," for further discussion.
	During the years ended December 31, 2014, 2013 and 2012, the Company's internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands):
		December 31,
		2014		2013		2012
	Development	$	1,749	$	156	$	57
	Redevelopment	184		194		353
	Tenant Improvements	3,261		3,323		4,259
	Total	$	5,194	$	3,673	$	4,669
	Impairment or Disposal of Long-Lived Assets
	The Company reviews its long-lived assets for impairment following the end of each quarter and when there is an event or change in circumstances that indicates an impairment in value. An impairment loss is recognized if the carrying amount of an asset is not recoverable and exceeds its fair value. In such case, an impairment loss is recognized in the amount of the excess of the carrying amount of the asset over its fair value. 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. Since cash flows on properties considered to be “long-lived assets to be held and used” are considered on an undiscounted basis to determine whether an asset has been impaired, the Company's established strategy of holding properties over the long term directly decreases the likelihood of recording an impairment loss. If the Company's holding strategy were to change or if market conditions were to otherwise dictate an earlier sale date, then an impairment loss may be recognized and such loss could be material. If the Company determines that impairment has occurred, the affected assets must be reduced to their fair value.
	The Company generally consider assets to be “held for sale” when the transaction has been approved by our Board of Trustees, or by officers vested with authority to approve the transaction and there are no known significant contingencies relating to the sale of the property within one year of the consideration date and the consummation of the transaction is otherwise considered probable.
	Following the classification of a property as “held for sale,” no further depreciation is recorded on the assets, and the asset is written down to the lower of carrying value or fair market value.
	The relevant accounting guidance for impairments requires that qualifying assets and liabilities and the results of operations that have been sold, or otherwise qualify as “held for sale,” be presented as discontinued operations in all periods presented if the disposal represents a strategic shift that has, or will have, a major effect on the Company's operations and financial results. The components of the property’s net income that is reflected as discontinued operations include the net gain (or loss) upon the disposition of the property held for sale, operating results, depreciation and interest expense (if the property is subject to a secured loan).
	The Company recorded a provision for impairment on assets held for sale during the twelve months ended December 31, 2014 of $1.8 million. These properties were sold on October 24, 2014, at which time the Company recorded a $0.2 million gain. For further information regarding the impairment, see Note 3, "Real Estate Investments." During its impairment review as of December 31, 2014, the Company determined that no additional impairment charges were necessary. The Company determined during its impairment review of the years ended December 31, 2013 and 2012, that no impairment charges were necessary.
	Cash and Cash Equivalents
	Cash and cash equivalents are highly-liquid investments with original maturities of three months or less. The Company maintains cash equivalents in financial institutions in excess of insured limits, but believes this risk is mitigated by only investing in or through major financial institutions.
	Restricted Cash
	Restricted cash consists of cash held as collateral to provide credit enhancement for the Company’s mortgage debt, cash for property taxes, capital expenditures and tenant improvements.
	Accounts Receivable and Accrued Rent Receivable
	Leases with tenants are accounted for as operating leases. Minimum annual rentals under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payment terms is recorded as “accrued rent receivable, net” on the accompanying balance sheets. Included in current tenant receivables are tenant reimbursements which are comprised of amounts recoverable from tenants for common area maintenance expenses and certain other recoverable expenses that are recognized as revenue in the period in which the related expenses are incurred. As of December 31, 2014 and 2013, no tenant represented more than 10% of accounts receivable and accrued rent receivable.
	Tenant receivables and accrued rent receivables are carried net of the allowances for doubtful accounts of $2.0 million and $13.4 million in 2014, respectively and $3.2 million and $13.0 million in 2013, respectively. The allowance is an estimate based on two calculations that are combined to determine the total amount reserved. First, the Company evaluates specific accounts where it has determined that a tenant may have an inability to meet its financial obligations. In these situations, the Company uses its judgment, based on the facts and circumstances, and records a specific reserve for that tenant against amounts due to reduce the receivable to the amount that the Company expects to collect. These reserves are reevaluated and adjusted as additional information becomes available. Second, a reserve is established for all tenants based on a range of percentages applied to receivable aging categories for tenant receivables. For accrued rent receivables, the Company considers the results of the evaluation of specific accounts and also considers other factors including assigning risk factors to different industries based on its tenants SIC classification. Considering various factors including assigning a risk factor to different industries, these percentages are based on historical collection and write-off experience adjusted for current market conditions, which requires management’s judgments.
	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. For Real Estate Ventures that are constructing assets to commence planned principal operations, the Company capitalizes interest expense using its weighted average interest rate of consolidated debt and  its investment balance as a basis. Planned principal operations commence when a property is available to lease and at that point in time the Company ceases capitalizing interest to its investment basis. During the twelve months ended December 31, 2014 and 2013 the Company capitalized interest expense of $2.0 million and $0.6 million, respectively.
	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.
	Deferred Costs
	Costs incurred in connection with property leasing are capitalized as deferred leasing costs. Deferred leasing costs consist primarily of leasing commissions and internal leasing costs that are amortized using the straight-line method over the life of the respective lease which generally ranges from 1 to 15 years. Management re-evaluates the remaining useful lives of leasing costs as economic and market conditions change.
	Costs incurred in connection with debt financing are capitalized as deferred financing costs and charged to interest expense over the terms of the related debt agreements. Deferred financing costs consist primarily of loan fees which are amortized over the related loan term on a basis that approximates the effective interest method. Deferred financing costs are accelerated, when debt is extinguished, as part of interest expense- amortization of deferred financing costs within the Company's consolidated statements of operations. Original issue discounts are recognized as part of the gain or loss on extinguishment of debt, as appropriate.
	Notes Receivable
	The Company accounts for notes receivable on its balance sheet at amortized cost, net of allowance for loan losses. Interest income is recognized over the term of the notes receivable and is calculated based on the terms on the contractual terms of each note agreement.
	Notes receivable are placed on nonaccrual status when management determines, after considering economic and business conditions and collection efforts, that the loans are impaired or collection of interest is doubtful. Uncollectible interest previously accrued is recognized as bad debt expense. Interest income on nonaccrual loans is recognized only to the extent that cash payments are received.
	On October 17, 2014, the Austin Venture acquired River Place and funded $88.0 million of the purchase price with a short-term loan, secured by a mortgage. The short-term financing was provided by the Company and the Austin Venture is currently seeking permanent financing. The debt agreement for the short-term loan provides financing through March 2015 at the following tiered interest rates; (i) 4.0% through December 31, 2014, (ii) 5.0% from January 1, 2015 through January 31, 2015, (iii) 7.0% from February 1, 2015 through February 28, 2015 and (iv) 9.0% from March 1, 2015 through March 31, 2015. The Austin Venture may repay the short-term loan at any time without penalty. During 2014 the Company recognized $0.7 million of interest income relating to this note. See Note 21, "Subsequent Events," for repayment of this note.
	As of December 31, 2013, 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. The borrower had previously defaulted on the note. As a result, a forbearance agreement dated October 2011, as amended by a second forbearance agreement dated July 9, 2013, was entered into between the Company and the borrower, outlining the repayment terms of the outstanding debt and capping interest at $1.5 million. The Company has determined that the loan modifications represent a troubled debt restructuring due to the fact that the borrower was considered to be in a financial difficulty when it defaulted on the mortgage debt, and that a concession was granted in the form of the forbearance agreements. In accordance with relevant the accounting guidance for troubled debt restructuring, this note remained in a non-accrual status through 2014 and as such, interest is recorded to income as received. During the twelve months ended December 31, 2014, the borrower fully repaid the principal balance of $7.0 million. As to the interest accrued on the notes, $1.5 million has been received in cash and recognized as interest income during the fourth quarter of 2014.
	During 2012, the $23.5 million seven year purchase money mortgage note receivable (balance as of the payment date, including accrued but unpaid interest), which related to the 2009 sale of two Trenton properties, was paid in full prior to its scheduled maturity of October 2016. The Company also recognized a $12.9 million deferred gain and $1.0 million of interest income at the time of payment, in accordance with the accounting standard for installment sales.
	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 $13.7 million in 2014, $17.7 million in 2013 and $21.1 million in 2012. 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 $2.4 million in each of 2014, 2013 and 2012. 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 decreased revenue by $1.5 million in 2014, $0.7 million in 2013, and $0.8 million in 2012.
	The Company's leases also typically provide for tenant reimbursement of a portion of common area maintenance expenses 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, the Company makes significant assumptions and judgments in determining the lease term, including assumptions when the lease provides the tenant with an early termination option. The lease term impacts the period over which the Company determines and records minimum rents and also impacts the period over which the Company amortizes lease-related costs.
	In addition, the Company's rental revenue is impacted by the Company's determination of whether improvements to the properties, whether made by the Company or by the tenant, are landlord assets. The determination of whether an improvement is a landlord asset requires judgment. In making this judgment, our primary consideration is whether the improvement would be utilizable by another tenant upon move out of the improved space by the then-existing tenant. If the Company has funded an improvement that it determines not to be landlord assets, then it treats the costs of the improvement as lease incentives. If the tenant has funded the improvement that the Company determines to be landlord assets, then the Company treats the costs of the improvement as deferred revenue and amortize this cost into revenue over the lease term.
	Recoveries from tenants, consisting of amounts due from tenants for common area maintenance expenses, real estate taxes and other recoverable costs are recognized as revenue in the period during which the expenses are incurred.
	Tenant reimbursements are recognized and presented in accordance with accounting guidance which requires that these reimbursements be recorded on a gross basis because the Company is generally the primary obligor with respect to the goods and services the purchase of which gives rise to the reimbursement obligation; because the Company has discretion in selecting the vendors and suppliers; and because the Company bears the credit risk in the event they do not reimburse the Company. The Company also receives payments from third parties for reimbursement of a portion of the payroll and payroll-related costs for certain of the Company's personnel allocated to perform services for these third parties and reflects these payments on a gross basis.
	The Company recognizes gains on sales of real estate at times and in amounts determined in accordance with the accounting guidance for sales of real estate. The guidance takes into account the terms of the transaction and any continuing involvement, including in the form of management, leasing of space or financial assistance associated with the properties. If the sales criteria for the full accrual method are not met, then the Company defers some or all of the gain recognition and account for the continued operations of the property by applying the finance, leasing, profit sharing, deposit, installment or cost recovery method, as appropriate, until the sales criteria are met.
	The Company derives parking revenues from leases, monthly parking and transient parking. The Company recognizes parking revenue as earned.
	The Company receives leasing commission income, management fees and development fees from third parties.
	Leasing commission income is earned based on a percentage of gross rental income upon a tenant signing a lease with a third party lessor. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The Company records development fees as earned taking into account the risk associated with each project. Profit on development fees earned from joint venture projects is recognized as revenue to the extent of the third party partners’ ownership interest.
	No tenant represented greater than 10% of the Company’s rental revenue in 2014, 2013 or 2012.
	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 tax basis of the Parent Company’s assets was $3.7 billion and $4.0 billion for the years ended December 31, 2014 and 2013, respectively.
The Parent Company is subject to a 4% federal excise tax if sufficient taxable income is not distributed within prescribed time limits. The excise tax equals 4% of the annual amount, if any, by which the sum of (a) 85% of the Parent Company’s ordinary income and (b) 95% of the Parent Company’s net capital gain exceeds cash distributions and certain taxes paid by the Parent Company. No excise tax was incurred in 2014, 2013, or 2012.
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. The Company’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items as of December 31, 2014 and 2013.
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 tax basis of the Operating Partnership’s assets was $3.7 billion and $4.0 billion for the years ended December 31, 2014 and 2013, respectively.
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 TRSs, which are subject to federal, state and local income tax.
Earnings Per Share
Basic earnings per share ("EPS") is computed by dividing net income available to common shareholders, as adjusted for unallocated earnings, if any, of certain securities, by the weighted average number of shares of common stock outstanding during the year. Diluted EPS reflects the potential dilution that could occur from shares issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options, and conversion of the noncontrolling interests in the Operating Partnership.
Earnings Per Unit
Basic EPS is computed by dividing net income available to common unitholders, as adjusted for unallocated earnings, if any, of certain securities issued by the Operating Partnership, by the weighted average number of common unit equivalents outstanding during the year. Diluted EPS reflects the potential dilution that could occur from shares issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options.
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. On June 2, 2010, the Parent Company’s shareholders approved amendments to the 1997 Plan that, among other things, increased the number of common shares available for future awards under the 1997 Plan by 6,000,000 (of which 3,600,000 shares are available solely for options and share appreciation rights). As of December 31, 2014, 4,304,006 common shares remained available for future awards under the 1997 Plan (including 2,684,795 shares available solely for options and share appreciation rights). Through December 31, 2014 all options awarded under the 1997 Plan had a one to ten-year term.
The Company incurred stock-based compensation expense of $6.1 million during 2014, of which $1.7 million was capitalized as part of the Company’s review of employee salaries eligible for capitalization. The Company incurred stock-based compensation expense of $8.3 million and $8.6 million during 2013 and 2012, of which $1.4 million and $2.6 million, respectively, were also capitalized. The expensed amounts are included in general and administrative expense on the Company’s consolidated income statement in the respective periods.
Comprehensive Income
Comprehensive income is recorded in accordance with the provisions of the accounting standard for comprehensive income. The accounting standard establishes standards for reporting comprehensive income and its components in the financial statements. Comprehensive income includes the effective portions of changes in the fair value of derivatives.
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 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.
Recent Accounting Pronouncements
In August 2014, the Financial Accounting Standards Board ("FASB") issued guidance regarding an Entity’s Ability to Continue as a Going Concern, which requires management to assess a company’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. Before this new standard, there was minimal guidance in U.S. GAAP specific to going concern. Under the new standard, disclosures are required when conditions give rise to substantial doubt about a company’s ability to continue as a going concern within one year from the financial statement issuance date. The guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period, with early adoption permitted. The Company has not yet determined the impact, if any, that the adoption of this guidance will have on its consolidated financial statements.
In May 2014 FASB issued guidance requiring revenue to be recognized in an amount that reflects the consideration expected to be received in exchange for goods and services. The guidance requires the disclosure of sufficient quantitative and qualitative information for financial statement users to understand the nature, amount, timing and uncertainty of revenue and associated cash flows arising from contracts with customers. The guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period, with early adoption precluded. The Company has not yet determined the impact, if any, that the adoption of this guidance will have on its consolidated financial position or results of operations.
In April 2014 the FASB issued revised guidance on discontinued operations and disclosures of disposals of components of an entity. The update revises the definition to include only disposals involving a strategic shift that has a major effect on the entity’s operations and financial results when the disposal asset or group meets the existing criterion for treatment as held for sale. Examples of a strategic shift include the withdrawal from a major geographic area, line of business, equity method investment or any other major parts of a business, as applicable. A component of the entity comprises operations and cash flows that can be clearly distinguished, operationally and for financial reporting purposes, from the rest of the entity. In addition, the revised standard no longer precludes presentation as a discontinued operation if there are operations and cash flows of the component that have not been eliminated from the reporting entity’s ongoing operations, or if there is significant continuing involvement with a component after its disposal.
The amendments require additional disclosures about discontinued operations including; the major classes of net income or loss where net income is otherwise presented, the operating and investing cash flows of discontinued operations where net income is otherwise presented, depreciation, amortization, capital expenditures and significant operating and investing non-cash items of the discontinued operation for the periods in which net income is otherwise presented and, if there is a non-controlling interest, the related allocation to the parent company.
Application is prospective, and required for periods beginning on or after December 15, 2014. This update should not be applied to assets classified as held for sale before the effective date even if the component of an entity is disposed of after the effective date. Early adoption is permitted for disposals or assets held for sale that have not been reported in the financial statements previously issued or available for issuance. The Company has elected to early adopt this standard as of January 1, 2014. All properties sold or determined held for sale prior to January 1, 2014 are classified as discontinued operations for all periods presented.

Real_Estate_Investments

Real Estate Investments	12 Months Ended
	Dec. 31, 2014
Real Estate [Abstract]
REAL ESTATE INVESTMENTS	REAL ESTATE INVESTMENTS
	As of December 31, 2014 and 2013 the gross carrying value of the Company’s Properties was as follows (in thousands):
		2014				2013
	Land	$	669,635			$	680,513
	Building and improvements	3,409,303				3,504,060
	Tenant improvements	524,754				484,716
		4,603,692				4,669,289
	Assets held for sale - real estate investments (a)	27,436				—
	Total	$	4,631,128			$	4,669,289
	(a)	Real estate investments related to assets held for sale above represents gross real estate assets and does not include accumulated depreciation or other assets on the balance sheets of the properties held for sale.
	Acquisitions and Dispositions
	2014
	Acquisitions
	On February 19, 2014, the Company acquired 54.1 acres of undeveloped land known as Encino Trace in Austin, Texas for $14.0 million. The land is fully entitled with a site plan and building permits in place allowing for the development of two four-story office buildings containing approximately 320,000 net rentable square feet. The purchase price included an in-place lease for 75% of the first building. The Company capitalized $8.4 million in construction in progress, recorded $4.6 million in land inventory and recorded a deposit for a portion of the future development fee held in escrow of $1.0 million. The Company funded the acquisition with available corporate funds.
	As of December 31, 2014, each of the two office buildings at Encino Trace was in development, and the Company had funded, through such date, $38.8 million, inclusive of the $14.0 million acquisition cost. During the second quarter of 2014, the Company reclassified the $4.6 million remaining in land inventory to construction in progress in connection with commencement of development of the second building.
	Dispositions
	On October 24, 2014, the Company sold the Valleybrooke Office Park, comprised of five properties consisting of 279,934 rentable square feet located in Malvern, Pennsylvania for a sales price of $37.9 million. During the third quarter of 2014, the Company recorded a $1.8 million impairment loss on these properties. On October 24, 2014, the Company recorded a gain of approximately $0.2 million upon settlement.
	On September 30, 2014, the Company sold an office building, commonly known as “Campus Pointe,” containing 172,943 rentable square feet at 1880 Campus Commons Drive in Reston, Virginia for a sales price of $42.5 million resulting in a gain on sale of real estate of $4.7 million after closing and other transaction related costs.
	On April 16, 2014, the Company sold a 5.3 acre parcel of land located in Dallas, Texas for a sales price of $1.6 million resulting in a nominal gain on sale after closing and other transaction related costs. The land parcel was undeveloped as of the date of sale.
	On April 3, 2014, the Company contributed two three-story, Class A office buildings, commonly known as “Four Points Centre,” containing an aggregate of approximately 192,396 net rentable square feet in Austin, Texas to an existing real estate venture (the "Austin Venture") that the Company formed in 2013 with G&I VII Austin Office LLC, an investment vehicle advised by DRA Advisors LLC ("DRA"). The Company contributed the properties to the Austin Venture at an agreed upon value of $41.5 million. In conjunction with the contribution: (i) the Austin Venture obtained a $29.0 million mortgage loan; (ii) DRA contributed $5.9 million in net cash to the capital of the Austin Venture; and (iii) the Austin Venture distributed $34.4 million to the Company and credited the Company with a $5.9 million capital contribution to the Austin Venture. The Company incurred a $0.2 million loss on the contribution, driven primarily by closing costs.
	On March 27, 2014, the Company sold a 16.8 acre undeveloped parcel of land located in Austin, Texas for a sales price of $3.5 million resulting in a $1.2 million gain on sale of undepreciated real estate after closing and other transaction related costs. The land parcel was undeveloped as of the date of sale.
	Held for Sale
	Subsequent to December 31, 2014, the Company sold two office properties, commonly known as "Atrium I," which includes 99,668 square feet of rentable space located in Mt Laurel, New Jersey and "Libertyview," which includes 121,737 square feet of rentable space located in Cherry Hill, New Jersey. See Note 21, "Subsequent Events," for further information regarding this disposition. As of December 31, 2014, the Company classified Atrium I and Libertyview as held for sale in accordance with applicable accounting standard for long lived assets. Accordingly, at December 31, 2014, the properties were required to be measured at the lower of their carrying value or the estimated fair value less costs to sell. No provision for impairment was recognized at December 31, 2014, as the estimated fair value of the properties (based on the executed agreement in place at December 31, 2014) less costs to sell exceeded the carrying value of the properties.
	The disposal of the properties referenced above does not represent a strategic shift that has a major effect on our operations and financial results. Accordingly, the operating results of these properties remain classified within continuing operations for all periods presented.
	2013
	Acquisitions
	One and Two Commerce Square
	On December 19, 2013, the Company acquired 99% of the common interests in the One and Two Common Square partnerships ("Commerce Square"), the entities which own two 41-story Trophy-class office towers in Philadelphia, Pennsylvania, from Parkway. The office towers contain 1,896,142 of net rentable square feet and were 86.7% occupied as of December 31, 2013.  The Company acquired Commerce Square for an aggregate purchase price of $331.8 million and funded the acquisition via assumption of $237.1 million of existing mortgage debt and a $73.1 million cash payment from available corporate funds.
	The Company previously accounted for our non-controlling interest in Commerce Square under the equity method of accounting. As a result of acquiring a 99% common interest in the partnerships the Company obtained control of Commerce Square and our existing investment balance was remeasured based on the fair value of the underlying properties acquired and the existing distribution provisions under the relevant partnership agreements. Accordingly, a loss on remeasurement of $1.0 million was recorded as a result of this transaction.
	The Company has treated this transaction as a business combination and allocated the purchase price to the tangible and intangible assets and liabilities. As discussed in Note 2, the Company utilized a number of sources in making estimates of fair values for purposes of allocating the purchase price to tangible and intangibles assets acquired and intangible liabilities assumed. The purchase price is allocated as follows:
			December 19, 2013
	Building, land and improvements		$	255,705
	Intangible assets acquired		85,036
	Below market lease liabilities assumed		(8,637		)
			$	332,104
	Mortgage debt assumed - at fair value (a)		(238,082		)
	Return of existing equity method investment		(30,424		)
	Net working capital assumed		10,423
	Non-controlling interest		(946		)
	Total cash payment at settlement		$	73,075
	(a) Principal outstanding on assumed mortgage debt at December 19, 2013 was $237.1 million.
	Intangible assets acquired and intangible liabilities assumed consist of the following (in thousands):
			December 19, 2013				Weighted Average Amortization Period (in years)
	Intangible assets:
	In-place lease value		$	80,916			7.9
	Above market tenant leases acquired		4,120				6.9
	Total		$	85,036
	Intangible liabilities:
	Below market leases acquired		$	(8,637	)		6.5
	In connection with the acquisition of One Commerce Square, the Company assumed a $125.1 million existing non-recourse first mortgage with a fixed interest rate of 5.67% and a maturity date of January 6, 2016. In accordance with generally accepted accounting principles, the mortgage was recorded at $130.2 million to reflect the fair value.
	In connection with the acquisition of Two Commerce Square, the Company assumed a $112.0 million existing non-recourse first mortgage with a fixed interest rate of 3.96% and a maturity date of April 5, 2023. In accordance with generally accepted accounting principles, the mortgage was recorded at $107.9 million to reflect the fair value.
	The Company recognized $0.9 million of acquisition related costs which are included as part of general and administrative expenses of the Company’s consolidated statement of operations.
	Four Points Centre
	On December 19, 2013, the Company acquired two three-story, Class A office buildings totaling 192,396 of net rentable square feet known as Four Points Centre, together with 22.3 acres of nearby parcels of land in Austin, Texas known for an aggregate $47.3 million. This property was 99.2% occupied as of December 31, 2013. The Company funded the acquisition price with available corporate funds, while recognizing $0.1 million of acquisition related costs, which are included as part of general and administrative expenses in the Company's consolidated statements of operations. The acquisition has been treated as a business combination and the total purchase price was allocated as follows: $36.0 million to building, $5.8 million to land, $6.5 million to intangible assets and $1.0 million to below market lease liabilities assumed.
	Six Tower Bridge
	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 then already own. See Note 4, "Investments in Unconsolidated Real Estate Ventures," for further discussion.
	The unaudited pro forma information below summarizes the Company’s combined results of operations for the years ended December 31, 2014 and 2013 as though the acquisition of One and Two Commerce Square, Four Points Centre and Six Tower Bridge were completed on January 1, 2012. The supplemental pro forma operating data is not necessarily indicative of what the actual results of operations would have been assuming the transaction had been completed as set forth above, nor do they purport to represent the Company’s results of operations for future periods (in thousands except for per share amounts).
			December 31,
			2013				2012
	Pro forma revenue		$	610,979			$	592,753
	Pro forma income (loss) from continuing operations		21,805				(60,011		)
	Pro forma net income (loss) available to common shareholders		25,957				(16,970		)
	Earnings per common share from continuing operations:
	Basic -- as reported		$	0.2			$	(0.36	)
Basic -- as pro forma		$	0.14			$	(0.42	)
Diluted -- as reported		$	0.2			$	(0.36	)
Diluted -- as pro forma		$	0.14			$	(0.42	)
Earnings per common share:
Basic -- as reported		$	0.23			$	(0.06	)
Basic -- as pro forma		$	0.17			$	(0.12	)
Diluted -- as reported		$	0.23			$	(0.06	)
Diluted -- as pro forma		$	0.17			$	(0.12	)
Included in the consolidated statements of income for the year ended December 31, 2013 are total revenues of $3.4 million and a net loss attributable to common shareholders of $0.2 million from acquisitions made during 2013.
Cira Centre
On November 19, 2013, the Company acquired a 0.8 acre land parcel underlying Cira Centre in Philadelphia, Pennsylvania for $24.6 million. The purchase terminates a long term ground lease agreement entered into during the development of Cira Centre. The Company has accounted for the transaction as an asset acquisition. Prior to the acquisition date, the Company recorded ground rent expense on a straight-line basis, resulting in accrued rent liability of $12.1 million. The accounting guidance for leases requires that an asset purchased which was previously subject to an operating lease cannot result in a gain, accordingly, the basis of the acquired land was reduced by the accrued rent liability and no income was recognized at acquisition. The Company capitalized $1.4 million of acquisition related costs as part of the basis in the operating land.
Three Logan Square
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 a below market ground lease intangible asset. As the sum of the purchase price of the land plus the $4.3 million remaining unamortized 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 December 19, 2013, the Company sold a 50,000 net rentable square feet office property located in King of Prussia, Pennsylvania known as 875 First Avenue, for a sales price of $3.8 million resulting in a $0.1 million gain on sale after closing and other transaction related costs.
On October 17, 2013, the Company sold a 39,330 net rentable square feet office property located in West Chester, Pennsylvania known as 1336 Enterprise Drive, for a sales price of $2.6 million resulting in a $0.2 million gain on sale after closing and other transaction related costs.
On October 16, 2013 the Austin portfolio was contributed to a newly formed real estate venture. For additional information, see Note 4, "Investments in Unconsolidated Ventures," to our consolidated financial statements.
On August 5, 2013, the Company sold an eight-acre parcel of land located in Richmond, Virginia known as Dabney Land East, for a sales price of $0.5 million resulting in a $0.1 million loss on sale after closing and other transaction related costs. The land parcel was undeveloped as of the date of sale.
On June 28, 2013, the Company sold 16870 West Bernardo Drive, a 68,708 net rentable square feet office property located in San Diego, California, for a sales price of $18.0 million resulting in a $0.9 million loss on sale after closing and other transaction related costs.
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 resulting in a $0.4 million loss on sale after closing and other transaction related costs.
On June 19, 2013, the Company sold 1700 Paoli Pike, a 28,000 net rentable square feet office property located in Malvern, Pennsylvania known as 100 Applebrook, for a sales price of $2.7 million resulting in a $0.4 million loss on sale after closing and other transaction related costs.
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 resulting in a $0.5 million loss on sale after closing and other transaction related costs.
On February 25, 2013, the Company sold a portfolio of eight office properties containing 800,546 square feet in Lawrenceville, New Jersey, known as "Princeton Pike Corporate Center," for an aggregate sales price of $121.0 million resulting in a $5.3 million gain on sale after closing and other transaction related costs.
The sales of these properties, with the exception of the Austin portfolio and Dabney Land East, are included in discontinued operations.
2012
Dispositions
On July 18, 2012, the Company sold a portfolio of 11 flex/office properties, totaling 466,719 square feet, in Exton, Pennsylvania, collectively known as "Oaklands Corporate Center," for a sales price of $52.7 million resulting in a $9.9 million gain on sale after closing and other transaction related costs.
On June 22, 2012, the Company sold Pacific Ridge Corporate Center, a 121,381 net rentable square feet, two-building office property located in Carlsbad, California, for a sales price of $29.0 million resulting in a $2.8 million loss on sale after closing and other transaction related costs.
On March 22, 2012, the Company sold South Lake at Dulles Corner, a 268,240 net rentable square feet office property located in Herndon, Virginia, for a sales price of $91.1 million resulting in a $14.5 million gain on sale after closing and other transaction related costs.
On January 17, 2012, the Company sold 304 Harper Drive, a 32,978 net rentable square feet office property located in Moorestown, New Jersey, for a sales price of $3.0 million resulting in a $0.2 million gain on sale after closing and other transaction related costs.

Investment_in_Unconsolidated_V

Investment in Unconsolidated Ventures	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENT IN UNCONSOLIDATED VENTURES	INVESTMENT IN UNCONSOLIDATED VENTURES
	As of December 31, 2014, the Company held ownership interests in 17 unconsolidated Real Estate Ventures for an aggregate investment balance of $223.8 million, of which $225.0 million is included in net assets and $1.2 million is included in other liabilities and represents the negative investment balance of one real estate venture. The Company formed or acquired interests in these ventures with unaffiliated parties to develop or manage office properties or to acquire land in anticipation of possible development of office or residential properties. As of December 31, 2014, eleven of the real estate ventures owned 65 office buildings that contain an aggregate of approximately 6.7 million net rentable square feet; one real estate venture owned 3 acres of undeveloped parcels of land; four real estate ventures owned 22.6 acres of land under active development; one Real Estate Venture owned a residential tower that contains 345 apartment units 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 Company’s investment in Real Estate Ventures as of December 31, 2014 and the Company’s share of the Real Estate Ventures’ income (loss) for the year ended December 31, 2014 was as follows (in thousands):
			Ownership			Carrying			Company’s Share			Real Estate		Current		Debt
			Percentage (a)			Amount			of 2014 Real			Venture		Interest		Maturity
									Estate Venture			Debt at 100%		Rate
									Income (Loss)
	Office Properties
		Broadmoor Austin Associates (b)	50	%		$	65,407		$	(460	)	$	53,516	7.04	%	Apr-23
		Brandywine-AI Venture LLC	50	%		45,712			(185		)	133,843		3.93	%	(c)
		DRA (G&I) Austin (b)	50	%		40,374			(574		)	382,100		3.57	%	(d)
		1000 Chesterbrook Blvd.	50	%		2,152			388			24,251		4.75	%	Dec-21
		Four Tower Bridge	65	%		1,474			(144		)	10,353		5.2	%	Feb-21
		PJP VII	25	%		911			177			5,785		L+2.65%		Dec-19
		PJP II	30	%		403			73			3,492		6.12	%	Nov-23
		PJP V	25	%		216			166			5,242		6.47	%	Aug-19
		PJP VI	25	%		45			(67		)	8,168		6.08	%	Apr-23
		G&I Interchange Office LLC (DRA — N. PA) (e) (b)	20	%		—			(658		)	174,595		5.78	%	Feb-15
		Invesco, L.P. (i)				—			989			—
		Coppell Associates (f)	50	%		(1,214		)	(45		)	15,747		5.75	%	Feb-16
	Other
		Residence Inn Tower Bridge	50	%		723			107			13,394		5.63	%	Feb-16
		HSRE-Campus Crest IX, LLC (b)	30	%		14,314			67			90,245		L+2.20%		Jul-16
	Development Properties
		4040 Wilson LLC	50	%		27,415			(132		)	—
		Brandywine 1919 Ventures (b) (g)	50	%		12,823			(21		)	—		L+2.25%		Oct-18
		TB-BDN Plymouth Apartments	50	%		12,720			(83		)	29,481		L+1.70%		Dec-17
		Seven Tower Bridge	20	%		315			(388		)	14,865		3.78	%	(h)
						$	223,790		$	(790	)	$	965,077
	(a)	Ownership percentage represents the Company's entitlement to residual distributions after payments of priority returns, where applicable.
	(b)	The basis differences associated with these ventures are allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).
	(c)	The debt for these properties is comprised of three fixed rate mortgages: (1) $39.3 million with a 4.40% fixed interest rate due January 1, 2019, (2) $28.0 million with a 4.65% fixed interest rate due January 1, 2022, and (3) $66.5 million with a 3.22% fixed interest rate due August 1, 2019, resulting in a time weighted average rate of 3.93%.
	(d)	The debt for these properties includes five mortgages: (1) $34.0 million that was swapped to a 1.59% fixed rate (or an all-in fixed rate of 3.52% incorporating the 1.93% spread) due November 1, 2018, (2) $56.0 million that was swapped to a 1.49% fixed rate (or an all-in rate of 3.19% incorporating the 1.70% spread) due October 15, 2018, (3) $140.6 million that was swapped to a 1.43% fixed rate (for an all-in fixed rate of 3.44% incorporating the 2.01% spread) due November 1, 2018, (4) $29.0 million with a 4.50% fixed interest rate due April 6, 2019, and (5) $34.5 million with a 3.87% fixed interest rate due August 6, 2019, resulting in a time and dollar weighted average rate of 3.57%. Also, includes an $88.0 million bridge loan from BDN Austin Properties, LLC, a subsidiary of Brandywine, carrying a 4.00% fixed interest rate until December 31, 2014 and increased to 5.00% through January 31, 2015. See Note 21, "Subsequent Events," for repayment of this note.
	(e)	Proceeds received by the Company from the sale of an 80% ownership stake in the properties exceeded the historical cost of those properties. No investment in the real estate venture was reflected on the balance sheet at formation.
	(f)	Carrying amount represents the negative investment balance of the venture and is included in other liabilities.
	(g)	The stated rate for the construction loan is LIBOR + 2.25%. The interest rate spread decreases to 2.00% upon receipt of certificate of occupancy. It is further reduced to 1.75% upon stabilization. To fulfill interest rate protection requirements an interest rate cap was purchased at 4.50%.
	(h)	Comprised of two fixed rate mortgages totaling $8.0 million that mature on March 1, 2017 and accrue interest at a current rate of 7.00%, a $1.0 million 3.00% fixed rate loan through its September 1, 2025 maturity, a $2.0 million 4.00% fixed rate loan with interest only through its February 7, 2016 maturity and a $3.9 million 3.00% fixed rate loan with interest only beginning March 11, 2018 through its March 11, 2020 maturity, resulting in a time and dollar weighted average rate of 3.78%.
	(i)	The ownership interest in this property was disposed of prior to December 31, 2014.
	The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2014 and December 31, 2013 (in thousands):
		December 31,				December 31,
		2014				2013
	Net property	$	1,281,282			$	965,475
	Other assets	195,121				164,152
	Other liabilities	68,481				49,442
	Debt	965,077				699,860
	Equity	442,845				380,325
	Company’s share of equity (Company’s basis) (a)	225,004			(b)	180,512
	(a)	This amount includes the effect of the basis difference between the Company's historical cost basis and the basis recorded at the Real Estate Venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from the impairment of investments, purchases of third party interests in existing Real Estate Ventures 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.
	(b)	Does not include the negative investment balance of one real estate venture totaling $1.2 million as of December 31, 2014, which is included in other liabilities.
	The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests as of December 31, 2014, 2013 and 2012 (in thousands):
		Years ended December 31,
		2014				2013			2012
	Revenue	$	147,236			$	102,919		$	164,013
	Operating expenses	(61,268		)		(40,436		)	(70,775		)
	Interest expense, net	(36,511		)		(26,529		)	(41,633		)
	Depreciation and amortization	(57,109		)		(35,138		)	(50,241		)
	Net income (loss)	(7,652		)		816			1,364
	Company’s share of income (loss) (Company’s basis)	(790		)		3,664			2,741
	As of December 31, 2014, the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands):
	2015	$	279,351
	2016	133,809
	2017	44,465
2018	231,030
2019	182,522
Thereafter	93,900
	$	965,077
1919 Ventures
On January 20, 2011, the Company acquired a one acre parcel of land in Philadelphia, Pennsylvania for $9.3 million. The Company thereafter contributed the acquired land into a then newly-formed general partnership, referred to below as “1919 Ventures” in return for a 50.0% general partner interest, with the remaining 50.0% interest owned by an unaffiliated third party, who contributed cash in exchange for its interest. On October 15, 2014, the Company acquired the interest of the unaffiliated third party at fair value, which approximates carrying value. No remeasurement gain or loss on our previous investment was recorded at that time.
On October 21, 2014, the Company admitted an unaffiliated third party, LCOR/CalSTRS ("LCOR") into 1919 Ventures, for $8.2 million, reflecting an agreed upon $16.4 million valuation of the land and improvements incurred by the Company on behalf of 1919 Ventures. After giving effect to settlement date contributions, distributions and credits, the Company and LCOR had each made, as of October 21, 2014, an additional $5.2 million capital contribution to 1919 Ventures for closing costs and development.
As of December 31, 2014, there was no outstanding balance on the construction loan and equity contributions totaled $13.4 million from each of us and LCOR.
Based upon the facts and circumstances at formation of 1919 Ventures, the Company determined that 1919 Ventures is a VIE in accordance with the accounting standard for the consolidation of VIEs since the equity investment at risk is not sufficient to permit the entity to finance its activities without additional financial support. The initial equity contributed to this entity was not sufficient to fully finance the real estate construction as development costs are funded by the partners throughout the construction period. The Company determined that it was not the primary beneficiary of this VIE based on the fact that the Company has shared control of this entity along with the entity’s partner and therefore does not have controlling financial interests in this VIE.
Austin Venture
On October 16, 2013, the Company contributed a portfolio of seven office properties containing an aggregate of 1,398,826 rentable square feet located in Austin, Texas (the "Austin Properties") to a newly-formed joint venture (the "Austin Venture") with G&I VII Austin Office LLC (“DRA”). DRA and the Company, based on arm's-length negotiation, agreed to an aggregate gross sales price of $330.0 million subject to an obligation on the Company's part to fund the first $5.2 million of post-closing capital expenditures, of which $0.8 million was funded by the Company during 2013 and the remaining $4.4 million was funded by the Company during the twelve months ended December 31, 2014.
DRA owns a 50% interest in the Austin Venture and the Company owns a 50% interest in the Austin Venture, subject to the Company's right to receive up to an additional 10% of distributions.
At the closing the Austin Venture obtained third party debt financing of approximately $230.6 million secured by mortgages on the Austin Properties and used proceeds of this financing together with $49.7 million of cash contributions by DRA (less $1.9 million of closing costs and $6.9 million of closing prorations and lender holdbacks) to fund a $271.5 million distribution to the Company. The Company agreed to fund the first $5.2 million of post-closing capital expenditures on behalf of the Austin Venture, resulting in net proceeds of $266.3 million after funding the Company's capital expenditure obligation. As part of the transaction, the Company's subsidiary management company executed an agreement with the Austin Venture to provide property management and leasing services to the Austin Venture in exchange for a market-based fee.
On April 3, 2014, the Company contributed two three-story, Class A office buildings, commonly known as “Four Points Centre,” containing an aggregate of 192,396 net rentable square feet in Austin, Texas to the Austin Venture. See Note 3, "Real Estate Investments," for further information on the contribution.
On July 31, 2014, the Austin Venture acquired the Crossings at Lakeline, comprised of two three-story buildings containing an aggregate of 232,274 rentable square feet located in Austin, TX for $48.2 million. The transaction was funded with $34.5 million of proceeds of a 3.87% fixed rate mortgage loan from a non-affiliated institutional lender and $12.8 million (net of $0.9 million in purchase adjustments) of cash capital contributions, with $6.4 million made by each of DRA and the Company. The Austin Venture expensed approximately $0.1 million of transaction costs to acquire the property, net of $0.6 million credit from the seller.
On October 17, 2014, the Austin Venture acquired River Place, comprised of seven Class A office buildings containing 590,881 rentable square feet located in Austin, Texas for $128.1 million. The transaction was funded through a combination of an $88.0 million short-term loan, secured by a mortgage, made by the Company to the Austin Venture and cash capital contributions of $18.9 million made by each of DRA and the Company to the Austin Venture. The short-term financing was provided by the Company and the Austin Venture was seeking permanent financing as of December 31, 2014. The Company accounted the short-term financing as a note receivable. See Note 2, "Summary of Significant Accounting Policies," for the Company's accounting treatment. The debt agreement for the short-term loan provides financing through March 2015 at the following tiered interest rates; (i) 4.0% through December 31, 2014, (ii) 5.0% from January 1, 2015 through January 31, 2015, (iii) 7.0% from February 1, 2015 through February 28, 2015 and (iv) 9.0% from March 1, 2015 through March 31, 2015. The Austin Venture may repay the short-term loan at any time without penalty. See Note 21, "Subsequent Events," for repayment of the short-term financing. The Austin Venture expensed approximately $0.2 million of transaction costs to acquire the property.
The Company and DRA, utilizing additional equity funding of up to $100.0 million per partner, of which approximately $69.0 million remained unfunded at December 31, 2014, intend to jointly pursue additional office opportunities in targeted Austin sub-markets that meet certain investment criteria.
Based upon the facts and circumstances at formation of the Austin Venture, the Company determined that the Austin Venture is not a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the voting interest model under the accounting standard for consolidation in order to determine whether to consolidate the Austin Venture. Based upon each member's substantive participating rights over the activities of the Austin Venture under the operating and related agreements of the Austin Venture, it is not consolidated by the Company, and is accounted for under the equity method of accounting. As a result, the Company measured its equity interest at fair value based on the fair value of the Austin Properties and the distribution provisions of the real estate venture agreement. Since the Company retains a non-controlling interest in the Austin Properties and there are no other facts and circumstances that preclude the consummation of a sale, the contribution qualifies as a partial sale of real estate under the relevant guidance for sales of real estate. Accordingly, during the fourth quarter of 2013, the Company recorded a gain of approximately $25.9 million, which is reflected in "Net gain (loss) on real estate venture transactions" on the accompanying statement of operations.
The reconsideration event caused by the $88.0 million short-term financing extended from the Company to the Austin Venture did not change this conclusion reached above at formation, as the Austin Venture has sufficient equity at risk, to support the operations of the venture. The equity at risk does not lack decision making rights. There have been no changes to the operating agreement as a result of the Austin Venture entering into the loan agreement with the Company. In addition, the Company concluded that the financing did not change the allocation of the economic benefits of the venture and remains proportionate to the equity ownership and voting rights.
4040 Wilson Venture
On July 31, 2013, the Company formed 4040 Wilson LLC Venture ("4040 Wilson"), a joint venture between the Company and Ashton Park Associates LLC (“Ashton Park”), an unaffiliated third party. Each of the Company and Ashton Park owns a 50% interest in 4040 Wilson. 4040 Wilson expects to construct a 426,900 square foot office representing the final phase of the eight building, mixed-use, Liberty Center complex developed by the parent company of Ashton Park in the Ballston submarket of Arlington, Virginia. 4040 Wilson expects to develop the office building on a 1.3-acre land parcel contributed by Ashton Park to 4040 Wilson at an agreed upon value of $36.0 million. The total estimated project costs are $194.6 million, which the Company expects will be financed through approximately $72.0 million of partner capital contributions (consisting of land with a value of $36.0 million from Ashton Park and $36.0 million in cash from the Company, of which $26.8 million has been funded to date) with the remaining balance funded by debt financing. As part of the 4040 Wilson venture, the Company has agreed to guarantee 100% of any lender mandated recourse. As of December 31, 2014, the Company had not provided any guarantees in respect of 4040 Wilson.
Based upon the facts and circumstances at formation of 4040 Wilson, the Company determined that 4040 Wilson 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 4040 Wilson. Based upon each member's shared power over the activities of 4040 Wilson under the operating and related agreements of 4040 Wilson, and the Company's lack of control over the development and construction phases of the project, 4040 Wilson is not consolidated by the Company, and is accounted for under the equity method of accounting.
Two and Six Tower Bridge Exchange Transaction
On June 19, 2013, the Company acquired, from an unaffiliated third party, the third party's ownership interest in the Six Tower Bridge real estate venture through a nonmonetary exchange for the Company's ownership interest in the Two Tower Bridge real estate venture. The Six Tower Bridge real estate venture owns an unencumbered office property in Conshohocken, PA. The Company previously accounted for its noncontrolling interest in Six Tower Bridge using the equity method. As a result of the exchange 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 "Net gain from remeasurement of investments in a real estate ventures" on the accompanying statement 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 transaction 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 non-controlling interest in Two Tower Bridge real estate venture in a nonmonetary transaction with an unaffiliated third party for the third party's 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, which is reflected in "Net gain (loss) on real estate venture transactions" on the accompanying statement of operations.
evo at Cira Centre South Venture
On January 25, 2013, the Company formed HSRE-Campus Crest IX Real Estate Venture ("evo at Cira"), a joint venture among the Company and two unaffiliated third parties: Campus Crest Properties, LLC ("Campus Crest") and HSRE-Campus Crest IXA, LLC ("HSRE"). evo at Cira has commenced construction of a 33-story, 850-bed student housing tower located in the University City submarket of Philadelphia, Pennsylvania. Each of the Company and Campus Crest owns a 30% interest in evo at Cira and HSRE owns a 40% interest. evo at Cira 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 evo at Cira 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 construction facilities provided by unaffiliated institutional lenders. As of December 31, 2014, the Company had funded 100% of its share of the equity contributions.
In connection with the development of evo at Cira, each of the Company and Campus Crest 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 $24.7 million).
The Company's historical cost basis in the development rights that it contributed to the evo at Cira was $4.0 million, thus creating a $4.5 million basis difference at December 31, 2013 between the Company's initial outside investment basis and its $8.5 million initial equity basis. As this basis difference is not related to a physical land parcel, but rather to development rights to construct evo at Cira, the Company will accrete the basis difference as a reduction of depreciation expense over the life of evo at Cira's assets.
Based upon the facts and circumstances at evo at Cira formation, the Company determined that evo at Cira 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 evo at Cira. Based upon each member's shared power over the activities of evo at Cira under the operating and related agreements of evo at Cira, and the Company's lack of exclusive control over the development and construction phases of the project, evo at Cira 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 evo at Cira were deconsolidated by the Company upon formation of evo at Cira.
During the third quarter of 2014, evo at Cira placed into service the student housing tower. At December 31, 2014, the project was substantially complete.
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.
Guarantees
As of December 31, 2014, the Company has provided guarantees on behalf of certain real estate ventures, consisting of (i) a $24.7 million payment guaranty on the construction loan for the project being undertaken by evo at Cira; (ii) a $3.2 million payment guarantee on the construction loan for a project being undertaken by TB-BDN Plymouth Apartments; and (iii) a $0.5 million payment guarantee on a loan provided to PJP VII. In addition, during construction undertaken by real estate ventures the Company provided and expects to continue to provide cost overrun and completion guarantees, with rights of contribution among partners in the venture, as well as customary environmental indemnities and guarantees of customary exceptions to nonrecourse provisions in loan agreements.

Deferred_Costs

Deferred Costs	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs [Text Block]	DEFERRED COSTS
	As of December 31, 2014 and 2013, the Company’s deferred costs were comprised of the following (in thousands):
		31-Dec-14
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	164,081	$	(64,065	)	$	100,016
	Financing Costs	40,401		(15,193		)	25,208
	Total	$	204,482	$	(79,258	)	$	125,224
		31-Dec-13
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	155,885	$	(58,805	)	$	97,080
	Financing Costs	40,317		(14,443		)	25,874
	Total	$	196,202	$	(73,248	)	$	122,954
	During the years ended December 31, 2014, 2013 and 2012, the Company capitalized internal direct leasing costs of $7.1 million, $7.5 million, and $7.5 million, respectively, in accordance with the accounting standard for the capitalization of leasing costs.

Intangible_Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS
	As of December 31, 2014 and 2013, the Company’s intangible assets were comprised of the following (in thousands):
		December 31, 2014
		Total Cost		Accumulated			Intangible Assets,
				Amortization			net
	In-place lease value	$	129,411	$	(42,068	)	$	87,343
	Tenant relationship value	34,172		(26,344		)	7,828
	Above market leases acquired	5,641		(1,409		)	4,232
	Total	$	169,224	$	(69,821	)	$	99,403
	Below market leases acquired	$	53,049	$	(27,039	)	$	26,010
		31-Dec-13
		Total Cost		Accumulated			Intangible Assets,
				Amortization			net
	In-place lease value	$	150,782	$	(35,607	)	$	115,175
	Tenant relationship value	38,692		(26,868		)	11,824
	Above market leases acquired	6,673		(1,343		)	5,330
	Total	$	196,147	$	(63,818	)	$	132,329
	Below market leases acquired	$	81,991	$	(47,547	)	$	34,444
	For the years ended December 31, 2014, 2013, and 2012, the Company wrote-off through the acceleration of amortization approximately $0.8 million, $1.6 million and $1.4 million, respectively, of intangible assets as a result of tenant move-outs prior to the end of the associated lease term. For the years ended December 31, 2014, December 31, 2013, and December 31, 2012 the Company accelerated amortization of a nominal amount of intangible liabilities as a result of tenant move-outs.
	As of December 31, 2014, the Company’s annual amortization for its intangible assets/liabilities was as follows (in thousands, and assuming no early lease terminations):
		Assets		Liabilities
	2015	$	21,363	$	5,212
	2016	16,898		3,253
	2017	15,148		2,664
	2018	11,399		2,241
	2019	10,086		1,909
	Thereafter	24,509		10,731
	Total	$	99,403	$	26,010

Debt_Obligations

Debt Obligations	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
DEBT OBLIGATIONS	DEBT OBLIGATIONS
	The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2014 and 2013 (in thousands):
		December 31,			December 31,			Effective					Maturity
		2014			2013			Interest					Date
								Rate
	MORTGAGE DEBT:
	Tysons Corner	$	89,513		$	91,395		5.36	%				Aug-15
	One Commerce Square	123,205			125,089			3.68	%		(a)		Jan-16
	Two Logan Square	87,767			88,583			7.57	%				Apr-16
	Fairview Eleven Tower	21,242			21,630			4.25	%		(b)		Jan-17
	Two Commerce Square	112,000			112,000			4.51	%		(a)		Apr-23
	IRS Philadelphia Campus	184,442			190,964			7	%				Sep-30
	Cira South Garage	37,765			40,101			7.12	%				Sep-30
	Principal balance outstanding	655,934			669,762
	Plus: fair market value premiums (discounts), net	(1,344		)	389
	Total mortgage indebtedness	$	654,590		$	670,151
	UNSECURED DEBT:
	Three-Year Term Loan - Swapped to fixed	$	—		$	150,000		2.6	%		(c)		Feb-15
	Four-Year Term Loan	—			100,000			LIBOR + 1.75%			(c), (d)		Feb-16
	Seven-Year Term Loan - Swapped to fixed	200,000			200,000			3.62	%				Feb-19
	$250.0M 5.40% Guaranteed Notes due 2014	—			218,549			5.53	%		(e)		Nov-14
	$250.0M 7.50% Guaranteed Notes due 2015	—			157,625			7.76	%		(e)		May-15
	$250.0M 6.00% Guaranteed Notes due 2016	149,919			149,919			5.95	%				Apr-16
	$300.0M 5.70% Guaranteed Notes due 2017	300,000			300,000			5.68	%				May-17
	$325.0M 4.95% Guaranteed Notes due 2018	325,000			325,000			5.13	%				Apr-18
	$250.0M 3.95% Guaranteed Notes due 2023	250,000			250,000			4.02	%				Feb-23
	$250.0M 4.10% Guaranteed Notes due 2024	250,000			—			4.23	%		(e)		Oct-24
	$250.0M 4.55% Guaranteed Notes due 2029	250,000			—			4.6	%		(e)		Oct-29
	Indenture IA (Preferred Trust I)	27,062			27,062			2.75	%				Mar-35
	Indenture IB (Preferred Trust I)	25,774			25,774			3.3	%				Apr-35
	Indenture II (Preferred Trust II)	25,774			25,774			3.09	%				Jul-35
	Principal balance outstanding	1,803,529			1,929,703
	plus: original issue premium (discount), net	(6,811		)	(4,473		)
	Total unsecured indebtedness	$	1,796,718		$	1,925,230
	Total Debt Obligations	$	2,451,308		$	2,595,381
	(a)	This loan was assumed upon acquisition of the related properties on December 19, 2013. The interest rate reflects the market rate at the time of acquisition.
	(b)	Represents the full debt amount of a property in a consolidated joint venture for which the Company maintains a 50% interest.
	(c)	On September 16, 2014, the Company repaid all balances outstanding under its $150.0 million three-year term loan and its $100.0 million four-year term loan prior to the scheduled maturity dates of February 1, 2015 and February 1, 2016, respectively.
	(d)	London Interbank Offered Rate (“LIBOR”).
	(e)	On September 16, 2014, the Company closed on an underwritten offering of $250.0 million 4.10% Guaranteed Notes due 2024 (the "2024 Notes") and $250.0 million 4.55% Guaranteed Notes due 2029 (the "2029 Notes"). The Company used the net proceeds, together with cash on hand, to redeem the remaining outstanding balance of its 5.40% Guaranteed Notes due November 1, 2014 (the "2014 Notes") and its 7.50% Guaranteed Notes due May 15, 2015 (the "2015 Notes"). (See further discussion below).
	During 2014, 2013, and 2012, the Company’s weighted-average effective interest rate on its mortgage notes payable was 5.72%, 5.73%, and 6.65%, respectively. As of December 31, 2014 and 2013, the net carrying value of the Company's Properties that are encumbered by mortgage indebtedness was $655.9 million and $669.8 million, respectively.
	On September 16, 2014, the Company closed on an underwritten offering of its 2024 Notes and 2029 Notes (as defined above). The 2024 Notes were priced at 99.388% of their face amount with a yield to maturity of 4.175%, representing a spread at the time of pricing of 1.70%. The 2029 Notes were priced at 99.191% of their face amount with a yield to maturity of 4.625%, representing a spread at the time of pricing of 2.15%. The 2024 Notes and 2029 Notes have been reflected net of discounts of $1.5 million and $2.0 million, respectively, in the consolidated balance sheet as of December 31, 2014.
	The Company used a portion of the net proceeds from the sale of the 2024 Notes and 2029 Notes, aggregating $492.9 million after the deduction for underwriting discounts and offering expenses, to fund its repurchase, through a tender offer, of a portion of 2014 Notes and 2015 Notes (as defined above). Specifically, on September 16, 2014, the Company funded, under the tender offer, $75.1 million in respect of the 2014 Notes and $42.7 million in respect of the 2015 Notes. The Company recognized a $2.6 million loss on early extinguishment of debt related to the total repurchase.
	On September 16, 2014, the Company repaid the entire $150.0 million three-year term loan and $100.0 million four-year term loan prior to their scheduled February 2015 and 2016 maturities, respectively. In connection with these repayments, the Company accelerated $0.3 million of deferred financing amortization expense and also incurred a $0.8 million charge on the termination of associated interest rate swap contracts, as reflected in the Company's consolidated statements of operations. See Note 9, "Risk Management and Use of Financial Instruments," for further information related to the termination of the interest rate swap contracts.
	On September 16, 2014, the Company gave notice of redemption, in full, of the $143.5 million of 2014 Notes that remained outstanding following completion of the tender offer. The Company completed the redemption of the 2014 Notes on October 16, 2014 at a cash redemption price of $1,026.88 per $1,000 principal amount of the 2014 Notes (inclusive of accrued interest to the redemption date). Also on September 16, 2014, the Company gave notice of redemption, in full, of the $114.9 million of 2015 Notes that remained outstanding following completion of the tender offer. The Company completed the redemption of the 2015 Notes on October 16, 2014 at a cash redemption price of $1,070.24 per $1,000 principal amount of the 2015 Notes (inclusive of accrued interest to the redemption date). The Company recognized a $5.0 million loss on early extinguishment of debt related to total repurchase.
	The following table provides additional information on the Company’s repurchase of $376.2 million in aggregate principal amount of its outstanding unsecured notes (consisting of the 2014 Notes and 2015 Notes, as indicated above) during the twelve months ended December 31, 2014 (in thousands):
	Notes	Principal			Repurchase			Gain (Loss) on Early Extinguishment of Debt (b)				Acceleration of Deferred Financing
					Amount (a)							Amortization
	2014 5.40% Notes	$	218,549		$	219,404		$	(855	)		$	9
	2015 7.50% Notes	157,625			164,364			(6,739		)		143
		$	376,174		$	383,768		$	(7,594	)		$	152
	During the year-ended December 31, 2013, the Company repurchased $29.3 million of its outstanding unsecured Notes in a series of transactions that are summarized in the following table (in thousands):
	Notes	Principal			Repurchase			Gain (Loss) on Early Extinguishment of Debt (b)				Acceleration of Deferred Financing
					Amount (a)							Amortization
	2014 5.40% Notes	$	19,830		$	20,853		$	(1,020	)		$	16
	2015 7.50% Notes	8,910			9,945			(1,036		)		23
	2016 6.00% Notes	510			571			(63		)		1
		$	29,250		$	31,369		$	(2,119	)		$	40
	During the year-ended December 31, 2012, the Company repurchased $165.0 million of its outstanding unsecured Notes in a series of transactions that are summarized in the following table (in thousands):
	Notes	Principal			Repurchase			Gain (Loss) on Early Extinguishment of Debt (b)				Acceleration of Deferred Financing Amortization
					Amount (a) (c)
	2012 5.75% Notes	$	301		$	303		$	(2	)		$	—
	2014 5.40% Notes	4,302			4,566			(264		)		8
	2015 7.50% Notes	60,794			69,497			(8,712		)		183
2016 6.00% Notes	99,571			112,541			(13,024		)		260
	$	164,968		$	186,907		$	(22,002	)		$	451
(a)	Includes cash losses with respect to redemption of debt.
(b)	Includes unamortized balance of the original issue discount.
(c)	Does not include $151.2 million of 5.75% Guaranteed Notes due 2012 that matured.
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 $600.0 million four-year unsecured revolving credit facility (the "Credit Facility") for general business purposes, including funding costs of acquisitions, developments and redevelopments and repayment of other debt. The scheduled maturity date of the Credit Facility in place at December 31, 2014 is February 1, 2016. The per annum variable interest rate on the outstanding balances 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. There were no outstanding borrowings under the credit facility during the year-ended December 31, 2014. For the year-ended December 31, 2013, the weighted-average interest rate associated with the Credit Facility was 0.29%. As of December 31, 2014, the Company did not have any outstanding borrowings on its Credit Facility, with $4.3 million in letters of credit outstanding, leaving $595.7 million of unused availability under the Credit Facility.
The Company has the option to increase the amounts available to be advanced under the Credit Facility, 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 date of the Credit Facility. The unsecured $200.0 million seven-year term loan (the "Term Loan") is subject to a prepayment penalty of 1.00% through February 1, 2015 with no penalty thereafter.
The spread to LIBOR for LIBOR-based loans under the Credit Facility will depend on our unsecured senior debt credit rating. Based on the Company's current credit rating, the spread will be 150 basis points under the Credit Facility and 190 basis points under the seven-year term loan, respectively. At our option, advances under the Credit Facility and Term Loan 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 us at a reduced rate. The Company executed a hedging transaction that fix the rate on the Term Loan at a 3.623% average for its full term. The hedge commenced on February 1, 2012 and the rate is inclusive of the LIBOR spread based on our current investment grade rating. See Note 9, "Risk Management and Use of Financial Instruments," for details of the interest rate swaps entered into as of December 31, 2014.
The Credit Facility and Term Loan contain financial and operating covenants and restrictions. The Company was in compliance with all such restrictions and financial covenants as of December 31, 2014. The Credit Facility restricts the Company's dividend distributions to the greater of 95% of funds from operations or the minimum amount necessary for the Company to maintain its status as a REIT.
As of December 31, 2014, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
2015	$	102,030
2016	367,703
2017	330,323
2018	336,954
2019	213,155
Thereafter	1,109,298
Total principal payments	2,459,463
Net unamortized premiums/(discounts)	(8,155		)
Outstanding indebtedness	$	2,451,308

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS
	The Company determined the fair values disclosed below using available market information and discounted cash flow analyses as of December 31, 2014 and 2013, 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 estimation methodologies may have a material effect on the estimated fair value amounts shown. The Company believes that the carrying amounts reflected in the consolidated balance sheets at December 31, 2014 and 2013 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):
		December 31, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Mortgage notes payable	$	654,590	$	707,241	$	670,151	$	715,244
	Unsecured notes payable	$	1,518,108	$	1,593,212	$	1,396,620	$	1,471,041
	Variable rate debt	$	278,610	$	257,188	$	528,610	$	526,693
	Notes receivable (a)	$	88,000	$	87,692	$	7,026	$	7,759
	(a)	See Note 2, "Summary of Significant Accounting Policies - Notes Receivable," for further discussion.
	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 December 31, 2014 and 2013. 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.
	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 for loans with similar terms, maturities and loan-to-value. 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.
	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 to calculate fair value as of December 31, 2014 was 4.256%. 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 December 31, 2014 and December 31, 2013. 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 December 31, 2014, and current estimates of fair value may differ from the amounts presented herein.

Risk_Management_and_Use_of_Fin

Risk Management and Use of Financial Instruments	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS	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
	In the U.S., market and economic conditions have been improving, resulting in an increase of the volume of real estate transactions in the market. If the economy deteriorates, vacancy rates may increase through 2015 and possibly beyond. The financial markets also have an effect on the Company’s Real Estate Venture partners and contractual counter parties, including counter parties in derivative contracts.
	The Company’s Credit Facility, term loans and the indenture governing its unsecured public debt securities (See Note 7, "Debt Obligations") contain restrictions, requirements and other limitations on the ability to incur indebtedness, including total debt to asset ratios, secured debt to total asset ratios, debt service coverage ratios and minimum ratios of unencumbered assets to unsecured debt which it must maintain. The ability to borrow under the Credit Facility is subject to compliance with such financial and other covenants. In the event that the Company fails to satisfy these covenants, it would be in default under the Credit Facility, the term loans and the indenture and may be required to repay such debt with capital from other sources. Under such circumstances, other sources of capital may not be available, or may be available only on unattractive terms.
	Availability of borrowings under the Credit Facility is subject to a traditional material adverse effect clause. Each time the Company borrows it must represent to the lenders that there have been no events of a nature which would have a material adverse effect on the business, assets, operations, condition (financial or otherwise) or prospects of the Company taken as a whole or which could negatively affect the ability of the Company to perform its obligations under the Credit Facility. While the Company believes that there are currently no material adverse effect events, it is possible that such an event could arise which would limit the Company’s borrowings under the Credit Facility. If an event occurs which is considered to have a material adverse effect, the lenders could consider the Company in default under the terms of the Credit Facility and any borrowings under the Credit Facility would become unavailable. If the Company is unable to obtain a waiver, this would have a material adverse effect on the Company’s financial position and results of operations.
	The Company was in compliance with all financial covenants as of December 31, 2014. Management continuously monitors the Company’s compliance with and anticipated compliance with the covenants. Certain of the covenants restrict management’s ability to obtain alternative sources of capital. While the Company currently believes it will remain in compliance with its covenants, in the event that the economy deteriorates in the future, the Company may not be able to remain in compliance with such covenants, in which case a default would result absent a lender waiver.
	Use of Derivative Financial Instruments
	The Company’s use of derivative instruments is limited to the utilization of interest rate agreements or other instruments to manage interest rate risk exposures and not for speculative purposes. The principal objective of such arrangements is to minimize the risks and/or costs associated with the Company’s operating and financial structure, as well as to hedge specific transactions. The counterparties to these arrangements are major financial institutions with which the Company and its affiliates may also have other financial relationships. The Company is potentially exposed to credit loss in the event of non-performance by these counterparties. However, because of the high credit ratings of the counterparties, the Company does not anticipate that any of the counterparties will fail to meet these obligations as they come due. The Company does not hedge credit or property value market risks through derivative financial instruments.
	The Company formally assesses, both at inception of a hedge and on an on-going basis, whether each derivative is highly-effective in offsetting changes in cash flows of the hedged item. If management determines that a derivative is not highly-effective as a hedge or if a derivative ceases to be a highly-effective hedge, the Company will discontinue hedge accounting prospectively. The related ineffectiveness would be charged to the consolidated statement of operations.
	The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves.
	To comply with the provisions of the accounting standard for fair value measurements and disclosures, the Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees.
	The following table summarizes the terms and fair values of the Company's derivative financial instruments as of December 31, 2014 and December 31, 2013. 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 and included in other liabilities on the Company's consolidated balance sheets).
	Hedge Product		Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
						12/31/14		12/31/13						12/31/14			12/31/13
	Assets/(Liabilities)
	Swap		Interest Rate	Cash Flow	(a)	$	25,774	$	25,774	3.3	%	December 22, 2011	January 30, 2021	$	(334	)	$	549
	Swap		Interest Rate	Cash Flow	(a)	25,774		25,774		3.09	%	6-Jan-12	30-Oct-19	(254		)	218
	Swap		Interest Rate	Cash Flow	(a)	200,000		200,000		3.623	%	December 6-13, 2011	February 1, 2019	(2,649		)	(545		)
	Swap		Interest Rate	Cash Flow	(a)	27,062		27,062		2.75	%	December 21, 2011	September 30, 2017	(253		)	(311		)
	Swap		Interest Rate	Cash Flow	(a), (b)	—		77,000		2.703	%	December 9-13, 2011	February 1, 2016	—			(887		)
	Swap		Interest Rate	Cash Flow	(a), (b)	—		50,000		2.47	%	December 13, 2011	February 1, 2015	—			(283		)
	Swap		Interest Rate	Cash Flow	(a), (b)	—		23,000		2.513	%	December 7-12, 2011	May 1, 2015	—			(162		)
						$	278,610	$	428,610					$	(3,490	)	$	(1,421	)
	(a)	Hedging unsecured variable rate debt.
	(b)	On September 16, 2014, the Company repaid the entire $150.0 million swapped to fixed portion of its previously mentioned three-year term loan (See Note 7, "Debt Obligations"), consisting of $150.0 million interest rate swaps maturing through February 1, 2016 (shown above). In connection with the repayment, the Company terminated associated hedging contracts, incurring a $0.8 million charge upon termination.
	The Company measures its derivative instruments at fair value and records them in the balance sheet as either an asset or liability. As of December 31, 2014, all interest rate swaps are included in other liabilities on the Company's consolidated balance sheet.
	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 2014, 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.

Discontinued_Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
DISCONTINUED OPERATIONS	DISCONTINUED OPERATIONS
	The Company had no property dispositions classified as discontinued operations during the year ended December 31, 2014. There was nominal income before gain on sales recognized during 2014 relating to properties classified into discontinued operations in prior periods and a $0.9 million gain relating to the post closing activity for the sale of the Princeton Pike Corporate Center completed in the first quarter of 2013.
	For the years ended December 31, 2014, 2013 and 2012, income from discontinued operations relates to an aggregate of 28 properties containing approximately 2.0 million net rentable square feet that the Company has sold since January 1, 2012.
	The following table summarizes revenue and expense information for the properties sold which qualify for discontinued operations reporting since January 1, 2012 (in thousands):
		Years ended December 31,
		2014		2013		2012
	Revenue:
	Rents	$	—	$	4,754	$	28,678
	Tenant reimbursements	26		355		2,353
	Termination fees	—		—		11
	Other	—		123		378
	Total revenue	26		5,232		31,420
	Expenses:
	Property operating expenses	8		1,839		8,687
	Real estate taxes	—		649		3,468
	Depreciation and amortization	—		1,921		10,208
	Total operating expenses	8		4,409		22,363
	Other income:
	Interest income	—		2		7
	Income from discontinued operations before gain on sale of interests in real estate	18		825		9,064
	Net gain on disposition of discontinued operations	900		3,382		34,774
	Income from discontinued operations	$	918	$	4,207	$	43,838
	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.

Non_Controlling_Interests_in_T

Non Controlling Interests in The Parent Company	12 Months Ended
	Dec. 31, 2014
Noncontrolling Interest [Abstract]
NON-CONTROLLING INTERESTS IN THE PARENT COMPANY	LIMITED PARTNERS' 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 and properties which are consolidated but not wholly owned.
	Operating Partnership
	The aggregate book value of the non-controlling interests associated with the redeemable common limited partnership interests that were consolidated in the accompanying consolidated balance sheet of the Parent Company as of December 31, 2014 and December 31, 2013, was $17.5 million and $20.3 million, respectively. Under the applicable accounting guidance, the redemption value of limited partnership units are carried at, on a limited partner basis, the greater of historical cost adjusted for the allocation of income and distributions or fair value. 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 $24.5 million and $24.8 million, respectively, as of December 31, 2014 and December 31, 2013.

Beneficiaries_Equity_of_the_Pa

Beneficiaries Equity of the Parent Company	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
BENEFICIARIES' EQUITY OF THE PARENT COMPANY	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):
		Year ended December 31,
		2014						2013						2012
		Basic			Diluted			Basic			Diluted			Basic			Diluted
	Numerator
	Income (loss) from continuing operations	$	6,024		$	6,024		$	38,982		$	38,982		$	(37,309	)	$	(37,309	)
	Net loss attributable to non-controlling interests - partners' share of consolidated real estate ventures	44			44			—			—			—			—
	Net (income) loss from continuing operations attributable to non-controlling interests	(1		)	(1		)	(357		)	(357		)	863			863
	Amount allocable to unvested restricted shareholders	(349		)	(349		)	(363		)	(363		)	(376		)	(376		)
	Preferred share dividends	(6,900		)	(6,900		)	(6,900		)	(6,900		)	(10,405		)	(10,405		)
	Preferred share redemption charge	—			—			—			—			(4,052		)	(4,052		)
	Income (loss) from continuing operations available to common shareholders	(1,182		)	(1,182		)	31,362			31,362			(51,279		)	(51,279		)
	Income from discontinued operations	918			918			4,207			4,207			43,838			43,838
	Discontinued operations attributable to non-controlling interests	(10		)	(10		)	(55		)	(55		)	(797		)	(797		)
	Discontinued operations attributable to common shareholders	908			908			4,152			4,152			43,041			43,041
	Net income (loss) attributable to common shareholders	$	(274	)	$	(274	)	$	35,514		$	35,514		$	(8,238	)	$	(8,238	)
	Denominator
	Weighted-average shares outstanding	166,202,649			166,202,649			153,140,458			153,140,458			143,257,097			143,257,097
	Contingent securities/Share based compensation	—			—			—			1,273,853			—			—
	Total weighted-average shares outstanding	166,202,649			166,202,649			153,140,458			154,414,311			143,257,097			143,257,097
	Earnings per Common Share:
	Income (loss) from continuing operations attributable to common shareholders	$	(0.01	)	$	(0.01	)	$	0.2		$	0.2		$	(0.36	)	$	(0.36	)
	Discontinued operations attributable to common shareholders	0.01			0.01			0.03			0.03			0.3			0.3
	Net income (loss) attributable to common shareholders	$	—		$	—		$	0.23		$	0.23		$	(0.06	)	$	(0.06	)
	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.
	Redeemable common limited partnership units, totaling 1,535,102 in 2014, 1,763,739 in 2013, and 1,845,737 in 2012, were excluded from the diluted earnings per share computations because they are not dilutive.
	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 years ended December 31, 2014, 2013 and 2012, earnings representing nonforfeitable dividends 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 December 9, 2014, the Parent Company declared a distribution of $0.15 per common share, totaling $27.2 million, which was paid on January 20, 2015 to shareholders of record as of January 6, 2015. On December 9, 2014, the Parent Company declared distributions on its Series E Preferred Shares to holders of record as of December 30, 2014. These shares are entitled to a preferential return of 6.90% per annum on the $25.00 per share liquidation preference. Distributions paid on January 15, 2015 to holders of Series E Preferred Shares totaled $1.7 million.
	On August 1, 2014, the Parent Company completed an underwritten offering of 21,850,000 common shares. The Parent Company contributed the net proceeds from the sale of the common shares, amounting to $335.0 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 intends 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 November 5, 2013, the Parent Company commenced a continuous equity offering program (the “Offering Program”), under which it may sell, in at-the-market offerings, up to an aggregate amount of 16,000,000 common shares until November 5, 2016. This Offering Program replaced a prior continuous equity offering program which expired on March 10, 2013. The Parent Company may sell common shares in amounts and at times to be determined by the Parent Company. Actual sales will depend on a variety of factors to be determined by the Parent Company, including, among others, market conditions, the trading price of the Company’s common shares of beneficial interest and determinations by the Parent Company of the appropriate sources of funding. In conjunction with the Offering Program, the Parent Company engages sales agents who receive compensation, in aggregate, of up to 2% of the gross sales price per share sold. From inception of the Offering Program through December 31, 2014, the Parent Company has not sold any shares under the program, resulting in 16,000,000 remaining shares available for sale.
	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 $181.5 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.
	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 year-ended December 31, 2014. As of December 31, 2014, the Parent Company may purchase an additional 539,200 shares under the program.
	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_Operati

Partners Equity of The Operating Partnership	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
PARTNERS' EQUITY OF THE OPERATING PARTNERSHIP	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):
		Year ended December 31,
		2014						2013						2012
		Basic			Diluted			Basic			Diluted			Basic			Diluted
	Numerator
	Income (loss) from continuing operations	$	6,024		$	6,024		$	38,982		$	38,982		$	(37,309	)	$	(37,309	)
	Amount allocable to unvested restricted unitholders	(349		)	(349		)	(363		)	(363		)	(376		)	(376		)
	Preferred unit dividends	(6,900		)	(6,900		)	(6,900		)	(6,900		)	(10,405		)	(10,405		)
	Net loss attributable to non-controlling interests	44			44			—			—			—			—
	Preferred unit redemption charge	—			—			—			—			(4,052		)	(4,052		)
	Income (loss) from continuing operations available to common unitholders	(1,181		)	(1,181		)	31,719			31,719			(52,142		)	(52,142		)
	Discontinued operations attributable to common unitholders	918			918			4,207			4,207			43,838			43,838
	Net income (loss) attributable to common unitholders	$	(263	)	$	(263	)	$	35,926		$	35,926		$	(8,304	)	$	(8,304	)
	Denominator
	Weighted-average units outstanding	167,942,246			167,942,246			154,929,545			154,929,545			145,883,217			145,883,217
	Contingent securities/Unit based compensation	—			—			—			1,273,853			—			—
	Total weighted-average units outstanding	167,942,246			167,942,246			154,929,545			156,203,398			145,883,217			145,883,217
	Earnings per Common Partnership Unit:
	Income (loss) from continuing operations attributable to common unitholders	$	(0.01	)	$	(0.01	)	$	0.2		$	0.2		$	(0.36	)	$	(0.36	)
	Discontinued operations attributable to common unitholders	0.01			0.01			0.03			0.03			0.3			0.3
	Net income (loss) attributable to common unitholders	$	—		$	—		$	0.23		$	0.23		$	(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 unit. For the years ended December 31, 2014, 2013 and 2012, earnings representing nonforfeitable dividends were allocated to the unvested restricted units issued to the Parent Company’s executives and other employees under the Parent Company's shareholder-approved long-term incentive plan.
	Common Partnership Units and Preferred Mirror Units
	The Operating Partnership issues partnership units to the Parent Company in exchange for the contribution of the net proceeds of any equity security issuance by the Parent Company. The number and terms of such partnership units correspond to the number and terms of the related equity securities issued by the Parent Company. In addition, the Operating Partnership may also issue separate classes of partnership units. Historically, the Operating Partnership has had the following types of partnership units outstanding (i) Preferred Partnership Units which have been issued to parties other than the Parent Company (ii) Preferred Mirror Partnership Units which have been issued to the Parent Company and (iii) Common Partnership Units which include both interests held by the Parent Company and those held by other limited partners.
	Preferred Mirror Partnership Units
	In exchange for the proceeds received in corresponding offerings by the Parent Company of preferred units of beneficial interest, the Operating Partnership has issued to the Parent Company a corresponding amount of Preferred Mirror Partnership Units with terms consistent with that of the preferred securities issued by the Parent Company.
	Common Partnership Units (Redeemable and General)
	The Operating Partnership has two classes of Common Partnership Units: (i) Class A Limited Partnership Interest which are held by both the Parent Company and outside third parties and (ii) General Partnership Interests which are held by the Parent Company (collectively, the Class A Limited Partnership Interest, and General Partnership Interests are referred to as “Common Partnership Units”). The holders of the Common Partnership Units are entitled to share in cash distributions from, and in profits and losses of, the Operating Partnership, in proportion to their respective percentage interests, subject to preferential distributions on the preferred mirror units and the preferred units.
	The Common Partnership Units held by the Parent Company (comprised of both General Partnership Units and Class A Limited Partnership Units) are presented as partner’s equity in the consolidated financial statements. Class A Limited Partnership Interest held by parties other than the Parent Company are redeemable at the option of the holder for a like number of common shares of the Parent Company, or cash, or a combination thereof, at the election of the Parent Company. Because the form of settlement of these redemption rights are not within the control of the Operating Partnership, these Common Partnership Units have been excluded from partner’s equity and are presented as redeemable limited partnership units measured at the potential cash redemption value as of the end of the periods presented based on the closing market price of the Parent Company’s common shares at December 31, 2014, 2013 and 2012, which was $15.98, $14.09, $12.19, respectively. As of December 31, 2014 and 2013, 1,535,102 and 1,763,739 of Class A Units, respectively, were outstanding and owned by outside limited partners of the Operating Partnership.
	On December 9, 2014, the Operating Partnership declared a distribution of $0.15 per common unit, totaling $27.2 million, which was paid on January 20, 2015 to unitholders of record as of January 6, 2015. On December 9, 2014, the Operating Partnership declared distributions on its Series E Preferred Units to holders of record as of December 30, 2014. These units are entitled to a preferential return of 6.90% per annum on the $25.00 per share liquidation preference. Distributions paid on January 15, 2015 to holders of Series E Preferred Shares totaled $1.7 million.
	On November 5, 2013, the Parent Company commenced a continuous equity offering program (the “Offering Program”), under which it may sell, in at-the-market offerings, up to an aggregate amount of 16,000,000 common shares until November 5, 2013. This Offering Program replaced a prior continuous equity offering program which expired on March 10, 2013. The Parent Company may sell common shares in amounts and at times to be determined by the Parent Company. Actual sales will depend on a variety of factors to be determined by the Parent Company, including, among others, market conditions, the trading price of the Company’s common shares of beneficial interest and determinations by the Parent Company of the appropriate sources of funding. In conjunction with the Offering Program, the Parent Company engages sales agents who receive compensation, in aggregate, of up to 2% of the gross sales price per share sold. From inception of the Offering Program through December 31, 2014 the Parent Company has not sold any shares under the program, resulting in 16,000,000 remaining shares available for sale. Generally, the Parent Company contributes the net proceeds from the sales to the Operating Partnership, which the Operating Partnership in turn uses for general corporate purposes.
	Common Unit Repurchases
	The Parent Company did not repurchase any shares under its share repurchase program during the year-ended December 31, 2014 and accordingly, during the year-ended December 31, 2014, the Operating Partnership did not repurchase any units in connection with the Parent Company’s share repurchase program.

Share_Based_and_Deferred_Compe

Share Based and Deferred Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHARE BASED AND DEFERRED COMPENSATION	SHARE BASED COMPENSATION, 401(k) PLAN AND DEFERRED COMPENSATION
	Stock Options
	At December 31, 2014, options exercisable for 2,684,795 common shares were outstanding under the Parent Company's shareholder approved equity incentive plan (referred to as the "Equity Incentive Plan"). During the year ended December 31, 2014, the Company recognized compensation expense related to unvested options that was nominal. For the years ended December 31, 2013 and 2012, the Company recognized compensation expense related to unvested options of $0.7 million, and $1.6 million, respectively. During the year ended December 31, 2014, the Company also capitalized a nominal amount of compensation expense as part of the Company’s review of employee salaries eligible for capitalization. For the years ended December 31, 2013 and 2012, the Company capitalized $0.1 million and $0.5 million, respectively.
	Option activity as of December 31, 2014 and changes during the year-ended December 31, 2014 were as follows:
		Shares			Weighted				Weighted Average	Aggregate Intrinsic
					Average				Remaining Contractual	Value
					Exercise Price				Term (in years)
	Outstanding at January 1, 2014	2,983,569			$	15.5			5.15	$	—
	Exercised	(184,116	)		$	11.65				671,008
	Forfeited/Expired	(114,658	)		$	20.61
	Outstanding at December 31, 2014	2,684,795			$	15.55			4.1	$	1,152,891
	Vested/Exercisable at December 31, 2014	2,684,795			$	15.55			4.1	$	1,152,891
	401(k) Plan
	The Company sponsors a 401(k) defined contribution plan for its employees. Each employee may contribute up to 100% of annual compensation, subject to specific limitations under the Internal Revenue Code. At its discretion, the Company can make matching contributions equal to a percentage of the employee’s elective contribution and profit sharing contributions. Employees automatically vest in employer contributions. The Company contributions were $0.4 million in each of 2014, 2013 and 2012.
	Restricted Share Awards
	As of December 31, 2014, 540,066 restricted shares were outstanding under the Equity Incentive Plan and vest over three years from the initial grant dates. The remaining compensation expense to be recognized at December 31, 2014 was approximately $2.4 million, and is expected to be recognized over a weighted average remaining vesting period of 1.4 years. During 2014, the Company recognized compensation expense related to outstanding restricted shares of $2.7 million, of which $0.6 million was capitalized as part of the Company’s review of employee salaries eligible for capitalization. For the years ended December 31, 2013 and 2012, the Company recognized $3.2 million (of which $0.6 million was capitalized) and $3.4 million (of which $0.9 million was capitalized), respectively, of compensation expense included in general and administrative expense in the respective periods related to outstanding restricted shares.
	The following table summarizes the Company’s restricted share activity during the year-ended December 31, 2014:
		Shares			Weighted
					Average Grant
					Date Fair value
	Non-vested at January 1, 2014	563,713			$	12.56
	Granted	229,119			14.47
	Vested	(234,169	)		13.44
	Forfeited	(18,597	)		12.67
	Non-vested at December 31, 2014	540,066			$	12.21
	On March 11, 2014 and March 12, 2014, the Compensation Committee of the Company’s Board of Trustees awarded restricted shares, of which 131,641 cliff vest after three years from the grant date. Of these shares, 2,396 were canceled, leaving 129,245 unvested as of December 31, 2014. The remaining 69,794 shares vest ratably over three years, of which 3,839 were canceled, leaving 65,955 unvested. In addition, on May 29, 2014, 27,684 restricted shares were granted and will vest ratably over three years. Restricted shares that cliff vest are subject to acceleration upon a change in control or if the recipient of the award were to die, become disabled or, in certain cases, retire in a qualifying retirement. Qualifying retirement generally 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
	The Compensation Committee of the Parent Company’s Board of Trustees has granted performance share-based awards (referred to as Restricted Performance Share Units, or RPSUs) to officers of the Parent Company. The RPSUs are settled in common shares, with the number of common shares issuable in settlement determined based on the Company’s total shareholder return over specified measurement periods compared to total shareholder returns of comparative groups over the measurement periods. The table below presents certain information as to RPSU awards.
			RPSU Grant
			3/1/12				2/25/13			3/11/14			3/12/14		Total
	(Amounts below in shares, unless otherwise noted)
	Non-vested at January 1, 2014		242,122				231,093			—			—		473,215
	Units Granted		—				—			134,284			61,720		196,004
	Units Canceled		(34,739		)		(31,516		)	(3,567		)	—		(69,822	)
	Non-vested at December 31, 2014		207,383				199,577			130,717			61,720		599,397
	Measurement Period Commencement Date		1/1/12				1/1/13			1/1/14			1/1/14
	Measurement Period End Date		12/31/14				12/31/15			12/31/16			12/31/16
	Units Granted		265,222				231,093			134,284			61,720
	Fair Value of Units on Grant Date (in thousands)		$	4,273			$	4,137		$	2,624		$	1,225
	The Company values each RPSU on its grant date using a Monte Carlo simulation. 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 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 during the schedule vesting period.
	For the year ended December 31, 2014, the Company recognized total compensation expense for the 2014, 2013 and 2012 RPSU awards of $3.2 million, of which $1.1 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the year ended December 31, 2013, the Company recognized total compensation expense for the 2013, 2012 and 2011 RPSU awards of $4.4 million, of which $0.8 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the year ended December 31, 2012, the Company recognized total compensation expense for the 2012, 2011 and 2010 RPSU awards of $3.5 million, of which $1.2 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation.
	The remaining compensation expense to be recognized at December 31, 2014 was approximately $2.1 million, and is expected to be recognized over a weighted average remaining vesting period of 1.0 year.
	The Company issued 150,829 common shares on March 1, 2014 in settlement of RPSUs that had been awarded on March 2, 2011 (with a three-year measurement period ended December 31, 2013). Holders of these RPSUs also received a cash dividend of $0.15 per share for these common shares on February 7, 2014.
	Employee Share Purchase Plan
	The Parent Company’s shareholders approved the 2007 Non-Qualified Employee Share Purchase Plan (the “ESPP”), which is intended to provide eligible employees with a convenient means to purchase common shares of the Parent Company through payroll deductions and voluntary cash purchases at an amount equal to 85% of the average closing price per share for a specified period. Under the plan document, the maximum participant contribution for the 2014 plan year is limited to the lesser of 20% of compensation or $50,000. The ESPP allows the Parent Company to make open market purchases, which reflects all purchases made under the plan to date. In addition, the number of shares separately reserved for issuance under the ESPP is 1.25 million. During the year-ended December 31, 2014, 2013 and 2012, employees made purchases under the ESPP of $0.4 million and the Company recognized $0.1 million of compensation expense related to the ESPP. Compensation expense represents the 15% discount on the purchase price. The Board of Trustees of the Parent Company may terminate the ESPP at its sole discretion at any time.
	Deferred Compensation
	In January 2005, the Parent Company adopted a Deferred Compensation Plan (the “Plan”) that allows trustees and certain key employees to voluntarily defer compensation. Compensation expense is recorded for the deferred compensation and a related liability is recognized. Participants may elect designated benchmark investment options for the notional investment of their deferred compensation. The deferred compensation obligation is adjusted for deemed income or loss related to the investments selected. At the time the participants defer compensation, the Company records a liability, which is included in the Company’s consolidated balance sheet. The liability is adjusted for changes in the market value of the participant-selected investments at the end of each accounting period, and the impact of adjusting the liability is recorded as an increase or decrease to compensation cost.
	The Company has purchased mutual funds which can be utilized as a funding source for the Company’s obligations under the Plan. Participants in the Plan have no interest in any assets set aside by the Company to meet its obligations under the Plan. For the year ended December 31, 2014, the Company recorded a nominal amount of deferred compensation costs, net of investments in the company-owned policies and mutual funds. For the years ended December 31, 2013 and 2012 the Company recorded net increases in compensation costs of $0.2 million and $0.3 million, respectively, net of investments in the company-owned policies and mutual funds.
	Participants in the Plan may elect to have all or a portion of their deferred compensation invested in the Company’s common shares. The Company holds these shares in a rabbi trust, which is subject to the claims of the Company’s creditors in the event of the Company’s bankruptcy or insolvency. The Plan does not permit diversification of a participant’s deferral allocated to the Company common shares and deferrals allocated to Company common shares can only be settled with a fixed number of shares. In accordance with the accounting standard for deferred compensation arrangements where amounts earned are held in a rabbi trust and invested, the deferred compensation obligation associated with the Company’s common shares is classified as a component of shareholder’s equity and the related shares are treated as shares to be issued and are included in total shares outstanding. At December 31, 2014 and 2013, 0.4 million and 0.3 million of such shares, respectively, were included in total shares outstanding. Subsequent changes in the fair value of the common shares are not reflected in operations or shareholders’ equity of the Company.

Distributions

Distributions	12 Months Ended
	Dec. 31, 2014
Distributions [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	DISTRIBUTIONS
		Years ended December 31,
		2014			2013			2012
		(in thousands, except per share amounts)
	Common Share Distributions:
	Ordinary income	$	0.41		$	0.52		$	0.39
	Capital gain	0.02			—			—
	Non-taxable distributions	0.17			0.08			0.21
	Distributions per share	$	0.6		$	0.6		$	0.6
	Percentage classified as ordinary income	69		%	87		%	65		%
	Percentage classified as capital gain	3.3		%	—		%	—		%
	Percentage classified as non-taxable distribution	27.7		%	13		%	35		%
	Preferred Share Distributions:
	Total distributions declared	$	6,900		$	6,900		$	10,405
	Percentage classified as ordinary income	100		%	100		%	100		%

Tax_Credit_Transactions

Tax Credit Transactions	12 Months Ended
	Dec. 31, 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 remaining USB contributions presented within the Company’s consolidated balance sheet amounted to $15.1 million as of December 31, 2014 and $26.8 million as of December 31, 2013. The contributions were recorded net of the amounts allocated to non-controlling interest for 2014 and 2013, as described above, of $3.0 million and $2.8 million at the end of the years ended December 31, 2014 and December 31, 2013, respectively, with the remaining balance being presented within deferred income. Beginning in September 2011 to September 2015, the Company recognized and will recognize 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. During the years-ended December 31, 2014 and 2013, the Company recognized $11.9 million of the cash received as revenue, net of $0.5 million of allocated expenses 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 costs at December 31, 2014 and December 31, 2013 are $0.5 million and $1.0 million, respectively, and are 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 aggregates to $1.4 million, for the years ended December 31, 2014 and 2013, respectively, and $1.3 million for the year ended December 31, 2012.
	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 $8.0 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 into 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. The said 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 the years ended December 31, 2014 and December 31, 2013. 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 the years ended December 31, 2014 and December 31, 2013 is $5.3 million, and is included in other assets in the Company’s consolidated balance sheet.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income (Loss) Note [Text Block]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)
	The following table details the components of accumulated other comprehensive income (loss) of the Parent Company and the Operating Partnership as of and for the three years ended December 31, 2014 (in thousands):
	Parent Company	Cash Flow
		Hedges
	Balance at January 1, 2012	$	(6,079	)
	Change during year	(7,338		)
	Non-controlling interest — consolidated real estate venture partner’s share of unrealized (gains)/losses on derivative financial instruments	187
	Settlement of interest rate swaps	(2,985		)
	Reclassification adjustments for (gains)/losses reclassified into operations	297
	Balance at December 31, 2012	$	(15,918	)
	Change during year	12,789
	Non-controlling interest — consolidated real estate venture partner’s share of unrealized (gains)/losses on derivative financial instruments	(152		)
	Reclassification adjustments for (gains)/losses reclassified into operations	286
	Balance at December 31, 2013	$	(2,995	)
	Change during year	(1,190		)
	Non-controlling interest — consolidated real estate venture partner’s share of unrealized (gains)/losses on derivative financial instruments	18
	Settlement of interest rate swaps	(828		)
	Reclassification adjustments for (gains)/losses reclassified into operations	388
	Balance at December 31, 2014	$	(4,607	)
	Operating Partnership	Cash Flow
		Hedges
	Balance at January 1, 2012	$	(6,426	)
	Change during year	(7,338		)
	Reclassification adjustments for (gains)/losses reclassified into operations	297
	Settlement of interest rate swaps	(2,985		)
	Balance at December 31, 2012	$	(16,452	)
	Change during year	12,789
	Reclassification adjustments for (gains)/losses reclassified into operations	286
	Balance at December 31, 2013	$	(3,377	)
	Change during year	(1,190		)
	Settlement of interest rate swaps	(828		)
	Reclassification adjustments for (gains)/losses reclassified into operations	388
	Balance at December 31, 2014	$	(5,007	)
	Over time, the unrealized gains and losses held in Accumulated Other Comprehensive Income (“AOCI”) will be reclassified to interest expense when the related hedged items are recognized in earnings. The current balance held in AOCI is expected to be reclassified to interest expense for realized losses on forecasted debt transactions over the related term of the debt obligation, as applicable.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION
	During the year ended December 31, 2014, the Company was managing its portfolio within seven 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 and Camden 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. On April 3, 2014, the Company contributed Four Points Centre to the Austin Venture. After contributing this property, the Company does not wholly own any operating properties in Austin, Texas (For additional information, see Note 4, "Investment In Unconsolidated Ventures"). The California segment includes properties in Oakland, Concord, and Carlsbad. 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.
	The following tables provide selected asset information and results of operations of the Company's reportable segments for the three years ended December 31, 2014, 2013 and 2012 (in thousands):
	Real estate investments, at cost:
			31-Dec-14			31-Dec-13			31-Dec-12
	Philadelphia CBD (a)		$	1,338,655		$	1,300,666		$	988,590
	Pennsylvania Suburbs		1,178,470			1,199,105			1,178,730
	Metropolitan Washington, D.C.		1,183,652			1,214,965			1,193,200
	New Jersey/Delaware		392,581			414,716			546,644
	Richmond, Virginia		317,076			310,397			309,923
	California		193,258			192,584			223,736
	Austin, Texas (b)		—			36,856			285,346
			$	4,603,692		$	4,669,289		$	4,726,169
	Assets held for sale (c)		27,436			—			—
	Operating Properties		$	4,631,128		$	4,669,289		$	4,726,169
	Corporate
	Construction-in-progress		$	201,360		$	74,174		$	48,950
	Land inventory		$	90,603		$	93,351		$	102,439
	(a)	On December 19, 2013, the Company acquired 99% of the common interests in the One and Two Common Square partnerships. See Note 3, "Real Estate Investments," for further information on the acquisition.
	(b)	On April 3, 2014, the Company contributed two three-story, Class A office buildings, containing an aggregate of 192,396 net rentable square feet, known as Four Points Centre in Austin, Texas to the Austin Venture. See Note 3, "Real Estate Investments," for further information on the contribution.
	(c)	On December 31, 2014, the Company was actively marketing for sale of its Atrium I and Libertyview properties, comprised of two office properties located in the New Jersey/Delaware segment. As of December 31, 2014 the properties were classified as held for sale on the consolidated balance sheet. See Note 3, "Real Estate Investments," for further information. The sale is not classified as a significant disposition under the accounting guidance for discontinued operations. Accordingly, the real estate investments remained in the New Jersey/Delaware segment as of December 31, 2014.
		Years ended
		December 31,
		2014									2013									2012
		Total revenue			Operating expenses (b)			Net operating income			Total revenue			Operating expenses (b)			Net operating income			Total revenue		Operating expenses			Net Operating income
	Philadelphia CBD	$	201,809		$	(75,262	)	$	126,547		$	146,081		$	(55,702	)	$	90,379		$	131,592	$	(50,787	)	$	80,805
	Pennsylvania Suburbs	160,630			(55,062		)	105,568			153,426			(54,506		)	98,920			150,075		(52,657		)	97,418
	Metropolitan Washington, D.C.	113,834			(43,399		)	70,435			116,048			(42,641		)	73,407			107,656		(41,485		)	66,171
	New Jersey/Delaware	60,403			(31,650		)	28,753			60,262			(29,981		)	30,281			59,671		(28,506		)	31,165
	Richmond, Virginia	34,180			(15,399		)	18,781			35,058			(14,916		)	20,142			35,701		(14,484		)	21,217
	California	19,388			(10,165		)	9,223			18,369			(9,411		)	8,958			17,463		(9,043		)	8,420
	Austin, Texas (a)	5,610			(3,223		)	2,387			31,451			(13,298		)	18,153			32,379		(13,951		)	18,428
	Corporate	1,128			(1,805		)	(677		)	1,515			(1,314		)	201			1,142		65			1,207
	Operating Properties	$	596,982		$	(235,965	)	$	361,017		$	562,210		$	(221,769	)	$	340,441		$	535,679	$	(210,848	)	$	324,831
	(a)	On April 3, 2014, the Company contributed two three-story, Class A office buildings, containing an aggregate of 192,396 net rentable square feet, known as Four Points Centre in Austin, Texas to the Austin Venture. See Note 3, "Real Estate Investments," for further information on the contribution. Accordingly, the Company's 50% interest in the financial results of this property for the period subsequent to April 3, 2014 is reported as a component of 'Equity in income (loss) of real estate ventures' in the Company's consolidated statements of operations and, as a result, no longer included as a component of net operating income.
	(b)	Includes property operating expense, real estate taxes and third party management expense.
	Unconsolidated real estate ventures:
		Investment in real estate ventures, at equity									Equity in income (loss) of real estate ventures
		As of									Years ended December 31,
		31-Dec-14			31-Dec-13			31-Dec-12			2014			2013			2012
	Philadelphia CBD (a)	$	27,137		$	19,975		$	27,859		$	46		$	1,547		$	1,113
	Pennsylvania Suburbs	17,385			17,272			33,160			(777		)	925			520
	Metropolitan Washington, D.C.	73,127			59,905			49,169			(317		)	130			(648		)
	New Jersey/Delaware	—			—			17,294			989			1,245			1,803
	Richmond, Virginia	1,574			1,400			1,245			349			381			269
	Austin, Texas (b) (c)	105,781			81,960			64,828			(1,080		)	(564		)	(316		)
	Total	$	225,004		$	180,512		$	193,555		$	(790	)	$	3,664		$	2,741
	(a)	During the fourth quarter of 2014, the Company made an additional $5.2 million capital contribution to 1919 Ventures. See Note 4, "Investment In Unconsolidated Ventures," for further information on this transaction.
	(b)	Investment in real estate ventures does not include the $1.2 million negative investment balance in one real estate venture as of December 31, 2014, which is included in other liabilities.
	(c)	On April 3, 2014, the Company contributed Four Points Centre to an unconsolidated real estate venture. On July 31, 2014, the Austin Venture completed the acquisition of the Crossings at Lakeline. On October 17, 2014, the Austin Venture acquired River Place. See Note 4, "Investment In Unconsolidated Ventures," for further information on these acquisitions.
	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 its 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. The following is a reconciliation of consolidated NOI to consolidated net income (loss), as defined by GAAP:
		Years Ended December 31,
		2014			2013			2012
	Consolidated net operating income	$	361,017		$	340,441		$	324,831
	Less:
	Interest expense	(124,329		)	(121,937		)	(132,939		)
	Interest expense - amortization of deferred financing costs	(5,148		)	(4,676		)	(6,208		)
	Interest expense - financing obligation	(1,144		)	(972		)	(850		)
	Depreciation and amortization	(208,569		)	(197,021		)	(188,382		)
	General and administrative expenses	(26,779		)	(27,628		)	(25,413		)
	Plus:
	Interest income	3,974			1,044			3,008
	Historic tax credit transaction income	11,853			11,853			11,840
	Recognized hedge activity	(828		)	—			(2,985		)
Equity in income (loss) of real estate ventures	(790		)	3,664			2,741
Net gain from remeasurement of investments in real estate ventures	458			6,866			—
Net gain on sales of interests in real estate	4,901			—			—
Net gain (loss) on sale of undepreciated real estate	1,184			(137		)	—
Net (loss) gain on real estate venture transactions	(417		)	29,604			(950		)
Provision for impairment on assets held for sale	(1,765		)	—			—
Loss on early extinguishment of debt	(7,594		)	(2,119		)	(22,002		)
Income (loss) from continuing operations	6,024			38,982			(37,309		)
Income from discontinued operations	918			4,207			43,838
Net income	$	6,942		$	43,189		$	6,529

Operating_Leases

Operating Leases	12 Months Ended
	Dec. 31, 2014
Leases, Operating [Abstract]
Operating Leases of Lessor Disclosure [Text Block]	OPERATING LEASES
	The Company leases properties to tenants under operating leases with various expiration dates extending to 2030. Minimum future rentals on non-cancelable leases at December 31, 2014 are as follows (in thousands):
	Year	Minimum Rent
	2015	$	461,215
	2016	443,383
	2017	411,288
	2018	362,370
	2019	315,196
	Thereafter	1,515,750
	Total minimum future rentals presented above do not include amounts to be received as tenant reimbursements for operating costs.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	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 will establish reserves for specific legal proceedings when we determine that the likelihood of an unfavorable outcome is probable and when the amount of loss is reasonably estimable. 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.
	Letters-of-Credit
	Under certain mortgages, the Company has funded required leasing and capital reserve accounts for the benefit of the mortgage lenders with letters-of-credit. There were no associated letters-of-credit at December 31, 2014 and December 31, 2013. Certain of the tenant rents at properties that secure these mortgage loans are deposited into the loan servicer’s depository accounts, which are used to fund debt service, operating expenses, capital expenditures and the escrow and reserve accounts, as necessary. Any excess cash is included in cash and cash equivalents.
	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-cancellable 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 7 to 75 years. Minimum future rental payments on non-cancelable leases at December 31, 2014 are as follows (in thousands):
	Year	Minimum Rent
	2015	$	1,378
	2016	1,378
	2017	1,378
	2018	1,378
	2019	1,378
	Thereafter	57,114
	Total	$	64,004
	The Company obtained ground tenancy rights related to two properties in Philadelphia, Pennsylvania, which provide for contingent rent participation by the lessor in certain capital transactions and net operating cash flows of the properties 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.
	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 December 31, 2014, the Company had a balance of $1.8 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 entered into a settlement agreement with the IRS which will not result in a material liability for the Company for federal income taxes. The contributor of partnership interests in the 2004 transaction has agreed not to assert a claim against the Company 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 December 31, 2014: 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. Similarly, as part of the 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to not sell these two properties in certain taxable transactions prior to October 20, 2021 without the holder’s consent.
	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. As part of our 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to maintain qualifying mortgage debt through October 20, 2021, in the amounts of not less than $125.0 million on One Commerce Square and $100.0 million on Two Commerce Square. Similarly, the Company has agreements in place with other contributors of assets that obligate it to maintain debt available for them to guaranty.
	In connection with the development of the IRS Philadelphia Campus and the Cira South Garage, during 2008, the Company entered into a historic tax credit and new markets 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 therefore, require a refund to US Bancorp or a 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 remaining compliance periods for its tax credit arrangements runs 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 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.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS
	On January 30, 2015, the Austin Venture closed on a mortgage loan with a non-affiliated institutional lender, and the proceeds of this loan were applied to repay in full our $88.0 million short-term loan related to the acquisition of River Place. See Note 4, "Investment In Unconsolidated Ventures," for further information regarding this acquisition.
	On January 8, 2015, the Company sold two office properties known as Atrium I, which includes 99,668 square feet of rentable space located in Mt Laurel, New Jersey and Libertyview, which includes 121,737 square feet of rentable space located in Cherry Hill, New Jersey, for a total sales price of $28.3 million resulting in a gain on sale of $9.0 million after closing and other transaction related costs.
	The Company has evaluated subsequent events through the date the financial statements were issued.

Summary_of_Quarterly_Results

Summary of Quarterly Results	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	SUMMARY OF QUARTERLY RESULTS (UNAUDITED)
	The following is a summary of quarterly financial information as of and for the years ended December 31, 2014 and 2013 (in thousands, except per share data):
		1st			2nd		3rd		4th
		Quarter			Quarter		Quarter		Quarter
	2014
	Total revenue	$	152,114		$	150,500	$	146,558	$	147,810
	Net income (loss)	(2,245		)	2,174		8,882		(1,869		)
	Net income (loss) allocated to Common Shares	(4,041		)	385		6,967		(3,585		)
	Basic earnings (loss) per Common Share	$	(0.03	)	$	—	$	0.04	$	(0.02	)
	Diluted earnings (loss) per Common Share	$	(0.03	)	$	—	$	0.04	$	(0.02	)
	2013
	Total revenue	$	139,554		$	140,664	$	143,354	$	138,658
	Net income	3,919			7,180		11,088		21,002
	Net income allocated to Common Shares	2,058			5,308		9,173		18,975
	Basic earnings per Common Share	$	0.01		$	0.03	$	0.06	$	0.12
	Diluted earnings per Common Share	$	0.01		$	0.03	$	0.06	$	0.12
	The summation of quarterly earnings per share amounts do not necessarily equal the full year amounts due to rounding. The above information was updated to reclassify amounts previously reported to reflect discontinued operations. See Note 2, "Summary Of Significant Accounting Policies," and Note 10, "Discontinued Operations."

Schedule_II_Valuation_and_Qual

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]	Brandywine Realty Trust and Brandywine Operating Partnership, L.P.
	Schedule II
	Valuation and Qualifying Accounts
	(in thousands)
	Description		Balance at		Additions		Deductions (1)		Balance
			Beginning						at End
			of Year						of Year
	Allowance for doubtful accounts:
	Year-ended December 31, 2014		$	16,248	$	790	$	1,691	$	15,347
	Year-ended December 31, 2013		$	16,646	$	1,384	$	1,782	$	16,248
	Year-ended December 31, 2012		$	15,485	$	1,891	$	730	$	16,646
	-1	Deductions represent amounts that the Company had fully reserved for in prior years and pursuit of collection of such amounts was ceased during the year.

Schedule_III_Real_Estate_and_A

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real Estate and Accumulated Depreciation Disclosure [Text Block]
																				Gross Amount at Which Carried
										Initial Cost										31-Dec-14
	Property Name		City		State		Encumbrances at			Land			Building and			Net				Land			Building and		Total (b)			Accumulated		Year of	Year	Depreciable
							December 31,						Improvements			Improvements							Improvements					Depreciation at		Construction	Acquired	Life
							2014 (a)									(Retirements)												December 31,
																Since												2014 (c)
																Acquisition
	PENNSYLVANIA SUBURBS
	400 Berwyn Park		Berwyn		PA		—			2,657			4,462			14,011				2,657			18,473		21,130			6,255		1999	1999	40
	300 Berwyn Park		Berwyn		PA		—			2,206			13,422			3,800				2,206			17,222		19,428			8,280		1989	1997	40
	1050 Westlakes Drive		Berwyn		PA		—			2,611			10,445			5,047				2,611			15,492		18,103			7,984		1984	1999	40
	1200 Swedesford Road		Berwyn		PA		—			2,595			11,809			3,534				2,595			15,343		17,938			6,457		1994	2001	40
	200 Berwyn Park		Berwyn		PA		—			1,533			9,460			2,466				1,533			11,926		13,459			5,751		1987	1997	40
	1180 Swedesford Road		Berwyn		PA		—			2,086			8,342			2,979				2,086			11,321		13,407			3,441		1987	2001	40
	100 Berwyn Park		Berwyn		PA		—			1,180			7,290			2,228				1,180			9,518		10,698			4,661		1986	1997	40
	1160 Swedesford Road		Berwyn		PA		—			1,781			7,124			4,255				2,045			11,115		13,160			2,961		1986	2001	40
	1100 Cassett Road		Berwyn		PA		—			1,695			6,779			1,269				1,695			8,048		9,743			2,561		1997	2001	40
	980 Harvest Drive		Blue Bell		PA		—			2,079			8,315			736				2,079			9,051		11,130			2,935		1988	2002	40
	910 Harvest Drive		Blue Bell		PA		—			1,224			8,645			(730		)		1,224			7,915		9,139			4,394		1990	1998	40
	925 Harvest Drive		Blue Bell		PA		—			1,671			6,606			993				1,671			7,599		9,270			3,480		1990	1998	40
	920 Harvest Drive		Blue Bell		PA		—			1,209			6,595			(684		)		1,209			5,911		7,120			3,134		1990	1998	40
	181 Washington Street		Conshohocken		PA		—			6,927			14,722			786				6,927			15,508		22,435			698		1999	2013	40
	426 Lancaster Avenue		Devon		PA		—			1,689			6,756			376				1,689			7,132		8,821			3,431		1990	1998	40
	52 Swedesford Square		East Whiteland Twp.		PA		—			4,241			16,579			3,262				4,241			19,841		24,082			8,392		1988	1998	40
	One Progress Drive		Horsham		PA		—			1,399			5,629			5,202				1,399			10,831		12,230			4,457		1986	1996	40
	500 Enterprise Drive		Horsham		PA		—			1,303			5,188			3,743				1,303			8,931		10,234			4,098		1990	1996	40
	640 Freedom Business Center		King Of Prussia		PA		—			4,222			16,891			4,686				4,222			21,577		25,799			9,535		1991	1998	40
	555 Croton Road		King of Prussia		PA		—			4,486			17,943			1,412				4,486			19,355		23,841			6,779		1999	2001	40
	630 Allendale Road		King of Prussia		PA		—			2,836			4,028			12,484				2,898			16,450		19,348			5,778		2000	2000	40
	620 Freedom Business Center		King Of Prussia		PA		—			2,770			11,014			3,375				2,770			14,389		17,159			7,515		1986	1998	40
	1000 First Avenue		King Of Prussia		PA		—			2,772			10,936			2,117				2,772			13,053		15,825			5,894		1980	1998	40
	1060 First Avenue		King Of Prussia		PA		—			2,712			10,953			4,522				2,712			15,475		18,187			6,646		1987	1998	40
	630 Freedom Business Center		King Of Prussia		PA		—			2,773			11,144			2,343				2,773			13,487		16,260			6,300		1989	1998	40
	1020 First Avenue		King Of Prussia		PA		—			2,168			8,576			7,617				2,168			16,193		18,361			6,766		1984	1998	40
	1040 First Avenue		King Of Prussia		PA		—			2,860			11,282			6,080				2,860			17,362		20,222			5,460		1985	1998	40
	610 Freedom Business Center		King Of Prussia		PA		—			2,017			8,070			2,393				2,017			10,463		12,480			4,883		1985	1998	40
	650 Park Avenue		King Of Prussia		PA		—			1,916			4,378			1,701				1,916			6,079		7,995			2,920		1968	1998	40
	500 North Gulph Road		King Of Prussia		PA		—			1,303			5,201			1,522				1,303			6,723		8,026			3,390		1979	1996	40
	741 First Avenue		King Of Prussia		PA		—			1,287			5,151			11				1,287			5,162		6,449			2,363		1966	1998	40
	751-761 Fifth Avenue		King Of Prussia		PA		—			1,097			4,391			31				1,097			4,422		5,519			2,021		1967	1998	40
	620 Allendale Road		King Of Prussia		PA		—			1,020			3,839			658				1,020			4,497		5,517			2,008		1961	1998	40
	600 Park Avenue		King Of Prussia		PA		—			1,012			4,048			385				1,012			4,433		5,445			2,045		1964	1998	40
																				Gross Amount at Which Carried
										Initial Cost										31-Dec-14
	Property Name		City		State		Encumbrances at			Land			Building and			Net				Land			Building and		Total (b)			Accumulated		Year of	Year	Depreciable
							December 31,						Improvements			Improvements							Improvements					Depreciation at		Construction	Acquired	Life
							2014 (a)									(Retirements)												December 31,
																Since												2014 (c)
																Acquisition
	660 Allendale Road		King Of Prussia		PA		$	—		$	396		$	948		$	2,957			$	1,085		$	3,216	$	4,301		$	921	2011	1998	40
	640 Allendale Road		King of Prussia		PA		—			439			432			1,580				439			2,012		2,451			802		2000	2000	40
	14 Campus Boulevard		Newtown Square		PA		—			2,244			4,217			1,533				2,244			5,750		7,994			3,322		1998	1998	40
	17 Campus Boulevard		Newtown Square		PA		—			1,108			5,155			(374		)		1,108			4,781		5,889			1,728		2001	1997	40
	11 Campus Boulevard		Newtown Square		PA		—			1,112			4,067			1,006				1,112			5,073		6,185			1,967		1998	1999	40
	15 Campus Boulevard		Newtown Square		PA		—			1,164			3,896			249				1,164			4,145		5,309			1,394		2002	2000	40
	18 Campus Boulevard		Newtown Square		PA		—			787			3,312			(77		)		787			3,235		4,022			1,631		1990	1996	40
	401 Plymouth Road		Plymouth Meeting		PA		—			6,198			16,131			16,130				6,198			32,261		38,459			9,982		2001	2000	40
	4000 Chemical Road		Plymouth Meeting		PA		—			4,373			24,546			1,467				4,373			26,013		30,386			4,864		2006	2001	40
	610 West Germantown Pike		Plymouth Meeting		PA		—			3,651			14,514			3,357				3,651			17,871		21,522			5,892		1987	2002	40
	600 West Germantown Pike		Plymouth Meeting		PA		—			3,652			15,288			1,609				3,652			16,897		20,549			5,659		1986	2002	40
	630 West Germantown Pike		Plymouth Meeting		PA		—			3,558			14,743			1,902				3,558			16,645		20,203			5,994		1988	2002	40
	620 West Germantown Pike		Plymouth Meeting		PA		—			3,572			14,435			1,339				3,572			15,774		19,346			5,378		1990	2002	40
	660 West Germantown Pike		Plymouth Meeting		PA		—			3,694			5,487			18,484				5,404			22,261		27,665			1,436		1987	2012	30
2240/2250 Butler Pike		Plymouth Meeting		PA		—			1,104			4,627			1,312				1,104			5,939		7,043			3,596		1984	1996	40
2260 Butler Pike		Plymouth Meeting		PA		—			661			2,727			2,115				661			4,842		5,503			2,165		1984	1996	40
120 West Germantown Pike		Plymouth Meeting		PA		—			685			2,773			729				685			3,502		4,187			1,767		1984	1996	40
140 West Germantown Pike		Plymouth Meeting		PA		—			481			1,976			282				481			2,258		2,739			1,079		1984	1996	40
351 Plymouth Road		Plymouth Meeting		PA		—			1,043			555			—				1,043			555		1,598			135		N/A	2000	40
150 Radnor Chester Road		Radnor		PA		—			11,925			36,986			12,549				11,897			49,563		61,460			16,431		1983	2004	29
One Radnor Corporate Center		Radnor		PA		—			7,323			28,613			23,182				7,323			51,795		59,118			18,406		1998	2004	29
201 King of Prussia Road		Radnor		PA		—			8,956			29,811			5,070				8,949			34,888		43,837			15,445		2001	2004	25
555 Lancaster Avenue		Radnor		PA		—		8,014			16,508		16,854		8,609			32,767			41,376		12,563	1973		2004	24
Four Radnor Corporate Center		Radnor		PA		—		5,406			21,390		8,501		5,705			29,592			35,297		10,480	1995		2004	30
Five Radnor Corporate Center		Radnor		PA		—		6,506			25,525		5,455		6,578			30,908			37,486		8,024	1998		2004	38
Three Radnor Corporate Center		Radnor		PA		—		4,773			17,961		2,645		4,791			20,588			25,379		8,094	1998		2004	29
Two Radnor Corporate Center		Radnor		PA		—		3,937			15,484		3,888		3,942			19,367			23,309		6,882	1998		2004	29
130 Radnor Chester Road		Radnor		PA		—		2,573			8,338		3,483		2,567			11,827			14,394		4,357	1983		2004	25
170 Radnor Chester Road		Radnor		PA		—		2,514			8,147		1,718		2,509			9,870			12,379		3,051	1983		2004	25
200 Radnor Chester Road		Radnor		PA		—		3,366			—		3,675		3,366			3,675			7,041		113	2014		2005	40
															Gross Amount at Which Carried
								Initial Cost							31-Dec-14
Property Name		City		State		Encumbrances at		Land			Building and		Net		Land			Building and			Total (b)		Accumulated	Year of		Year	Depreciable
						December 31,					Improvements		Improvements					Improvements					Depreciation at	Construction		Acquired	Life
						2014 (a)							(Retirements)										December 31,
													Since										2014 (c)
													Acquisition
101 West Elm Street		W. Conshohocken		PA		—		6,251			25,209		3,189		6,251			28,398			34,649		7,640	1999		2005	40
1 West Elm Street		W. Conshohocken		PA		—		3,557			14,249		3,876		3,557			18,125			21,682		4,204	1999		2005	40
595 East Swedesford Road		Wayne		PA		—		2,729			10,917		2,307		2,729			13,224			15,953		4,464	1998		2003	40
575 East Swedesford Road		Wayne		PA		—		2,178			8,712		1,681		2,178			10,393			12,571		3,692	1985		2003	40
565 East Swedesford Road		Wayne		PA		—		1,872			7,489		1,744		1,872			9,233			11,105		3,166	1984		2003	40
585 East Swedesford Road		Wayne		PA		—		1,350			5,401		1,350		1,350			6,751			8,101		1,551	1998		2003	40
PHILADELPHIA CBD
2970 Market Street		Philadelphia		PA		184,442		22,430			217,763		12,021		22,430			229,784			252,214		27,560	2010		2007	40
2929 Arch Street		Philadelphia		PA		—		—			208,570		29,302		12,586			225,286			237,872		85,000	2005		N/A	40
1717 Arch Street		Philadelphia		PA		—		—			98,188		66,550		25,195			139,543			164,738		19,000	1990		2010	40
2001 Market Street		Philadelphia		PA		112,000		15,323			120,842		2,125		15,323			122,967			138,290		3,371	1992		2013	40
130 North 18th Street		Philadelphia		PA		—		14,496			107,736		17,397		14,473			125,156			139,629		37,755	1998		2004	34
100 North 18th Street		Philadelphia		PA		87,767		16,066			100,255		10,925		16,066			111,180			127,246		35,435	1988		2004	36
2005 Market Street		Philadelphia		PA		123,205		15,161			122,486		(11,726	)	15,161			110,760			125,921		2,959	1987		2013	40
2930 Chestnut Street		Philadelphia		PA		37,765		—			76,008		2,644		—			78,652			78,652		8,677	2010		N/A	40
1900 Market Street		Philadelphia		PA		—		7,768			17,263		481		7,768			17,744			25,512		1,246	1981		2012	30
3020 Market Street		Philadelphia		PA		—		—			21,417		6,225		—			27,642			27,642		3,260	1959		2011	26
101 - 103 Juniper Street		Philadelphia		PA		—		—			14,401		324		478			14,247			14,725		1,865	2010		2006	40
Philadelphia Marine Center		Philadelphia		PA		—		532			2,196		3,444		628			5,544			6,172		2,408	Various		1998	40
METROPOLITAN WASHINGTON, D.C.
11720 Beltsville Drive		Beltsville		MD		—		3,831			16,661		3,399		3,904			19,987			23,891		5,887	1987		2006	46
11700 Beltsville Drive		Beltsville		MD		—		2,808			12,081		293		2,863			12,319			15,182		2,702	1981		2006	46
11710 Beltsville Drive		Beltsville		MD		—		2,278			11,100		(814	)	2,321			10,243			12,564		2,370	1987		2006	46
6600 Rockledge Drive		Bethesda		MD		—		—			37,421		11,303		—			48,724			48,724		15,070	1981		2006	50
11740 Beltsville Drive		Bethesda		MD		—		198			870		42		202			908			1,110		211	1987		2006	46
12015 Lee Jackson Memorial Highway		Fairfax		VA		—		3,770			22,895		3,987		3,841			26,811			30,652		7,188	1985		2006	42
11781 Lee Jackson Memorial Highway		Fairfax		VA		—		3,246			19,836		567		3,307			20,342			23,649		4,748	1982		2006	40
4401 Fair Lakes Court		Fairfax		VA		—		1,569			11,982		247		1,599			12,199			13,798		2,456	1988		2006	52
3141 Fairview Park Drive (d)		Falls Church		VA		21,242		5,918			40,981		12,017		7,080			51,836			58,916		10,264	1988		2006	51
2340 Dulles Corner Boulevard		Herndon		VA		—		16,345			65,379		18,280		16,129			83,875			100,004		28,064	1987		2006	40
2291 Wood Oak Drive		Herndon		VA		—		8,243			52,413		13,499		8,782			65,373			74,155		13,524	1999		2006	55
196/198 Van Buren Street		Herndon		VA		—		7,931			43,812		9,040		8,348			52,435			60,783		10,308	1991		2006	53
2251 Corporate Park Drive		Herndon		VA		—		11,472			45,893		2,276		11,472			48,169			59,641		9,758	2000		2006	40
2355 Dulles Corner Boulevard		Herndon		VA		—		10,365			43,876		4,648		10,365			48,524			58,889		12,675	1988		2006	40
2411 Dulles Corner Park		Herndon		VA		—		7,279			46,340		117		7,417			46,319			53,736		8,645	1990		2006	50
13880 Dulles Corner Lane		Herndon		VA		—		7,236			39,213		3,369		7,373			42,445			49,818		7,824	1997		2006	55
															Gross Amount at Which Carried
								Initial Cost							31-Dec-14
Property Name		City		State		Encumbrances at		Land			Building and		Net		Land			Building and			Total (b)		Accumulated	Year of		Year	Depreciable
						December 31,					Improvements		Improvements					Improvements					Depreciation at	Construction		Acquired	Life
						2014 (a)							(Retirements)										December 31,
													Since										2014 (c)
													Acquisition
2121 Cooperative Way		Herndon		VA		—		5,598			38,639		2,532		5,795			40,974			46,769		7,665	2000		2006	54
2201 Cooperative Way		Herndon		VA		—		4,809			34,093		4,513		4,809			38,606			43,415		7,153	1990		2006	54
13825 Sunrise Valley Drive		Herndon		VA		—		3,794			19,365		2,121		3,866			21,414			25,280		4,441	1989		2006	46
1676 International Drive		Mclean		VA		58,470		18,437			97,538		3,183		18,785			100,373			119,158		16,619	1999		2006	55
8260 Greensboro Drive		Mclean		VA		31,043		7,952			33,964		1,641		8,102			35,455			43,557		7,320	1980		2006	52
2273 Research Boulevard		Rockville		MD		—		5,167			31,110		3,764		5,237			34,804			40,041		10,191	1999		2006	45
2275 Research Boulevard		Rockville		MD		—		5,059			29,668		6,479		5,154			36,052			41,206		7,672	1990		2006	45
2277 Research Boulevard		Rockville		MD		—		4,649			26,952		695		4,733			27,563			32,296		5,724	1986		2006	45
1900 Gallows Road		Vienna		VA		—		7,797			47,817		10,849		7,944			58,519			66,463		11,008	1989		2006	52
8521 Leesburg Pike		Vienna		VA		—		4,316			30,885		4,858		4,397			35,662			40,059		6,399	1984		2006	51
NEW JERSEY/DELAWARE
457 Haddonfield Road (e)		Cherry Hill		NJ		—		2,142			9,120		1,402		2,142			10,522			12,664		5,273	1990		1996	40
200 Lake Drive East		Cherry Hill		NJ		—		2,069			8,275		1,328		2,069			9,603			11,672		3,635	1989		2001	40
220 Lake Drive East		Cherry Hill		NJ		—		2,144			8,798		825		2,144			9,623			11,767		3,490	1988		2001	40
210 Lake Drive East		Cherry Hill		NJ		—		1,645			6,579		1,917		1,645			8,496			10,141		2,812	1986		2001	40
20 East Clementon Road		Gibbsboro		NJ		—		769			3,055		480		769			3,535			4,304		1,682	1986		1997	40
10 Foster Avenue		Gibbsboro		NJ		—		244			971		78		244			1,049			1,293		497	1983		1997	40
7 Foster Avenue		Gibbsboro		NJ		—		231			921		123		231			1,044			1,275		475	1983		1997	40
50 East Clementon Road		Gibbsboro		NJ		—		114			964		653		114			1,617			1,731		483	1986		1997	40
2 Foster Avenue		Gibbsboro		NJ		—		185			730		16		185			746			931		351	1974		1997	40
4 Foster Avenue		Gibbsboro		NJ		—		183			726		16		183			742			925		343	1974		1997	40
1 Foster Avenue		Gibbsboro		NJ		—		93			364		57		93			421			514		215	1972		1997	40
5 U.S. Avenue		Gibbsboro		NJ		—		21			81		3		21			84			105		39	1987		1997	40
5 Foster Avenue		Gibbsboro		NJ		—		9			32		26		9			58			67		28	1968		1997	40
Two Eves Drive		Marlton		NJ		—		818			3,461		234		818			3,695			4,513		1,825	1987		1997	40
Five Eves Drive		Marlton		NJ		—		703			2,819		665		703			3,484			4,187		1,643	1986		1997	40
Four B Eves Drive		Marlton		NJ		—		588			2,369		420		588			2,789			3,377		1,449	1987		1997	40
Four A Eves Drive		Marlton		NJ		—		539			2,168		322		539			2,490			3,029		1,122	1987		1997	40
308 Harper Drive		Moorestown		NJ		—		1,643			6,663		739		1,643			7,402			9,045		3,258	1976		1998	40
1120 Executive Boulevard		Mt. Laurel		NJ		—		2,074			8,415		4,398		2,074			12,813			14,887		5,143	1987		1997	40
10000 Midlantic Drive		Mt. Laurel		NJ		—		3,206			12,857		4,228		3,206			17,085			20,291		7,138	1990		1997	40
700 East Gate Drive		Mt. Laurel		NJ		—		3,569			14,436		2,243		3,569			16,679			20,248		7,576	1984		1998	40
15000 Midlantic Drive		Mt. Laurel		NJ		—		3,061			12,254		1,619		3,061			13,873			16,934		6,518	1991		1997	40
1000 Howard Boulevard		Mt. Laurel		NJ		—		2,297			9,288		3,922		2,297			13,210			15,507		5,900	1988		1997	40
1000 Atrium Way (e)		Mt. Laurel		NJ		—		2,061			8,180		4,531		2,061			12,711			14,772		5,894	1989		1997	40
2000 Midlantic Drive		Mt. Laurel		NJ		—		2,202			8,823		2,970		2,202			11,793			13,995		5,349	1989		1997	40
701 East Gate Drive		Mt. Laurel		NJ		—		1,736			6,877		1,768		1,736			8,645			10,381		3,715	1986		1998	40
															Gross Amount at Which Carried
								Initial Cost							31-Dec-14
Property Name		City		State		Encumbrances at		Land			Building and		Net		Land			Building and			Total (b)		Accumulated	Year of		Year	Depreciable
						December 31,					Improvements		Improvements					Improvements					Depreciation at	Construction		Acquired	Life
						2014(a)							(Retirements)										December 31,
													Since										2014 (c)
													Acquisition
9000 Midlantic Drive		Mt. Laurel		NJ		—		1,472			5,895		2,185		1,472			8,080			9,552		3,503	1989		1997	40
307 Fellowship Drive		Mt. Laurel		NJ		—		1,565			6,342		1,517		1,565			7,859			9,424		3,472	1981		1998	40
305 Fellowship Drive		Mt. Laurel		NJ		—		1,421			5,768		1,631		1,421			7,399			8,820		3,122	1980		1998	40
303 Fellowship Drive		Mt. Laurel		NJ		—		1,493			6,055		851		1,493			6,906			8,399		3,114	1979		1998	40
309 Fellowship Drive		Mt. Laurel		NJ		—		1,518			6,154		780		1,518			6,934			8,452		3,070	1982		1998	40
1000 Bishops Gate		Mt. Laurel		NJ		—		934			6,287		(647	)	934			5,640			6,574		1,534	2005		2000	40
161 Gaither Drive		Mt. Laurel		NJ		—		1,016			4,064		731		1,016			4,795			5,811		1,855	1987		2001	40
815 East Gate Drive		Mt. Laurel		NJ		—		636			2,584		550		636			3,134			3,770		1,436	1986		1998	40
4000 Midlantic Drive		Mt. Laurel		NJ		—		714			5,085		(1,833	)	714			3,252			3,966		1,531	1998		1997	40
817 East Gate Drive		Mt. Laurel		NJ		—		611			2,426		263		611			2,689			3,300		1,159	1986		1998	40
400 Commerce Drive		Newark		DE		—		2,528			9,220		1,086		2,528			10,306			12,834		3,911	1997		2002	40
100 Commerce Drive		Newark		DE		—		1,160			4,633		859		1,160			5,492			6,652		2,595	1989		1997	40
200 Commerce Drive		Newark		DE		—		911			4,414		1,018		911			5,432			6,343		2,180	1998		2002	40
Main Street - Plaza 1000		Voorhees		NJ		—		2,732			10,942		2,933		2,732			13,875			16,607		13,211	1988		1997	40
Main Street - Piazza		Voorhees		NJ		—		696			2,802		3,034		696			5,836			6,532		1,714	1990		1997	40
Main Street - Promenade		Voorhees		NJ		—		531			2,052		444		531			2,496			3,027		1,218	1988		1997	40
920 North King Street		Wilmington		DE		—		6,141			21,140		2,669		6,141			23,809			29,950		7,669	1989		2004	30
300 Delaware Avenue		Wilmington		DE		—		6,368			13,739		2,548		6,368			16,287			22,655		6,642	1989		2004	23
Two Righter Parkway		Wilmington		DE		—		2,802			11,217		6,172		2,802			17,389			20,191		4,822	1987		2001	40
One Righter Parkway		Wilmington		DE		—		2,545			10,195		5,864		2,545			16,059			18,604		8,839	1989		1996	40
RICHMOND
4364 South Alston Avenue		Durham		NC		—		1,622			6,419		1,357		1,581			7,817			9,398		3,174	1985		1998	40
4805 Lake Brooke Drive		Glen Allen		VA		—		1,640			6,567		1,537		1,640			8,104			9,744		3,243	1996		1998	40
Overlook I		Glen Allen		VA		—		748			3,976		599		790			4,533			5,323		677	1998		2011	40
Overlook II		Glen Allen		VA		—		748			4,492		364		790			4,814			5,604		671	2000		2011	40
2812 Emerywood Parkway		Henrico		VA		—		1,069			4,281		515		1,069			4,796			5,865		2,182	1980		1998	40
300 Arboretum Place		Richmond		VA		—		5,450			21,892		6,917		5,450			28,809			34,259		10,862	1988		1998	40
7501 Boulders View Drive		Richmond		VA		—		4,669			19,699		2,071		4,925			21,514			26,439		4,786	1989		2007	40
7300 Beaufont Springs Drive		Richmond		VA		—		4,672			19,689		2,857		4,922			22,296			27,218		4,223	2000		2007	40
6800 Paragon Place		Richmond		VA		—		4,552			18,414		2,163		4,552			20,577			25,129		4,651	1987		2006	40
6802 Paragon Place		Richmond		VA		—		2,917			11,454		3,143		2,917			14,597			17,514		5,312	1989		2002	40
1025 Boulders Parkway		Richmond		VA		—		2,574			11,297		1,704		2,824			12,751			15,575		2,545	1994		2007	40
2100-2116 West Laburnam Avenue		Richmond		VA		—		2,482			8,846		2,770		2,482			11,616			14,098		5,162	1984		1998	40
7401 Beaufont Springs Drive		Richmond		VA		—		2,349			10,396		1,011		2,599			11,157			13,756		2,289	1998		2007	40
7325 Beaufont Springs Drive		Richmond		VA		—		2,344			10,377		630		2,594			10,757			13,351		2,049	1999		2007	40
															Gross Amount at Which Carried
								Initial Cost							31-Dec-14
Property Name		City		State		Encumbrances at		Land			Building and		Net		Land			Building and			Total (b)		Accumulated	Year of		Year	Depreciable
						December 31,					Improvements		Improvements					Improvements					Depreciation at	Construction		Acquired	Life
						2014(a)							(Retirements)										December 31,
													Since										2014 (c)
													Acquisition
9011 Arboretum Parkway		Richmond		VA		—		1,857			7,702		940		1,857			8,642			10,499		3,854	1991		1998	40
6806 Paragon Place		Richmond		VA		—		—			10,288		(37	)	402			9,849			10,251		2,660	2007		2005	40
9100 Arboretum Parkway		Richmond		VA		—		1,362			5,489		979		1,362			6,468			7,830		2,807	1987		1998	40
2511 Brittons Hill Road		Richmond		VA		—		1,202			4,820		1,221		1,202			6,041			7,243		2,846	1987		1998	40
100 Gateway Centre Parkway		Richmond		VA		—		391			5,410		617		391			6,027			6,418		1,922	2001		1998	40
9200 Arboretum Parkway		Richmond		VA		—		985			3,973		1,252		985			5,225			6,210		2,348	1987		1998	40
9210 Arboretum Parkway		Richmond		VA		—		1,110			4,474		517		1,110			4,991			6,101		2,239	1988		1998	40
2201-2245 Tomlynn Street		Richmond		VA		—		1,020			4,067		1,046		1,020			5,113			6,133		2,154	1989		1998	40
9211 Arboretum Parkway		Richmond		VA		—		582			2,433		844		582			3,277			3,859		1,317	1991		1998	40
2221-2245 Dabney Road		Richmond		VA		—		530			2,123		359		530			2,482			3,012		990	1994		1998	40
2212-2224 Tomlynn Street		Richmond		VA		—		502			2,014		395		502			2,409			2,911		1,020	1985		1998	40
2244 Dabney Road		Richmond		VA		—		550			2,203		—		550			2,203			2,753		964	1993		1998	40
2277 Dabney Road		Richmond		VA		—		507			2,034		294		507			2,328			2,835		977	1986		1998	40
2248 Dabney Road		Richmond		VA		—		512			2,049		57		512			2,106			2,618		923	1989		1998	40
2161-2179 Tomlynn Street		Richmond		VA		—		423			1,695		315		423			2,010			2,433		842	1985		1998	40
2246 Dabney Road		Richmond		VA		—		455			1,822		—		455			1,822			2,277		797	1987		1998	40
2251 Dabney Road		Richmond		VA		—		387			1,552		95		387			1,647			2,034		738	1983		1998	40
2256 Dabney Road		Richmond		VA		—		356			1,427		182		356			1,609			1,965		751	1982		1998	40
2130-2146 Tomlynn Street		Richmond		VA		—		353			1,416		214		353			1,630			1,983		704	1988		1998	40
2112-2124 Tomlynn Street		Richmond		VA		—		281			1,125		300		281			1,425			1,706		625	1984		1998	40
2240 Dabney Road		Richmond		VA		—		264			1,059		88		264			1,147			1,411		478	1984		1998	40
Boulders Land		Richmond		VA		—		1,256			—		28		1,259			25			1,284		2	N/A		2007	N/A
CALIFORNIA
5900 & 5950 La Place Court		Carlsbad		CA		—			3,706			11,185			3,613				3,955			14,549		18,504			3,645		1988	2006	48
5963 La Place Court		Carlsbad		CA		—			2,824			9,413			2,117				2,999			11,355		14,354			2,486		1987	2006	55
2035 Corte Del Nogal		Carlsbad		CA		—			3,261			6,077			1,167				3,499			7,006		10,505			2,038		1991	2006	39
1200 Concord Avenue		Concord		CA		—			6,395			24,664			808				6,515			25,352		31,867			7,949		1984	2006	34
1220 Concord Avenue		Concord		CA		—			6,476			24,966			260				6,476			25,226		31,702			7,622		1984	2006	34
155 Grand Avenue		Oakland		CA		—			13,556			54,267			6,316				13,556			60,583		74,139			12,652		1990	2007	40
Two Kaiser Plaza		Oakland		CA		—			7,841			—			—				7,841			—		7,841			—		N/A	2006	N/A
Oakland Lot B		Oakland		CA		—			4,342			—			—				4,342			—		4,342			—		N/A	2006	N/A
		Total:				$	655,934		$	625,594		$	3,362,277		$	643,257			$	673,838		$	3,957,290	$	4,631,128		$	1,078,996
(a)	Excludes the effect of any net interest premium / (discount).
(b)	Reconciliation of Real Estate:
The following table reconciles the real estate investments from January 1, 2012 to December 31, 2014 (in thousands):
	2014				2013			2012
Balance at beginning of year	$	4,669,289			$	4,726,169		$	4,793,080
Additions:
Acquisitions	—				347,510			50,579
Capital expenditures and assets placed into service	132,149				109,740			90,619
Less:
Dispositions	(126,471		)		(474,275		)	(168,408		)
Retirements	(43,839		)		(39,855		)	(39,701		)
Balance at end of year	$	4,631,128			$	4,669,289		$	4,726,169
Less:
Assets held for sale (e)	27,436				—			—
Per consolidated balance sheet	$	4,603,692			$	4,669,289		$	4,726,169
The aggregate cost for federal income tax purposes is $3.7 billion as of December 31, 2014.
(c)	Reconciliation of Accumulated Depreciation:
The following table reconciles the accumulated depreciation on real estate investments from January 1, 2012 to December 31, 2014 (in thousands):
	2014				2013			2012
Balance at beginning of year	$	983,808			$	954,665		$	865,710
Additions:
Depreciation expense — continuing operations	160,641				150,236			154,095
Depreciation expense — discontinued operations	—				9,164			2,143
Less:
Dispositions	(22,459		)		(91,890		)	(28,270		)
Retirements	(42,994		)		(38,367		)	(39,013		)
Balance at end of year	$	1,078,996			$	983,808		$	954,665
Less:
Assets held for sale (e)	(11,167		)		—			—
Per consolidated balance sheet	$	1,067,829			$	983,808		$	954,665
(d) This property was contributed to an unconsolidated real estate venture, however, the Company will continue to consolidate this property due to its continuing involvement in this property resulting from its ongoing lease at this property and its 50% ownership interest in the venture. Please see Note 3, "Real Estate Investments," to the consolidated financial statements for additional information.
(e) The office properties known as Atrium I, located at 1000 Atrium Way in Mt Laurel, New Jersey and Libertyview, located 457 Haddonfield Road in Cherry Hill, New Jersey, were categorized as held for sale as of December 31, 2014. For further information see Note 3, "Real Estate Investments."

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Reclassifications	Reclassifications
	Reclassifications are related to the treatment of sold properties as discontinued operations on the statement of operations for all periods presented. See Recent Accounting Pronouncements below for revisions to the accounting guidance for discontinued operations.
Principles of Consolidation	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 of December 31, 2014, the Company has provided guarantees on behalf of certain real estate ventures, consisting of (i) a $24.7 million payment guaranty on the construction loan for the project being undertaken by evo at Cira; (ii) a $3.2 million payment guarantee on the construction loan for a project being undertaken by TB-BDN Plymouth Apartments; and (iii) a $0.5 million payment guarantee on a loan provided to PJP VII.
	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/managing member, or the general partners/managing members as a group, controls a limited partnership or similar entity when the limited partners/non-managing members 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 for which the Company maintains an ownership interest through its general partner/managing member status, but the limited partners/non-managing members in the entity have the substantive ability to dissolve the entity or remove the Company without cause or have substantive participating rights.  Currently there are no real estate ventures that a limited partner/non-managing member has the unilateral right to dissolve. 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/non-managing members 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, LLC and other real estate venture 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.
Use of Estimates	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
	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 costs related to business combinations are expensed as incurred, whereas the costs related to asset acquisitions are capitalized 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	Purchase Price Allocation
	The Company allocates the purchase price of properties considered to be business combinations 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 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 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 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 four 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. Though the Company considers the value of tenant relationships, the amounts are determined on a tenant-specific basis. On certain of our acquisitions this intangible has been deemed immaterial. In these instances no related intangible value is assigned.
	In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) are recorded to revenue.
Depreciation and Amortization [Policy Text Block]	Depreciation and Amortization
	The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements (5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset, 1 to 16 years, or (ii) the lease term).
Construction in Progress	Construction in Progress
	Project costs directly associated with the development and construction of a real estate project are capitalized as construction in progress. Construction in progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. Internal direct costs are capitalized to projects in which qualifying expenditures are being incurred. Internal direct construction costs totaling $5.2 million in 2014, $3.7 million in 2013, $4.7 million in 2012 and interest totaling $4.8 million in 2014, $2.6 million in 2013, and $2.6 million in 2012 were capitalized related to development of certain properties and land holdings. The increase in capitalized costs is due to the development activity. See Item 1., "Business - Developments," for further discussion.
	During the years ended December 31, 2014, 2013 and 2012, the Company's internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands):
		December 31,
		2014		2013		2012
	Development	$	1,749	$	156	$	57
	Redevelopment	184		194		353
	Tenant Improvements	3,261		3,323		4,259
	Total	$	5,194	$	3,673	$	4,669
Impairment or Disposal of Long-Lived Assets	Impairment or Disposal of Long-Lived Assets
	The Company reviews its long-lived assets for impairment following the end of each quarter and when there is an event or change in circumstances that indicates an impairment in value. An impairment loss is recognized if the carrying amount of an asset is not recoverable and exceeds its fair value. In such case, an impairment loss is recognized in the amount of the excess of the carrying amount of the asset over its fair value. 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. Since cash flows on properties considered to be “long-lived assets to be held and used” are considered on an undiscounted basis to determine whether an asset has been impaired, the Company's established strategy of holding properties over the long term directly decreases the likelihood of recording an impairment loss. If the Company's holding strategy were to change or if market conditions were to otherwise dictate an earlier sale date, then an impairment loss may be recognized and such loss could be material. If the Company determines that impairment has occurred, the affected assets must be reduced to their fair value.
	The Company generally consider assets to be “held for sale” when the transaction has been approved by our Board of Trustees, or by officers vested with authority to approve the transaction and there are no known significant contingencies relating to the sale of the property within one year of the consideration date and the consummation of the transaction is otherwise considered probable.
	Following the classification of a property as “held for sale,” no further depreciation is recorded on the assets, and the asset is written down to the lower of carrying value or fair market value.
	The relevant accounting guidance for impairments requires that qualifying assets and liabilities and the results of operations that have been sold, or otherwise qualify as “held for sale,” be presented as discontinued operations in all periods presented if the disposal represents a strategic shift that has, or will have, a major effect on the Company's operations and financial results. The components of the property’s net income that is reflected as discontinued operations include the net gain (or loss) upon the disposition of the property held for sale, operating results, depreciation and interest expense (if the property is subject to a secured loan).
	The Company recorded a provision for impairment on assets held for sale during the twelve months ended December 31, 2014 of $1.8 million. These properties were sold on October 24, 2014, at which time the Company recorded a $0.2 million gain. For further information regarding the impairment, see Note 3, "Real Estate Investments." During its impairment review as of December 31, 2014, the Company determined that no additional impairment charges were necessary. The Company determined during its impairment review of the years ended December 31, 2013 and 2012, that no impairment charges were necessary.
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and Cash Equivalents
	Cash and cash equivalents are highly-liquid investments with original maturities of three months or less. The Company maintains cash equivalents in financial institutions in excess of insured limits, but believes this risk is mitigated by only investing in or through major financial institutions.
Restricted Cash, Policy [Policy Text Block]	Restricted Cash
	Restricted cash consists of cash held as collateral to provide credit enhancement for the Company’s mortgage debt, cash for property taxes, capital expenditures and tenant improvements.
Accounts receivable and accrued rent receivable policy [Policy Text Block]	Accounts Receivable and Accrued Rent Receivable
	Leases with tenants are accounted for as operating leases. Minimum annual rentals under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payment terms is recorded as “accrued rent receivable, net” on the accompanying balance sheets. Included in current tenant receivables are tenant reimbursements which are comprised of amounts recoverable from tenants for common area maintenance expenses and certain other recoverable expenses that are recognized as revenue in the period in which the related expenses are incurred. As of December 31, 2014 and 2013, no tenant represented more than 10% of accounts receivable and accrued rent receivable.
	Tenant receivables and accrued rent receivables are carried net of the allowances for doubtful accounts of $2.0 million and $13.4 million in 2014, respectively and $3.2 million and $13.0 million in 2013, respectively. The allowance is an estimate based on two calculations that are combined to determine the total amount reserved. First, the Company evaluates specific accounts where it has determined that a tenant may have an inability to meet its financial obligations. In these situations, the Company uses its judgment, based on the facts and circumstances, and records a specific reserve for that tenant against amounts due to reduce the receivable to the amount that the Company expects to collect. These reserves are reevaluated and adjusted as additional information becomes available. Second, a reserve is established for all tenants based on a range of percentages applied to receivable aging categories for tenant receivables. For accrued rent receivables, the Company considers the results of the evaluation of specific accounts and also considers other factors including assigning risk factors to different industries based on its tenants SIC classification. Considering various factors including assigning a risk factor to different industries, these percentages are based on historical collection and write-off experience adjusted for current market conditions, which requires management’s judgments.
Investments in Unconsolidated Real Estate Ventures	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. For Real Estate Ventures that are constructing assets to commence planned principal operations, the Company capitalizes interest expense using its weighted average interest rate of consolidated debt and  its investment balance as a basis. Planned principal operations commence when a property is available to lease and at that point in time the Company ceases capitalizing interest to its investment basis. During the twelve months ended December 31, 2014 and 2013 the Company capitalized interest expense of $2.0 million and $0.6 million, respectively.
	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.
Deferred Costs, Policy [Policy Text Block]	Deferred Costs
	Costs incurred in connection with property leasing are capitalized as deferred leasing costs. Deferred leasing costs consist primarily of leasing commissions and internal leasing costs that are amortized using the straight-line method over the life of the respective lease which generally ranges from 1 to 15 years. Management re-evaluates the remaining useful lives of leasing costs as economic and market conditions change.
	Costs incurred in connection with debt financing are capitalized as deferred financing costs and charged to interest expense over the terms of the related debt agreements. Deferred financing costs consist primarily of loan fees which are amortized over the related loan term on a basis that approximates the effective interest method. Deferred financing costs are accelerated, when debt is extinguished, as part of interest expense- amortization of deferred financing costs within the Company's consolidated statements of operations. Original issue discounts are recognized as part of the gain or loss on extinguishment of debt, as appropriate.
Notes Receivable	Notes Receivable
	The Company accounts for notes receivable on its balance sheet at amortized cost, net of allowance for loan losses. Interest income is recognized over the term of the notes receivable and is calculated based on the terms on the contractual terms of each note agreement.
	Notes receivable are placed on nonaccrual status when management determines, after considering economic and business conditions and collection efforts, that the loans are impaired or collection of interest is doubtful. Uncollectible interest previously accrued is recognized as bad debt expense. Interest income on nonaccrual loans is recognized only to the extent that cash payments are received.
	On October 17, 2014, the Austin Venture acquired River Place and funded $88.0 million of the purchase price with a short-term loan, secured by a mortgage. The short-term financing was provided by the Company and the Austin Venture is currently seeking permanent financing. The debt agreement for the short-term loan provides financing through March 2015 at the following tiered interest rates; (i) 4.0% through December 31, 2014, (ii) 5.0% from January 1, 2015 through January 31, 2015, (iii) 7.0% from February 1, 2015 through February 28, 2015 and (iv) 9.0% from March 1, 2015 through March 31, 2015. The Austin Venture may repay the short-term loan at any time without penalty. During 2014 the Company recognized $0.7 million of interest income relating to this note. See Note 21, "Subsequent Events," for repayment of this note.
	As of December 31, 2013, 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. The borrower had previously defaulted on the note. As a result, a forbearance agreement dated October 2011, as amended by a second forbearance agreement dated July 9, 2013, was entered into between the Company and the borrower, outlining the repayment terms of the outstanding debt and capping interest at $1.5 million. The Company has determined that the loan modifications represent a troubled debt restructuring due to the fact that the borrower was considered to be in a financial difficulty when it defaulted on the mortgage debt, and that a concession was granted in the form of the forbearance agreements. In accordance with relevant the accounting guidance for troubled debt restructuring, this note remained in a non-accrual status through 2014 and as such, interest is recorded to income as received. During the twelve months ended December 31, 2014, the borrower fully repaid the principal balance of $7.0 million. As to the interest accrued on the notes, $1.5 million has been received in cash and recognized as interest income during the fourth quarter of 2014.
	During 2012, the $23.5 million seven year purchase money mortgage note receivable (balance as of the payment date, including accrued but unpaid interest), which related to the 2009 sale of two Trenton properties, was paid in full prior to its scheduled maturity of October 2016. The Company also recognized a $12.9 million deferred gain and $1.0 million of interest income at the time of payment, in accordance with the accounting standard for installment sales.
Revenue Recognition	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 $13.7 million in 2014, $17.7 million in 2013 and $21.1 million in 2012. 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 $2.4 million in each of 2014, 2013 and 2012. 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 decreased revenue by $1.5 million in 2014, $0.7 million in 2013, and $0.8 million in 2012.
	The Company's leases also typically provide for tenant reimbursement of a portion of common area maintenance expenses 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, the Company makes significant assumptions and judgments in determining the lease term, including assumptions when the lease provides the tenant with an early termination option. The lease term impacts the period over which the Company determines and records minimum rents and also impacts the period over which the Company amortizes lease-related costs.
	In addition, the Company's rental revenue is impacted by the Company's determination of whether improvements to the properties, whether made by the Company or by the tenant, are landlord assets. The determination of whether an improvement is a landlord asset requires judgment. In making this judgment, our primary consideration is whether the improvement would be utilizable by another tenant upon move out of the improved space by the then-existing tenant. If the Company has funded an improvement that it determines not to be landlord assets, then it treats the costs of the improvement as lease incentives. If the tenant has funded the improvement that the Company determines to be landlord assets, then the Company treats the costs of the improvement as deferred revenue and amortize this cost into revenue over the lease term.
	Recoveries from tenants, consisting of amounts due from tenants for common area maintenance expenses, real estate taxes and other recoverable costs are recognized as revenue in the period during which the expenses are incurred.
	Tenant reimbursements are recognized and presented in accordance with accounting guidance which requires that these reimbursements be recorded on a gross basis because the Company is generally the primary obligor with respect to the goods and services the purchase of which gives rise to the reimbursement obligation; because the Company has discretion in selecting the vendors and suppliers; and because the Company bears the credit risk in the event they do not reimburse the Company. The Company also receives payments from third parties for reimbursement of a portion of the payroll and payroll-related costs for certain of the Company's personnel allocated to perform services for these third parties and reflects these payments on a gross basis.
	The Company recognizes gains on sales of real estate at times and in amounts determined in accordance with the accounting guidance for sales of real estate. The guidance takes into account the terms of the transaction and any continuing involvement, including in the form of management, leasing of space or financial assistance associated with the properties. If the sales criteria for the full accrual method are not met, then the Company defers some or all of the gain recognition and account for the continued operations of the property by applying the finance, leasing, profit sharing, deposit, installment or cost recovery method, as appropriate, until the sales criteria are met.
	The Company derives parking revenues from leases, monthly parking and transient parking. The Company recognizes parking revenue as earned.
	The Company receives leasing commission income, management fees and development fees from third parties.
	Leasing commission income is earned based on a percentage of gross rental income upon a tenant signing a lease with a third party lessor. Property management fees are recorded and earned based on a percentage of collected rents at the properties under management, and not on a straight-line basis, because such fees are contingent upon the collection of rents. The Company records development fees as earned taking into account the risk associated with each project. Profit on development fees earned from joint venture projects is recognized as revenue to the extent of the third party partners’ ownership interest.
	No tenant represented greater than 10% of the Company’s rental revenue in 2014, 2013 or 2012
Income Taxes	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 tax basis of the Parent Company’s assets was $3.7 billion and $4.0 billion for the years ended December 31, 2014 and 2013, respectively.
	The Parent Company is subject to a 4% federal excise tax if sufficient taxable income is not distributed within prescribed time limits. The excise tax equals 4% of the annual amount, if any, by which the sum of (a) 85% of the Parent Company’s ordinary income and (b) 95% of the Parent Company’s net capital gain exceeds cash distributions and certain taxes paid by the Parent Company. No excise tax was incurred in 2014, 2013, or 2012.
	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. The Company’s taxable REIT subsidiaries did not have significant tax provisions or deferred income tax items as of December 31, 2014 and 2013.
	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 tax basis of the Operating Partnership’s assets was $3.7 billion and $4.0 billion for the years ended December 31, 2014 and 2013, respectively.
	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 TRSs, which are subject to federal, state and local income tax.
Earnings Per Share, Policy [Policy Text Block]	Earnings Per Share
	Basic earnings per share ("EPS") is computed by dividing net income available to common shareholders, as adjusted for unallocated earnings, if any, of certain securities, by the weighted average number of shares of common stock outstanding during the year. Diluted EPS reflects the potential dilution that could occur from shares issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options, and conversion of the noncontrolling interests in the Operating Partnership.
	Earnings Per Unit
	Basic EPS is computed by dividing net income available to common unitholders, as adjusted for unallocated earnings, if any, of certain securities issued by the Operating Partnership, by the weighted average number of common unit equivalents outstanding during the year. Diluted EPS reflects the potential dilution that could occur from shares issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options
Stock-Based Compensation Plans	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. On June 2, 2010, the Parent Company’s shareholders approved amendments to the 1997 Plan that, among other things, increased the number of common shares available for future awards under the 1997 Plan by 6,000,000 (of which 3,600,000 shares are available solely for options and share appreciation rights). As of December 31, 2014, 4,304,006 common shares remained available for future awards under the 1997 Plan (including 2,684,795 shares available solely for options and share appreciation rights). Through December 31, 2014 all options awarded under the 1997 Plan had a one to ten-year term.
	The Company incurred stock-based compensation expense of $6.1 million during 2014, of which $1.7 million was capitalized as part of the Company’s review of employee salaries eligible for capitalization. The Company incurred stock-based compensation expense of $8.3 million and $8.6 million during 2013 and 2012, of which $1.4 million and $2.6 million, respectively, were also capitalized. The expensed amounts are included in general and administrative expense on the Company’s consolidated income statement in the respective periods.
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income
	Comprehensive income is recorded in accordance with the provisions of the accounting standard for comprehensive income. The accounting standard establishes standards for reporting comprehensive income and its components in the financial statements. Comprehensive income includes the effective portions of changes in the fair value of derivatives.
Accounting for Derivative Instruments and Hedging Activities	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	Fair Value Measurements
	The Company estimates the fair value of its derivatives 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.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements
	In August 2014, the Financial Accounting Standards Board ("FASB") issued guidance regarding an Entity’s Ability to Continue as a Going Concern, which requires management to assess a company’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. Before this new standard, there was minimal guidance in U.S. GAAP specific to going concern. Under the new standard, disclosures are required when conditions give rise to substantial doubt about a company’s ability to continue as a going concern within one year from the financial statement issuance date. The guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period, with early adoption permitted. The Company has not yet determined the impact, if any, that the adoption of this guidance will have on its consolidated financial statements.
	In May 2014 FASB issued guidance requiring revenue to be recognized in an amount that reflects the consideration expected to be received in exchange for goods and services. The guidance requires the disclosure of sufficient quantitative and qualitative information for financial statement users to understand the nature, amount, timing and uncertainty of revenue and associated cash flows arising from contracts with customers. The guidance is effective for annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period, with early adoption precluded. The Company has not yet determined the impact, if any, that the adoption of this guidance will have on its consolidated financial position or results of operations.
	In April 2014 the FASB issued revised guidance on discontinued operations and disclosures of disposals of components of an entity. The update revises the definition to include only disposals involving a strategic shift that has a major effect on the entity’s operations and financial results when the disposal asset or group meets the existing criterion for treatment as held for sale. Examples of a strategic shift include the withdrawal from a major geographic area, line of business, equity method investment or any other major parts of a business, as applicable. A component of the entity comprises operations and cash flows that can be clearly distinguished, operationally and for financial reporting purposes, from the rest of the entity. In addition, the revised standard no longer precludes presentation as a discontinued operation if there are operations and cash flows of the component that have not been eliminated from the reporting entity’s ongoing operations, or if there is significant continuing involvement with a component after its disposal.
	The amendments require additional disclosures about discontinued operations including; the major classes of net income or loss where net income is otherwise presented, the operating and investing cash flows of discontinued operations where net income is otherwise presented, depreciation, amortization, capital expenditures and significant operating and investing non-cash items of the discontinued operation for the periods in which net income is otherwise presented and, if there is a non-controlling interest, the related allocation to the parent company.
	Application is prospective, and required for periods beginning on or after December 15, 2014. This update should not be applied to assets classified as held for sale before the effective date even if the component of an entity is disposed of after the effective date. Early adoption is permitted for disposals or assets held for sale that have not been reported in the financial statements previously issued or available for issuance. The Company has elected to early adopt this standard as of January 1, 2014. All properties sold or determined held for sale prior to January 1, 2014 are classified as discontinued operations for all periods presented.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Schedule of Capitalized Salaries Including Bonuses and Benefits [Table Text Block]	During the years ended December 31, 2014, 2013 and 2012, the Company's internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands):
		December 31,
		2014		2013		2012
	Development	$	1,749	$	156	$	57
	Redevelopment	184		194		353
	Tenant Improvements	3,261		3,323		4,259
	Total	$	5,194	$	3,673	$	4,669

Real_Estate_Investments_Tables

Real Estate Investments (Tables)	12 Months Ended
	Dec. 31, 2014					Dec. 31, 2013
Real Estate [Abstract]
Gross carrying value of the Company's Properties	As of December 31, 2014 and 2013 the gross carrying value of the Company’s Properties was as follows (in thousands):
		2014		2013
	Land	$	669,635	$	680,513
	Building and improvements	3,409,303		3,504,060
	Tenant improvements	524,754		484,716
		4,603,692		4,669,289
	Assets held for sale - real estate investments (a)	27,436		—
	Total	$	4,631,128	$	4,669,289
	(a)	Real estate investments related to assets held for sale above represents gross real estate assets and does not include accumulated depreciation or other assets on the balance sheets of the properties held for sale.
Schedule of Business Acquisitions, by Acquisition [Table Text Block]						The Company has treated this transaction as a business combination and allocated the purchase price to the tangible and intangible assets and liabilities. As discussed in Note 2, the Company utilized a number of sources in making estimates of fair values for purposes of allocating the purchase price to tangible and intangibles assets acquired and intangible liabilities assumed. The purchase price is allocated as follows:
							December 19, 2013
						Building, land and improvements	$	255,705
						Intangible assets acquired	85,036
						Below market lease liabilities assumed	(8,637		)
							$	332,104
						Mortgage debt assumed - at fair value (a)	(238,082		)
						Return of existing equity method investment	(30,424		)
						Net working capital assumed	10,423
						Non-controlling interest	(946		)
						Total cash payment at settlement	$	73,075
						(a) Principal outstanding on assumed mortgage debt at December 19, 2013 was $237.1 million.
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]						Intangible assets acquired and intangible liabilities assumed consist of the following (in thousands):
							December 19, 2013			Weighted Average Amortization Period (in years)
						Intangible assets:
						In-place lease value	$	80,916		7.9
						Above market tenant leases acquired	4,120			6.9
						Total	$	85,036
						Intangible liabilities:
						Below market leases acquired	$	(8,637	)	6.5
Business Acquisition, Pro Forma Information [Table Text Block]						The unaudited pro forma information below summarizes the Company’s combined results of operations for the years ended December 31, 2014 and 2013 as though the acquisition of One and Two Commerce Square, Four Points Centre and Six Tower Bridge were completed on January 1, 2012. The supplemental pro forma operating data is not necessarily indicative of what the actual results of operations would have been assuming the transaction had been completed as set forth above, nor do they purport to represent the Company’s results of operations for future periods (in thousands except for per share amounts).
							December 31,
							2013			2012
						Pro forma revenue	$	610,979		$	592,753
						Pro forma income (loss) from continuing operations	21,805			(60,011		)
						Pro forma net income (loss) available to common shareholders	25,957			(16,970		)
						Earnings per common share from continuing operations:
						Basic -- as reported	$	0.2		$	(0.36	)
						Basic -- as pro forma	$	0.14		$	(0.42	)
						Diluted -- as reported	$	0.2		$	(0.36	)
						Diluted -- as pro forma	$	0.14		$	(0.42	)
						Earnings per common share:
						Basic -- as reported	$	0.23		$	(0.06	)
						Basic -- as pro forma	$	0.17		$	(0.12	)
						Diluted -- as reported	$	0.23		$	(0.06	)
						Diluted -- as pro forma	$	0.17		$	(0.12	)
						Included in the consolidated statements of income for the year ended December 31, 2013 are total revenues of $3.4 million and a net loss attributable to common shareholders of $0.2 million from acquisitions made during 2013.

Investment_in_Unconsolidated_V1

Investment in Unconsolidated Ventures (Tables)	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Method Investments [Table Text Block]	The Company’s investment in Real Estate Ventures as of December 31, 2014 and the Company’s share of the Real Estate Ventures’ income (loss) for the year ended December 31, 2014 was as follows (in thousands):
			Ownership			Carrying			Company’s Share			Real Estate		Current		Debt
			Percentage (a)			Amount			of 2014 Real			Venture		Interest		Maturity
									Estate Venture			Debt at 100%		Rate
									Income (Loss)
	Office Properties
		Broadmoor Austin Associates (b)	50	%		$	65,407		$	(460	)	$	53,516	7.04	%	Apr-23
		Brandywine-AI Venture LLC	50	%		45,712			(185		)	133,843		3.93	%	(c)
		DRA (G&I) Austin (b)	50	%		40,374			(574		)	382,100		3.57	%	(d)
		1000 Chesterbrook Blvd.	50	%		2,152			388			24,251		4.75	%	Dec-21
		Four Tower Bridge	65	%		1,474			(144		)	10,353		5.2	%	Feb-21
		PJP VII	25	%		911			177			5,785		L+2.65%		Dec-19
		PJP II	30	%		403			73			3,492		6.12	%	Nov-23
		PJP V	25	%		216			166			5,242		6.47	%	Aug-19
		PJP VI	25	%		45			(67		)	8,168		6.08	%	Apr-23
		G&I Interchange Office LLC (DRA — N. PA) (e) (b)	20	%		—			(658		)	174,595		5.78	%	Feb-15
		Invesco, L.P. (i)				—			989			—
		Coppell Associates (f)	50	%		(1,214		)	(45		)	15,747		5.75	%	Feb-16
	Other
		Residence Inn Tower Bridge	50	%		723			107			13,394		5.63	%	Feb-16
		HSRE-Campus Crest IX, LLC (b)	30	%		14,314			67			90,245		L+2.20%		Jul-16
	Development Properties
		4040 Wilson LLC	50	%		27,415			(132		)	—
		Brandywine 1919 Ventures (b) (g)	50	%		12,823			(21		)	—		L+2.25%		Oct-18
		TB-BDN Plymouth Apartments	50	%		12,720			(83		)	29,481		L+1.70%		Dec-17
		Seven Tower Bridge	20	%		315			(388		)	14,865		3.78	%	(h)
						$	223,790		$	(790	)	$	965,077
	(a)	Ownership percentage represents the Company's entitlement to residual distributions after payments of priority returns, where applicable.
	(b)	The basis differences associated with these ventures are allocated between cost and the underlying equity in the net assets of the investee and is accounted for as if the entity were consolidated (i.e., allocated to the Company’s relative share of assets and liabilities with an adjustment to recognize equity in earnings for the appropriate depreciation/amortization).
	(c)	The debt for these properties is comprised of three fixed rate mortgages: (1) $39.3 million with a 4.40% fixed interest rate due January 1, 2019, (2) $28.0 million with a 4.65% fixed interest rate due January 1, 2022, and (3) $66.5 million with a 3.22% fixed interest rate due August 1, 2019, resulting in a time weighted average rate of 3.93%.
	(d)	The debt for these properties includes five mortgages: (1) $34.0 million that was swapped to a 1.59% fixed rate (or an all-in fixed rate of 3.52% incorporating the 1.93% spread) due November 1, 2018, (2) $56.0 million that was swapped to a 1.49% fixed rate (or an all-in rate of 3.19% incorporating the 1.70% spread) due October 15, 2018, (3) $140.6 million that was swapped to a 1.43% fixed rate (for an all-in fixed rate of 3.44% incorporating the 2.01% spread) due November 1, 2018, (4) $29.0 million with a 4.50% fixed interest rate due April 6, 2019, and (5) $34.5 million with a 3.87% fixed interest rate due August 6, 2019, resulting in a time and dollar weighted average rate of 3.57%. Also, includes an $88.0 million bridge loan from BDN Austin Properties, LLC, a subsidiary of Brandywine, carrying a 4.00% fixed interest rate until December 31, 2014 and increased to 5.00% through January 31, 2015. See Note 21, "Subsequent Events," for repayment of this note.
	(e)	Proceeds received by the Company from the sale of an 80% ownership stake in the properties exceeded the historical cost of those properties. No investment in the real estate venture was reflected on the balance sheet at formation.
	(f)	Carrying amount represents the negative investment balance of the venture and is included in other liabilities.
	(g)	The stated rate for the construction loan is LIBOR + 2.25%. The interest rate spread decreases to 2.00% upon receipt of certificate of occupancy. It is further reduced to 1.75% upon stabilization. To fulfill interest rate protection requirements an interest rate cap was purchased at 4.50%.
	(h)	Comprised of two fixed rate mortgages totaling $8.0 million that mature on March 1, 2017 and accrue interest at a current rate of 7.00%, a $1.0 million 3.00% fixed rate loan through its September 1, 2025 maturity, a $2.0 million 4.00% fixed rate loan with interest only through its February 7, 2016 maturity and a $3.9 million 3.00% fixed rate loan with interest only beginning March 11, 2018 through its March 11, 2020 maturity, resulting in a time and dollar weighted average rate of 3.78%.
	(i)	The ownership interest in this property was disposed of prior to December 31, 2014.
Financial position of unconsolidated Real Estate Ventures	The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2014 and December 31, 2013 (in thousands):
		December 31,				December 31,
		2014				2013
	Net property	$	1,281,282			$	965,475
	Other assets	195,121				164,152
	Other liabilities	68,481				49,442
	Debt	965,077				699,860
	Equity	442,845				380,325
	Company’s share of equity (Company’s basis) (a)	225,004			(b)	180,512
	(a)	This amount includes the effect of the basis difference between the Company's historical cost basis and the basis recorded at the Real Estate Venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from the impairment of investments, purchases of third party interests in existing Real Estate Ventures 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.
	(b)	Does not include the negative investment balance of one real estate venture totaling $1.2 million as of December 31, 2014, which is included in other liabilities.
Summary of results of operations of unconsolidated Real Estate Ventures	The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests as of December 31, 2014, 2013 and 2012 (in thousands):
		Years ended December 31,
		2014				2013			2012
	Revenue	$	147,236			$	102,919		$	164,013
	Operating expenses	(61,268		)		(40,436		)	(70,775		)
	Interest expense, net	(36,511		)		(26,529		)	(41,633		)
	Depreciation and amortization	(57,109		)		(35,138		)	(50,241		)
	Net income (loss)	(7,652		)		816			1,364
	Company’s share of income (loss) (Company’s basis)	(790		)		3,664			2,741
Schedule of Maturities of Long-term Debt [Table Text Block]	As of December 31, 2014, the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands):
	2015	$	279,351
	2016	133,809
	2017	44,465
	2018	231,030
	2019	182,522
	Thereafter	93,900
		$	965,077
	As of December 31, 2014, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
	2015	$	102,030
	2016	367,703
	2017	330,323
	2018	336,954
	2019	213,155
	Thereafter	1,109,298
	Total principal payments	2,459,463
	Net unamortized premiums/(discounts)	(8,155		)
	Outstanding indebtedness	$	2,451,308

Deferred_Costs_Tables

Deferred Costs (Tables)	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Table Text Block]	As of December 31, 2014 and 2013, the Company’s deferred costs were comprised of the following (in thousands):
		31-Dec-14
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	164,081	$	(64,065	)	$	100,016
	Financing Costs	40,401		(15,193		)	25,208
	Total	$	204,482	$	(79,258	)	$	125,224
		31-Dec-13
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	155,885	$	(58,805	)	$	97,080
	Financing Costs	40,317		(14,443		)	25,874
	Total	$	196,202	$	(73,248	)	$	122,954
	During the years ended December 31, 2014, 2013 and 2012, the Company capitalized internal direct leasing costs of $7.1 million, $7.5 million, and $7.5 million, respectively, in accordance with the accounting standard for the capitalization of leasing costs.

Intangible_Assets_Tables

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets	As of December 31, 2014 and 2013, the Company’s intangible assets were comprised of the following (in thousands):
		December 31, 2014
		Total Cost		Accumulated			Intangible Assets,
				Amortization			net
	In-place lease value	$	129,411	$	(42,068	)	$	87,343
	Tenant relationship value	34,172		(26,344		)	7,828
	Above market leases acquired	5,641		(1,409		)	4,232
	Total	$	169,224	$	(69,821	)	$	99,403
	Below market leases acquired	$	53,049	$	(27,039	)	$	26,010
		31-Dec-13
		Total Cost		Accumulated			Intangible Assets,
				Amortization			net
	In-place lease value	$	150,782	$	(35,607	)	$	115,175
	Tenant relationship value	38,692		(26,868		)	11,824
	Above market leases acquired	6,673		(1,343		)	5,330
	Total	$	196,147	$	(63,818	)	$	132,329
	Below market leases acquired	$	81,991	$	(47,547	)	$	34,444
Annual amortization of intangible assets and liabilities	As of December 31, 2014, the Company’s annual amortization for its intangible assets/liabilities was as follows (in thousands, and assuming no early lease terminations):
		Assets		Liabilities
	2015	$	21,363	$	5,212
	2016	16,898		3,253
	2017	15,148		2,664
	2018	11,399		2,241
	2019	10,086		1,909
	Thereafter	24,509		10,731
	Total	$	99,403	$	26,010

Debt_Obligations_Tables

Debt Obligations (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Consolidated debt obligations	The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2014 and 2013 (in thousands):
		December 31,			December 31,			Effective					Maturity
		2014			2013			Interest					Date
								Rate
	MORTGAGE DEBT:
	Tysons Corner	$	89,513		$	91,395		5.36	%				Aug-15
	One Commerce Square	123,205			125,089			3.68	%		(a)		Jan-16
	Two Logan Square	87,767			88,583			7.57	%				Apr-16
	Fairview Eleven Tower	21,242			21,630			4.25	%		(b)		Jan-17
	Two Commerce Square	112,000			112,000			4.51	%		(a)		Apr-23
	IRS Philadelphia Campus	184,442			190,964			7	%				Sep-30
	Cira South Garage	37,765			40,101			7.12	%				Sep-30
	Principal balance outstanding	655,934			669,762
	Plus: fair market value premiums (discounts), net	(1,344		)	389
	Total mortgage indebtedness	$	654,590		$	670,151
	UNSECURED DEBT:
	Three-Year Term Loan - Swapped to fixed	$	—		$	150,000		2.6	%		(c)		Feb-15
	Four-Year Term Loan	—			100,000			LIBOR + 1.75%			(c), (d)		Feb-16
	Seven-Year Term Loan - Swapped to fixed	200,000			200,000			3.62	%				Feb-19
	$250.0M 5.40% Guaranteed Notes due 2014	—			218,549			5.53	%		(e)		Nov-14
	$250.0M 7.50% Guaranteed Notes due 2015	—			157,625			7.76	%		(e)		May-15
	$250.0M 6.00% Guaranteed Notes due 2016	149,919			149,919			5.95	%				Apr-16
	$300.0M 5.70% Guaranteed Notes due 2017	300,000			300,000			5.68	%				May-17
	$325.0M 4.95% Guaranteed Notes due 2018	325,000			325,000			5.13	%				Apr-18
	$250.0M 3.95% Guaranteed Notes due 2023	250,000			250,000			4.02	%				Feb-23
	$250.0M 4.10% Guaranteed Notes due 2024	250,000			—			4.23	%		(e)		Oct-24
	$250.0M 4.55% Guaranteed Notes due 2029	250,000			—			4.6	%		(e)		Oct-29
	Indenture IA (Preferred Trust I)	27,062			27,062			2.75	%				Mar-35
	Indenture IB (Preferred Trust I)	25,774			25,774			3.3	%				Apr-35
	Indenture II (Preferred Trust II)	25,774			25,774			3.09	%				Jul-35
	Principal balance outstanding	1,803,529			1,929,703
	plus: original issue premium (discount), net	(6,811		)	(4,473		)
	Total unsecured indebtedness	$	1,796,718		$	1,925,230
	Total Debt Obligations	$	2,451,308		$	2,595,381
	(a)	This loan was assumed upon acquisition of the related properties on December 19, 2013. The interest rate reflects the market rate at the time of acquisition.
	(b)	Represents the full debt amount of a property in a consolidated joint venture for which the Company maintains a 50% interest.
	(c)	On September 16, 2014, the Company repaid all balances outstanding under its $150.0 million three-year term loan and its $100.0 million four-year term loan prior to the scheduled maturity dates of February 1, 2015 and February 1, 2016, respectively.
	(d)	London Interbank Offered Rate (“LIBOR”).
	(e)	On September 16, 2014, the Company closed on an underwritten offering of $250.0 million 4.10% Guaranteed Notes due 2024 (the "2024 Notes") and $250.0 million 4.55% Guaranteed Notes due 2029 (the "2029 Notes"). The Company used the net proceeds, together with cash on hand, to redeem the remaining outstanding balance of its 5.40% Guaranteed Notes due November 1, 2014 (the "2014 Notes") and its 7.50% Guaranteed Notes due May 15, 2015 (the "2015 Notes"). (See further discussion below).
Summary of debt repurchases	The following table provides additional information on the Company’s repurchase of $376.2 million in aggregate principal amount of its outstanding unsecured notes (consisting of the 2014 Notes and 2015 Notes, as indicated above) during the twelve months ended December 31, 2014 (in thousands):
	Notes	Principal			Repurchase			Gain (Loss) on Early Extinguishment of Debt (b)				Acceleration of Deferred Financing
					Amount (a)							Amortization
	2014 5.40% Notes	$	218,549		$	219,404		$	(855	)		$	9
	2015 7.50% Notes	157,625			164,364			(6,739		)		143
		$	376,174		$	383,768		$	(7,594	)		$	152
	During the year-ended December 31, 2013, the Company repurchased $29.3 million of its outstanding unsecured Notes in a series of transactions that are summarized in the following table (in thousands):
	Notes	Principal			Repurchase			Gain (Loss) on Early Extinguishment of Debt (b)				Acceleration of Deferred Financing
					Amount (a)							Amortization
	2014 5.40% Notes	$	19,830		$	20,853		$	(1,020	)		$	16
	2015 7.50% Notes	8,910			9,945			(1,036		)		23
	2016 6.00% Notes	510			571			(63		)		1
		$	29,250		$	31,369		$	(2,119	)		$	40
	During the year-ended December 31, 2012, the Company repurchased $165.0 million of its outstanding unsecured Notes in a series of transactions that are summarized in the following table (in thousands):
	Notes	Principal			Repurchase			Gain (Loss) on Early Extinguishment of Debt (b)				Acceleration of Deferred Financing Amortization
					Amount (a) (c)
	2012 5.75% Notes	$	301		$	303		$	(2	)		$	—
	2014 5.40% Notes	4,302			4,566			(264		)		8
	2015 7.50% Notes	60,794			69,497			(8,712		)		183
	2016 6.00% Notes	99,571			112,541			(13,024		)		260
		$	164,968		$	186,907		$	(22,002	)		$	451
	(a)	Includes cash losses with respect to redemption of debt.
	(b)	Includes unamortized balance of the original issue discount.
	(c)	Does not include $151.2 million of 5.75% Guaranteed Notes due 2012 that matured.
Schedule of principal payments of debt obligations	As of December 31, 2014, the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands):
	2015	$	279,351
	2016	133,809
	2017	44,465
	2018	231,030
	2019	182,522
	Thereafter	93,900
		$	965,077
	As of December 31, 2014, the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
	2015	$	102,030
	2016	367,703
	2017	330,323
	2018	336,954
	2019	213,155
	Thereafter	1,109,298
	Total principal payments	2,459,463
	Net unamortized premiums/(discounts)	(8,155		)
	Outstanding indebtedness	$	2,451,308

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of financial instruments with fair values different from their carrying amount	The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands):
		December 31, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Mortgage notes payable	$	654,590	$	707,241	$	670,151	$	715,244
	Unsecured notes payable	$	1,518,108	$	1,593,212	$	1,396,620	$	1,471,041
	Variable rate debt	$	278,610	$	257,188	$	528,610	$	526,693
	Notes receivable (a)	$	88,000	$	87,692	$	7,026	$	7,759
	(a)	See Note 2, "Summary of Significant Accounting Policies - Notes Receivable," for further discussion.

Risk_Management_and_Use_of_Fin1

Risk Management and Use of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of derivative instruments in statement of financial position, fair value	The following table summarizes the terms and fair values of the Company's derivative financial instruments as of December 31, 2014 and December 31, 2013. 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 and included in other liabilities on the Company's consolidated balance sheets).
	Hedge Product		Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
						12/31/14		12/31/13						12/31/14			12/31/13
	Assets/(Liabilities)
	Swap		Interest Rate	Cash Flow	(a)	$	25,774	$	25,774	3.3	%	December 22, 2011	January 30, 2021	$	(334	)	$	549
	Swap		Interest Rate	Cash Flow	(a)	25,774		25,774		3.09	%	6-Jan-12	30-Oct-19	(254		)	218
	Swap		Interest Rate	Cash Flow	(a)	200,000		200,000		3.623	%	December 6-13, 2011	February 1, 2019	(2,649		)	(545		)
	Swap		Interest Rate	Cash Flow	(a)	27,062		27,062		2.75	%	December 21, 2011	September 30, 2017	(253		)	(311		)
	Swap		Interest Rate	Cash Flow	(a), (b)	—		77,000		2.703	%	December 9-13, 2011	February 1, 2016	—			(887		)
	Swap		Interest Rate	Cash Flow	(a), (b)	—		50,000		2.47	%	December 13, 2011	February 1, 2015	—			(283		)
	Swap		Interest Rate	Cash Flow	(a), (b)	—		23,000		2.513	%	December 7-12, 2011	May 1, 2015	—			(162		)
						$	278,610	$	428,610					$	(3,490	)	$	(1,421	)
	(a)	Hedging unsecured variable rate debt.
	(b)	On September 16, 2014, the Company repaid the entire $150.0 million swapped to fixed portion of its previously mentioned three-year term loan (See Note 7, "Debt Obligations"), consisting of $150.0 million interest rate swaps maturing through February 1, 2016 (shown above). In connection with the repayment, the Company terminated associated hedging contracts, incurring a $0.8 million charge upon termination.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]
Revenue and expenses information for the property classified as discontinued operations	The following table summarizes revenue and expense information for the properties sold which qualify for discontinued operations reporting since January 1, 2012 (in thousands):
		Years ended December 31,
		2014		2013		2012
	Revenue:
	Rents	$	—	$	4,754	$	28,678
	Tenant reimbursements	26		355		2,353
	Termination fees	—		—		11
	Other	—		123		378
	Total revenue	26		5,232		31,420
	Expenses:
	Property operating expenses	8		1,839		8,687
	Real estate taxes	—		649		3,468
	Depreciation and amortization	—		1,921		10,208
	Total operating expenses	8		4,409		22,363
	Other income:
	Interest income	—		2		7
	Income from discontinued operations before gain on sale of interests in real estate	18		825		9,064
	Net gain on disposition of discontinued operations	900		3,382		34,774
	Income from discontinued operations	$	918	$	4,207	$	43,838

Recovered_Sheet1

Beneficiaries Equity of The Parent Company (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
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):
		Year ended December 31,
		2014						2013						2012
		Basic			Diluted			Basic			Diluted			Basic			Diluted
	Numerator
	Income (loss) from continuing operations	$	6,024		$	6,024		$	38,982		$	38,982		$	(37,309	)	$	(37,309	)
	Net loss attributable to non-controlling interests - partners' share of consolidated real estate ventures	44			44			—			—			—			—
	Net (income) loss from continuing operations attributable to non-controlling interests	(1		)	(1		)	(357		)	(357		)	863			863
	Amount allocable to unvested restricted shareholders	(349		)	(349		)	(363		)	(363		)	(376		)	(376		)
	Preferred share dividends	(6,900		)	(6,900		)	(6,900		)	(6,900		)	(10,405		)	(10,405		)
	Preferred share redemption charge	—			—			—			—			(4,052		)	(4,052		)
	Income (loss) from continuing operations available to common shareholders	(1,182		)	(1,182		)	31,362			31,362			(51,279		)	(51,279		)
	Income from discontinued operations	918			918			4,207			4,207			43,838			43,838
	Discontinued operations attributable to non-controlling interests	(10		)	(10		)	(55		)	(55		)	(797		)	(797		)
	Discontinued operations attributable to common shareholders	908			908			4,152			4,152			43,041			43,041
	Net income (loss) attributable to common shareholders	$	(274	)	$	(274	)	$	35,514		$	35,514		$	(8,238	)	$	(8,238	)
	Denominator
	Weighted-average shares outstanding	166,202,649			166,202,649			153,140,458			153,140,458			143,257,097			143,257,097
	Contingent securities/Share based compensation	—			—			—			1,273,853			—			—
	Total weighted-average shares outstanding	166,202,649			166,202,649			153,140,458			154,414,311			143,257,097			143,257,097
	Earnings per Common Share:
	Income (loss) from continuing operations attributable to common shareholders	$	(0.01	)	$	(0.01	)	$	0.2		$	0.2		$	(0.36	)	$	(0.36	)
	Discontinued operations attributable to common shareholders	0.01			0.01			0.03			0.03			0.3			0.3
	Net income (loss) attributable to common shareholders	$	—		$	—		$	0.23		$	0.23		$	(0.06	)	$	(0.06	)

Partners_Equity_of_The_Operati1

Partners Equity of The Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
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):
		Year ended December 31,
		2014						2013						2012
		Basic			Diluted			Basic			Diluted			Basic			Diluted
	Numerator
	Income (loss) from continuing operations	$	6,024		$	6,024		$	38,982		$	38,982		$	(37,309	)	$	(37,309	)
	Amount allocable to unvested restricted unitholders	(349		)	(349		)	(363		)	(363		)	(376		)	(376		)
	Preferred unit dividends	(6,900		)	(6,900		)	(6,900		)	(6,900		)	(10,405		)	(10,405		)
	Net loss attributable to non-controlling interests	44			44			—			—			—			—
	Preferred unit redemption charge	—			—			—			—			(4,052		)	(4,052		)
	Income (loss) from continuing operations available to common unitholders	(1,181		)	(1,181		)	31,719			31,719			(52,142		)	(52,142		)
	Discontinued operations attributable to common unitholders	918			918			4,207			4,207			43,838			43,838
	Net income (loss) attributable to common unitholders	$	(263	)	$	(263	)	$	35,926		$	35,926		$	(8,304	)	$	(8,304	)
	Denominator
	Weighted-average units outstanding	167,942,246			167,942,246			154,929,545			154,929,545			145,883,217			145,883,217
	Contingent securities/Unit based compensation	—			—			—			1,273,853			—			—
	Total weighted-average units outstanding	167,942,246			167,942,246			154,929,545			156,203,398			145,883,217			145,883,217
	Earnings per Common Partnership Unit:
	Income (loss) from continuing operations attributable to common unitholders	$	(0.01	)	$	(0.01	)	$	0.2		$	0.2		$	(0.36	)	$	(0.36	)
	Discontinued operations attributable to common unitholders	0.01			0.01			0.03			0.03			0.3			0.3
	Net income (loss) attributable to common unitholders	$	—		$	—		$	0.23		$	0.23		$	(0.06	)	$	(0.06	)

Share_Based_and_Deferred_Compe1

Share Based and Deferred Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Option activity	Option activity as of December 31, 2014 and changes during the year-ended December 31, 2014 were as follows:
		Shares			Weighted				Weighted Average	Aggregate Intrinsic
					Average				Remaining Contractual	Value
					Exercise Price				Term (in years)
	Outstanding at January 1, 2014	2,983,569			$	15.5			5.15	$	—
	Exercised	(184,116	)		$	11.65				671,008
	Forfeited/Expired	(114,658	)		$	20.61
	Outstanding at December 31, 2014	2,684,795			$	15.55			4.1	$	1,152,891
	Vested/Exercisable at December 31, 2014	2,684,795			$	15.55			4.1	$	1,152,891
Company's restricted share activity	The following table summarizes the Company’s restricted share activity during the year-ended December 31, 2014:
		Shares			Weighted
					Average Grant
					Date Fair value
	Non-vested at January 1, 2014	563,713			$	12.56
	Granted	229,119			14.47
	Vested	(234,169	)		13.44
	Forfeited	(18,597	)		12.67
	Non-vested at December 31, 2014	540,066			$	12.21
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Performance-Based Units, Vested and Expected to Vest [Table Text Block]	The table below presents certain information as to RPSU awards.
			RPSU Grant
			3/1/12				2/25/13			3/11/14			3/12/14		Total
	(Amounts below in shares, unless otherwise noted)
	Non-vested at January 1, 2014		242,122				231,093			—			—		473,215
	Units Granted		—				—			134,284			61,720		196,004
	Units Canceled		(34,739		)		(31,516		)	(3,567		)	—		(69,822	)
	Non-vested at December 31, 2014		207,383				199,577			130,717			61,720		599,397
	Measurement Period Commencement Date		1/1/12				1/1/13			1/1/14			1/1/14
	Measurement Period End Date		12/31/14				12/31/15			12/31/16			12/31/16
	Units Granted		265,222				231,093			134,284			61,720
	Fair Value of Units on Grant Date (in thousands)		$	4,273			$	4,137		$	2,624		$	1,225

Distributions_Distributions_Ta

Distributions Distributions (Tables)	12 Months Ended
	Dec. 31, 2014
Distributions [Abstract]
Schedule of Dividends Payable [Table Text Block]
		Years ended December 31,
		2014			2013			2012
		(in thousands, except per share amounts)
	Common Share Distributions:
	Ordinary income	$	0.41		$	0.52		$	0.39
	Capital gain	0.02			—			—
	Non-taxable distributions	0.17			0.08			0.21
	Distributions per share	$	0.6		$	0.6		$	0.6
	Percentage classified as ordinary income	69		%	87		%	65		%
	Percentage classified as capital gain	3.3		%	—		%	—		%
	Percentage classified as non-taxable distribution	27.7		%	13		%	35		%
	Preferred Share Distributions:
	Total distributions declared	$	6,900		$	6,900		$	10,405
	Percentage classified as ordinary income	100		%	100		%	100		%

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table details the components of accumulated other comprehensive income (loss) of the Parent Company and the Operating Partnership as of and for the three years ended December 31, 2014 (in thousands):
	Parent Company	Cash Flow
		Hedges
	Balance at January 1, 2012	$	(6,079	)
	Change during year	(7,338		)
	Non-controlling interest — consolidated real estate venture partner’s share of unrealized (gains)/losses on derivative financial instruments	187
	Settlement of interest rate swaps	(2,985		)
	Reclassification adjustments for (gains)/losses reclassified into operations	297
	Balance at December 31, 2012	$	(15,918	)
	Change during year	12,789
	Non-controlling interest — consolidated real estate venture partner’s share of unrealized (gains)/losses on derivative financial instruments	(152		)
	Reclassification adjustments for (gains)/losses reclassified into operations	286
	Balance at December 31, 2013	$	(2,995	)
	Change during year	(1,190		)
	Non-controlling interest — consolidated real estate venture partner’s share of unrealized (gains)/losses on derivative financial instruments	18
	Settlement of interest rate swaps	(828		)
	Reclassification adjustments for (gains)/losses reclassified into operations	388
	Balance at December 31, 2014	$	(4,607	)
	Operating Partnership	Cash Flow
		Hedges
	Balance at January 1, 2012	$	(6,426	)
	Change during year	(7,338		)
	Reclassification adjustments for (gains)/losses reclassified into operations	297
	Settlement of interest rate swaps	(2,985		)
	Balance at December 31, 2012	$	(16,452	)
	Change during year	12,789
	Reclassification adjustments for (gains)/losses reclassified into operations	286
	Balance at December 31, 2013	$	(3,377	)
	Change during year	(1,190		)
	Settlement of interest rate swaps	(828		)
	Reclassification adjustments for (gains)/losses reclassified into operations	388
	Balance at December 31, 2014	$	(5,007	)

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment information	The following tables provide selected asset information and results of operations of the Company's reportable segments for the three years ended December 31, 2014, 2013 and 2012 (in thousands):
	Real estate investments, at cost:
			31-Dec-14			31-Dec-13			31-Dec-12
	Philadelphia CBD (a)		$	1,338,655		$	1,300,666		$	988,590
	Pennsylvania Suburbs		1,178,470			1,199,105			1,178,730
	Metropolitan Washington, D.C.		1,183,652			1,214,965			1,193,200
	New Jersey/Delaware		392,581			414,716			546,644
	Richmond, Virginia		317,076			310,397			309,923
	California		193,258			192,584			223,736
	Austin, Texas (b)		—			36,856			285,346
			$	4,603,692		$	4,669,289		$	4,726,169
	Assets held for sale (c)		27,436			—			—
	Operating Properties		$	4,631,128		$	4,669,289		$	4,726,169
	Corporate
	Construction-in-progress		$	201,360		$	74,174		$	48,950
	Land inventory		$	90,603		$	93,351		$	102,439
	(a)	On December 19, 2013, the Company acquired 99% of the common interests in the One and Two Common Square partnerships. See Note 3, "Real Estate Investments," for further information on the acquisition.
	(b)	On April 3, 2014, the Company contributed two three-story, Class A office buildings, containing an aggregate of 192,396 net rentable square feet, known as Four Points Centre in Austin, Texas to the Austin Venture. See Note 3, "Real Estate Investments," for further information on the contribution.
	(c)	On December 31, 2014, the Company was actively marketing for sale of its Atrium I and Libertyview properties, comprised of two office properties located in the New Jersey/Delaware segment. As of December 31, 2014 the properties were classified as held for sale on the consolidated balance sheet. See Note 3, "Real Estate Investments," for further information. The sale is not classified as a significant disposition under the accounting guidance for discontinued operations. Accordingly, the real estate investments remained in the New Jersey/Delaware segment as of December 31, 2014.
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block]
		Years ended
		December 31,
		2014									2013									2012
		Total revenue			Operating expenses (b)			Net operating income			Total revenue			Operating expenses (b)			Net operating income			Total revenue		Operating expenses			Net Operating income
	Philadelphia CBD	$	201,809		$	(75,262	)	$	126,547		$	146,081		$	(55,702	)	$	90,379		$	131,592	$	(50,787	)	$	80,805
	Pennsylvania Suburbs	160,630			(55,062		)	105,568			153,426			(54,506		)	98,920			150,075		(52,657		)	97,418
	Metropolitan Washington, D.C.	113,834			(43,399		)	70,435			116,048			(42,641		)	73,407			107,656		(41,485		)	66,171
	New Jersey/Delaware	60,403			(31,650		)	28,753			60,262			(29,981		)	30,281			59,671		(28,506		)	31,165
	Richmond, Virginia	34,180			(15,399		)	18,781			35,058			(14,916		)	20,142			35,701		(14,484		)	21,217
	California	19,388			(10,165		)	9,223			18,369			(9,411		)	8,958			17,463		(9,043		)	8,420
	Austin, Texas (a)	5,610			(3,223		)	2,387			31,451			(13,298		)	18,153			32,379		(13,951		)	18,428
	Corporate	1,128			(1,805		)	(677		)	1,515			(1,314		)	201			1,142		65			1,207
	Operating Properties	$	596,982		$	(235,965	)	$	361,017		$	562,210		$	(221,769	)	$	340,441		$	535,679	$	(210,848	)	$	324,831
	(a)	On April 3, 2014, the Company contributed two three-story, Class A office buildings, containing an aggregate of 192,396 net rentable square feet, known as Four Points Centre in Austin, Texas to the Austin Venture. See Note 3, "Real Estate Investments," for further information on the contribution. Accordingly, the Company's 50% interest in the financial results of this property for the period subsequent to April 3, 2014 is reported as a component of 'Equity in income (loss) of real estate ventures' in the Company's consolidated statements of operations and, as a result, no longer included as a component of net operating income.
	(b)	Includes property operating expense, real estate taxes and third party management expense.
Reconciliation of Other Significant Reconciling Items from Segments to Consolidated [Table Text Block]
	Unconsolidated real estate ventures:
		Investment in real estate ventures, at equity									Equity in income (loss) of real estate ventures
		As of									Years ended December 31,
		31-Dec-14			31-Dec-13			31-Dec-12			2014			2013			2012
	Philadelphia CBD (a)	$	27,137		$	19,975		$	27,859		$	46		$	1,547		$	1,113
	Pennsylvania Suburbs	17,385			17,272			33,160			(777		)	925			520
	Metropolitan Washington, D.C.	73,127			59,905			49,169			(317		)	130			(648		)
	New Jersey/Delaware	—			—			17,294			989			1,245			1,803
	Richmond, Virginia	1,574			1,400			1,245			349			381			269
	Austin, Texas (b) (c)	105,781			81,960			64,828			(1,080		)	(564		)	(316		)
	Total	$	225,004		$	180,512		$	193,555		$	(790	)	$	3,664		$	2,741
	(a)	During the fourth quarter of 2014, the Company made an additional $5.2 million capital contribution to 1919 Ventures. See Note 4, "Investment In Unconsolidated Ventures," for further information on this transaction.
	(b)	Investment in real estate ventures does not include the $1.2 million negative investment balance in one real estate venture as of December 31, 2014, which is included in other liabilities.
	(c)	On April 3, 2014, the Company contributed Four Points Centre to an unconsolidated real estate venture. On July 31, 2014, the Austin Venture completed the acquisition of the Crossings at Lakeline. On October 17, 2014, the Austin Venture acquired River Place. See Note 4, "Investment In Unconsolidated Ventures," for further information on these acquisitions.
Reconciliation of consolidated net operating income	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 its 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. The following is a reconciliation of consolidated NOI to consolidated net income (loss), as defined by GAAP:
		Years Ended December 31,
		2014			2013			2012
	Consolidated net operating income	$	361,017		$	340,441		$	324,831
	Less:
	Interest expense	(124,329		)	(121,937		)	(132,939		)
	Interest expense - amortization of deferred financing costs	(5,148		)	(4,676		)	(6,208		)
	Interest expense - financing obligation	(1,144		)	(972		)	(850		)
	Depreciation and amortization	(208,569		)	(197,021		)	(188,382		)
	General and administrative expenses	(26,779		)	(27,628		)	(25,413		)
	Plus:
	Interest income	3,974			1,044			3,008
	Historic tax credit transaction income	11,853			11,853			11,840
	Recognized hedge activity	(828		)	—			(2,985		)
	Equity in income (loss) of real estate ventures	(790		)	3,664			2,741
	Net gain from remeasurement of investments in real estate ventures	458			6,866			—
	Net gain on sales of interests in real estate	4,901			—			—
	Net gain (loss) on sale of undepreciated real estate	1,184			(137		)	—
	Net (loss) gain on real estate venture transactions	(417		)	29,604			(950		)
	Provision for impairment on assets held for sale	(1,765		)	—			—
	Loss on early extinguishment of debt	(7,594		)	(2,119		)	(22,002		)
	Income (loss) from continuing operations	6,024			38,982			(37,309		)
	Income from discontinued operations	918			4,207			43,838
	Net income	$	6,942		$	43,189		$	6,529

Operating_Leases_Tables

Operating Leases (Tables)	12 Months Ended
	Dec. 31, 2014
Leases, Operating [Abstract]
Operating Leases Future Minimum Payments Due [Table Text Block]	The Company leases properties to tenants under operating leases with various expiration dates extending to 2030. Minimum future rentals on non-cancelable leases at December 31, 2014 are as follows (in thousands):
	Year	Minimum Rent
	2015	$	461,215
	2016	443,383
	2017	411,288
	2018	362,370
	2019	315,196
	Thereafter	1,515,750

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity Schedule [Table Text Block]	Future minimum rental payments under the terms of all non-cancellable 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 7 to 75 years. Minimum future rental payments on non-cancelable leases at December 31, 2014 are as follows (in thousands):
	Year	Minimum Rent
	2015	$	1,378
	2016	1,378
	2017	1,378
	2018	1,378
	2019	1,378
	Thereafter	57,114
	Total	$	64,004

Summary_of_Quarterly_Results_T

Summary of Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	The following is a summary of quarterly financial information as of and for the years ended December 31, 2014 and 2013 (in thousands, except per share data):
		1st			2nd		3rd		4th
		Quarter			Quarter		Quarter		Quarter
	2014
	Total revenue	$	152,114		$	150,500	$	146,558	$	147,810
	Net income (loss)	(2,245		)	2,174		8,882		(1,869		)
	Net income (loss) allocated to Common Shares	(4,041		)	385		6,967		(3,585		)
	Basic earnings (loss) per Common Share	$	(0.03	)	$	—	$	0.04	$	(0.02	)
	Diluted earnings (loss) per Common Share	$	(0.03	)	$	—	$	0.04	$	(0.02	)
	2013
	Total revenue	$	139,554		$	140,664	$	143,354	$	138,658
	Net income	3,919			7,180		11,088		21,002
	Net income allocated to Common Shares	2,058			5,308		9,173		18,975
	Basic earnings per Common Share	$	0.01		$	0.03	$	0.06	$	0.12
	Diluted earnings per Common Share	$	0.01		$	0.03	$	0.06	$	0.12

Organization_of_The_Parent_Com1

Organization of The Parent Company and The Operating Partnership (Details)	Dec. 31, 2014
	acre
	sqft
Parent Company [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Ownership in the Operating Partnership	99.00%
Net rentable square feet	25,100,000
Area Owned by Company of Undeveloped Parcels Of Land	415
Area of additional undeveloped parcels of land with option to purchase	63
Total potential development capacity	6,000,000
Unconsolidated real estate ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of unconsolidated real estate ventures	17
Net rentable square feet	6,700,000
Wholly-owned management company subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	33,900,000
Third Parties and Unconsolidated Real Estate Ventures [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	8,900,000
Subsidiaries [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Ownership in the Operating Partnership	100.00%
Total Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	200
Office Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	167
Industrial facilities [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	20
Mixed-use properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	5
Retail Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	1
Core Properties [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	193
Development Property [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	3
Assets Held-for-sale [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	2
Redevelopment Property [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	1
Re-entitlement Property [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Number of properties with ownership interest	1
Wholly Owned Properties [Member] | Parent Company [Member]
Organization of The Parent Company and The Operating Partnership (Textuals) [Abstract]
Net rentable square feet	25,000,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 02, 2010
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Increased revenue due to amortization of deferred rent	$2.40	$2.40	$2.40
Decrease in revenue due to amortization of lease incentives	1.5	0.7	0.8
Increase in shares due to amendments in plan, shares solely available for options and share appreciation rights	2,684,795			3,600,000
Revenue increased by straight-line rent adjustment	13.7	17.7	21.1
Increase in Common shares available for future awards				6,000,000
Common shares available for future awards	4,304,006
Options awarded, term	one to ten-year
Stock-based compensation expense	6.1	8.3	8.6
Stock-based compensation expense, capitalized	1.7	1.4	2.6
Capitalized interest	4.8	2.6	2.6
Concentration Risk, Percentage	10.00%	10.00%	10.00%
The Grove at Cira Centre South [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Guaranty Liabilities	24.7
PJP VII [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Guaranty Liabilities	0.5
TB-BDN Plymouth Apartments [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Guaranty Liabilities	3.2
Maximum [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Property, Plant and Equipment, Useful Life	55 years 0 months 0 days
TenantImprovementsUsefulLives	16 years 0 months 0 days
Minimum [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Property, Plant and Equipment, Useful Life	5 years 0 months 0 days
TenantImprovementsUsefulLives	1 year 0 months 0 days
Equity Method Investments [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Capitalized interest	2	0.6
Accounts receivable and accrued rent receivable [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Concentration Risk, Percentage	10.00%	10.00%
Accrued Rent Receivable [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Allowance for Doubtful Accounts Receivable	$13.40	$13
Tenant relationship value [Member]
Summary Of Significant Accounting Policies (Textuals) [Abstract]
Concentration Risk, Percentage	10.00%	10.00%	10.00%

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Notes Receivable) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%
Capitalized interest	$4,800,000	$2,600,000	$2,600,000
Interest Income	3,974,000	1,044,000	3,008,000
Notes receivable	88,000,000	7,026,000
Accrued Rent Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	13,400,000	13,000,000
River Place [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Income	700,000
Notes receivable	88,000,000
Accounts receivable and accrued rent receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration Risk, Percentage	10.00%	10.00%
20 Year Amortization Period [Member] | Purchase money mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable		7,000,000
Mortgage Loans on Real Estate, Interest Rate		8.50%
Notes Receivable Amortization Period, Years	20 years	20 years
20 Year Amortization Period [Member] | Accrued interest received [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Income	1,500,000
Trenton Properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Income	1,000,000
Number of properties sold			2
Gross deferred gain on sale of properties			12,900,000
Equity Method Investments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Capitalized interest	$2,000,000	$600,000

Summary_of_Significant_Account5

Summary of Significant Accounting Policies Construction in Progress (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Construction in Progress [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$5,200,000	$3,700,000	$4,700,000
Capitalized interest	4,800,000	2,600,000	2,600,000
Salaries including bonuses and benefits, capitalized during the period	5,194,000	3,673,000	4,669,000
Development [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	1,749,000	156,000	57,000
Redevelopment [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	184,000	194,000	353,000
Tenant Improvements [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	$3,261,000	$3,323,000	$4,259,000

Summary_of_Significant_Account6

Summary of Significant Accounting Policies Impairment or DIsposal of Long-Lived Assets (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Acquisitions and Disposals [Line Items]
Provision for impairment on assets held for sale	$1,765	$0	$0
Gains (Losses) on Sales of Investment Real Estate	4,901	0	0
Valleybrooke Office Park [Member]
Significant Acquisitions and Disposals [Line Items]
Provision for impairment on assets held for sale	1,765
Gains (Losses) on Sales of Investment Real Estate	$200

Summary_of_Significant_Account7

Summary of Significant Accounting Policies Accounts Receivable and Accrued Rent Receivable (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration Risk, Percentage	10.00%	10.00%	10.00%
Straight Line Rent Adjustments	($13,700,000)	($17,700,000)	($21,100,000)
Proceeds from repayment of mortgage notes receivable	7,026,000	200,000	23,364,000
Accounts receivable and accrued rent receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration Risk, Percentage	10.00%	10.00%
Tenant Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	2,000,000	3,200,000
Accrued Rent Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for Doubtful Accounts Receivable	13,400,000	13,000,000
20 Year Amortization Period [Member] | Purchase money mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable Amortization Period, Years	20 years	20 years
Mortgage Loans on Real Estate, Interest Rate		8.50%
Notes Receivable Due Two Thousand Sixteen [Member] | Purchase money mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from repayment of mortgage notes receivable			23,500,000
Trenton Properties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred Gain on Sale of Property			$12,900,000

Summary_of_Significant_Account8

Summary of Significant Accounting Policies Schedule of Other Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Assets [Abstract]
Other assets	$65,111	$62,377

Summary_of_Significant_Account9

Summary of Significant Accounting Policies Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Contingency [Line Items]
Increase In Revenue Due To Amortization Of Deferred Rent	$2,400,000	$2,400,000	$2,400,000
Distributable Income Minimum Percentage	90.00%
Federal excise tax if sufficient taxable income is not distributed within prescribed time limits	4.00%
Excise tax equal to annual amount	4.00%
Excise tax, if sum of ordinary income	85.00%
Excise tax, if Net capital gain exceeds cash distributions and certain taxes paid	95.00%
Tax Basis of Assets, Cost for Income Tax Purposes	3,700,000,000	4,000,000,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Income Tax Contingency [Line Items]
Tax Basis of Assets, Cost for Income Tax Purposes	$3,700,000,000	$4,000,000,000

Recovered_Sheet2

Summary of Significant Accounting Policies Deferred Costs (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Operating Leased Assets [Line Items]
Intangible Assets, net	99,403	$132,329
Service Life [Member]
Operating Leased Assets [Line Items]
Remaining Lease Period - Minimum	1 year 0 months 0 days
Remaining Lease Period - Maximum	15 years 0 months 0 days

Recovered_Sheet3

Summary of Significant Accounting Policies Finite-lived intangible assets (Details)	Dec. 31, 2014
	Y
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	7
Maximum remaining lease period	75

Real_Estate_Investments_Real_E

Real Estate Investments Real Estate Investments, Business Combinations (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 19, 2013
One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		$255,705
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		85,036
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other		8,637
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		332,104
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt		238,082
Business Combination, return of capital on equity method investment		-30,424
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other		10,423
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		-946
Business Combination, Total Cash Payment at Settlement		73,075
Leases, Acquired-in-Place [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		80,916
Above Market Leases [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		4,120
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 10 months 24 days
Below Market Lease [Member] | One and Two Commerce Square [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		($8,637)
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 6 months
One and Two Commerce Square [Member] | Leases, Acquired-in-Place [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 10 months 24 days

Real_Estate_Investments_Pro_Fo

Real Estate Investments, Pro Forma of Acquired Properties (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue										$610,979	$592,753
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax										21,805	-60,011
Business Acquisition, Pro Forma Net Income (Loss)										$25,957	($16,970)
Continuing operations (in dollars per share)									($0.01)	$0.20	($0.36)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Basic										$0.14	($0.42)
Income (Loss) from Continuing Operations, Per Diluted Share									($0.01)	$0.20	($0.36)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Diluted										$0.14	($0.42)
Earnings Per Share, Basic	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Pro Forma, Earnings Per Share, Basic										$0.17	($0.12)
Earnings Per Share, Diluted	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Pro Forma Earnings Per Share, Diluted										$0.17	($0.12)

Real_Estate_Investments_Gross_

Real Estate Investments, Gross Carrying Value of Company's Properties (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Gross carrying value of rental properties
Land	$669,635		$680,513
Building and improvements	3,409,303		3,504,060
Tenant improvements	524,754		484,716
Rental properties	4,603,692		4,669,289		4,726,169
Real Estate Held-for-sale	27,436	[1]	0	[1]	0
Real Estate Investment Property, at Cost, Gross of Held For Sale	$4,631,128		$4,669,289		$4,726,169
[1]	(a)Real estate investments related to assets held for sale above represents gross real estate assets and does not include accumulated depreciation or other assets on the balance sheets of the properties held for sale.

Real_Estate_Investments_Acquis

Real Estate Investments, Acquisitions and Dispositions (Details) (USD $)	3 Months Ended								12 Months Ended			0 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 19, 2013	Oct. 17, 2013	Jun. 14, 2013	Apr. 07, 2014	Jul. 18, 2012	Jun. 22, 2012	Mar. 22, 2012	Jan. 17, 2012	Jun. 28, 2013	Jun. 19, 2013	Feb. 19, 2014	Apr. 25, 2013	Apr. 03, 2014	Oct. 16, 2013	Nov. 19, 2013	Mar. 27, 2014	Apr. 16, 2014	Aug. 05, 2013	Feb. 25, 2013	Oct. 17, 2014	Jul. 31, 2014
	acre								acre			sqft	sqft	sqft		sqft	sqft	sqft	sqft	sqft	sqft	Properties	acre			acre	acre	acre	acre	sqft	sqft	Properties
												Storey										Storey								Properties	Real_Estate_Investments
																						sqft
																						acre
Significant Acquisitions and Disposals [Line Items]
Provision for impairment on assets held for sale									$1,765,000	$0	$0
Business Acquisition, Pro Forma Revenue										610,979,000	592,753,000
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual										3,400,000
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual										200,000
Net gain (loss) on sale of undepreciated real estate									458,000	6,866,000	0
Land	669,635,000				680,513,000				669,635,000	680,513,000
Adjustment to Record Land Acquisition to Fair Value									0	7,752,000	0
Payments to Acquire Real Estate									18,443,000	161,604,000	77,555,000
Gains (Losses) on Sales of Investment Real Estate									4,901,000	0	0
Equity Method Investments	225,004,000				180,512,000				225,004,000	180,512,000	193,555,000
Secured Debt	654,590,000				670,151,000				654,590,000	670,151,000
Balance of the Financing Obligation	37,558,000				32,923,000				37,558,000	32,923,000
Gain (Loss) on Sale of Properties									900,000	3,382,000	34,774,000
Net gain (loss) on sale of undepreciated real estate									1,184,000	-137,000	0
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land	3								3
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax										21,805,000	-60,011,000
Business Acquisition, Pro Forma Net Income (Loss)										25,957,000	-16,970,000
Continuing operations (in dollars per share)									($0.01)	$0.20	($0.36)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Basic										$0.14	($0.42)
Income (Loss) from Continuing Operations, Per Diluted Share									($0.01)	$0.20	($0.36)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Diluted										$0.14	($0.42)
Earnings Per Share, Basic	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Pro Forma, Earnings Per Share, Basic										$0.17	($0.12)
Earnings Per Share, Diluted	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Pro Forma Earnings Per Share, Diluted										$0.17	($0.12)
Other assets	65,111,000				62,377,000				65,111,000	62,377,000
One and Two Commerce Square [Member]
Significant Acquisitions and Disposals [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment												255,705,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage												99.00%
Net gain (loss) on sale of undepreciated real estate												981,000
Number of floors of a building												41
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds												331,800,000
Business Combination, Assumption of Existing Mortgage Debt												237,100,000
Lease percentage of acquired property					86.70%					86.70%
Net rentable space of property acquired												1,896,142
Acquisition related costs												900,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles												85,036,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other												-8,637,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net												332,104,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt												-238,082,000
Business Combination, return of capital on equity method investment												-30,424,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other												10,423,000
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value												-946,000
Business Combination, Total Cash Payment at Settlement												73,075,000
Four Points Centre [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Land												22.3
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds												47,300,000
Lease percentage of acquired property												99.20%
Business Acquisition Purchase Price Allocation Intangible Assets												6,500,000
Business Acquisition Purchase Price Allocated To Market Lease Liabilities												1,000,000
Net rentable space of property acquired												192,396
Acquisition related costs												100,000
Business Acquisition Purchase Price Allocation Building												36,000,000
Business Acquisition Purchase Price Allocation, Land Portion												5,800,000
Cira Ground Land Parcel [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Land																										0.8
Ground Lease Buy-out, Total Cost																										24,600,000
Accrued Rent																										12,100,000
Acquisition related costs																										1,400,000
Rob Roy - Land [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Land																											16.8
Sales price of properties sold																											3,500,000
Net gain (loss) on sale of undepreciated real estate									1,200,000
1000 Atrium Way and Libertyview [Member] [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Real Estate Properties	2								2
Valleybrooke Office Park [Member]
Significant Acquisitions and Disposals [Line Items]
Disposal group, number of properties held for sale	5								5
Net rentable square feet of properties sold	279,934								279,934
Sales price of properties sold	37,900,000								37,900,000
Campus Pointe [Member]
Significant Acquisitions and Disposals [Line Items]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal									4,700,000
Net rentable square feet of properties sold		172,943
Sales price of properties sold		42,500,000
West Point II Land [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Land																												5.3
Sales price of properties sold																												1,600,000
1000 Atrium Way [Member]
Significant Acquisitions and Disposals [Line Items]
Net rentable space of property acquired	99,668								99,668
875 First Avenue [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties												100,000
Net rentable square feet of properties sold												50,000
Sales price of properties sold												3,800,000
1336 Enterprise Drive [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties													200,000
Net rentable square feet of properties sold													39,330
Sales price of properties sold													2,600,000
Dabney Land, East [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Land																													8
Sales price of properties sold																													500,000
Net gain (loss) on sale of undepreciated real estate										-100,000
Pacific View Plaza [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties														-500,000
Net rentable square feet of properties sold														51,695
Sales price of properties sold														10,300,000
Princeton Pike Corporate Center [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties										5,300,000					900,000
Number of flex/office properties sold																														8
Net rentable square feet of properties sold																														800,546
Sales price of properties sold																														121,000,000
Oaklands Corporate Center [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																9,900,000
Number of flex/office properties sold																11
Net rentable square feet of properties sold																466,719
Sales price of properties sold																52,700,000
Pacific Ridge Corporate Center [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																	-2,800,000
Net rentable square feet of properties sold																	121,381
Sales price of properties sold																	29,000,000
South Lake at Dulles Corner [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																		14,500,000
Net rentable square feet of properties sold																		268,240
Sales price of properties sold																		91,100,000
304 Harper Drive [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																			200,000
Net rentable square feet of properties sold																			32,978
Sales price of properties sold																			3,000,000
The Bluffs [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																				-900,000
Net rentable square feet of properties sold																				68,708
Sales price of properties sold																				18,000,000
100 Arrandale Boulevard [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																				-400,000
Net rentable square feet of properties sold																				34,931
Sales price of properties sold																				3,500,000
1700 Paoli Pike [Member]
Significant Acquisitions and Disposals [Line Items]
Gain (Loss) on Sale of Properties																					-400,000
Net rentable square feet of properties sold																					28,000
Sales price of properties sold																					2,700,000
Four Points Centre [Member]
Significant Acquisitions and Disposals [Line Items]
Number of floors of a building												3												3
Net rentable space of property acquired																								192,396
Number of Real Estate Properties																								2
Libertyview [Member]
Significant Acquisitions and Disposals [Line Items]
Net rentable space of property acquired	121,737								121,737
Austin Joint Venture [Member]
Significant Acquisitions and Disposals [Line Items]
Equity Method Investments	40,374,000								40,374,000
Company's Ownership Percentage in the Real Estate Venture	50.00%								50.00%
Net rentable space of property acquired																															590,881
Number of Real Estate Properties																															7	2
Austin Joint Venture [Member] | Four Points Centre [Member]
Significant Acquisitions and Disposals [Line Items]
Non-Recourse Debt																								29,000,000
Brandywine - Al Venture [Member]
Significant Acquisitions and Disposals [Line Items]
Equity Method Investments	45,712,000								45,712,000
Company's Ownership Percentage in the Real Estate Venture	50.00%								50.00%
Encino Trace - Land [Member]
Significant Acquisitions and Disposals [Line Items]
Number of potential development properties																						2
Number of floors of a building																						4
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds																						14,000,000
Total potential development capacity																						320,000
Land			4,600,000
Escrow Deposit																						1,000,000
Construction in Progress, Gross																						8,400,000
Lease percentage of acquired property																						75.00%
Area Owned by Company of Undeveloped Parcels Of Land																						54.1
Three Logan Square [Member]
Significant Acquisitions and Disposals [Line Items]
Area of Land																							1.8
Ground Lease Buy-out, Total Cost																							20,800,000
Adjustment to Record Land Acquisition to Fair Value																							4,300,000
Acquisition related costs																							100,000
Secured Debt [Member]
Significant Acquisitions and Disposals [Line Items]
Long-term Debt, Gross	655,934,000				669,762,000				655,934,000	669,762,000
Secured Debt	654,590,000				670,151,000				654,590,000	670,151,000
Secured Debt [Member] | Two Commerce Square [Member]
Significant Acquisitions and Disposals [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate												3.96%
Long-term Debt, Fair Value												107,900,000
Long-term Debt, Gross												112,000,000
Secured Debt [Member] | One Commerce Square [Member]
Significant Acquisitions and Disposals [Line Items]
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate												5.67%
Long-term Debt, Fair Value												130,200,000
Long-term Debt, Gross												125,100,000
Subsidiaries [Member]
Significant Acquisitions and Disposals [Line Items]
Provision for impairment on assets held for sale									1,765,000	0	0
Net gain (loss) on sale of undepreciated real estate									458,000	6,866,000	0
Adjustment to Record Land Acquisition to Fair Value									0	7,752,000
Payments to Acquire Real Estate									18,443,000	161,604,000	77,555,000
Gains (Losses) on Sales of Investment Real Estate									4,901,000	0	0
Equity Method Investments	225,004,000				180,512,000				225,004,000	180,512,000
Secured Debt	654,590,000				670,151,000				654,590,000	670,151,000
Balance of the Financing Obligation	37,558,000				32,923,000				37,558,000	32,923,000
Gain (Loss) on Sale of Properties									900,000	3,382,000	34,774,000
Net gain (loss) on real estate venture transactions									-417,000	3,683,000	0
Net gain (loss) on sale of undepreciated real estate									1,184,000	-137,000	0
Continuing operations (in dollars per share)									($0.01)	$0.20	($0.36)
Income (Loss) from Continuing Operations, Per Diluted Share									($0.01)	$0.20	($0.36)
Earnings Per Share, Basic									$0	$0.23	($0.06)
Earnings Per Share, Diluted									$0	$0.23	($0.06)
Other assets	65,111,000				62,377,000				65,111,000	62,377,000
Brandywine Realty Trust [Member] | Austin Joint Venture [Member]
Significant Acquisitions and Disposals [Line Items]
Company's Ownership Percentage in the Real Estate Venture	50.00%								50.00%
Aggregate gross sales price of a joint venture																									330,000,000
Brandywine Realty Trust [Member] | Austin Joint Venture [Member] | Four Points Centre [Member]
Significant Acquisitions and Disposals [Line Items]
Aggregate gross sales price of a joint venture																								41,500,000
Amount Of Participant Contribution																								5,900,000
Net gain (loss) on real estate venture transactions									-200,000
Proceeds from Equity Method Investment, Dividends or Distributions																								34,400,000
DRA Advisors LLC [Member] | Austin Joint Venture [Member]
Significant Acquisitions and Disposals [Line Items]
Company's Ownership Percentage in the Real Estate Venture	50.00%								50.00%
Non-Recourse Debt																									230,600,000
Amount Of Participant Contribution																									49,700,000
Proceeds from Equity Method Investment, Dividends or Distributions																									271,500,000
DRA Advisors LLC [Member] | Austin Joint Venture [Member] | Four Points Centre [Member]
Significant Acquisitions and Disposals [Line Items]
Amount Of Participant Contribution																								5,900,000
Encino Trace - Building I [Member]
Significant Acquisitions and Disposals [Line Items]
Construction in Progress, Gross	38,800,000								38,800,000
Valleybrooke Office Park [Member]
Significant Acquisitions and Disposals [Line Items]
Provision for impairment on assets held for sale									1,765,000
Gains (Losses) on Sales of Investment Real Estate									$200,000

Investment_in_Unconsolidated_V2

Investment in Unconsolidated Ventures (Narrative) (Details) (USD $)

12 Months Ended

0 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Oct. 17, 2014

Jul. 31, 2014

Jul. 31, 2013

Jun. 19, 2013

Oct. 16, 2013

Apr. 03, 2014

Jan. 20, 2011

Mar. 26, 2013

Jan. 25, 2013

Oct. 20, 2014

Oct. 21, 2014

Dec. 19, 2013

sqft

acre

acre

beds

Storey

Buildings

sqft

Storey

Real_Estate_Ventures

acre

Room

acre

ApartmentUnits

Schedule of Equity Method Investments [Line Items]

Number of apartment units in a Real Estate Venture

345

Net gain (loss) on real estate venture transactions

($417,000)

$29,604,000

($950,000)

Net proceeds from the contribution of land to an unconsolidated real estate venture

8,212,000

0

0

Payments to Acquire Equity Method Investments

46,098,000

33,069,000

65,354,000

Company's share of equity (Company's basis)

225,004,000

180,512,000

193,555,000

Net gain on real estate venture transactions

-417,000

3,683,000

0

Number of unconsolidated Real Estate Ventures

17

Equity Method Investments including net liabilities

223,790,000

Number of real estate ventures that owns 51 office buildings

11

Number of office buildings owned by 15 Real Estate Ventures

65

Net rentable square feet of 51 office buildings owned the 15 Real Estate Ventures

6,700,000

Number of real estate ventures that owns undeveloped land

1

Area of undeveloped parcels of land (in acres) owned by a Real Estate Venture

3

Number of real estate ventures that owns land under development

4

Area Owned By Real Estate Venture in Parcels Of Land Under Development

22.6

Number of real estate ventures developed hotel property

1

Number of rooms in a hotel property developed by one Real Estate Venture

137

Minimum ownership interest in unconsolidated Real Estate Ventures

20.00%

Maximum ownership interest in unconsolidated Real Estate Ventures

65.00%

Net gain (loss) on sale of undepreciated real estate

458,000

6,866,000

0

Brandywine Nineteen Nineteen Ventures [Member]

Schedule of Equity Method Investments [Line Items]

Equity Method Investment, Ownership Percentage

50.00%

50.00%

Company's share of equity (Company's basis)

12,823,000

Area of undeveloped parcels of land (in acres) owned by a Real Estate Venture

1

Payments to Acquire Land

9,300,000

Austin, Texas [Member]

Schedule of Equity Method Investments [Line Items]

Number of floors of a building

3

BDN Beacon Venture LLC [Member]

Schedule of Equity Method Investments [Line Items]

Equity Method Investment, Ownership Percentage

20.00%

Company's share of equity (Company's basis)

17,000,000

Austin Joint Venture [Member]

Schedule of Equity Method Investments [Line Items]

Equity method investment, Consideration transferred

128,100,000

48,200,000

Short-term Bank Loans and Notes Payable

88,000,000

Number of Real Estate Properties

7

2

Potential future capital contributions under joint ventures which are not contractually binding

100,000,000

Equity method investments, Cash contributions

69,000,000

12,800,000

Equity method investments, Closing costs

200,000

100,000

Equity Method Investment, Ownership Percentage

50.00%

Company's share of equity (Company's basis)

40,374,000

Two Tower Bridge [Member]

Schedule of Equity Method Investments [Line Items]

Company's share of equity (Company's basis)

-100,000

Net gain on real estate venture transactions

3,683,000

Investments, Fair Value Disclosure

3,600,000

4040 Wilson Venture [Member]

Schedule of Equity Method Investments [Line Items]

Area of Real Estate Property

426,900

Equity Method Investment, Ownership Percentage

50.00%

Equity Method Investment, Budgeted Total Project Cost

194,600,000

Payments to Acquire Equity Method Investments

72,000,000

Guaranty Percentage

100.00%

Company's share of equity (Company's basis)

27,415,000

Area of undeveloped parcels of land (in acres) owned by a Real Estate Venture

1.3

Six Tower Bridge [Member]

Schedule of Equity Method Investments [Line Items]

Net gain (loss) on sale of undepreciated real estate

7,800,000

Business Combination, Step Acquisition, Equity Interest in Acquiree, Fair Value

24,500,000

Business Acquisition Purchase Price Allocation Building

14,800,000

Business Acquisition Purchase Price Allocation, Land Portion

6,900,000

Business Acquisition Purchase Price Allocation Intangible Assets

3,300,000

Business Acquisition Purchase Price Allocated To Market Lease Liabilities

500,000

The Grove at Cira Centre South [Member]

Schedule of Equity Method Investments [Line Items]

Equity method investments, Cash contributions

0

Number of floors of a building

33

Student housing bed capacity

850

Equity Method Investment, Budgeted Total Project Cost

158,500,000

Payments to Acquire Equity Method Investments

60,700,000

Construction Loan

97,800,000

Equity Method Investment, Aggregate Cost

4,000,000

Area of undeveloped parcels of land (in acres) owned by a Real Estate Venture

1

Equity Method Investment, Underlying Equity in Net Assets

8,500,000

Equity Method Investment, Difference Between Carrying Amount and Underlying Equity

4,500,000

TB-BDN Plymouth Apartments [Member]

Schedule of Equity Method Investments [Line Items]

Guaranty Liabilities

3,200,000

PJP VII [Member]

Schedule of Equity Method Investments [Line Items]

Guaranty Liabilities

500,000

The Grove at Cira Centre South [Member]

Schedule of Equity Method Investments [Line Items]

Guaranty Liabilities

24,700,000

Third Parties and Real Estate Ventures [Member] | Brandywine Nineteen Nineteen Ventures [Member]

Schedule of Equity Method Investments [Line Items]

Equity Method Investment, Ownership Percentage

50.00%

LCOR/Calstrs [Member] | Brandywine Nineteen Nineteen Ventures [Member]

Schedule of Equity Method Investments [Line Items]

Aggregate gross sales price of a joint venture

16,400,000

General Partners' Contributed Capital

5,200,000

Equity method investments, Cash contributions

13,400,000

Net proceeds from the contribution of land to an unconsolidated real estate venture

8,200,000

Ashton Park [Member] | 4040 Wilson Venture [Member]

Schedule of Equity Method Investments [Line Items]

Fair value of land, net of amount encumbered

36,000,000

Brandywine Realty Trust [Member] | Austin, Texas [Member]

Schedule of Equity Method Investments [Line Items]

Equity method investment, agreement to pay future capital expenditures

4,400,000

Brandywine Realty Trust [Member] | Austin Joint Venture [Member]

Schedule of Equity Method Investments [Line Items]

Number of properties contributed to a joint venture

7

Area of Real Estate Property

1,398,826

Aggregate gross sales price of a joint venture

330,000,000

Equity method investment, agreement to pay future capital expenditures

800,000

5,200,000

Equity method investments, Cash contributions

18,900,000

6,400,000

Net gain (loss) on real estate venture transactions

25,900,000

Equity Method Investment, Ownership Percentage

50.00%

Equity Method Investment, Additional Distribution Rights

10.00%

Brandywine Realty Trust [Member] | 4040 Wilson Venture [Member]

Schedule of Equity Method Investments [Line Items]

Payments to Acquire Interest in Joint Venture

26,800,000

36,000,000

DRA Advisors LLC [Member] | Austin Joint Venture [Member]

Schedule of Equity Method Investments [Line Items]

Equity Method Investment, Distribution, Net of Initial Funding Agreement

266,300,000

Amount Of Participant Contribution

49,700,000

Equity method investments, Closing costs

1,900,000

Closing Prorations and Lender Holdbacks

6,900,000

Proceeds from Equity Method Investment, Dividends or Distributions

271,500,000

Equity Method Investment, Ownership Percentage

50.00%

Non-Recourse Debt

230,600,000

Campus Crest Properties, LLC [Member] | The Grove at Cira Centre South [Member]

Schedule of Equity Method Investments [Line Items]

Equity Method Investment, Ownership Percentage

30.00%

HSRE, LLC [Member] [Member] | The Grove at Cira Centre South [Member]

Schedule of Equity Method Investments [Line Items]

Equity Method Investment, Ownership Percentage

40.00%

Four Points Centre [Member]

Schedule of Equity Method Investments [Line Items]

Number of Real Estate Properties

2

Number of floors of a building

3

3

Four Points Centre [Member] | Austin Joint Venture [Member]

Schedule of Equity Method Investments [Line Items]

Non-Recourse Debt

29,000,000

Four Points Centre [Member] | Brandywine Realty Trust [Member] | Austin Joint Venture [Member]

Schedule of Equity Method Investments [Line Items]

Aggregate gross sales price of a joint venture

41,500,000

Amount Of Participant Contribution

5,900,000

Proceeds from Equity Method Investment, Dividends or Distributions

34,400,000

Four Points Centre [Member] | DRA Advisors LLC [Member] | Austin Joint Venture [Member]

Schedule of Equity Method Investments [Line Items]

Amount Of Participant Contribution

$5,900,000

Investment_in_Unconsolidated_V3

Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2014
Financial position of the Real Estate Ventures
Equity Method Investment Summarized Financial Information Debt	$965,077
Company's share of equity (Company's basis)	225,004	180,512	193,555
PJP Two [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Maturity Date	1-Nov-23
Financial position of the Real Estate Ventures
Equity Method Investment Summarized Financial Information Debt	3,492
Company's share of equity (Company's basis)	403
Coppell Associates [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Maturity Date	1-Feb-16
Financial position of the Real Estate Ventures
Equity Method Investment Summarized Financial Information Debt	15,747
Company's share of equity (Company's basis)	-1,214
Unconsolidated real estate ventures [Member]
Financial position of the Real Estate Ventures
Net property	1,281,282	965,475
Other Assets	195,121	164,152
Other Liabilities	68,481	49,442
Equity Method Investment Summarized Financial Information Debt	965,077	699,860
Equity	442,845	380,325
Company's share of equity (Company's basis)	225,004	180,512
PJP Five [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Maturity Date	11-Aug-19
Financial position of the Real Estate Ventures
Equity Method Investment Summarized Financial Information Debt	5,242
Company's share of equity (Company's basis)	216
Austin Joint Venture [Member]
Financial position of the Real Estate Ventures
Equity Method Investment Summarized Financial Information Debt	382,100			34,500
Company's share of equity (Company's basis)	$40,374

Investment_in_Unconsolidated_V4

Investment in Unconsolidated Ventures (Summary of Results of Operations of Unconsolidated Real Estate Ventures) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of results of operations of Real Estate Ventures
Income (Loss) from Equity Method Investments	($790)	$3,664	$2,741
Unconsolidated real estate ventures [Member]
Summary of results of operations of Real Estate Ventures
Revenue	147,236	102,919	164,013
Operating expenses	-61,268	-40,436	-70,775
Interest expense, net	-36,511	-26,529	-41,633
Depreciation and amortization	-57,109	-35,138	-50,241
Net income	-7,652	816	1,364
Income (Loss) from Equity Method Investments	($790)	$3,664	$2,741

Investment_in_Unconsolidated_V5

Investment in Unconsolidated Ventures Company's Investment in Real Estate Ventures and the Company's Share of the Real Estate Ventures' Income (Loss) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2013	Jul. 31, 2014	Mar. 26, 2013	Jan. 20, 2011	Jun. 19, 2013	Apr. 03, 2014
	acre			acre			acre
Schedule of Equity Method Investments [Line Items]
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land	3
Equity Method Investments	$225,004,000	$180,512,000	$193,555,000
Income (Loss) from Equity Method Investments	-790,000	3,664,000	2,741,000
Equity Method Investment Summarized Financial Information Debt	965,077,000
Equity Method Investments including net liabilities	223,790,000
Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	965,077,000
Broadmoor Austin Associates [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	65,407,000
Income (Loss) from Equity Method Investments	-460,000
Equity Method Investment Summarized Financial Information Debt	53,516,000
Debt Instrument, Interest Rate, Effective Percentage	7.04%
Debt Instrument, Maturity Date	10-Apr-23
HSRE, LLC [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	30.00%
Equity Method Investments	14,314,000
Income (Loss) from Equity Method Investments	67,000
Equity Method Investment Summarized Financial Information Debt	90,245,000
Debt Instrument, Interest Rate Terms	L+2.20%
Debt Instrument, Maturity Date	25-Jul-16
4040 Wilson Venture [Member]
Schedule of Equity Method Investments [Line Items]
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land				1.3
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	27,415,000
Income (Loss) from Equity Method Investments	-132,000
Equity Method Investment Summarized Financial Information Debt	0
Brandywine - Al Venture [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	45,712,000
Income (Loss) from Equity Method Investments	-185,000
Equity Method Investment Summarized Financial Information Debt	133,843,000
Debt Instrument, Interest Rate, Effective Percentage	3.93%
Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	40,374,000
Income (Loss) from Equity Method Investments	-574,000
Equity Method Investment Summarized Financial Information Debt	382,100,000				34,500,000
Debt Instrument, Interest Rate, Effective Percentage	3.57%
Equity method investments, Closing costs	200,000				100,000
BDN Beacon Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage						20.00%
Equity Method Investments						17,000,000
TB-BDN Plymouth Apartments [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	12,720,000
Income (Loss) from Equity Method Investments	-83,000
Equity Method Investment Summarized Financial Information Debt	29,481,000
Debt Instrument, Interest Rate Terms	L+1.70%
Debt Instrument, Maturity Date	20-Dec-17
Brandywine Nineteen Nineteen Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land							1
Equity Method Investment, Ownership Percentage	50.00%						50.00%
Equity Method Investments	12,823,000
Income (Loss) from Equity Method Investments	-21,000
Equity Method Investment Summarized Financial Information Debt	0
Debt Instrument, Interest Rate Terms	L+2.25%
Debt Instrument, Maturity Date	21-Oct-18
Debt Instrument, Interest Rate Terms	LIBOR + 2.25%
Interest rate upon receipt of certificate of occupancy	2.00%
Interest rate upon stabilization	1.75%
Interest rate protection cap	4.50%
One Thousand Chesterbrook Blvd. [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	2,152,000
Income (Loss) from Equity Method Investments	388,000
Equity Method Investment Summarized Financial Information Debt	24,251,000
Debt Instrument, Interest Rate, Effective Percentage	4.75%
Debt Instrument, Maturity Date	1-Dec-21
Four Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	65.00%
Equity Method Investments	1,474,000
Income (Loss) from Equity Method Investments	-144,000
Equity Method Investment Summarized Financial Information Debt	10,353,000
Debt Instrument, Interest Rate, Effective Percentage	5.20%
Debt Instrument, Maturity Date	10-Feb-21
Residence Inn Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	723,000
Income (Loss) from Equity Method Investments	107,000
Equity Method Investment Summarized Financial Information Debt	13,394,000
Debt Instrument, Interest Rate, Effective Percentage	5.63%
Debt Instrument, Maturity Date	11-Feb-16
PJP VII [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	25.00%
Equity Method Investments	911,000
Income (Loss) from Equity Method Investments	177,000
Equity Method Investment Summarized Financial Information Debt	5,785,000
Debt Instrument, Interest Rate Terms	L+2.65%
Debt Instrument, Maturity Date	31-Dec-19
PJP Two [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	30.00%
Equity Method Investments	403,000
Income (Loss) from Equity Method Investments	73,000
Equity Method Investment Summarized Financial Information Debt	3,492,000
Debt Instrument, Interest Rate, Effective Percentage	6.12%
Debt Instrument, Maturity Date	1-Nov-23
G&I Interchange Office LLC (DRA — N. PA) [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Equity Method Investments	0
Income (Loss) from Equity Method Investments	-658,000
Equity Method Investment Summarized Financial Information Debt	174,595,000
Debt Instrument, Interest Rate, Effective Percentage	5.78%
Debt Instrument, Maturity Date	28-Feb-15
Sale of ownership in properties	80.00%
Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	20.00%
Equity Method Investments	315,000
Income (Loss) from Equity Method Investments	-388,000
Equity Method Investment Summarized Financial Information Debt	14,865,000
Debt Instrument, Interest Rate, Effective Percentage	3.78%
PJP Five [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	25.00%
Equity Method Investments	216,000
Income (Loss) from Equity Method Investments	166,000
Equity Method Investment Summarized Financial Information Debt	5,242,000
Debt Instrument, Interest Rate, Effective Percentage	6.47%
Debt Instrument, Maturity Date	11-Aug-19
Two Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments								-100,000
PJP Six [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	25.00%
Equity Method Investments	45,000
Income (Loss) from Equity Method Investments	-67,000
Equity Method Investment Summarized Financial Information Debt	8,168,000
Debt Instrument, Interest Rate, Effective Percentage	6.08%
Debt Instrument, Maturity Date	1-Apr-23
Coppell Associates [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Equity Method Investments	-1,214,000
Income (Loss) from Equity Method Investments	-45,000
Equity Method Investment Summarized Financial Information Debt	15,747,000
Debt Instrument, Interest Rate, Effective Percentage	5.75%
Debt Instrument, Maturity Date	1-Feb-16
Invesco, L.P. [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investments	0
Income (Loss) from Equity Method Investments	989,000
Secured Debt [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt, Weighted Average Interest Rate	5.72%	5.73%	6.65%
Secured Debt [Member] | Brandywine - Al Venture [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt, Weighted Average Interest Rate	3.93%
Secured Debt [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt, Weighted Average Interest Rate	3.57%
Secured Debt [Member] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt, Weighted Average Interest Rate	3.78%
Secured Debt [Member] | Fifth mortgage - swapped to fixed [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	34,500,000
Debt Instrument, Interest Rate, Stated Percentage	3.87%
Secured Debt [Member] | Fixed rate loan maturing January 2019 [Member] | Brandywine - Al Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	39,300,000
Debt Instrument, Interest Rate, Stated Percentage	4.40%
Secured Debt [Member] | Fixed rate loan maturing January 2022 [Member] | Brandywine - Al Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	28,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.65%
Secured Debt [Member] | Fixed rate loan maturing August 2019 [Member] | Brandywine - Al Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	66,500,000
Debt Instrument, Interest Rate, Stated Percentage	3.22%
Secured Debt [Member] | First mortgage - swapped to fixed [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	34,000,000
Derivative, Fixed Interest Rate	1.59%
Derivative, Basis Spread on Variable Rate	1.93%
Debt Instrument, Interest Rate, Effective Percentage	3.52%
Secured Debt [Member] | Second mortgage - swapped to fixed [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	56,000,000
Derivative, Fixed Interest Rate	1.49%
Derivative, Basis Spread on Variable Rate	1.70%
Debt Instrument, Interest Rate, Effective Percentage	3.19%
Secured Debt [Member] | Third mortgage - swapped to fixed [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	140,600,000
Derivative, Fixed Interest Rate	1.43%
Derivative, Basis Spread on Variable Rate	2.01%
Debt Instrument, Interest Rate, Effective Percentage	3.44%
Secured Debt [Member] | Fourth mortgage - swapped to fixed [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	29,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Secured Debt [Member] | Mortgage Maturing February 2015 [Domain] | Brandywine - Al Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Number of Fixed Rate Mortgages	3
Secured Debt [Member] | Mortgage Maturing February 2015 [Domain] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	8,000,000
Debt Instrument, Number of Fixed Rate Mortgages	2
Debt Instrument, Interest Rate, Stated Percentage	7.00%
Secured Debt [Member] | Fixed Rate Loan Maturing September 2025 [Member] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	1,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.00%
Secured Debt [Member] | Fixed Rate Loan Maturing February 2016 [Member] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	2,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Secured Debt [Member] | Fixed Rate Loan Maturing March 2020 [Member] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	3,900,000
Debt Instrument, Interest Rate, Stated Percentage	0.00%
Four Points Centre [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Non-Recourse Debt									29,000,000
Secured Debt [Member] | Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Face Amount	$88,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.00%

Investment_in_Unconsolidated_V6

Investment in Unconsolidated Ventures Aggregate Principal Payments of Recourse and Non-recourse Debt Payable to Third-parties (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Loss on real estate venture formation	$0	$0	($950)
Schedule of Equity Method Investments [Line Items]
2015	102,030
2016	367,703
2017	330,323
2018	336,954
2019	213,155
Thereafter	1,109,298
Equity Method Investment Summarized Financial Information Debt	965,077
Brandywine Nineteen Nineteen Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	0
Austin Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	382,100			34,500
Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
2015	279,351
2016	133,809
2017	44,465
2018	231,030
2019	182,522
Thereafter	93,900
Equity Method Investment Summarized Financial Information Debt	965,077
Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	14,865
Fixed Rate Loan Maturing February 2016 [Member] | Secured Debt [Member] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	2,000
Fixed Rate Loan Maturing March 2020 [Member] | Secured Debt [Member] | Seven Tower Bridge [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment Summarized Financial Information Debt	$3,900

Investment_in_Unconsolidated_V7

Investment in Unconsolidated Ventures Notes Receivable (Details) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Jul. 31, 2014	Dec. 31, 2013	Oct. 17, 2014	Oct. 16, 2013
				Real_Estate_Investments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Real Estate Investments in residential towers	1
Equity Method Investment, Summarized financial information debt	965,077,000
Financing Receivable, Net	88,000,000		7,026,000
Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short-term Debt, Terms	4.0% through December 31, 2014, (ii) 5.0% from January 1, 2015 through January 31, 2015, (iii) 7.0% from February 1, 2015 through February 28, 2015 and (iv) 9.0% from March 1, 2015 through March 31, 2015.
River Place [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Net	88,000,000
Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Rentable Area		232,274
Equity Method Investment, Summarized financial information debt	382,100,000	34,500,000
Equity method investments, Cash contributions	69,000,000	12,800,000
Equity method investments, Closing costs	200,000	100,000
Equity method investments, Purchase adjustments		900,000
Equity method investments, Credit from seller		600,000
Number of Real Estate Properties		2		7
Austin, Texas [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of floors of a building		3
Secured Debt [Member] | Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Short-term Debt, Terms	0.05
DRA Advisors LLC [Member] | Austin Joint Venture [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity method investments, Closing costs					$1,900,000

Deferred_Costs_Details

Deferred Costs (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Components of Deferred Costs Net [Abstract]
Leasing Costs, Total Cost	$164,081	$155,885
Financing Costs, Total Cost	40,401	40,317
Total Cost	204,482	196,202
Leasing Costs, Accumulated Amortization	-64,065	-58,805
Financing Costs, Accumulated Amortization	-15,193	-14,443
Total, Accumulated Amortization	-79,258	-73,248
Leasing Costs, Deferred Costs, net	100,016	97,080
Financing Costs, Deferred Costs, net	25,208	25,874
Deferred Costs	$125,224	$122,954

Deferred_Costs_Details_Textual

Deferred Costs (Details Textuals) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Leased Assets [Line Items]
Deferred Costs, Leasing, Net	$100,016,000	$97,080,000
Deferred Costs (Textuals) [Abstract]
Capitalized internal direct leasing costs	$7,100,000	$7,500,000	$7,500,000

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Intangible assets
Total Cost	$169,224	$196,147
Accumulated Amortization	-69,821	-63,818
Intangible Assets, net	99,403	132,329
Leases, Acquired-in-Place [Member]
Intangible assets
Total Cost	129,411	150,782
Accumulated Amortization	-42,068	-35,607
Intangible Assets, net	87,343	115,175
Tenant relationship value [Member]
Intangible assets
Total Cost	34,172	38,692
Accumulated Amortization	-26,344	-26,868
Intangible Assets, net	7,828	11,824
Above market leases acquired [Member]
Intangible assets
Total Cost	5,641	6,673
Accumulated Amortization	-1,409	-1,343
Intangible Assets, net	4,232	5,330
Below market leases acquired [Member]
Intangible assets
Total Cost	-53,049	-81,991
Accumulated Amortization	27,039	47,547
Intangible Assets, net	($26,010)	($34,444)

Intangible_Assets_Details_1

Intangible Assets (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Annual amortization of intangible assets and liabilities
Intangible Assets, net	$99,403,000	$132,329,000
Assets [Member]
Annual amortization of intangible assets and liabilities
2015	21,363,000
2016	16,898,000
2017	15,148,000
2018	11,399,000
2019	10,086,000
Thereafter	24,509,000
Intangible Assets, net	99,403,000
Liabilities [Member]
Annual amortization of intangible assets and liabilities
2015	-5,212,000
2016	-3,253,000
2017	-2,664,000
2018	-2,241,000
2019	-1,909,000
Thereafter	-10,731,000
Intangible Assets, net	-26,010,000
Tenant Move-Outs Prior to End of the Lease Term [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets Written Off Through Accelerated Amortization	$800,000	$1,600,000	$1,400,000

Debt_Obligations_Consolidated_

Debt Obligations (Consolidated Debt Obligations Outstanding) (Details) (USD $)	0 Months Ended	12 Months Ended
	Sep. 16, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount		$376,174,000	$29,250,000	$164,968,000
Early Repayment of Senior Debt		383,768,000	31,369,000	338,097,000
Gain (Loss) on Early Extinguishment of Debt		-7,594,000	-2,119,000	-22,002,000
Write off of Deferred Debt Issuance Cost		152,000	40,000	451,000
Gains (Losses) on Extinguishment of Debt	2,606,000	7,594,000	2,119,000	22,002,000
Consolidated debt obligations
Plus: premiums/(discounts), net		-8,155,000
Total mortgage indebtedness		654,590,000	670,151,000
Total Debt Obligations		2,451,308,000	2,595,381,000
Repayments of Unsecured Debt		250,828,000	0	190,485,000
Long Term Debt Maturities Repayments Of Principal		2,459,463,000
Recognized hedge activity	800,000	828,000	0	2,985,000
Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		655,934,000	669,762,000
Plus: premiums/(discounts), net		-1,344,000	389,000
Total mortgage indebtedness		654,590,000	670,151,000
Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		1,803,529,000	1,929,703,000
Plus: premiums/(discounts), net		-6,811,000	-4,473,000
Total unsecured indebtedness		1,796,718,000	1,925,230,000
Note Five [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount	42,700,000
Gains (Losses) on Extinguishment of Debt		5,000,000
Consolidated debt obligations
Long-term Debt, Gross		0	157,625,000
Debt Instrument, Maturity Date		15-May-15
Effective interest rate		7.76%
Debt Instrument, Interest Rate, Stated Percentage		7.50%
Debt Instrument, Face Amount		250,000,000
Debt Instrument, Repurchased Face Amount	114,900,000
Debt Instrument, Redemption, Description	$1,070.24 per $1,000
New Revolving Credit Facility [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		600,000,000
Consolidated debt obligations
Debt instrument, basis spread on variable rate		1.50%
Three-Year Term Loan - Swapped to fixed [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		0	150,000,000
Debt Instrument, Maturity Date		1-Feb-15
Effective interest rate		2.60%
Debt Instrument, Repurchased Face Amount	150,000,000
Four-Year Term Loan - Swapped to fixed [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Debt Instrument, Repurchased Face Amount	100,000,000
Three and Four Year Term Loan [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Write off of Deferred Debt Issuance Cost	300,000
Four-Year Term Loan - Variable [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		0	100,000,000
Debt Instrument, Maturity Date		1-Feb-16
Debt Instrument, Interest Rate Terms		LIBOR + 1.75%
Seven Year Term Loan - Swapped to fixed [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		200,000,000	200,000,000
Debt Instrument, Maturity Date		1-Feb-19
Effective interest rate		3.62%
Debt Instrument, Term		7 years
Debt Instrument, Face Amount		200,000,000
Line of Credit and Seven Year Term Loan [Member]
Consolidated debt obligations
Debt Instrument, Interest Rate Terms		Based on the Company's current credit rating, the spread will be 150 basis points under the Credit Facility and 190 basis points under the seven-year term loan
Debt Instrument, Interest Rate Terms		federal funds rate plus 0.50%
$300.0M 5.750% Guaranteed Notes due 2012 [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Debt Instrument, Interest Rate, Stated Percentage		5.75%
$250.0M 5.400% Guaranteed Notes due 2014 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount	75,100,000
Consolidated debt obligations
Long-term Debt, Gross		0	218,549,000
Debt Instrument, Maturity Date		1-Nov-14
Effective interest rate		5.53%
Debt Instrument, Interest Rate, Stated Percentage		5.40%
Debt Instrument, Face Amount		250,000,000
Debt Instrument, Repurchased Face Amount	143,500,000
Debt Instrument, Redemption, Description	$1,026.88 per $1,000
$250.0M 6.000% Guaranteed Notes due 2016 [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		149,919,000	149,919,000
Debt Instrument, Maturity Date		1-Apr-16
Effective interest rate		5.95%
Debt Instrument, Interest Rate, Stated Percentage		6.00%
Debt Instrument, Face Amount		250,000,000
$300.0M 5.700% Guaranteed Notes due 2017 [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		300,000,000	300,000,000
Debt Instrument, Maturity Date		1-May-17
Effective interest rate		5.68%
Debt Instrument, Interest Rate, Stated Percentage		5.70%
Debt Instrument, Face Amount		300,000,000
$325.0M 4.950% Guaranteed Notes due 2018 [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		325,000,000	325,000,000
Debt Instrument, Maturity Date		15-Apr-18
Effective interest rate		5.13%
Debt Instrument, Interest Rate, Stated Percentage		4.95%
Debt Instrument, Face Amount		325,000,000
Note 2023 [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		250,000,000	250,000,000
Debt Instrument, Maturity Date		15-Feb-23
Effective interest rate		4.02%
Debt Instrument, Interest Rate, Stated Percentage		3.95%
Debt Instrument, Face Amount		250,000,000
Note 2024 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt instrument, Unamortized discount, Percent of face amount	99.39%
Debt instrument, Yield to maturity	4.18%
Debt instrument, Yield to maturity spread at time of pricing	1.70%
Debt Instrument, Unamortized Discount		1,500,000
Consolidated debt obligations
Long-term Debt, Gross		250,000,000	0
Debt Instrument, Maturity Date		1-Oct-24
Effective interest rate		4.23%
Debt Instrument, Interest Rate, Stated Percentage		4.10%
Debt Instrument, Face Amount		250,000,000
Note 2029 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt instrument, Unamortized discount, Percent of face amount	99.19%
Debt instrument, Yield to maturity	4.63%
Debt instrument, Yield to maturity spread at time of pricing	2.15%
Debt Instrument, Unamortized Discount		2,000,000
Consolidated debt obligations
Long-term Debt, Gross		250,000,000	0
Debt Instrument, Maturity Date		1-Oct-29
Effective interest rate		4.60%
Debt Instrument, Interest Rate, Stated Percentage		4.55%
Debt Instrument, Face Amount		250,000,000
Notes 2024 and 2029 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Proceeds from Notes Payable	492,900,000
Indenture IA (Preferred Trust I) [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		27,062,000	27,062,000
Debt Instrument, Maturity Date		30-Mar-35
Effective interest rate		2.75%
Indenture IB (Preferred Trust I) [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		25,774,000	25,774,000
Debt Instrument, Maturity Date		30-Apr-35
Effective interest rate		3.30%
Indenture II (Preferred Trust II) [Member] | Unsecured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		25,774,000	25,774,000
Debt Instrument, Maturity Date		30-Jul-35
Effective interest rate		3.09%
Tysons Corner [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		89,513,000	91,395,000
Debt Instrument, Maturity Date		1-Aug-15
Effective interest rate		5.36%
One Commerce Square [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		123,205,000	125,089,000
Debt Instrument, Maturity Date		6-Jan-16
Effective interest rate		3.68%
Two Logan Square [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		87,767,000	88,583,000
Debt Instrument, Maturity Date		1-Apr-16
Effective interest rate		7.57%
Fairview Eleven Tower [Member]
Participating Mortgage Loans [Line Items]
Equity Method Investment, Ownership Percentage		50.00%
Fairview Eleven Tower [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		21,242,000	21,630,000
Debt Instrument, Maturity Date		1-Jan-17
Effective interest rate		4.25%
Two Commerce Square [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		112,000,000	112,000,000
Debt Instrument, Maturity Date		5-Apr-23
Effective interest rate		4.51%
IRS Philadelphia Campus [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		184,442,000	190,964,000
Debt Instrument, Maturity Date		10-Sep-30
Effective interest rate		7.00%
Cira South Garage [Member] | Secured Debt [Member]
Consolidated debt obligations
Long-term Debt, Gross		37,765,000	40,101,000
Debt Instrument, Maturity Date		10-Sep-30
Effective interest rate		7.12%
Note Four [Member]
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount		218,549,000	19,830,000	4,302,000
Early Repayment of Senior Debt		219,404,000	20,853,000	4,566,000
Gain (Loss) on Early Extinguishment of Debt		-855,000	-1,020,000	-264,000
Write off of Deferred Debt Issuance Cost		9,000	16,000	8,000
Note Three [Member]
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount				301,000
Early Repayment of Senior Debt				303,000
Gain (Loss) on Early Extinguishment of Debt				-2,000
Write off of Deferred Debt Issuance Cost				0
Note Five [Member]
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount		157,625,000	8,910,000	60,794,000
Early Repayment of Senior Debt		164,364,000	9,945,000	69,497,000
Gain (Loss) on Early Extinguishment of Debt		-6,739,000	-1,036,000	-8,712,000
Write off of Deferred Debt Issuance Cost		143,000	23,000	183,000
Note Six [Member]
Participating Mortgage Loans [Line Items]
Extinguishment of Debt, Amount			510,000	99,571,000
Early Repayment of Senior Debt			571,000	112,541,000
Gain (Loss) on Early Extinguishment of Debt			-63,000	-13,024,000
Write off of Deferred Debt Issuance Cost			1,000	260,000
Discharge of Debt [Member]
Participating Mortgage Loans [Line Items]
Early Repayment of Senior Debt		$383,768,000	$31,369,000	$186,907,000

Debt_Obligations_Outstanding_U

Debt Obligations (Outstanding Unsecured Notes in Series of Transactions) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of principal payments of debt obligations
Principal	$376,174	$29,250	$164,968
Repurchase Amount	383,768	31,369	338,097
Gain (Loss) on Early Extinguishment of Debt	-7,594	-2,119	-22,002
Acceleration of Deferred Financing Amortization	152	40	451
Note Three [Member]
Schedule of principal payments of debt obligations
Principal			301
Repurchase Amount			303
Gain (Loss) on Early Extinguishment of Debt			-2
Acceleration of Deferred Financing Amortization			0
Note Four [Member]
Schedule of principal payments of debt obligations
Principal	218,549	19,830	4,302
Repurchase Amount	219,404	20,853	4,566
Gain (Loss) on Early Extinguishment of Debt	-855	-1,020	-264
Acceleration of Deferred Financing Amortization	9	16	8
Note Five [Member]
Schedule of principal payments of debt obligations
Principal	157,625	8,910	60,794
Repurchase Amount	164,364	9,945	69,497
Gain (Loss) on Early Extinguishment of Debt	-6,739	-1,036	-8,712
Acceleration of Deferred Financing Amortization	143	23	183
Note Six [Member]
Schedule of principal payments of debt obligations
Principal		510	99,571
Repurchase Amount		571	112,541
Gain (Loss) on Early Extinguishment of Debt		-63	-13,024
Acceleration of Deferred Financing Amortization		1	260
Discharge of Debt [Member]
Schedule of principal payments of debt obligations
Repurchase Amount	$383,768	$31,369	$186,907

Debt_Obligations_Aggregate_Sch

Debt Obligations (Aggregate Scheduled Principal Payments of Debt Obligation, Excluding Amortization of Discounts and Premiums) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Summary of debt repurchases
2015	$102,030
2016	367,703
2017	330,323
2018	336,954
2019	213,155
Thereafter	1,109,298
Total principal payments	2,459,463
Net unamortized premiums/(discounts)	-8,155
Total Debt Obligations	$2,451,308	$2,595,381

Debt_Obligations_Details_Textu

Debt Obligations (Details Textuals) (USD $)	0 Months Ended	12 Months Ended
	Sep. 16, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt obligations (Textuals)
Early Repayment of Senior Debt		$383,768,000	$31,369,000	$338,097,000
Amortization of Financing Costs		5,148,000	4,676,000	6,208,000
Loss on early extinguishment of debt	-2,606,000	-7,594,000	-2,119,000	-22,002,000
Unsecured Debt [Member]
Debt obligations (Textuals)
Long-term Debt, Gross		1,803,529,000	1,929,703,000
Secured Debt [Member]
Participating Mortgage Loans [Line Items]
Properties encumbered mortgage indebtedness carrying value, net		655,900,000	669,800,000
Debt obligations (Textuals)
Long-term Debt, Gross		655,934,000	669,762,000
Letter of Credit [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Debt obligations (Textuals)
Letters of credit outstanding		4,300,000
New Revolving Credit Facility [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Debt obligations (Textuals)
Unused availability under the Credit Facility		595,700,000
Note 2023 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.95%
Debt obligations (Textuals)
Debt instrument, face amount		250,000,000
Long-term Debt, Gross		250,000,000	250,000,000
$300.0M 5.750% Guaranteed Notes due 2012 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.75%
$250.0M 5.400% Guaranteed Notes due 2014 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Redemption, Description	$1,026.88 per $1,000
Debt Instrument, Repurchased Face Amount	143,500,000
Debt Instrument, Interest Rate, Stated Percentage		5.40%
Debt obligations (Textuals)
Debt instrument, face amount		250,000,000
Long-term Debt, Gross		0	218,549,000
$250.0M 7.500% Guaranteed Notes due 2015 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Redemption, Description	$1,070.24 per $1,000
Debt Instrument, Repurchased Face Amount	114,900,000
Debt Instrument, Interest Rate, Stated Percentage		7.50%
Debt obligations (Textuals)
Debt instrument, face amount		250,000,000
Long-term Debt, Gross		0	157,625,000
Loss on early extinguishment of debt		-5,000,000
$250.0M 6.000% Guaranteed Notes due 2016 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.00%
Debt obligations (Textuals)
Debt instrument, face amount		250,000,000
Long-term Debt, Gross		149,919,000	149,919,000
$300.0M 5.700% Guaranteed Notes due 2017 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.70%
Debt obligations (Textuals)
Debt instrument, face amount		300,000,000
Long-term Debt, Gross		300,000,000	300,000,000
$325.0M 4.950% Guaranteed Notes due 2018 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.95%
Debt obligations (Textuals)
Debt instrument, face amount		325,000,000
Long-term Debt, Gross		325,000,000	325,000,000
Three Year Term Loan [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Repurchased Face Amount	150,000,000
Debt obligations (Textuals)
Long-term Debt, Gross		0	150,000,000
Seven Year Term Loan [Member] | Unsecured Debt [Member]
Debt obligations (Textuals)
Debt instrument, face amount		200,000,000
Derivative, Average Fixed Interest Rate		3.62%
Long-term Debt, Gross		200,000,000	200,000,000
Note 2024 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.10%
Debt obligations (Textuals)
Debt instrument, face amount		250,000,000
Long-term Debt, Gross		250,000,000	0
Note 2029 [Member] | Unsecured Debt [Member]
Participating Mortgage Loans [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.55%
Debt obligations (Textuals)
Debt instrument, face amount		250,000,000
Long-term Debt, Gross		250,000,000	0
Subsidiaries [Member]
Debt obligations (Textuals)
Early Repayment of Senior Debt		383,768,000	31,369,000	338,097,000
Amortization of Financing Costs		5,148,000	4,676,000	6,208,000
Loss on early extinguishment of debt		-7,594,000	-2,119,000	-22,002,000
Subsidiaries [Member] | $300.0M 5.750% Guaranteed Notes due 2012 [Member]
Debt obligations (Textuals)
Early Repayment of Senior Debt				$151,200,000

Debt_Obligations_Details_Textu1

Debt Obligations (Details Textuals 2) (USD $)	0 Months Ended	12 Months Ended
	Sep. 16, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Long Term Debt Maturities Repayments Of Principal		$2,459,463,000
Extinguishment of Debt, Amount		376,174,000	29,250,000	164,968,000
Amortization of Financing Costs		5,148,000	4,676,000	6,208,000
Derivative, Gain (Loss) on Derivative, Net	-800,000	-828,000	0	-2,985,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period			0.29%
Long-term Debt, Gross		1,803,529,000	1,929,703,000
Unsecured Debt [Member] | Three Year Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		0	150,000,000
Unsecured Debt [Member] | Four-Year Term Loan - Variable [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		0	100,000,000
Unsecured Debt [Member] | Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Declining prepayment penalty in year three		1.00%
Derivative, Average Fixed Interest Rate		3.62%
Long-term Debt, Gross		200,000,000	200,000,000
Unsecured Debt [Member] | Note 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		250,000,000	250,000,000
Unsecured Debt [Member] | Note Five [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		0	157,625,000
Extinguishment of Debt, Amount	42,700,000
Unsecured Debt [Member] | Note Six [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		149,919,000	149,919,000
Unsecured Debt [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Letters of Credit Outstanding, Amount		4,300,000
Unsecured Debt [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.50%
Line of Credit Facility, Remaining Borrowing Capacity		595,700,000
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Weighted Average Interest Rate		5.72%	5.73%	6.65%
Long-term Debt, Gross		655,934,000	669,762,000
Note Six [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount			$510,000	$99,571,000

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Company's estimates of fair value differ from the carrying amounts
Secured Debt	$654,590	$670,151
Mortgage notes payable, Fair Value	707,241	715,244
Unsecured notes payable, Carrying Amount	1,518,108	1,396,620
Unsecured notes payable, Fair Value	1,593,212	1,471,041
Variable rate debt instruments, Carrying Amount	278,610	528,610
Variable rate debt instruments, Fair Value	257,188	526,693
Notes receivable, Carrying Amount	88,000	7,026
Notes receivable, Fair Value	$87,692	$7,759

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments (Details Textuals) (Variable rate and mortgage debt [Member])	12 Months Ended
	Dec. 31, 2014
Variable rate and mortgage debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Inputs, Discount Rate	4.26%

Risk_Management_and_Use_of_Fin2

Risk Management and Use of Financial Instruments (Fair Values of Derivative Financial Instruments) (Details) (USD $)	0 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 16, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Concentration Risk, Percentage		10.00%	10.00%	10.00%
Long Term Debt Maturities Repayments Of Principal		$2,459,463
Derivative, Gain (Loss) on Derivative, Net	-800	-828	0	-2,985
Note Five [Member] | Unsecured Debt [Member]
Derivatives, Fair Value [Line Items]
Debt Instrument, Repurchased Face Amount	114,900
Three Year Term Loan [Member] | Unsecured Debt [Member]
Derivatives, Fair Value [Line Items]
Debt Instrument, Repurchased Face Amount	150,000
Other Assets [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 3.300% Interest Rate Swap Maturing January 30, 2021 [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement			549
Other Assets [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 3.090% Interest Rate Swap Maturing October 30, 2019 [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement			218
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Notional Amount		278,610	428,610
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		-3,490	-1,421
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 3.623% Interest Rate Swap Maturing February 1, 2019 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		3.62%
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		-2,649	-545
Derivative Liability, Notional Amount		200,000	200,000
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 2.703% Interest Rate Swap Maturing February 1, 2016 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		2.70%
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0	-887
Derivative Liability, Notional Amount		0	77,000
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 2.470% Interest Rate Swap Maturing February 1, 2015 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		2.47%
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0	-283
Derivative Liability, Notional Amount		0	50,000
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 2.513% Interest Rate Swap Maturing May 1, 2015 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		2.51%
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		0	-162
Derivative Liability, Notional Amount		0	23,000
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 2.750% Interest Rate Swap Maturing September 30, 2017 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		2.75%
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		-253	-311
Derivative Liability, Notional Amount		27,062	27,062
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 3.300% Interest Rate Swap Maturing January 30, 2021 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		3.30%
Derivative Asset, Notional Amount		25,774	25,774
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		-334
Other Liabilities [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | 3.090% Interest Rate Swap Maturing October 30, 2019 [Member]
Derivatives, Fair Value [Line Items]
Derivative, Fixed Interest Rate		3.09%
Derivative Asset, Notional Amount		25,774	25,774
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		($254)

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended								12 Months Ended			0 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 07, 2014	Feb. 25, 2013
													sqft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations									$918	$4,207	$43,838
Revenue:
Rents									483,682	461,387	437,560
Tenant Reimbursements									84,879	79,087	77,060
Termination fees									8,000	4,497	3,233
Other									3,221	4,186	5,710
Total revenue	147,810	146,558	150,500	152,114	138,658	143,354	140,664	139,554	596,982	562,210	535,679
Expenses:
Property operating expenses									177,330	160,406	152,319
Real estate taxes									51,844	55,612	53,402
Depreciation and amortization									208,569	197,021	188,382
Total operating expenses									471,313	446,418	424,643
Interest Income									3,974	1,044	3,008
Income from discontinued operations before gain on sale of interests in real estate									18	825	9,064
Net gain (loss) on disposition of discontinued operations									900	3,382	34,774
Princeton Pike Corporate Center [Member]
Expenses:
Net gain (loss) on disposition of discontinued operations										5,300		900
Net Rentable Space Sold													800,546
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations									918	4,207	43,838
Revenue:
Rents									0	4,754	28,678
Tenant Reimbursements									26	355	2,353
Termination fees									0	0	11
Other									0	123	378
Total revenue									26	5,232	31,420
Expenses:
Property operating expenses									8	1,839	8,687
Real estate taxes									0	649	3,468
Depreciation and amortization									0	1,921	10,208
Total operating expenses									8	4,409	22,363
Interest Income									0	2	7
Income from discontinued operations before gain on sale of interests in real estate									18	825	9,064
Net gain (loss) on disposition of discontinued operations									$900	$3,382	$34,774
Net Rentable Space Sold	2,000,000								2,000,000
Number of properties sold (in properties)									28

Non_Controlling_Interests_in_T1

Non Controlling Interests in The Parent Company (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Noncontrolling Interest [Abstract]
Aggregate amount related to non-controlling interests classified within equity	$17.50	$20.30
Settlement value of non controlling interest in operating partnership	$24.50	$24.80

Beneficiaries_Equity_of_The_Pa1

Beneficiaries Equity of The Parent Company (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator
Income (loss) from continuing operations, Basic									$6,024	$38,982	($37,309)
Income (loss) from continuing operations, Diluted									6,024	38,982	-37,309
Net loss attributable to non-controlling interests									44	0	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted									44	0	0
Net (income) loss attributable to non-controlling interests — LP units									-1	-357	863
Noncontrolling Interest In Net Income Loss of Limited Partnerships, Redeemable Diluted									-1	-357	863
Amount allocated to unvested restricted shareholders									-349	-363	-376
Amount allocable to unvested restricted shareholders, Diluted									-349	-363	-376
Preferred share/unit dividends, Basic									-6,900	-6,900	-10,405
Preferred share/unit dividends, Diluted									-6,900	-6,900	-10,405
Preferred share/unit redemption premium, basic									0	0	-4,052
Preferred share/unit redemption Premium, Diluted									0	0	-4,052
Income Loss from continuing operations available to common shareholders/unitholders, Basic									-1,182	31,362	-51,279
Income Loss from continuing operations available to common shareholders Diluted									-1,182	31,362	-51,279
Discontinued operations attributable to common unitholders									918	4,207	43,838
Income (loss) from discontinued operations, Diluted									918	4,207	43,838
Discontinued operations attributable to non-controlling interests - LP units									-10	-55	-797
Discontinued operations attributable to non-controlling interests, diluted									-10	-55	-797
Discontinued operations attributable to common shareholders, Basic									908	4,152	43,041
Discontinued operations attributable to common shareholders, Diluted									908	4,152	43,041
Net income (loss) attributable to Common Shareholders/Unitholders									-274	35,514	-8,238
Net income (loss) available to common shareholders/unitholders, Diluted									($274)	$35,514	($8,238)
Denominator
Weighted-average shares/units outstanding, Basic									166,202,649	153,140,458	143,257,097
Contingent securities/Stock based compensation									0	1,273,853	0
Weighted-average shares/units outstanding, Diluted									166,202,649	154,414,311	143,257,097
Earnings per Common Share:
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Basic									($0.01)	$0.20	($0.36)
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Diluted									($0.01)	$0.20	($0.36)
Discontinued operations attributable to common shareholders/unitholders, Basic									$0.01	$0.03	$0.30
Discontinued operations attributable to common shareholders, Diluted									$0.01	$0.03	$0.30
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Net income (loss) attributable to common shareholders/unitholders, Diluted	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)

Beneficiaries_Equity_of_The_Pa2

Beneficiaries Equity of The Parent Company (DetailsTextuals) (USD $)	0 Months Ended	12 Months Ended			0 Months Ended
In Thousands, except Share data, unless otherwise specified	Apr. 10, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 15, 2015	Jan. 06, 2015	Nov. 05, 2013	Dec. 09, 2014
Class of Stock [Line Items]
Stock Redeemed or Called During Period, Value				$103,448
Net proceeds from issuance of preferred shares		0	0	96,237
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Distributions Declared, Per Share		$0.60	$0.60	$0.60
Preferred Stock, Shares Issued		4,000,000	4,000,000
Issuance of Common Shares of Beneficial Interest, shares	12,650,000	21,850,000
Issuance of Common Shares of Beneficial Interest		335,398	182,034	96,850
Additional shares Expected to be purchased under program		539,200
Dividends paid for preferred shares		6,900	6,900	10,405
Additional shares granted under option to purchase in public offering	1,650,000
Proceeds from Issuance of Common Stock	181,500	335,016	181,527	0
Percentage of Preferential return		6.90%	6.90%
Dividends Payable, Amount		28,871	25,584
Preferred share/unit redemption charge		0	0	-4,052
Dividend Paid
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Dividends Payable, Amount						27,200
Series E Preferred Stock [Member]
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Percentage of Preferential return		6.90%
Preferred Stock, Liquidation Preference Per Share		$25
Series E Preferred Stock [Member] | Dividend Paid
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Dividends paid for preferred shares					1,700
Class A Units [Member]
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Antidilutive securities excluded from computation of earnings per share		1,535,102	1,763,739	1,845,737
Offering Program [Member]
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Shares authorized for Equity Offering Program							16,000,000
Remaining shares available for sales		16,000,000
Subsidiaries [Member]
Class of Stock [Line Items]
Net proceeds from issuance of preferred shares		0	0	96,237
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Preferred Stock, Shares Issued		4,000,000	4,000,000
Proceeds from Issuance of Common Stock		335,016	181,527	0
Percentage of Preferential return		6.90%	6.90%
Dividends Payable, Amount		28,871	25,584
Preferred share/unit redemption charge		$0	$0	($4,052)
Dividend Declared [Member] | Subsidiaries [Member]
Beneficiaries Equity of The Parent Company (Textuals) [Abstract]
Dividends Payable, Amount Per Share								$0.15

Partners_Equity_of_The_Operati2

Partners Equity of The Operating Partnership (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 09, 2014
Earnings per Common Partnership Unit [Line Items]
Dividends Payable, Amount	$28,871				$25,584				$28,871	$25,584
Dividends, Preferred Stock, Cash									6,900	6,900	10,405
Preferred shares, dividend rate (as a percent)									6.90%	6.90%
Numerator
Income (loss) from continuing operations, Basic									6,024	38,982	-37,309
Income (loss) from continuing operations, Diluted									6,024	38,982	-37,309
Amount allocated to unvested restricted shareholders									-349	-363	-376
Amount allocated to unvested restricted shareholders, Diluted									-349	-363	-376
Preferred share/unit dividends, Basic									-6,900	-6,900	-10,405
Preferred share/unit dividends, Diluted									-6,900	-6,900	-10,405
Net loss attributable to non-controlling interests									44	0	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted									-44	0	0
Preferred share/unit redemption charge									0	0	-4,052
Preferred share/unit redemption Premium, Diluted									0	0	-4,052
Income Loss from continuing operations available to common shareholders/unitholders, Basic									-1,182	31,362	-51,279
Income Loss from continuing operations available to common shareholders Diluted									-1,182	31,362	-51,279
Discontinued operations attributable to common unitholders									918	4,207	43,838
Net income (loss) attributable to Common Shareholders/Unitholders									-274	35,514	-8,238
Net income (loss) available to common shareholders/unitholders, Diluted									-274	35,514	-8,238
Denominator
Weighted-average shares/units outstanding, Basic									166,202,649	153,140,458	143,257,097
Contingent securities/Stock based compensation									0	1,273,853	0
Weighted-average shares/units outstanding, Diluted									166,202,649	154,414,311	143,257,097
Income per Common Partnership Unit:
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Basic									($0.01)	$0.20	($0.36)
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Diluted									($0.01)	$0.20	($0.36)
Discontinued operations attributable to common shareholders/unitholders, Basic									$0.01	$0.03	$0.30
Discontinued operations attributable to common shareholders, Diluted									$0.01	$0.03	$0.30
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Net income (loss) attributable to common shareholders/unitholders, Diluted	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Dividends Payable, Amount	28,871				25,584				28,871	25,584
Preferred shares, dividend rate (as a percent)									6.90%	6.90%
Numerator
Income (loss) from continuing operations, Basic									6,024	38,982	-37,309
Income (loss) from continuing operations, Diluted									6,024	38,982	-37,309
Amount allocated to unvested restricted shareholders									-349	-363	-376
Amount allocated to unvested restricted shareholders, Diluted									-349	-363	-376
Preferred share/unit dividends, Basic									-6,900	-6,900	-10,405
Preferred share/unit dividends, Diluted									-6,900	-6,900	-10,405
Net loss attributable to non-controlling interests									44	0	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted									-44	0	0
Preferred share/unit redemption charge									0	0	-4,052
Preferred share/unit redemption Premium, Diluted									0	0	-4,052
Income Loss from continuing operations available to common shareholders/unitholders, Basic									-1,181	31,719	-52,142
Income Loss from continuing operations available to common shareholders Diluted									-1,181	31,719	-52,142
Discontinued operations attributable to common unitholders									918	4,207	43,838
Discontinued operations attributable to common unitholders, Diluted									918	4,207	43,838
Net income (loss) attributable to Common Shareholders/Unitholders									-263	35,926	-8,304
Net income (loss) available to common shareholders/unitholders, Diluted									($263)	$35,926	($8,304)
Denominator
Weighted-average shares/units outstanding, Basic									167,942,246	154,929,545	145,883,217
Contingent securities/Stock based compensation									0	1,273,853	0
Weighted-average shares/units outstanding, Diluted									167,942,246	156,203,398	145,883,217
Income per Common Partnership Unit:
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Basic									($0.01)	$0.20	($0.36)
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Diluted									($0.01)	$0.20	($0.36)
Discontinued operations attributable to common shareholders/unitholders, Basic									$0.01	$0.03	$0.30
Discontinued operations attributable to common shareholders, Diluted									$0.01	$0.03	$0.30
Net income (loss) attributable to common shareholders/unitholders, Basic									$0	$0.23	($0.06)
Net income (loss) attributable to common shareholders/unitholders, Diluted									$0	$0.23	($0.06)
Dividend Declared [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Dividends Payable, Amount Per Share												$0.15

Partners_Equity_of_The_Operati3

Partners Equity of The Operating Partnership (DetailsTextuals) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 05, 2013
Earnings per Common Partnership Unit [Line Items]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest									$6,024,000	$38,982,000	($37,309,000)
Income Loss From Continuing Operations Including Portion Attributable To Non controlling Interest Diluted									6,024,000	38,982,000	-37,309,000
Amount allocated to unvested restricted shareholders									349,000	363,000	376,000
Amount allocated to unvested restricted shareholders, Diluted									-349,000	-363,000	-376,000
Preferred share/unit dividends, Basic									-6,900,000	-6,900,000	-10,405,000
Preferred share/unit dividends, Diluted									-6,900,000	-6,900,000	-10,405,000
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable									-44,000	0	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted									-44,000	0	0
Preferred share/unit redemption premium, basic									0	0	-4,052,000
Preferred share/unit redemption Premium, Diluted									0	0	-4,052,000
Income Loss from continuing operations available to common shareholders/unitholders, Basic									-1,182,000	31,362,000	-51,279,000
Income Loss from continuing operations available to common shareholders Diluted									-1,182,000	31,362,000	-51,279,000
Discontinued operations attributable to common unitholders									918,000	4,207,000	43,838,000
Net Income (Loss) Available to Common Stockholders, Basic									-274,000	35,514,000	-8,238,000
Net Income (Loss) Available to Common Stockholders, Diluted									-274,000	35,514,000	-8,238,000
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									0	1,273,853	0
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Basic									($0.01)	$0.20	($0.36)
Income (Loss) from Continuing Operations, Per Diluted Share									($0.01)	$0.20	($0.36)
Discontinued operations attributable to common shareholders/unitholders, Basic									$0.01	$0.03	$0.30
Discontinued operations attributable to common shareholders, Diluted									$0.01	$0.03	$0.30
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Net income (loss) attributable to common shareholders/unitholders, Diluted	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Dividends Payable, Amount	28,871,000				25,584,000				28,871,000	25,584,000
Percentage of Preferential return									6.90%	6.90%
Dividends, Preferred Stock, Cash									-6,900,000	-6,900,000	-10,405,000
Partners' Capital Account, Redemptions											9,741,000
Weighted-average shares/units outstanding, Basic									166,202,649	153,140,458	143,257,097
Weighted-average shares/units outstanding, Diluted									166,202,649	154,414,311	143,257,097
Series E Preferred Stock [Member]
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Percentage of Preferential return									6.90%
Preferred Stock, Liquidation Preference Per Share	$25								$25
Class A Units [Member]
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Redeemable Limited Partnership Units Potential Cash Redemption Value Closing Market Price	$15.98				$14.09				$15.98	$14.09	$12.19
Limited Partners' Capital Account, Units Outstanding	1,535,102				1,763,739				1,535,102	1,763,739
Offering Program [Member]
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Shares Authorized For Equity Offering Program												16,000,000
Remaining Shares Available For Sales	16,000,000								16,000,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest									6,024,000	38,982,000	-37,309,000
Income Loss From Continuing Operations Including Portion Attributable To Non controlling Interest Diluted									6,024,000	38,982,000	-37,309,000
Amount allocated to unvested restricted shareholders									349,000	363,000	376,000
Amount allocated to unvested restricted shareholders, Diluted									-349,000	-363,000	-376,000
Preferred share/unit dividends, Basic									-6,900,000	-6,900,000	-10,405,000
Preferred share/unit dividends, Diluted									-6,900,000	-6,900,000	-10,405,000
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable									-44,000	0	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted									-44,000	0	0
Preferred share/unit redemption premium, basic									0	0	-4,052,000
Preferred share/unit redemption Premium, Diluted									0	0	-4,052,000
Income Loss from continuing operations available to common shareholders/unitholders, Basic									-1,181,000	31,719,000	-52,142,000
Income Loss from continuing operations available to common shareholders Diluted									-1,181,000	31,719,000	-52,142,000
Discontinued operations attributable to common unitholders									918,000	4,207,000	43,838,000
Discontinued operations attributable to common unitholders, Diluted									918,000	4,207,000	43,838,000
Net Income (Loss) Available to Common Stockholders, Basic									-263,000	35,926,000	-8,304,000
Net Income (Loss) Available to Common Stockholders, Diluted									-263,000	35,926,000	-8,304,000
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									0	1,273,853	0
Income (Loss) from continuing operations attributable to common shareholders/unitholders, Basic									($0.01)	$0.20	($0.36)
Income (Loss) from Continuing Operations, Per Diluted Share									($0.01)	$0.20	($0.36)
Discontinued operations attributable to common shareholders/unitholders, Basic									$0.01	$0.03	$0.30
Discontinued operations attributable to common shareholders, Diluted									$0.01	$0.03	$0.30
Net income (loss) attributable to common shareholders/unitholders, Basic									$0	$0.23	($0.06)
Net income (loss) attributable to common shareholders/unitholders, Diluted									$0	$0.23	($0.06)
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Dividends Payable, Amount	28,871,000				25,584,000				28,871,000	25,584,000
Percentage of Preferential return									6.90%	6.90%
Weighted-average shares/units outstanding, Basic									167,942,246	154,929,545	145,883,217
Weighted-average shares/units outstanding, Diluted									167,942,246	156,203,398	145,883,217
Maximum [Member]
Partners Equity of The Operating Partnership (Textuals) [Abstract]
Fees and Commissions									$0.02

Share_Based_and_Deferred_Compe2

Share Based and Deferred Compensation (Option Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 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, Exercisable, Number	2,684,795
Stock-based compensation expense	$6,100,000	$8,300,000	$8,600,000
Stock-based compensation expense, capitalized	1,700,000	1,400,000	2,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	1,152,891
Option activity
Outstanding at beginning of year, shares	2,983,569
Exercised, shares	-184,116
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period	-114,658
Outstanding at end of year, shares	2,684,795	2,983,569
Outstanding at beginning of year, Weighted Average Exercise Price	$15.50
Exercised, Weighted Average Exercise Price	$11.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	671,008
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$20.61
Outstanding at end of year, Weighted Average Exercise Price	$15.55	$15.50
Vested/Exercisable at end of period, Weighted Average Exercise Price	$15.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	4 years 1 month 5 days	5 years 1 month 25 days
Vested/Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	4 years 1 month 5 days
Outstanding at beginning of year, Aggregate Intrinsic Value	0
Outstanding at end of year, Aggregate Intrinsic Value	1,152,891	0
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0	700,000	1,600,000
Stock-based compensation expense, capitalized	$0	$100,000	$500,000
Option activity
Outstanding at end of year, shares	2,684,795

Share_Based_and_Deferred_Compe3

Share Based and Deferred Compensation (Restricted Share Activity) (Details) (USD $)	12 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Mar. 01, 2014	Mar. 12, 2014	29-May-14	Feb. 07, 2014	Mar. 11, 2014	Feb. 25, 2013	Mar. 01, 2012
Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$2.40
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 5 months 6 days
Company's restricted share activity
Non-vested at January 1, 2012, shares	563,713
Non-vested at January 1, 2012, Weighted Average Grant Date Fair value	$12.56
Granted, shares	229,119
Granted, Weighted Average Grant Date Fair value	$14.47
Vested, shares	-234,169
Vested, Weighted Average Grant Date Fair value	$13.44
Forfeited, shares	-18,597
Forfeited, Weighted Average Grant Date Fair Value	$12.67
Non-vested at December 31, 2012, shares	540,066
Non-vested at December 31, 2012, Weighted Average Grant Date Fair value	$12.21
Restricted Performance Share Units Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$2.10
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 0 months 0 days
Company's restricted share activity
Vested, shares		-150,829
Dividends Payable, Amount Per Share					$0.15
Executive Officer [Member] | Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	65,955		129,245
Age limit of voluntary termination of employment	57
Company's restricted share activity
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	15 years
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			61,720			134,284	231,093	265,222
Company's restricted share activity
Non-vested at January 1, 2012, shares	473,215
Granted, shares	196,004
Forfeited, shares	-69,822
Non-vested at December 31, 2012, shares	599,397
Cliff Vesting [Member] | Executive Officer [Member] | Restricted Share Awards [Member]
Company's restricted share activity
Granted, shares			131,641
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights			after three years from the grant date
Forfeited, shares	-2,396
Cliff Vesting [Member] | Executive Officer [Member] | Restricted Performance Share Units Plan [Member]
Company's restricted share activity
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights			three year cliff vesting period
Ratable Vesting [Member] | Restricted Share Awards [Member]
Company's restricted share activity
Granted, shares				27,684
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights				ratably over three years
Ratable Vesting [Member] | Executive Officer [Member] | Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	3,839
Company's restricted share activity
Granted, shares			69,794
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights			ratably over three years

Share_Based_and_Deferred_Compe4

Share Based and Deferred Compensation (Details Textuals) (USD $)	12 Months Ended			3 Months Ended	0 Months Ended			12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Mar. 11, 2014	Mar. 12, 2014	Mar. 01, 2012	Feb. 25, 2014	Feb. 25, 2013
Share Based and Deferred Compensation (Textuals) [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	2,684,795	2,983,569		2,684,795
Stock-based compensation expense, capitalized	$1,700,000	$1,400,000	$2,600,000
Stock-based compensation expense	6,100,000	8,300,000	8,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	184,116
Defined Contribution Plan, Employer Discretionary Contribution Amount	400,000	400,000	400,000
Stock Option [Member]
Share Based and Deferred Compensation (Textuals) [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	2,684,795			2,684,795
Stock-based compensation expense, capitalized	0	100,000	500,000
Stock-based compensation expense	0	700,000	1,600,000
Deferred Compensation Plan [Member]
Share Based and Deferred Compensation (Textuals) [Abstract]
Deferred compensation arrangement with individual increase in compensation expense.	0	200,000	300,000
Number of shares to be issued under deferred compensation plan included in total shares outstanding	400,000	300,000		400,000
Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	229,119
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	18,597
Share Based and Deferred Compensation (Textuals) [Abstract]
Unrecognized compensation expenses	2,400,000			2,400,000
Weighted average period over which options will be recognized	1 year 5 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	540,066	563,713		540,066
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	three years from the initial grant dates
Stock-based compensation expense	2,700,000	3,200,000	3,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost		600,000	900,000	600,000
Share-based Compensation Arrangement by Share-based Payment Award, Cliff Vesting, Minimum	3 years
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
Restricted Performance Share Units Plan [Member]
Share Based and Deferred Compensation (Textuals) [Abstract]
Unrecognized compensation expenses	2,100,000			2,100,000
Weighted average period over which options will be recognized	1 year 0 months 0 days
Stock-based compensation expense		4,400,000	3,500,000	3,200,000
Vesting Period, Minimum	3 years
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost		800,000	1,200,000	1,100,000
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
Employee Share Purchase Plan [Member]
Share Based and Deferred Compensation (Textuals) [Abstract]
Stock-based compensation expense	100,000	100,000	100,000
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	15.00%
Aggregate share-based awards awarded to executives	1,250,000			1,250,000
Stock Issued During Period, Value, Employee Stock Purchase Plan	400,000	400,000	400,000
Share purchases made by employees under ESPP	85% of the average closing price per share for a specified period
Percentage of plan contribution	20.00%
Amount of participant contribution	50,000			50,000
Executive Officer [Member] | Restricted Share Awards [Member]
Share Based and Deferred Compensation (Textuals) [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares	65,955			65,955		129,245
Age limit of voluntary termination of employment	57
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, Equity Instruments Other than Options, Grants in Period	196,004
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	69,822
Share Based and Deferred Compensation (Textuals) [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	599,397	473,215		599,397
Aggregate share-based awards awarded to executives					134,284	61,720	265,222		231,093
Fair value of awards on the grant date					$2,624,000	$1,225,000	$4,273,000	$4,137,000
Cliff Vesting [Member] | Executive Officer [Member] | Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period						131,641
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	2,396

Share_Based_and_Deferred_Compe5

Share Based and Deferred Compensation 401(K) Plan (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	100.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$0.40	$0.40	$0.40

Share_Based_Deferred_Compensat

Share Based Deferred Compensation (Restricted Performance Share Units) (Details) (Executive Officer [Member], Restricted Performance Share Units Plan [Member], USD $)	0 Months Ended			12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 11, 2014	Mar. 12, 2014	Mar. 01, 2012	Dec. 31, 2014	Feb. 25, 2014	Dec. 31, 2013	Feb. 25, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$2,624	$1,225	$4,273		$4,137
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				599,397		473,215
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				196,004
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period				-69,822
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	134,284	61,720	265,222				231,093
March 1, 2012 RSPU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				207,383		242,122
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period				-34,739
February 25, 2013 RSPU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				199,577		231,093
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period				-31,516
March 11, 2014 RSPU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				130,717		0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				134,284
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period				-3,567
March 12, 2014 RSPU Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number				61,720		0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				61,720
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period				0
Cliff Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights		three year cliff vesting period

Distributions_Details

Distributions (Details) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Distributions [Abstract]
Common Share Distributions Payments of Ordinary Dividends	$0.41	$0.52	$0.39
Common Share Distributions Capital Gain	$0.02	$0	$0
Common Share Distributions Non-taxable Distributions	$0.17	$0.08	$0.21
Common Stock, Dividends, Per Share, Declared	$0.60	$0.60	$0.60
Percentage Of Distributions classified as ordinary income	69.00%	87.00%	65.00%
Percentage Of Distributions classified as capital gain	3.30%	0.00%	0.00%
Percentage Of Distributions classified as non-taxable distribution	27.70%	13.00%	35.00%
Dividends, Preferred Stock	$6,900	$6,900	$10,405
Percentage Of Preferred Distributions classified as ordinary income	100.00%	100.00%	100.00%

Tax_Credit_Transactions_Detail

Tax Credit Transactions (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 17, 2008	Aug. 27, 2010
				sqft
Tax Credit Transactions (Textuals) [Abstract]
Historic tax credit transaction income	$11,853,000	$11,853,000	$11,840,000
Deferred transaction costs	125,224,000	122,954,000
Historic Tax Credit Transaction [Member]
Tax Credit Transactions (Textuals) [Abstract]
Area of IRS Philadelphia Campus building (in square foot)				862,692
Percentage of building leased to IRS				100.00%
Percentage of tax credit recapture	20.00%
Contribution allocated in non controlling interest	3,000,000	2,800,000
Recognition of cash received as revenue net of allocated expenses on or after September 2011, period	over the five year credit recapture period as defined in the Internal Revenue Code
Historic tax credit transaction income	11,900,000	-11,900,000
Allocated expenses within other income (expense)	500,000
Deferred transaction costs	500,000	1,000,000
Rate of return on noncontrolling interest expected	2.00%
Accretion of non-controlling interest liability	-1,400,000		-1,300,000
Recognition of cash received as revenue net of allocated expenses on or after September 2011, period in years	5 years
New Markets Tax Credit Transaction [Member]
Tax Credit Transactions (Textuals) [Abstract]
Percentage of tax credit recapture	100.00%
Percentage of qualified investments	39.00%
Recognition of cash received as revenue net of allocated expenses on or after September 2011, period in years	7 years
Brandywine Realty Trust [Member] | New Markets Tax Credit Transaction [Member]
Tax Credit Transactions (Textuals) [Abstract]
Deferred transaction costs	5,300,000	5,300,000
USB [Member] | Historic Tax Credit Transaction [Member]
Tax Credit Transactions (Textuals) [Abstract]
Agreed contribution in project cost by USB					64,100,000
USB contributions presented within deferred income	15,100,000	26,800,000
Allocated expenses within other income (expense)		-500,000
USB [Member] | New Markets Tax Credit Transaction [Member]
Tax Credit Transactions (Textuals) [Abstract]
USB contributions presented within deferred income	$13,300,000

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	0 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 16, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1,		($2,995)
Change during year		-1,190	12,789	-7,338
Loss on settlement of interest rate swaps	-800	-828	0	-2,985
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net		388	286	297
Balance at December 31,		-4,607	-2,995
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1,		-2,995	-15,918	-6,079
Change during year		-1,190	12,789	-7,338
Non-controlling interest- consolidated real estate venture partner's share of unrealized (gains)/losses on derivative financial instruments		18	-152	187
Loss on settlement of interest rate swaps		-828		-2,985
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net		388	286	297
Balance at December 31,		-4,607	-2,995	-15,918
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1,		-3,377
Change during year		-1,190	12,789	-7,338
Loss on settlement of interest rate swaps		-828	0	-2,985
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net		388	286	297
Balance at December 31,		-5,007	-3,377
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1,		-3,377	-16,452	-6,426
Change during year		-1,190	12,789	-7,338
Loss on settlement of interest rate swaps		-828		-2,985
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net		388	286	297
Balance at December 31,		($5,007)	($3,377)	($16,452)

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended										12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Oct. 17, 2014	Jul. 31, 2014	Apr. 03, 2014	Dec. 19, 2013
											Reportable_Segments					sqft	Properties		Storey
																Real_Estate_Investments
Segment Reporting Information [Line Items]
Number of Reportable Segments											7
Real estate investments, at cost:
Operating properties	$4,603,692					$4,669,289					$4,603,692		$4,669,289		$4,726,169
Real Estate Held-for-sale	27,436	[1]				0	[1]				27,436	[1]	0	[1]	0
Real Estate Investment Property, at Cost, Gross of Held For Sale	4,631,128					4,669,289					4,631,128		4,669,289		4,726,169
Construction-in-progress	201,360					74,174					201,360		74,174
Land inventory	90,603					93,351					90,603		93,351
Total revenue	147,810		146,558	150,500	152,114	138,658		143,354	140,664	139,554	596,982		562,210		535,679
Property operating expenses, real estate taxes and third party management expenses											-235,965		-221,769		-210,848
Net operating income											361,017		340,441		324,831
Equity Method Investments	225,004					180,512					225,004		180,512		193,555
Equity in income (loss) of real estate ventures											-790		3,664		2,741
Pennsylvania Suburbs [Member]
Real estate investments, at cost:
Operating properties	1,178,470					1,199,105					1,178,470		1,199,105		1,178,730
Total revenue											160,630		153,426		150,075
Property operating expenses, real estate taxes and third party management expenses											-55,062		-54,506		-52,657
Net operating income											105,568		98,920		97,418
Equity Method Investments	17,385					17,272					17,385		17,272		33,160
Equity in income (loss) of real estate ventures											-777		925		520
Philadelphia CBD [Member]
Real estate investments, at cost:
Operating properties	1,338,655					1,300,666					1,338,655		1,300,666		988,590
Total revenue											201,809		146,081		131,592
Property operating expenses, real estate taxes and third party management expenses											-75,262		-55,702		-50,787
Net operating income											126,547		90,379		80,805
Equity Method Investments	27,137					19,975					27,137		19,975		27,859
Equity in income (loss) of real estate ventures											46		1,547		1,113
Metropolitan, D.C. [Member]
Real estate investments, at cost:
Operating properties	1,183,652					1,214,965					1,183,652		1,214,965		1,193,200
Total revenue											113,834		116,048		107,656
Property operating expenses, real estate taxes and third party management expenses											-43,399		-42,641		-41,485
Net operating income											70,435		73,407		66,171
Equity Method Investments	73,127					59,905					73,127		59,905		49,169
Equity in income (loss) of real estate ventures											-317		130		-648
New Jersey/ Delaware [Member]
Real estate investments, at cost:
Operating properties	392,581					414,716					392,581		414,716		546,644
Total revenue											60,403		60,262		59,671
Property operating expenses, real estate taxes and third party management expenses											-31,650		-29,981		-28,506
Net operating income											28,753		30,281		31,165
Equity Method Investments	0					0					0		0		17,294
Equity in income (loss) of real estate ventures											989		1,245		1,803
Richmond, Virginia [Member]
Real estate investments, at cost:
Operating properties	317,076					310,397					317,076		310,397		309,923
Total revenue											34,180		35,058		35,701
Property operating expenses, real estate taxes and third party management expenses											-15,399		-14,916		-14,484
Net operating income											18,781		20,142		21,217
Equity Method Investments	1,574					1,400					1,574		1,400		1,245
Equity in income (loss) of real estate ventures											349		381		269
CALIFORNIA
Real estate investments, at cost:
Operating properties	193,258					192,584					193,258		192,584		223,736
Total revenue											19,388		18,369		17,463
Property operating expenses, real estate taxes and third party management expenses											-10,165		-9,411		-9,043
Net operating income											9,223		8,958		8,420
Austin, Texas [Member]
Real estate investments, at cost:
Operating properties	0					36,856					0		36,856		285,346
Total revenue											5,610		31,451		32,379
Property operating expenses, real estate taxes and third party management expenses											-3,223		-13,298		-13,951
Net operating income											2,387		18,153		18,428
Equity Method Investments	105,781					81,960					105,781		81,960		64,828
Equity in income (loss) of real estate ventures											-1,080		-564		-316
Corporate [Member]
Real estate investments, at cost:
Construction-in-progress	201,360					74,174					201,360		74,174		48,950
Land inventory	90,603					93,351					90,603		93,351		102,439
Total revenue											1,128		1,515		1,142
Property operating expenses, real estate taxes and third party management expenses											-1,805		-1,314		65
Net operating income											-677		201		1,207
Operating Segments [Member]
Real estate investments, at cost:
Operating properties	4,603,692					4,669,289					4,603,692		4,669,289		4,726,169
Assets Held-for-sale [Member]
Real estate investments, at cost:
Real Estate Held-for-sale	27,436					0					27,436		0		0
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real estate investments, at cost:
Operating properties	4,603,692					4,669,289					4,603,692		4,669,289
Construction-in-progress	201,360					74,174					201,360		74,174
Land inventory	90,603					93,351					90,603		93,351
Total revenue											596,982		562,210		535,679
Equity Method Investments	225,004					180,512					225,004		180,512
Equity in income (loss) of real estate ventures											-790		3,664		2,741
Austin Joint Venture [Member]
Segment Reporting Information [Line Items]
Net Rentable Space																590,881
Number of Real Estate Properties																7	2
Real estate investments, at cost:
Equity Method Investments	40,374										40,374
Equity in income (loss) of real estate ventures											($574)
Durham, NC [Member]
Segment Reporting Information [Line Items]
Number of Real Estate Properties	0										0
Four Points Centre [Member]
Segment Reporting Information [Line Items]
Number of floors of a building																		3	3
Net Rentable Space																		192,396
Number of Real Estate Properties																		2
1000 Atrium Way and Libertyview [Member] [Member]
Segment Reporting Information [Line Items]
Number of Real Estate Properties	2										2
[1]	(a)Real estate investments related to assets held for sale above represents gross real estate assets and does not include accumulated depreciation or other assets on the balance sheets of the properties held for sale.

Segment_Information_Details_1

Segment Information (Details 1) (USD $)	0 Months Ended	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Sep. 16, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total revenue		$147,810	$146,558	$150,500	$152,114	$138,658	$143,354	$140,664	$139,554	$596,982	$562,210	$535,679
Reconciliation of consolidated net operating income
Consolidated net operating income										361,017	340,441	324,831
Less:
Interest expense										-124,329	-121,937	-132,939
Interest expense - amortization of deferred financing costs										-5,148	-4,676	-6,208
Interest expense — financing obligation										-1,144	-972	-850
Depreciation and amortization										-208,569	-197,021	-188,382
Administrative expenses										-26,779	-27,628	-25,413
Plus:
Interest Income										3,974	1,044	3,008
Historic tax credit transaction income										11,853	11,853	11,840
Recognized hedge activity	-800									-828	0	-2,985
Equity in income (loss) of real estate ventures										-790	3,664	2,741
Net gain (loss) on sale of undepreciated real estate										458	6,866	0
Net gain from remeasurement of investments in real estate ventures										4,901	0	0
Net gain (loss) on sale of undepreciated real estate										1,184	-137	0
Net gain (loss) on real estate venture transactions										-417	29,604	-950
Provision for impairment on assets held for sale										-1,765	0	0
Gain (loss) on early extinguishment of debt	-2,606									-7,594	-2,119	-22,002
Income (loss) from continuing operations										6,024	38,982	-37,309
Income from discontinued operations										918	4,207	43,838
Net income (loss)		-1,869	8,882	2,174	-2,245	21,002	11,088	7,180	3,919	6,942	43,189	6,529
Philadelphia CBD [Member]
Segment Reporting Information [Line Items]
Total revenue										201,809	146,081	131,592
Reconciliation of consolidated net operating income
Consolidated net operating income										126,547	90,379	80,805
Plus:
Equity in income (loss) of real estate ventures										46	1,547	1,113
New Jersey/ Delaware [Member]
Segment Reporting Information [Line Items]
Total revenue										60,403	60,262	59,671
Reconciliation of consolidated net operating income
Consolidated net operating income										28,753	30,281	31,165
Plus:
Equity in income (loss) of real estate ventures										989	1,245	1,803
Richmond, Virginia [Member]
Segment Reporting Information [Line Items]
Total revenue										34,180	35,058	35,701
Reconciliation of consolidated net operating income
Consolidated net operating income										18,781	20,142	21,217
Plus:
Equity in income (loss) of real estate ventures										349	381	269
Austin, Texas [Member]
Segment Reporting Information [Line Items]
Total revenue										5,610	31,451	32,379
Reconciliation of consolidated net operating income
Consolidated net operating income										2,387	18,153	18,428
Plus:
Equity in income (loss) of real estate ventures										($1,080)	($564)	($316)

Operating_Leases_Details

Operating Leases (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Operating Leases, Future Minimum Payments Receivable [Abstract]
Operating Leases, Future Minimum Payments Receivable, Current	$461,215
Operating Leases, Future Minimum Payments Receivable, in Two Years	443,383
Operating Leases, Future Minimum Payments Receivable, in Three Years	411,288
Operating Leases, Future Minimum Payments Receivable, in Four Years	362,370
Operating Leases, Future Minimum Payments Receivable, in Five Years	315,196
Operating Leases, Future Minimum Payments Receivable, Thereafter	$1,515,750

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2004	Dec. 31, 2014	Dec. 31, 2012
		sqft
		Y
Commitments and Contingencies (Textuals) [Abstract]
Minimum remaining lease period		7
Maximum remaining lease period		75
Leased Area Of Building		708,844
Amount to be paid if the Company takes fee title to Two Logan Square upon foreclosure of related mortgage		$2.90
Liability related to acquisition of TRC	0.7	1.8
Agreed holding period (not to sell) for properties acquired as part of the TRC acquisition		15 years
One Commerce Square [Member]
Commitments and Contingencies (Textuals) [Abstract]
Tax guarantee obligation		125
Two Commerce Square [Member]
Commitments and Contingencies (Textuals) [Abstract]
Tax guarantee obligation		100
One and Two Commerce Square [Member]
Commitments and Contingencies (Textuals) [Abstract]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		1.00%
Historic Tax Credit Transaction [Member]
Long-term Purchase Commitment [Line Items]
Accretion Of Non Controlling Interest Liability		1.4	1.3
New Markets Tax Credit Transaction [Member]
Commitments and Contingencies (Textuals) [Abstract]
Tax Credit Carryforward, Amount		$8

Commitments_and_Contingencies_2

Commitments and Contingencies (Ground Rent) (Details) (Ground Rent [Member], USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Ground Rent [Member]
Minimum future rental payments on non-cancelable leases
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$1,378
Operating Leases, Future Minimum Payments, Due in Two Years	1,378
Operating Leases, Future Minimum Payments, Due in Three Years	1,378
Operating Leases, Future Minimum Payments, Due in Four Years	1,378
Operating Leases, Future Minimum Payments, Due in Five Years	1,378
Operating Leases, Future Minimum Payments, Due Thereafter	57,114
Total	$64,004

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	0 Months Ended
	Jan. 30, 2015	Jan. 08, 2015
River Place [Member]
Subsequent Event [Line Items]
Proceeds from Collection of Notes Receivable	$88,000,000
1000 Atrium Way and Libertyview [Member] [Member]
Subsequent Event [Line Items]
Number of Real Estate Properties		2
Sale Consideration Of Sold Property		28,300,000
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		$9,000,000
1000 Atrium Way [Member]
Subsequent Event [Line Items]
Net Rentable Space Sold		99,668
Libertyview [Member]
Subsequent Event [Line Items]
Net Rentable Space Sold		121,737

Summary_of_Quarterly_Results_D

Summary of Quarterly Results (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information [Line Items]
Total revenue	$147,810	$146,558	$150,500	$152,114	$138,658	$143,354	$140,664	$139,554	$596,982	$562,210	$535,679
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	-1,869	8,882	2,174	-2,245	21,002	11,088	7,180	3,919	6,942	43,189	6,529
Net Income (Loss) Attributable to Parent	($3,585)	$6,967	$385	($4,041)	$18,975	$9,173	$5,308	$2,058	$6,975	$42,777	$6,595
Earnings Per Share, Basic	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)
Earnings Per Share, Diluted	($0.02)	$0.04	$0	($0.03)	$0.12	$0.06	$0.03	$0.01	$0	$0.23	($0.06)

Schedule_II_Valuation_and_Qual1

Schedule II - Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance at Beginning of Period	$16,248	$16,646	$15,485
Valuation Allowances and Reserves, Additions	790	1,384	1,891
Valuation Allowances and Reserves, Deductions	1,691	1,782	730
Valuation Allowances and Reserves, Balance at End of Period	$15,347	$16,248	$16,646

Schedule_III_Real_Estate_and_A1

Schedule III - Real Estate and Accumulated Depreciation (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	$655,934
Initial Cost [Abstract]
Land	625,594
Buildings and Improvements	3,362,277
Net Improvements (Retirements) Since Acquisition	643,257
Carrying Amount at Which Carried [Abstract]
Land	673,838
Buildings and Improvements	3,957,290
Total	4,631,128	4,669,289	4,726,169	4,793,080
Accumulated Depreciation at December 31, 2013	1,078,996	983,808	954,665	865,710
400 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,657
Buildings and Improvements	4,462
Net Improvements (Retirements) Since Acquisition	14,011
Carrying Amount at Which Carried [Abstract]
Land	2,657
Buildings and Improvements	18,473
Total	21,130
Accumulated Depreciation at December 31, 2013	6,255
Depreciable Life (Years)	40 years
300 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,206
Buildings and Improvements	13,422
Net Improvements (Retirements) Since Acquisition	3,800
Carrying Amount at Which Carried [Abstract]
Land	2,206
Buildings and Improvements	17,222
Total	19,428
Accumulated Depreciation at December 31, 2013	8,280
Depreciable Life (Years)	40 years
1050 Westlakes Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,611
Buildings and Improvements	10,445
Net Improvements (Retirements) Since Acquisition	5,047
Carrying Amount at Which Carried [Abstract]
Land	2,611
Buildings and Improvements	15,492
Total	18,103
Accumulated Depreciation at December 31, 2013	7,984
Depreciable Life (Years)	40 years
1200 Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,595
Buildings and Improvements	11,809
Net Improvements (Retirements) Since Acquisition	3,534
Carrying Amount at Which Carried [Abstract]
Land	2,595
Buildings and Improvements	15,343
Total	17,938
Accumulated Depreciation at December 31, 2013	6,457
Depreciable Life (Years)	40 years
200 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,533
Buildings and Improvements	9,460
Net Improvements (Retirements) Since Acquisition	2,466
Carrying Amount at Which Carried [Abstract]
Land	1,533
Buildings and Improvements	11,926
Total	13,459
Accumulated Depreciation at December 31, 2013	5,751
Depreciable Life (Years)	40 years
1180 Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,086
Buildings and Improvements	8,342
Net Improvements (Retirements) Since Acquisition	2,979
Carrying Amount at Which Carried [Abstract]
Land	2,086
Buildings and Improvements	11,321
Total	13,407
Accumulated Depreciation at December 31, 2013	3,441
Depreciable Life (Years)	40 years
100 Berwyn Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,180
Buildings and Improvements	7,290
Net Improvements (Retirements) Since Acquisition	2,228
Carrying Amount at Which Carried [Abstract]
Land	1,180
Buildings and Improvements	9,518
Total	10,698
Accumulated Depreciation at December 31, 2013	4,661
Depreciable Life (Years)	40 years
1160 Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,781
Buildings and Improvements	7,124
Net Improvements (Retirements) Since Acquisition	4,255
Carrying Amount at Which Carried [Abstract]
Land	2,045
Buildings and Improvements	11,115
Total	13,160
Accumulated Depreciation at December 31, 2013	2,961
Depreciable Life (Years)	40 years
1100 Cassett Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,695
Buildings and Improvements	6,779
Net Improvements (Retirements) Since Acquisition	1,269
Carrying Amount at Which Carried [Abstract]
Land	1,695
Buildings and Improvements	8,048
Total	9,743
Accumulated Depreciation at December 31, 2013	2,561
Depreciable Life (Years)	40 years
980 Harvest Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,079
Buildings and Improvements	8,315
Net Improvements (Retirements) Since Acquisition	736
Carrying Amount at Which Carried [Abstract]
Land	2,079
Buildings and Improvements	9,051
Total	11,130
Accumulated Depreciation at December 31, 2013	2,935
Depreciable Life (Years)	40 years
910 Harvest Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,224
Buildings and Improvements	8,645
Net Improvements (Retirements) Since Acquisition	-730
Carrying Amount at Which Carried [Abstract]
Land	1,224
Buildings and Improvements	7,915
Total	9,139
Accumulated Depreciation at December 31, 2013	4,394
Depreciable Life (Years)	40 years
925 Harvest Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,671
Buildings and Improvements	6,606
Net Improvements (Retirements) Since Acquisition	993
Carrying Amount at Which Carried [Abstract]
Land	1,671
Buildings and Improvements	7,599
Total	9,270
Accumulated Depreciation at December 31, 2013	3,480
Depreciable Life (Years)	40 years
920 Harvest Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,209
Buildings and Improvements	6,595
Net Improvements (Retirements) Since Acquisition	-684
Carrying Amount at Which Carried [Abstract]
Land	1,209
Buildings and Improvements	5,911
Total	7,120
Accumulated Depreciation at December 31, 2013	3,134
Depreciable Life (Years)	40 years
Six Tower Bridge [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,927
Buildings and Improvements	14,722
Net Improvements (Retirements) Since Acquisition	786
Carrying Amount at Which Carried [Abstract]
Land	6,927
Buildings and Improvements	15,508
Total	22,435
Accumulated Depreciation at December 31, 2013	698
Depreciable Life (Years)	40 years
426 Lancaster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,689
Buildings and Improvements	6,756
Net Improvements (Retirements) Since Acquisition	376
Carrying Amount at Which Carried [Abstract]
Land	1,689
Buildings and Improvements	7,132
Total	8,821
Accumulated Depreciation at December 31, 2013	3,431
Depreciable Life (Years)	40 years
52 Swedesford Square [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,241
Buildings and Improvements	16,579
Net Improvements (Retirements) Since Acquisition	3,262
Carrying Amount at Which Carried [Abstract]
Land	4,241
Buildings and Improvements	19,841
Total	24,082
Accumulated Depreciation at December 31, 2013	8,392
Depreciable Life (Years)	40 years
One Progress Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,399
Buildings and Improvements	5,629
Net Improvements (Retirements) Since Acquisition	5,202
Carrying Amount at Which Carried [Abstract]
Land	1,399
Buildings and Improvements	10,831
Total	12,230
Accumulated Depreciation at December 31, 2013	4,457
Depreciable Life (Years)	40 years
500 Enterprise Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,303
Buildings and Improvements	5,188
Net Improvements (Retirements) Since Acquisition	3,743
Carrying Amount at Which Carried [Abstract]
Land	1,303
Buildings and Improvements	8,931
Total	10,234
Accumulated Depreciation at December 31, 2013	4,098
Depreciable Life (Years)	40 years
640 Freedom Business Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,222
Buildings and Improvements	16,891
Net Improvements (Retirements) Since Acquisition	4,686
Carrying Amount at Which Carried [Abstract]
Land	4,222
Buildings and Improvements	21,577
Total	25,799
Accumulated Depreciation at December 31, 2013	9,535
Depreciable Life (Years)	40 years
555 Croton Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,486
Buildings and Improvements	17,943
Net Improvements (Retirements) Since Acquisition	1,412
Carrying Amount at Which Carried [Abstract]
Land	4,486
Buildings and Improvements	19,355
Total	23,841
Accumulated Depreciation at December 31, 2013	6,779
Depreciable Life (Years)	40 years
630 Allendale Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,836
Buildings and Improvements	4,028
Net Improvements (Retirements) Since Acquisition	12,484
Carrying Amount at Which Carried [Abstract]
Land	2,898
Buildings and Improvements	16,450
Total	19,348
Accumulated Depreciation at December 31, 2013	5,778
Depreciable Life (Years)	40 years
620 Freedom Business Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,770
Buildings and Improvements	11,014
Net Improvements (Retirements) Since Acquisition	3,375
Carrying Amount at Which Carried [Abstract]
Land	2,770
Buildings and Improvements	14,389
Total	17,159
Accumulated Depreciation at December 31, 2013	7,515
Depreciable Life (Years)	40 years
1000 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,772
Buildings and Improvements	10,936
Net Improvements (Retirements) Since Acquisition	2,117
Carrying Amount at Which Carried [Abstract]
Land	2,772
Buildings and Improvements	13,053
Total	15,825
Accumulated Depreciation at December 31, 2013	5,894
Depreciable Life (Years)	40 years
1060 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,712
Buildings and Improvements	10,953
Net Improvements (Retirements) Since Acquisition	4,522
Carrying Amount at Which Carried [Abstract]
Land	2,712
Buildings and Improvements	15,475
Total	18,187
Accumulated Depreciation at December 31, 2013	6,646
Depreciable Life (Years)	40 years
630 Freedom Business Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,773
Buildings and Improvements	11,144
Net Improvements (Retirements) Since Acquisition	2,343
Carrying Amount at Which Carried [Abstract]
Land	2,773
Buildings and Improvements	13,487
Total	16,260
Accumulated Depreciation at December 31, 2013	6,300
Depreciable Life (Years)	40 years
1040 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,860
Buildings and Improvements	11,282
Net Improvements (Retirements) Since Acquisition	6,080
Carrying Amount at Which Carried [Abstract]
Land	2,860
Buildings and Improvements	17,362
Total	20,222
Accumulated Depreciation at December 31, 2013	5,460
Depreciable Life (Years)	40 years
1020 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,168
Buildings and Improvements	8,576
Net Improvements (Retirements) Since Acquisition	7,617
Carrying Amount at Which Carried [Abstract]
Land	2,168
Buildings and Improvements	16,193
Total	18,361
Accumulated Depreciation at December 31, 2013	6,766
Depreciable Life (Years)	40 years
610 Freedom Business Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,017
Buildings and Improvements	8,070
Net Improvements (Retirements) Since Acquisition	2,393
Carrying Amount at Which Carried [Abstract]
Land	2,017
Buildings and Improvements	10,463
Total	12,480
Accumulated Depreciation at December 31, 2013	4,883
Depreciable Life (Years)	40 years
650 Park Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,916
Buildings and Improvements	4,378
Net Improvements (Retirements) Since Acquisition	1,701
Carrying Amount at Which Carried [Abstract]
Land	1,916
Buildings and Improvements	6,079
Total	7,995
Accumulated Depreciation at December 31, 2013	2,920
Depreciable Life (Years)	40 years
500 North Gulph Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,303
Buildings and Improvements	5,201
Net Improvements (Retirements) Since Acquisition	1,522
Carrying Amount at Which Carried [Abstract]
Land	1,303
Buildings and Improvements	6,723
Total	8,026
Accumulated Depreciation at December 31, 2013	3,390
Depreciable Life (Years)	40 years
741 First Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,287
Buildings and Improvements	5,151
Net Improvements (Retirements) Since Acquisition	11
Carrying Amount at Which Carried [Abstract]
Land	1,287
Buildings and Improvements	5,162
Total	6,449
Accumulated Depreciation at December 31, 2013	2,363
Depreciable Life (Years)	40 years
751-761 Fifth Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,097
Buildings and Improvements	4,391
Net Improvements (Retirements) Since Acquisition	31
Carrying Amount at Which Carried [Abstract]
Land	1,097
Buildings and Improvements	4,422
Total	5,519
Accumulated Depreciation at December 31, 2013	2,021
Depreciable Life (Years)	40 years
600 Park Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,012
Buildings and Improvements	4,048
Net Improvements (Retirements) Since Acquisition	385
Carrying Amount at Which Carried [Abstract]
Land	1,012
Buildings and Improvements	4,433
Total	5,445
Accumulated Depreciation at December 31, 2013	2,045
Depreciable Life (Years)	40 years
620 Allendale Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,020
Buildings and Improvements	3,839
Net Improvements (Retirements) Since Acquisition	658
Carrying Amount at Which Carried [Abstract]
Land	1,020
Buildings and Improvements	4,497
Total	5,517
Accumulated Depreciation at December 31, 2013	2,008
Depreciable Life (Years)	40 years
660 Allendale Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	396
Buildings and Improvements	948
Net Improvements (Retirements) Since Acquisition	2,957
Carrying Amount at Which Carried [Abstract]
Land	1,085
Buildings and Improvements	3,216
Total	4,301
Accumulated Depreciation at December 31, 2013	921
Depreciable Life (Years)	40 years
640 Allendale Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	439
Buildings and Improvements	432
Net Improvements (Retirements) Since Acquisition	1,580
Carrying Amount at Which Carried [Abstract]
Land	439
Buildings and Improvements	2,012
Total	2,451
Accumulated Depreciation at December 31, 2013	802
Depreciable Life (Years)	40 years
14 Campus Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,244
Buildings and Improvements	4,217
Net Improvements (Retirements) Since Acquisition	1,533
Carrying Amount at Which Carried [Abstract]
Land	2,244
Buildings and Improvements	5,750
Total	7,994
Accumulated Depreciation at December 31, 2013	3,322
Depreciable Life (Years)	40 years
11 Campus Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,112
Buildings and Improvements	4,067
Net Improvements (Retirements) Since Acquisition	1,006
Carrying Amount at Which Carried [Abstract]
Land	1,112
Buildings and Improvements	5,073
Total	6,185
Accumulated Depreciation at December 31, 2013	1,967
Depreciable Life (Years)	40 years
17 Campus Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,108
Buildings and Improvements	5,155
Net Improvements (Retirements) Since Acquisition	-374
Carrying Amount at Which Carried [Abstract]
Land	1,108
Buildings and Improvements	4,781
Total	5,889
Accumulated Depreciation at December 31, 2013	1,728
Depreciable Life (Years)	40 years
15 Campus Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,164
Buildings and Improvements	3,896
Net Improvements (Retirements) Since Acquisition	249
Carrying Amount at Which Carried [Abstract]
Land	1,164
Buildings and Improvements	4,145
Total	5,309
Accumulated Depreciation at December 31, 2013	1,394
Depreciable Life (Years)	40 years
18 Campus Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	787
Buildings and Improvements	3,312
Net Improvements (Retirements) Since Acquisition	-77
Carrying Amount at Which Carried [Abstract]
Land	787
Buildings and Improvements	3,235
Total	4,022
Accumulated Depreciation at December 31, 2013	1,631
Depreciable Life (Years)	40 years
401 Plymouth Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,198
Buildings and Improvements	16,131
Net Improvements (Retirements) Since Acquisition	16,130
Carrying Amount at Which Carried [Abstract]
Land	6,198
Buildings and Improvements	32,261
Total	38,459
Accumulated Depreciation at December 31, 2013	9,982
Depreciable Life (Years)	40 years
4000 Chemical Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,373
Buildings and Improvements	24,546
Net Improvements (Retirements) Since Acquisition	1,467
Carrying Amount at Which Carried [Abstract]
Land	4,373
Buildings and Improvements	26,013
Total	30,386
Accumulated Depreciation at December 31, 2013	4,864
Depreciable Life (Years)	40 years
610 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,651
Buildings and Improvements	14,514
Net Improvements (Retirements) Since Acquisition	3,357
Carrying Amount at Which Carried [Abstract]
Land	3,651
Buildings and Improvements	17,871
Total	21,522
Accumulated Depreciation at December 31, 2013	5,892
Depreciable Life (Years)	40 years
600 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,652
Buildings and Improvements	15,288
Net Improvements (Retirements) Since Acquisition	1,609
Carrying Amount at Which Carried [Abstract]
Land	3,652
Buildings and Improvements	16,897
Total	20,549
Accumulated Depreciation at December 31, 2013	5,659
Depreciable Life (Years)	40 years
630 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,558
Buildings and Improvements	14,743
Net Improvements (Retirements) Since Acquisition	1,902
Carrying Amount at Which Carried [Abstract]
Land	3,558
Buildings and Improvements	16,645
Total	20,203
Accumulated Depreciation at December 31, 2013	5,994
Depreciable Life (Years)	40 years
620 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,572
Buildings and Improvements	14,435
Net Improvements (Retirements) Since Acquisition	1,339
Carrying Amount at Which Carried [Abstract]
Land	3,572
Buildings and Improvements	15,774
Total	19,346
Accumulated Depreciation at December 31, 2013	5,378
Depreciable Life (Years)	40 years
660 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,694
Buildings and Improvements	5,487
Net Improvements (Retirements) Since Acquisition	18,484
Carrying Amount at Which Carried [Abstract]
Land	5,404
Buildings and Improvements	22,261
Total	27,665
Accumulated Depreciation at December 31, 2013	1,436
Depreciable Life (Years)	30 years
2240/2250 Butler Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,104
Buildings and Improvements	4,627
Net Improvements (Retirements) Since Acquisition	1,312
Carrying Amount at Which Carried [Abstract]
Land	1,104
Buildings and Improvements	5,939
Total	7,043
Accumulated Depreciation at December 31, 2013	3,596
Depreciable Life (Years)	40 years
2260 Butler Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	661
Buildings and Improvements	2,727
Net Improvements (Retirements) Since Acquisition	2,115
Carrying Amount at Which Carried [Abstract]
Land	661
Buildings and Improvements	4,842
Total	5,503
Accumulated Depreciation at December 31, 2013	2,165
Depreciable Life (Years)	40 years
120 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	685
Buildings and Improvements	2,773
Net Improvements (Retirements) Since Acquisition	729
Carrying Amount at Which Carried [Abstract]
Land	685
Buildings and Improvements	3,502
Total	4,187
Accumulated Depreciation at December 31, 2013	1,767
Depreciable Life (Years)	40 years
140 West Germantown Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	481
Buildings and Improvements	1,976
Net Improvements (Retirements) Since Acquisition	282
Carrying Amount at Which Carried [Abstract]
Land	481
Buildings and Improvements	2,258
Total	2,739
Accumulated Depreciation at December 31, 2013	1,079
Depreciable Life (Years)	40 years
351 Plymouth Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,043
Buildings and Improvements	555
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	1,043
Buildings and Improvements	555
Total	1,598
Accumulated Depreciation at December 31, 2013	135
Depreciable Life (Years)	40 years
150 Radnor Chester Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	11,925
Buildings and Improvements	36,986
Net Improvements (Retirements) Since Acquisition	12,549
Carrying Amount at Which Carried [Abstract]
Land	11,897
Buildings and Improvements	49,563
Total	61,460
Accumulated Depreciation at December 31, 2013	16,431
Depreciable Life (Years)	29 years
One Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,323
Buildings and Improvements	28,613
Net Improvements (Retirements) Since Acquisition	23,182
Carrying Amount at Which Carried [Abstract]
Land	7,323
Buildings and Improvements	51,795
Total	59,118
Accumulated Depreciation at December 31, 2013	18,406
Depreciable Life (Years)	29 years
201 King of Prussia Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	8,956
Buildings and Improvements	29,811
Net Improvements (Retirements) Since Acquisition	5,070
Carrying Amount at Which Carried [Abstract]
Land	8,949
Buildings and Improvements	34,888
Total	43,837
Accumulated Depreciation at December 31, 2013	15,445
Depreciable Life (Years)	25 years
555 Lancaster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	8,014
Buildings and Improvements	16,508
Net Improvements (Retirements) Since Acquisition	16,854
Carrying Amount at Which Carried [Abstract]
Land	8,609
Buildings and Improvements	32,767
Total	41,376
Accumulated Depreciation at December 31, 2013	12,563
Depreciable Life (Years)	24 years
Four Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	5,406
Buildings and Improvements	21,390
Net Improvements (Retirements) Since Acquisition	8,501
Carrying Amount at Which Carried [Abstract]
Land	5,705
Buildings and Improvements	29,592
Total	35,297
Accumulated Depreciation at December 31, 2013	10,480
Depreciable Life (Years)	30 years
Five Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,506
Buildings and Improvements	25,525
Net Improvements (Retirements) Since Acquisition	5,455
Carrying Amount at Which Carried [Abstract]
Land	6,578
Buildings and Improvements	30,908
Total	37,486
Accumulated Depreciation at December 31, 2013	8,024
Depreciable Life (Years)	38 years
Three Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,773
Buildings and Improvements	17,961
Net Improvements (Retirements) Since Acquisition	2,645
Carrying Amount at Which Carried [Abstract]
Land	4,791
Buildings and Improvements	20,588
Total	25,379
Accumulated Depreciation at December 31, 2013	8,094
Depreciable Life (Years)	29 years
Two Radnor Corporate Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,937
Buildings and Improvements	15,484
Net Improvements (Retirements) Since Acquisition	3,888
Carrying Amount at Which Carried [Abstract]
Land	3,942
Buildings and Improvements	19,367
Total	23,309
Accumulated Depreciation at December 31, 2013	6,882
Depreciable Life (Years)	29 years
130 Radnor Chester Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,573
Buildings and Improvements	8,338
Net Improvements (Retirements) Since Acquisition	3,483
Carrying Amount at Which Carried [Abstract]
Land	2,567
Buildings and Improvements	11,827
Total	14,394
Accumulated Depreciation at December 31, 2013	4,357
Depreciable Life (Years)	25 years
170 Radnor Chester Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,514
Buildings and Improvements	8,147
Net Improvements (Retirements) Since Acquisition	1,718
Carrying Amount at Which Carried [Abstract]
Land	2,509
Buildings and Improvements	9,870
Total	12,379
Accumulated Depreciation at December 31, 2013	3,051
Depreciable Life (Years)	25 years
200 N. Radnor Chester Rd. [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,366
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	3,675
Carrying Amount at Which Carried [Abstract]
Land	3,366
Buildings and Improvements	3,675
Total	7,041
Accumulated Depreciation at December 31, 2013	113
Depreciable Life (Years)	40 years
101 West Elm Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,251
Buildings and Improvements	25,209
Net Improvements (Retirements) Since Acquisition	3,189
Carrying Amount at Which Carried [Abstract]
Land	6,251
Buildings and Improvements	28,398
Total	34,649
Accumulated Depreciation at December 31, 2013	7,640
Depreciable Life (Years)	40 years
1 West Elm Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,557
Buildings and Improvements	14,249
Net Improvements (Retirements) Since Acquisition	3,876
Carrying Amount at Which Carried [Abstract]
Land	3,557
Buildings and Improvements	18,125
Total	21,682
Accumulated Depreciation at December 31, 2013	4,204
Depreciable Life (Years)	40 years
595 East Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,729
Buildings and Improvements	10,917
Net Improvements (Retirements) Since Acquisition	2,307
Carrying Amount at Which Carried [Abstract]
Land	2,729
Buildings and Improvements	13,224
Total	15,953
Accumulated Depreciation at December 31, 2013	4,464
Depreciable Life (Years)	40 years
575 East Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,178
Buildings and Improvements	8,712
Net Improvements (Retirements) Since Acquisition	1,681
Carrying Amount at Which Carried [Abstract]
Land	2,178
Buildings and Improvements	10,393
Total	12,571
Accumulated Depreciation at December 31, 2013	3,692
Depreciable Life (Years)	40 years
565 East Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,872
Buildings and Improvements	7,489
Net Improvements (Retirements) Since Acquisition	1,744
Carrying Amount at Which Carried [Abstract]
Land	1,872
Buildings and Improvements	9,233
Total	11,105
Accumulated Depreciation at December 31, 2013	3,166
Depreciable Life (Years)	40 years
585 East Swedesford Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,350
Buildings and Improvements	5,401
Net Improvements (Retirements) Since Acquisition	1,350
Carrying Amount at Which Carried [Abstract]
Land	1,350
Buildings and Improvements	6,751
Total	8,101
Accumulated Depreciation at December 31, 2013	1,551
Depreciable Life (Years)	40 years
2970 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	184,442
Initial Cost [Abstract]
Land	22,430
Buildings and Improvements	217,763
Net Improvements (Retirements) Since Acquisition	12,021
Carrying Amount at Which Carried [Abstract]
Land	22,430
Buildings and Improvements	229,784
Total	252,214
Accumulated Depreciation at December 31, 2013	27,560
Depreciable Life (Years)	40 years
2929 Arch Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	208,570
Net Improvements (Retirements) Since Acquisition	29,302
Carrying Amount at Which Carried [Abstract]
Land	12,586
Buildings and Improvements	225,286
Total	237,872
Accumulated Depreciation at December 31, 2013	85,000
Depreciable Life (Years)	40 years
1717 Arch Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	98,188
Net Improvements (Retirements) Since Acquisition	66,550
Carrying Amount at Which Carried [Abstract]
Land	25,195
Buildings and Improvements	139,543
Total	164,738
Accumulated Depreciation at December 31, 2013	19,000
Depreciable Life (Years)	40 years
2001 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	112,000
Initial Cost [Abstract]
Land	15,323
Buildings and Improvements	120,842
Net Improvements (Retirements) Since Acquisition	2,125
Carrying Amount at Which Carried [Abstract]
Land	15,323
Buildings and Improvements	122,967
Total	138,290
Accumulated Depreciation at December 31, 2013	3,371
Depreciable Life (Years)	40 years
130 North 18th Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	14,496
Buildings and Improvements	107,736
Net Improvements (Retirements) Since Acquisition	17,397
Carrying Amount at Which Carried [Abstract]
Land	14,473
Buildings and Improvements	125,156
Total	139,629
Accumulated Depreciation at December 31, 2013	37,755
Depreciable Life (Years)	34 years
100 North 18th Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	87,767
Initial Cost [Abstract]
Land	16,066
Buildings and Improvements	100,255
Net Improvements (Retirements) Since Acquisition	10,925
Carrying Amount at Which Carried [Abstract]
Land	16,066
Buildings and Improvements	111,180
Total	127,246
Accumulated Depreciation at December 31, 2013	35,435
Depreciable Life (Years)	36 years
2005 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	123,205
Initial Cost [Abstract]
Land	15,161
Buildings and Improvements	122,486
Net Improvements (Retirements) Since Acquisition	-11,726
Carrying Amount at Which Carried [Abstract]
Land	15,161
Buildings and Improvements	110,760
Total	125,921
Accumulated Depreciation at December 31, 2013	2,959
Depreciable Life (Years)	40 years
2930 Chestnut Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	37,765
Initial Cost [Abstract]
Land	0
Buildings and Improvements	76,008
Net Improvements (Retirements) Since Acquisition	2,644
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	78,652
Total	78,652
Accumulated Depreciation at December 31, 2013	8,677
Depreciable Life (Years)	40 years
1900 Market [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,768
Buildings and Improvements	17,263
Net Improvements (Retirements) Since Acquisition	481
Carrying Amount at Which Carried [Abstract]
Land	7,768
Buildings and Improvements	17,744
Total	25,512
Accumulated Depreciation at December 31, 2013	1,246
Depreciable Life (Years)	30 years
3020 Market Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	21,417
Net Improvements (Retirements) Since Acquisition	6,225
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	27,642
Total	27,642
Accumulated Depreciation at December 31, 2013	3,260
Depreciable Life (Years)	26 years
101-103 Juniper Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	14,401
Net Improvements (Retirements) Since Acquisition	324
Carrying Amount at Which Carried [Abstract]
Land	478
Buildings and Improvements	14,247
Total	14,725
Accumulated Depreciation at December 31, 2013	1,865
Depreciable Life (Years)	40 years
Philadelphia Marine Center [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	532
Buildings and Improvements	2,196
Net Improvements (Retirements) Since Acquisition	3,444
Carrying Amount at Which Carried [Abstract]
Land	628
Buildings and Improvements	5,544
Total	6,172
Accumulated Depreciation at December 31, 2013	2,408
Depreciable Life (Years)	40 years
11720 Beltsville Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,831
Buildings and Improvements	16,661
Net Improvements (Retirements) Since Acquisition	3,399
Carrying Amount at Which Carried [Abstract]
Land	3,904
Buildings and Improvements	19,987
Total	23,891
Accumulated Depreciation at December 31, 2013	5,887
Depreciable Life (Years)	46 years
11700 Beltsville Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,808
Buildings and Improvements	12,081
Net Improvements (Retirements) Since Acquisition	293
Carrying Amount at Which Carried [Abstract]
Land	2,863
Buildings and Improvements	12,319
Total	15,182
Accumulated Depreciation at December 31, 2013	2,702
Depreciable Life (Years)	46 years
11710 Beltsville Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,278
Buildings and Improvements	11,100
Net Improvements (Retirements) Since Acquisition	-814
Carrying Amount at Which Carried [Abstract]
Land	2,321
Buildings and Improvements	10,243
Total	12,564
Accumulated Depreciation at December 31, 2013	2,370
Depreciable Life (Years)	46 years
6600 Rockledge Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	37,421
Net Improvements (Retirements) Since Acquisition	11,303
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	48,724
Total	48,724
Accumulated Depreciation at December 31, 2013	15,070
Depreciable Life (Years)	50 years
11740 Beltsville Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	198
Buildings and Improvements	870
Net Improvements (Retirements) Since Acquisition	42
Carrying Amount at Which Carried [Abstract]
Land	202
Buildings and Improvements	908
Total	1,110
Accumulated Depreciation at December 31, 2013	211
Depreciable Life (Years)	46 years
12015 Lee Jackson Memorial Highway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,770
Buildings and Improvements	22,895
Net Improvements (Retirements) Since Acquisition	3,987
Carrying Amount at Which Carried [Abstract]
Land	3,841
Buildings and Improvements	26,811
Total	30,652
Accumulated Depreciation at December 31, 2013	7,188
Depreciable Life (Years)	42 years
11781 Lee Jackson Memorial Highway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,246
Buildings and Improvements	19,836
Net Improvements (Retirements) Since Acquisition	567
Carrying Amount at Which Carried [Abstract]
Land	3,307
Buildings and Improvements	20,342
Total	23,649
Accumulated Depreciation at December 31, 2013	4,748
Depreciable Life (Years)	40 years
4401 Fair Lakes Court [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,569
Buildings and Improvements	11,982
Net Improvements (Retirements) Since Acquisition	247
Carrying Amount at Which Carried [Abstract]
Land	1,599
Buildings and Improvements	12,199
Total	13,798
Accumulated Depreciation at December 31, 2013	2,456
Depreciable Life (Years)	52 years
3141 Fairview Park Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	21,242
Initial Cost [Abstract]
Land	5,918
Buildings and Improvements	40,981
Net Improvements (Retirements) Since Acquisition	12,017
Carrying Amount at Which Carried [Abstract]
Land	7,080
Buildings and Improvements	51,836
Total	58,916
Accumulated Depreciation at December 31, 2013	10,264
Depreciable Life (Years)	51 years
2340 Dulles Corner Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	16,345
Buildings and Improvements	65,379
Net Improvements (Retirements) Since Acquisition	18,280
Carrying Amount at Which Carried [Abstract]
Land	16,129
Buildings and Improvements	83,875
Total	100,004
Accumulated Depreciation at December 31, 2013	28,064
Depreciable Life (Years)	40 years
2291 Wood Oak Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	8,243
Buildings and Improvements	52,413
Net Improvements (Retirements) Since Acquisition	13,499
Carrying Amount at Which Carried [Abstract]
Land	8,782
Buildings and Improvements	65,373
Total	74,155
Accumulated Depreciation at December 31, 2013	13,524
Depreciable Life (Years)	55 years
196/198 Van Buren Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,931
Buildings and Improvements	43,812
Net Improvements (Retirements) Since Acquisition	9,040
Carrying Amount at Which Carried [Abstract]
Land	8,348
Buildings and Improvements	52,435
Total	60,783
Accumulated Depreciation at December 31, 2013	10,308
Depreciable Life (Years)	53 years
2251 Corporate Park Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	11,472
Buildings and Improvements	45,893
Net Improvements (Retirements) Since Acquisition	2,276
Carrying Amount at Which Carried [Abstract]
Land	11,472
Buildings and Improvements	48,169
Total	59,641
Accumulated Depreciation at December 31, 2013	9,758
Depreciable Life (Years)	40 years
2355 Dulles Corner Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	10,365
Buildings and Improvements	43,876
Net Improvements (Retirements) Since Acquisition	4,648
Carrying Amount at Which Carried [Abstract]
Land	10,365
Buildings and Improvements	48,524
Total	58,889
Accumulated Depreciation at December 31, 2013	12,675
Depreciable Life (Years)	40 years
2411 Dulles Corner Park [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,279
Buildings and Improvements	46,340
Net Improvements (Retirements) Since Acquisition	117
Carrying Amount at Which Carried [Abstract]
Land	7,417
Buildings and Improvements	46,319
Total	53,736
Accumulated Depreciation at December 31, 2013	8,645
Depreciable Life (Years)	50 years
13880 Dulles Corner Lane [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,236
Buildings and Improvements	39,213
Net Improvements (Retirements) Since Acquisition	3,369
Carrying Amount at Which Carried [Abstract]
Land	7,373
Buildings and Improvements	42,445
Total	49,818
Accumulated Depreciation at December 31, 2013	7,824
Depreciable Life (Years)	55 years
2121 Cooperative Way [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	5,598
Buildings and Improvements	38,639
Net Improvements (Retirements) Since Acquisition	2,532
Carrying Amount at Which Carried [Abstract]
Land	5,795
Buildings and Improvements	40,974
Total	46,769
Accumulated Depreciation at December 31, 2013	7,665
Depreciable Life (Years)	54 years
2201 Cooperative Way [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,809
Buildings and Improvements	34,093
Net Improvements (Retirements) Since Acquisition	4,513
Carrying Amount at Which Carried [Abstract]
Land	4,809
Buildings and Improvements	38,606
Total	43,415
Accumulated Depreciation at December 31, 2013	7,153
Depreciable Life (Years)	54 years
13825 Sunrise Valley Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,794
Buildings and Improvements	19,365
Net Improvements (Retirements) Since Acquisition	2,121
Carrying Amount at Which Carried [Abstract]
Land	3,866
Buildings and Improvements	21,414
Total	25,280
Accumulated Depreciation at December 31, 2013	4,441
Depreciable Life (Years)	46 years
1676 International Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	58,470
Initial Cost [Abstract]
Land	18,437
Buildings and Improvements	97,538
Net Improvements (Retirements) Since Acquisition	3,183
Carrying Amount at Which Carried [Abstract]
Land	18,785
Buildings and Improvements	100,373
Total	119,158
Accumulated Depreciation at December 31, 2013	16,619
Depreciable Life (Years)	55 years
8260 Greensboro Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	31,043
Initial Cost [Abstract]
Land	7,952
Buildings and Improvements	33,964
Net Improvements (Retirements) Since Acquisition	1,641
Carrying Amount at Which Carried [Abstract]
Land	8,102
Buildings and Improvements	35,455
Total	43,557
Accumulated Depreciation at December 31, 2013	7,320
Depreciable Life (Years)	52 years
2273 Research Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	5,167
Buildings and Improvements	31,110
Net Improvements (Retirements) Since Acquisition	3,764
Carrying Amount at Which Carried [Abstract]
Land	5,237
Buildings and Improvements	34,804
Total	40,041
Accumulated Depreciation at December 31, 2013	10,191
Depreciable Life (Years)	45 years
2275 Research Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	5,059
Buildings and Improvements	29,668
Net Improvements (Retirements) Since Acquisition	6,479
Carrying Amount at Which Carried [Abstract]
Land	5,154
Buildings and Improvements	36,052
Total	41,206
Accumulated Depreciation at December 31, 2013	7,672
Depreciable Life (Years)	45 years
2277 Research Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,649
Buildings and Improvements	26,952
Net Improvements (Retirements) Since Acquisition	695
Carrying Amount at Which Carried [Abstract]
Land	4,733
Buildings and Improvements	27,563
Total	32,296
Accumulated Depreciation at December 31, 2013	5,724
Depreciable Life (Years)	45 years
1900 Gallows Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,797
Buildings and Improvements	47,817
Net Improvements (Retirements) Since Acquisition	10,849
Carrying Amount at Which Carried [Abstract]
Land	7,944
Buildings and Improvements	58,519
Total	66,463
Accumulated Depreciation at December 31, 2013	11,008
Depreciable Life (Years)	52 years
8521 Leesburg Pike [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,316
Buildings and Improvements	30,885
Net Improvements (Retirements) Since Acquisition	4,858
Carrying Amount at Which Carried [Abstract]
Land	4,397
Buildings and Improvements	35,662
Total	40,059
Accumulated Depreciation at December 31, 2013	6,399
Depreciable Life (Years)	51 years
457 Haddonfield Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,142
Buildings and Improvements	9,120
Net Improvements (Retirements) Since Acquisition	1,402
Carrying Amount at Which Carried [Abstract]
Land	2,142
Buildings and Improvements	10,522
Total	12,664
Accumulated Depreciation at December 31, 2013	5,273
Depreciable Life (Years)	40 years
200 Lake Drive East [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,069
Buildings and Improvements	8,275
Net Improvements (Retirements) Since Acquisition	1,328
Carrying Amount at Which Carried [Abstract]
Land	2,069
Buildings and Improvements	9,603
Total	11,672
Accumulated Depreciation at December 31, 2013	3,635
Depreciable Life (Years)	40 years
220 Lake Drive East [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,144
Buildings and Improvements	8,798
Net Improvements (Retirements) Since Acquisition	825
Carrying Amount at Which Carried [Abstract]
Land	2,144
Buildings and Improvements	9,623
Total	11,767
Accumulated Depreciation at December 31, 2013	3,490
Depreciable Life (Years)	40 years
210 Lake Drive East [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,645
Buildings and Improvements	6,579
Net Improvements (Retirements) Since Acquisition	1,917
Carrying Amount at Which Carried [Abstract]
Land	1,645
Buildings and Improvements	8,496
Total	10,141
Accumulated Depreciation at December 31, 2013	2,812
Depreciable Life (Years)	40 years
20 East Clementon Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	769
Buildings and Improvements	3,055
Net Improvements (Retirements) Since Acquisition	480
Carrying Amount at Which Carried [Abstract]
Land	769
Buildings and Improvements	3,535
Total	4,304
Accumulated Depreciation at December 31, 2013	1,682
Depreciable Life (Years)	40 years
10 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	244
Buildings and Improvements	971
Net Improvements (Retirements) Since Acquisition	78
Carrying Amount at Which Carried [Abstract]
Land	244
Buildings and Improvements	1,049
Total	1,293
Accumulated Depreciation at December 31, 2013	497
Depreciable Life (Years)	40 years
7 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	231
Buildings and Improvements	921
Net Improvements (Retirements) Since Acquisition	123
Carrying Amount at Which Carried [Abstract]
Land	231
Buildings and Improvements	1,044
Total	1,275
Accumulated Depreciation at December 31, 2013	475
Depreciable Life (Years)	40 years
50 East Clementon Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	114
Buildings and Improvements	964
Net Improvements (Retirements) Since Acquisition	653
Carrying Amount at Which Carried [Abstract]
Land	114
Buildings and Improvements	1,617
Total	1,731
Accumulated Depreciation at December 31, 2013	483
Depreciable Life (Years)	40 years
2 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	185
Buildings and Improvements	730
Net Improvements (Retirements) Since Acquisition	16
Carrying Amount at Which Carried [Abstract]
Land	185
Buildings and Improvements	746
Total	931
Accumulated Depreciation at December 31, 2013	351
Depreciable Life (Years)	40 years
4 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	183
Buildings and Improvements	726
Net Improvements (Retirements) Since Acquisition	16
Carrying Amount at Which Carried [Abstract]
Land	183
Buildings and Improvements	742
Total	925
Accumulated Depreciation at December 31, 2013	343
Depreciable Life (Years)	40 years
1 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	93
Buildings and Improvements	364
Net Improvements (Retirements) Since Acquisition	57
Carrying Amount at Which Carried [Abstract]
Land	93
Buildings and Improvements	421
Total	514
Accumulated Depreciation at December 31, 2013	215
Depreciable Life (Years)	40 years
5 U.S. Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	21
Buildings and Improvements	81
Net Improvements (Retirements) Since Acquisition	3
Carrying Amount at Which Carried [Abstract]
Land	21
Buildings and Improvements	84
Total	105
Accumulated Depreciation at December 31, 2013	39
Depreciable Life (Years)	40 years
5 Foster Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	9
Buildings and Improvements	32
Net Improvements (Retirements) Since Acquisition	26
Carrying Amount at Which Carried [Abstract]
Land	9
Buildings and Improvements	58
Total	67
Accumulated Depreciation at December 31, 2013	28
Depreciable Life (Years)	40 years
1120 Executive Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,074
Buildings and Improvements	8,415
Net Improvements (Retirements) Since Acquisition	4,398
Carrying Amount at Which Carried [Abstract]
Land	2,074
Buildings and Improvements	12,813
Total	14,887
Accumulated Depreciation at December 31, 2013	5,143
Depreciable Life (Years)	40 years
Two Eves Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	818
Buildings and Improvements	3,461
Net Improvements (Retirements) Since Acquisition	234
Carrying Amount at Which Carried [Abstract]
Land	818
Buildings and Improvements	3,695
Total	4,513
Accumulated Depreciation at December 31, 2013	1,825
Depreciable Life (Years)	40 years
Five Eves Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	703
Buildings and Improvements	2,819
Net Improvements (Retirements) Since Acquisition	665
Carrying Amount at Which Carried [Abstract]
Land	703
Buildings and Improvements	3,484
Total	4,187
Accumulated Depreciation at December 31, 2013	1,643
Depreciable Life (Years)	40 years
Four B Eves Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	588
Buildings and Improvements	2,369
Net Improvements (Retirements) Since Acquisition	420
Carrying Amount at Which Carried [Abstract]
Land	588
Buildings and Improvements	2,789
Total	3,377
Accumulated Depreciation at December 31, 2013	1,449
Depreciable Life (Years)	40 years
Four A Eves Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	539
Buildings and Improvements	2,168
Net Improvements (Retirements) Since Acquisition	322
Carrying Amount at Which Carried [Abstract]
Land	539
Buildings and Improvements	2,490
Total	3,029
Accumulated Depreciation at December 31, 2013	1,122
Depreciable Life (Years)	40 years
308 Harper Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,643
Buildings and Improvements	6,663
Net Improvements (Retirements) Since Acquisition	739
Carrying Amount at Which Carried [Abstract]
Land	1,643
Buildings and Improvements	7,402
Total	9,045
Accumulated Depreciation at December 31, 2013	3,258
Depreciable Life (Years)	40 years
10000 Midlantic Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,206
Buildings and Improvements	12,857
Net Improvements (Retirements) Since Acquisition	4,228
Carrying Amount at Which Carried [Abstract]
Land	3,206
Buildings and Improvements	17,085
Total	20,291
Accumulated Depreciation at December 31, 2013	7,138
Depreciable Life (Years)	40 years
700 East Gate Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,569
Buildings and Improvements	14,436
Net Improvements (Retirements) Since Acquisition	2,243
Carrying Amount at Which Carried [Abstract]
Land	3,569
Buildings and Improvements	16,679
Total	20,248
Accumulated Depreciation at December 31, 2013	7,576
Depreciable Life (Years)	40 years
15000 Midlantic Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,061
Buildings and Improvements	12,254
Net Improvements (Retirements) Since Acquisition	1,619
Carrying Amount at Which Carried [Abstract]
Land	3,061
Buildings and Improvements	13,873
Total	16,934
Accumulated Depreciation at December 31, 2013	6,518
Depreciable Life (Years)	40 years
1000 Howard Boulevard [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,297
Buildings and Improvements	9,288
Net Improvements (Retirements) Since Acquisition	3,922
Carrying Amount at Which Carried [Abstract]
Land	2,297
Buildings and Improvements	13,210
Total	15,507
Accumulated Depreciation at December 31, 2013	5,900
Depreciable Life (Years)	40 years
1000 Atrium Way [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,061
Buildings and Improvements	8,180
Net Improvements (Retirements) Since Acquisition	4,531
Carrying Amount at Which Carried [Abstract]
Land	2,061
Buildings and Improvements	12,711
Total	14,772
Accumulated Depreciation at December 31, 2013	5,894
Depreciable Life (Years)	40 years
2000 Midlantic Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,202
Buildings and Improvements	8,823
Net Improvements (Retirements) Since Acquisition	2,970
Carrying Amount at Which Carried [Abstract]
Land	2,202
Buildings and Improvements	11,793
Total	13,995
Accumulated Depreciation at December 31, 2013	5,349
Depreciable Life (Years)	40 years
701 East Gate Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,736
Buildings and Improvements	6,877
Net Improvements (Retirements) Since Acquisition	1,768
Carrying Amount at Which Carried [Abstract]
Land	1,736
Buildings and Improvements	8,645
Total	10,381
Accumulated Depreciation at December 31, 2013	3,715
Depreciable Life (Years)	40 years
9000 Midlantic Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,472
Buildings and Improvements	5,895
Net Improvements (Retirements) Since Acquisition	2,185
Carrying Amount at Which Carried [Abstract]
Land	1,472
Buildings and Improvements	8,080
Total	9,552
Accumulated Depreciation at December 31, 2013	3,503
Depreciable Life (Years)	40 years
307 Fellowship Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,565
Buildings and Improvements	6,342
Net Improvements (Retirements) Since Acquisition	1,517
Carrying Amount at Which Carried [Abstract]
Land	1,565
Buildings and Improvements	7,859
Total	9,424
Accumulated Depreciation at December 31, 2013	3,472
Depreciable Life (Years)	40 years
305 Fellowship Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,421
Buildings and Improvements	5,768
Net Improvements (Retirements) Since Acquisition	1,631
Carrying Amount at Which Carried [Abstract]
Land	1,421
Buildings and Improvements	7,399
Total	8,820
Accumulated Depreciation at December 31, 2013	3,122
Depreciable Life (Years)	40 years
303 Fellowship Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,493
Buildings and Improvements	6,055
Net Improvements (Retirements) Since Acquisition	851
Carrying Amount at Which Carried [Abstract]
Land	1,493
Buildings and Improvements	6,906
Total	8,399
Accumulated Depreciation at December 31, 2013	3,114
Depreciable Life (Years)	40 years
309 Fellowship Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,518
Buildings and Improvements	6,154
Net Improvements (Retirements) Since Acquisition	780
Carrying Amount at Which Carried [Abstract]
Land	1,518
Buildings and Improvements	6,934
Total	8,452
Accumulated Depreciation at December 31, 2013	3,070
Depreciable Life (Years)	40 years
1000 Bishops Gate [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	934
Buildings and Improvements	6,287
Net Improvements (Retirements) Since Acquisition	-647
Carrying Amount at Which Carried [Abstract]
Land	934
Buildings and Improvements	5,640
Total	6,574
Accumulated Depreciation at December 31, 2013	1,534
Depreciable Life (Years)	40 years
161 Gaither Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,016
Buildings and Improvements	4,064
Net Improvements (Retirements) Since Acquisition	731
Carrying Amount at Which Carried [Abstract]
Land	1,016
Buildings and Improvements	4,795
Total	5,811
Accumulated Depreciation at December 31, 2013	1,855
Depreciable Life (Years)	40 years
815 East Gate Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	636
Buildings and Improvements	2,584
Net Improvements (Retirements) Since Acquisition	550
Carrying Amount at Which Carried [Abstract]
Land	636
Buildings and Improvements	3,134
Total	3,770
Accumulated Depreciation at December 31, 2013	1,436
Depreciable Life (Years)	40 years
4000 Midlantic Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	714
Buildings and Improvements	5,085
Net Improvements (Retirements) Since Acquisition	-1,833
Carrying Amount at Which Carried [Abstract]
Land	714
Buildings and Improvements	3,252
Total	3,966
Accumulated Depreciation at December 31, 2013	1,531
Depreciable Life (Years)	40 years
817 East Gate Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	611
Buildings and Improvements	2,426
Net Improvements (Retirements) Since Acquisition	263
Carrying Amount at Which Carried [Abstract]
Land	611
Buildings and Improvements	2,689
Total	3,300
Accumulated Depreciation at December 31, 2013	1,159
Depreciable Life (Years)	40 years
400 Commerce Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,528
Buildings and Improvements	9,220
Net Improvements (Retirements) Since Acquisition	1,086
Carrying Amount at Which Carried [Abstract]
Land	2,528
Buildings and Improvements	10,306
Total	12,834
Accumulated Depreciation at December 31, 2013	3,911
Depreciable Life (Years)	40 years
100 Commerce Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,160
Buildings and Improvements	4,633
Net Improvements (Retirements) Since Acquisition	859
Carrying Amount at Which Carried [Abstract]
Land	1,160
Buildings and Improvements	5,492
Total	6,652
Accumulated Depreciation at December 31, 2013	2,595
Depreciable Life (Years)	40 years
200 Commerce Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	911
Buildings and Improvements	4,414
Net Improvements (Retirements) Since Acquisition	1,018
Carrying Amount at Which Carried [Abstract]
Land	911
Buildings and Improvements	5,432
Total	6,343
Accumulated Depreciation at December 31, 2013	2,180
Depreciable Life (Years)	40 years
Main Street-Plaza 1000 [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,732
Buildings and Improvements	10,942
Net Improvements (Retirements) Since Acquisition	2,933
Carrying Amount at Which Carried [Abstract]
Land	2,732
Buildings and Improvements	13,875
Total	16,607
Accumulated Depreciation at December 31, 2013	13,211
Depreciable Life (Years)	40 years
Main Street-Piazza [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	696
Buildings and Improvements	2,802
Net Improvements (Retirements) Since Acquisition	3,034
Carrying Amount at Which Carried [Abstract]
Land	696
Buildings and Improvements	5,836
Total	6,532
Accumulated Depreciation at December 31, 2013	1,714
Depreciable Life (Years)	40 years
Main Street-Promenade [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	531
Buildings and Improvements	2,052
Net Improvements (Retirements) Since Acquisition	444
Carrying Amount at Which Carried [Abstract]
Land	531
Buildings and Improvements	2,496
Total	3,027
Accumulated Depreciation at December 31, 2013	1,218
Depreciable Life (Years)	40 years
920 North King Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,141
Buildings and Improvements	21,140
Net Improvements (Retirements) Since Acquisition	2,669
Carrying Amount at Which Carried [Abstract]
Land	6,141
Buildings and Improvements	23,809
Total	29,950
Accumulated Depreciation at December 31, 2013	7,669
Depreciable Life (Years)	30 years
300 Delaware Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,368
Buildings and Improvements	13,739
Net Improvements (Retirements) Since Acquisition	2,548
Carrying Amount at Which Carried [Abstract]
Land	6,368
Buildings and Improvements	16,287
Total	22,655
Accumulated Depreciation at December 31, 2013	6,642
Depreciable Life (Years)	23 years
Two Righter Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,802
Buildings and Improvements	11,217
Net Improvements (Retirements) Since Acquisition	6,172
Carrying Amount at Which Carried [Abstract]
Land	2,802
Buildings and Improvements	17,389
Total	20,191
Accumulated Depreciation at December 31, 2013	4,822
Depreciable Life (Years)	40 years
One Righter Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,545
Buildings and Improvements	10,195
Net Improvements (Retirements) Since Acquisition	5,864
Carrying Amount at Which Carried [Abstract]
Land	2,545
Buildings and Improvements	16,059
Total	18,604
Accumulated Depreciation at December 31, 2013	8,839
Depreciable Life (Years)	40 years
4364 South Alston Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,622
Buildings and Improvements	6,419
Net Improvements (Retirements) Since Acquisition	1,357
Carrying Amount at Which Carried [Abstract]
Land	1,581
Buildings and Improvements	7,817
Total	9,398
Accumulated Depreciation at December 31, 2013	3,174
Depreciable Life (Years)	40 years
4805 Lake Brooke Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,640
Buildings and Improvements	6,567
Net Improvements (Retirements) Since Acquisition	1,537
Carrying Amount at Which Carried [Abstract]
Land	1,640
Buildings and Improvements	8,104
Total	9,744
Accumulated Depreciation at December 31, 2013	3,243
Depreciable Life (Years)	40 years
Overlook I [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	748
Buildings and Improvements	3,976
Net Improvements (Retirements) Since Acquisition	599
Carrying Amount at Which Carried [Abstract]
Land	790
Buildings and Improvements	4,533
Total	5,323
Accumulated Depreciation at December 31, 2013	677
Depreciable Life (Years)	40 years
Overlook II [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	748
Buildings and Improvements	4,492
Net Improvements (Retirements) Since Acquisition	364
Carrying Amount at Which Carried [Abstract]
Land	790
Buildings and Improvements	4,814
Total	5,604
Accumulated Depreciation at December 31, 2013	671
Depreciable Life (Years)	40 years
2812 Emerywood Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,069
Buildings and Improvements	4,281
Net Improvements (Retirements) Since Acquisition	515
Carrying Amount at Which Carried [Abstract]
Land	1,069
Buildings and Improvements	4,796
Total	5,865
Accumulated Depreciation at December 31, 2013	2,182
Depreciable Life (Years)	40 years
300 Arboretum Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	5,450
Buildings and Improvements	21,892
Net Improvements (Retirements) Since Acquisition	6,917
Carrying Amount at Which Carried [Abstract]
Land	5,450
Buildings and Improvements	28,809
Total	34,259
Accumulated Depreciation at December 31, 2013	10,862
Depreciable Life (Years)	40 years
7501 Boulders View Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,669
Buildings and Improvements	19,699
Net Improvements (Retirements) Since Acquisition	2,071
Carrying Amount at Which Carried [Abstract]
Land	4,925
Buildings and Improvements	21,514
Total	26,439
Accumulated Depreciation at December 31, 2013	4,786
Depreciable Life (Years)	40 years
7300 Beaufont Springs Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,672
Buildings and Improvements	19,689
Net Improvements (Retirements) Since Acquisition	2,857
Carrying Amount at Which Carried [Abstract]
Land	4,922
Buildings and Improvements	22,296
Total	27,218
Accumulated Depreciation at December 31, 2013	4,223
Depreciable Life (Years)	40 years
6800 Paragon Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,552
Buildings and Improvements	18,414
Net Improvements (Retirements) Since Acquisition	2,163
Carrying Amount at Which Carried [Abstract]
Land	4,552
Buildings and Improvements	20,577
Total	25,129
Accumulated Depreciation at December 31, 2013	4,651
Depreciable Life (Years)	40 years
6802 Paragon Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,917
Buildings and Improvements	11,454
Net Improvements (Retirements) Since Acquisition	3,143
Carrying Amount at Which Carried [Abstract]
Land	2,917
Buildings and Improvements	14,597
Total	17,514
Accumulated Depreciation at December 31, 2013	5,312
Depreciable Life (Years)	40 years
1025 Boulders Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,574
Buildings and Improvements	11,297
Net Improvements (Retirements) Since Acquisition	1,704
Carrying Amount at Which Carried [Abstract]
Land	2,824
Buildings and Improvements	12,751
Total	15,575
Accumulated Depreciation at December 31, 2013	2,545
Depreciable Life (Years)	40 years
2100-2116 West Laburnam Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,482
Buildings and Improvements	8,846
Net Improvements (Retirements) Since Acquisition	2,770
Carrying Amount at Which Carried [Abstract]
Land	2,482
Buildings and Improvements	11,616
Total	14,098
Accumulated Depreciation at December 31, 2013	5,162
Depreciable Life (Years)	40 years
7401 Beaufont Springs Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,349
Buildings and Improvements	10,396
Net Improvements (Retirements) Since Acquisition	1,011
Carrying Amount at Which Carried [Abstract]
Land	2,599
Buildings and Improvements	11,157
Total	13,756
Accumulated Depreciation at December 31, 2013	2,289
Depreciable Life (Years)	40 years
7325 Beaufont Springs Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,344
Buildings and Improvements	10,377
Net Improvements (Retirements) Since Acquisition	630
Carrying Amount at Which Carried [Abstract]
Land	2,594
Buildings and Improvements	10,757
Total	13,351
Accumulated Depreciation at December 31, 2013	2,049
Depreciable Life (Years)	40 years
9011 Arboretum Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,857
Buildings and Improvements	7,702
Net Improvements (Retirements) Since Acquisition	940
Carrying Amount at Which Carried [Abstract]
Land	1,857
Buildings and Improvements	8,642
Total	10,499
Accumulated Depreciation at December 31, 2013	3,854
Depreciable Life (Years)	40 years
6806 Paragon Place [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	10,288
Net Improvements (Retirements) Since Acquisition	-37
Carrying Amount at Which Carried [Abstract]
Land	402
Buildings and Improvements	9,849
Total	10,251
Accumulated Depreciation at December 31, 2013	2,660
Depreciable Life (Years)	40 years
9100 Arboretum Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,362
Buildings and Improvements	5,489
Net Improvements (Retirements) Since Acquisition	979
Carrying Amount at Which Carried [Abstract]
Land	1,362
Buildings and Improvements	6,468
Total	7,830
Accumulated Depreciation at December 31, 2013	2,807
Depreciable Life (Years)	40 years
2511 Brittons Hill Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,202
Buildings and Improvements	4,820
Net Improvements (Retirements) Since Acquisition	1,221
Carrying Amount at Which Carried [Abstract]
Land	1,202
Buildings and Improvements	6,041
Total	7,243
Accumulated Depreciation at December 31, 2013	2,846
Depreciable Life (Years)	40 years
100 Gateway Centre Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	391
Buildings and Improvements	5,410
Net Improvements (Retirements) Since Acquisition	617
Carrying Amount at Which Carried [Abstract]
Land	391
Buildings and Improvements	6,027
Total	6,418
Accumulated Depreciation at December 31, 2013	1,922
Depreciable Life (Years)	40 years
9200 Arboretum Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	985
Buildings and Improvements	3,973
Net Improvements (Retirements) Since Acquisition	1,252
Carrying Amount at Which Carried [Abstract]
Land	985
Buildings and Improvements	5,225
Total	6,210
Accumulated Depreciation at December 31, 2013	2,348
Depreciable Life (Years)	40 years
9210 Arboretum Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,110
Buildings and Improvements	4,474
Net Improvements (Retirements) Since Acquisition	517
Carrying Amount at Which Carried [Abstract]
Land	1,110
Buildings and Improvements	4,991
Total	6,101
Accumulated Depreciation at December 31, 2013	2,239
Depreciable Life (Years)	40 years
2201-2245 Tomlynn Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,020
Buildings and Improvements	4,067
Net Improvements (Retirements) Since Acquisition	1,046
Carrying Amount at Which Carried [Abstract]
Land	1,020
Buildings and Improvements	5,113
Total	6,133
Accumulated Depreciation at December 31, 2013	2,154
Depreciable Life (Years)	40 years
9211 Arboretum Parkway [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	582
Buildings and Improvements	2,433
Net Improvements (Retirements) Since Acquisition	844
Carrying Amount at Which Carried [Abstract]
Land	582
Buildings and Improvements	3,277
Total	3,859
Accumulated Depreciation at December 31, 2013	1,317
Depreciable Life (Years)	40 years
2221-2245 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	530
Buildings and Improvements	2,123
Net Improvements (Retirements) Since Acquisition	359
Carrying Amount at Which Carried [Abstract]
Land	530
Buildings and Improvements	2,482
Total	3,012
Accumulated Depreciation at December 31, 2013	990
Depreciable Life (Years)	40 years
2212-2224 Tomlynn Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	502
Buildings and Improvements	2,014
Net Improvements (Retirements) Since Acquisition	395
Carrying Amount at Which Carried [Abstract]
Land	502
Buildings and Improvements	2,409
Total	2,911
Accumulated Depreciation at December 31, 2013	1,020
Depreciable Life (Years)	40 years
2244 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	550
Buildings and Improvements	2,203
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	550
Buildings and Improvements	2,203
Total	2,753
Accumulated Depreciation at December 31, 2013	964
Depreciable Life (Years)	40 years
2277 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	507
Buildings and Improvements	2,034
Net Improvements (Retirements) Since Acquisition	294
Carrying Amount at Which Carried [Abstract]
Land	507
Buildings and Improvements	2,328
Total	2,835
Accumulated Depreciation at December 31, 2013	977
Depreciable Life (Years)	40 years
2248 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	512
Buildings and Improvements	2,049
Net Improvements (Retirements) Since Acquisition	57
Carrying Amount at Which Carried [Abstract]
Land	512
Buildings and Improvements	2,106
Total	2,618
Accumulated Depreciation at December 31, 2013	923
Depreciable Life (Years)	40 years
2161-2179 Tomlynn Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	423
Buildings and Improvements	1,695
Net Improvements (Retirements) Since Acquisition	315
Carrying Amount at Which Carried [Abstract]
Land	423
Buildings and Improvements	2,010
Total	2,433
Accumulated Depreciation at December 31, 2013	842
Depreciable Life (Years)	40 years
2246 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	455
Buildings and Improvements	1,822
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	455
Buildings and Improvements	1,822
Total	2,277
Accumulated Depreciation at December 31, 2013	797
Depreciable Life (Years)	40 years
2251 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	387
Buildings and Improvements	1,552
Net Improvements (Retirements) Since Acquisition	95
Carrying Amount at Which Carried [Abstract]
Land	387
Buildings and Improvements	1,647
Total	2,034
Accumulated Depreciation at December 31, 2013	738
Depreciable Life (Years)	40 years
2256 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	356
Buildings and Improvements	1,427
Net Improvements (Retirements) Since Acquisition	182
Carrying Amount at Which Carried [Abstract]
Land	356
Buildings and Improvements	1,609
Total	1,965
Accumulated Depreciation at December 31, 2013	751
Depreciable Life (Years)	40 years
2130-2146 Tomlynn Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	353
Buildings and Improvements	1,416
Net Improvements (Retirements) Since Acquisition	214
Carrying Amount at Which Carried [Abstract]
Land	353
Buildings and Improvements	1,630
Total	1,983
Accumulated Depreciation at December 31, 2013	704
Depreciable Life (Years)	40 years
2120 Tomlynn Street [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	281
Buildings and Improvements	1,125
Net Improvements (Retirements) Since Acquisition	300
Carrying Amount at Which Carried [Abstract]
Land	281
Buildings and Improvements	1,425
Total	1,706
Accumulated Depreciation at December 31, 2013	625
Depreciable Life (Years)	40 years
2240 Dabney Road [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	264
Buildings and Improvements	1,059
Net Improvements (Retirements) Since Acquisition	88
Carrying Amount at Which Carried [Abstract]
Land	264
Buildings and Improvements	1,147
Total	1,411
Accumulated Depreciation at December 31, 2013	478
Depreciable Life (Years)	40 years
Boulders Land [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	1,256
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	28
Carrying Amount at Which Carried [Abstract]
Land	1,259
Buildings and Improvements	25
Total	1,284
Accumulated Depreciation at December 31, 2013	2
5900 & 5950 La Place Court [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,706
Buildings and Improvements	11,185
Net Improvements (Retirements) Since Acquisition	3,613
Carrying Amount at Which Carried [Abstract]
Land	3,955
Buildings and Improvements	14,549
Total	18,504
Accumulated Depreciation at December 31, 2013	3,645
Depreciable Life (Years)	48 years
5963 La Place Court [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	2,824
Buildings and Improvements	9,413
Net Improvements (Retirements) Since Acquisition	2,117
Carrying Amount at Which Carried [Abstract]
Land	2,999
Buildings and Improvements	11,355
Total	14,354
Accumulated Depreciation at December 31, 2013	2,486
Depreciable Life (Years)	55 years
2035 Corte Del Nogal [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	3,261
Buildings and Improvements	6,077
Net Improvements (Retirements) Since Acquisition	1,167
Carrying Amount at Which Carried [Abstract]
Land	3,499
Buildings and Improvements	7,006
Total	10,505
Accumulated Depreciation at December 31, 2013	2,038
Depreciable Life (Years)	39 years
1200 Concord Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,395
Buildings and Improvements	24,664
Net Improvements (Retirements) Since Acquisition	808
Carrying Amount at Which Carried [Abstract]
Land	6,515
Buildings and Improvements	25,352
Total	31,867
Accumulated Depreciation at December 31, 2013	7,949
Depreciable Life (Years)	34 years
1220 Concord Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	6,476
Buildings and Improvements	24,966
Net Improvements (Retirements) Since Acquisition	260
Carrying Amount at Which Carried [Abstract]
Land	6,476
Buildings and Improvements	25,226
Total	31,702
Accumulated Depreciation at December 31, 2013	7,622
Depreciable Life (Years)	34 years
155 Grand Avenue [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	13,556
Buildings and Improvements	54,267
Net Improvements (Retirements) Since Acquisition	6,316
Carrying Amount at Which Carried [Abstract]
Land	13,556
Buildings and Improvements	60,583
Total	74,139
Accumulated Depreciation at December 31, 2013	12,652
Depreciable Life (Years)	40 years
Two Kaiser Plaza [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	7,841
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	7,841
Buildings and Improvements	0
Total	7,841
Accumulated Depreciation at December 31, 2013	0
Oakland Lot B [Member]
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances at December 31, 2012	0
Initial Cost [Abstract]
Land	4,342
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	4,342
Buildings and Improvements	0
Total	4,342
Accumulated Depreciation at December 31, 2013	$0

Schedule_III_Real_Estate_and_A2

Schedule III - Real Estate and Accumulated Depreciation (Reconciliation of Real Estate and Accumulated Depreciation) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year	$4,669,289		$4,726,169		$4,793,080
Additions:
Acquisitions	0		347,510		50,579
Capital Expenditures	132,149		109,740		90,619
Less:
Dispositions	-126,471		-474,275		-168,408
SEC Schedule III, Real Estate, Other Deductions	-43,839		-39,855		-39,701
Balance at the End of the Year	4,631,128		4,669,289		4,726,169
Real Estate Held-for-sale	27,436	[1]	0	[1]	0
Operating properties	4,603,692		4,669,289		4,726,169
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	983,808		954,665		865,710
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense — continuing operations	160,641		150,236		154,095
Depreciation expense — discontinued operations	0		9,164		2,143
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions	-22,459		-91,890		-28,270
SEC Schedule III, Real Estate Accumulated Depreciation, Other Deductions	-42,994		-38,367		-39,013
Balance at the end of the year	1,078,996		983,808		954,665
SchIIIRealEstateAccumulatedDepreciationAssetsHeldForSale	-11,167		0		0
Real Estate Investment Property, Accumulated Depreciation	1,067,829		983,808
Accumulated Depreciation, including HFS [Member]
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Real Estate Investment Property, Accumulated Depreciation	$1,067,829		$983,808		$954,665
[1]	(a)Real estate investments related to assets held for sale above represents gross real estate assets and does not include accumulated depreciation or other assets on the balance sheets of the properties held for sale.

Schedule_III_Real_Estate_and_A3

Schedule III - Real Estate and Accumulated Depreciation (Aggregate Costs for Federal Income Tax Purposes and Ownership Percentage) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Billions, unless otherwise specified
Real Estate and Accumulated Depreciation [Line Items]
Tax Basis of Assets, Cost for Income Tax Purposes	$3.70	$4
3141 Fairview Park Drive [Member]
Real Estate and Accumulated Depreciation [Line Items]
Equity Method Investment, Ownership Percentage	50.00%