Brandywine Operating Partnership 10-Q 31 Oct 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	9 Months Ended
	Sep. 30, 2014	Oct. 29, 2014
Document Information [Line Items]	'	'
Entity Registrant Name	'BRANDYWINE REALTY TRUST	'
Entity Central Index Key	'0000790816	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	178,982,369
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Document Information [Line Items]	'	'
Entity Registrant Name	'BRANDYWINE OPERATING PARTNERSHIP, L.P.	'
Entity Central Index Key	'0001060386	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Non-accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Amendment Flag	'false	'
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Real estate investments:	'	'
Operating properties	$4,608,895	$4,669,289
Accumulated depreciation	-1,053,571	-983,808
Operating real estate investments, net	3,555,324	3,685,481
Construction-in-progress	140,456	74,174
Land inventory	90,842	93,351
Total real estate investments, net	3,786,622	3,853,006
Cash and cash equivalents	671,943	263,207
Accounts receivable, net	19,825	17,389
Accrued rent receivable, net	131,211	126,295
Assets held for sale	37,647	0
Investment in real estate ventures, at equity	197,539	180,512
Deferred costs, net	122,881	122,954
Intangible assets, net	105,300	132,329
Other assets	75,383	69,403
Total assets	5,148,351	4,765,095
LIABILITIES AND BENEFICIARIES’ EQUITY	'	'
Mortgage notes payable	658,601	670,151
Unsecured term loans	200,000	450,000
Unsecured senior notes, net of discounts	1,854,779	1,475,230
Accounts payable and accrued expenses	97,022	83,693
Distributions payable	28,857	25,584
Deferred income, gains and rent	53,219	71,635
Acquired lease intangibles, net	27,388	34,444
Other liabilities	36,824	32,923
Liabilities related to assets held for sale	1,771	0
Total liabilities	2,958,461	2,843,660
Commitments and contingencies (Note 16)	'	'
Equity:	'	'
6.90% Series E Preferred Shares/Units, $0.01 par value; 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; shares authorized 400,000,000; 178,982,369 and 156,731,993 issued and outstanding in 2014 and 2013, respectively	1,790	1,566
Additional paid-in capital	3,310,313	2,971,596
Deferred compensation payable in common shares	6,219	5,407
Common shares in grantor trust, 384,536 in 2014 and 312,280 in 2013	-6,219	-5,407
Cumulative earnings	531,294	522,528
Accumulated other comprehensive loss	-2,658	-2,995
Cumulative distributions	-1,671,888	-1,592,515
Total equity, excluding non-controlling interest	2,168,891	1,900,220
Non-controlling interests	20,999	21,215
Total beneficiaries' equity	2,189,890	1,921,435
Total liabilities and beneficiaries' equity	5,148,351	4,765,095
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Real estate investments:	'	'
Operating properties	4,608,895	4,669,289
Accumulated depreciation	-1,053,571	-983,808
Operating real estate investments, net	3,555,324	3,685,481
Construction-in-progress	140,456	74,174
Land inventory	90,842	93,351
Total real estate investments, net	3,786,622	3,853,006
Cash and cash equivalents	671,943	263,207
Accounts receivable, net	19,825	17,389
Accrued rent receivable, net	131,211	126,295
Assets held for sale	37,647	0
Investment in real estate ventures, at equity	197,539	180,512
Deferred costs, net	122,881	122,954
Intangible assets, net	105,300	132,329
Other assets	75,383	69,403
Total assets	5,148,351	4,765,095
LIABILITIES AND BENEFICIARIES’ EQUITY	'	'
Mortgage notes payable	658,601	670,151
Unsecured term loans	200,000	450,000
Unsecured senior notes, net of discounts	1,854,779	1,475,230
Accounts payable and accrued expenses	97,022	83,693
Distributions payable	28,857	25,584
Deferred income, gains and rent	53,219	71,635
Acquired lease intangibles, net	27,388	34,444
Other liabilities	36,824	32,923
Liabilities related to assets held for sale	1,771	0
Total liabilities	2,958,461	2,843,660
Commitments and contingencies (Note 16)	'	'
Redeemable limited partnership units at redemption value;	'	'
Redeemable limited partnership units at redemption value; 1,721,905 and 1,763,739 issued and outstanding in 2014 and 2013, respectively	25,985	26,486
Equity:	'	'
6.90% Series E Preferred Shares/Units, $0.01 par value; issued and outstanding- 4,000,000 in 2014 and 2013	96,850	96,850
General Partnership Capital, 178,982,369 and 156,731,993 units issued and outstanding in 2014 and 2013, respectively	2,069,031	1,800,530
Accumulated other comprehensive loss	-3,042	-3,377
Total equity, excluding non-controlling interest	2,162,839	1,894,003
Non-controlling interests	1,066	946
Total beneficiaries' equity	2,163,905	1,894,949
Total liabilities and beneficiaries' equity	$5,148,351	$4,765,095

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Preferred Stock, Shares Authorized	20,000,000	20,000,000
Preferred Stock, Dividend Rate, Percentage	6.90%	6.90%
Preferred Stock, Shares Issued	4,000,000	4,000,000
Preferred Stock, Shares Outstanding	4,000,000	4,000,000
Preferred Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	400,000,000	200,000,000
Common Stock, Shares, Issued	178,982,369	156,731,993
Common Stock, Shares, Outstanding	178,982,369	156,731,993
Common shares in grantor trust	384,536	312,280
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Preferred Stock, Dividend Rate, Percentage	6.90%	6.90%
Preferred Stock, Shares Issued	4,000,000	4,000,000
Preferred Stock, Shares Outstanding	4,000,000	4,000,000
Redeemable Limited Partnership Units Issued	1,721,905	1,763,739
Redeemable Limited Partnership Units Outstanding	1,721,905	1,763,739
General Partners' Capital Account, Units Issued	178,982,369	156,731,993
General Partners' Capital Account, Units Outstanding	178,982,369	156,731,993

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenue:	'	'	'	'
Rents	$120,288	$116,382	$363,581	$347,054
Tenant reimbursements	20,095	20,694	64,057	60,595
Termination fees	1,418	2,040	6,970	2,946
Third party management fees, labor reimbursement and leasing	3,932	3,263	12,269	9,652
Other	825	975	2,295	3,305
Total revenue	146,558	143,354	449,172	423,552
Expenses:	'	'	'	'
Property operating expenses	42,675	40,639	132,612	119,421
Real estate taxes	12,869	14,167	39,167	42,639
Third party management expenses	1,687	1,317	5,133	4,105
Depreciation and amortization	52,616	50,583	157,773	149,300
General and administrative expenses	5,900	6,436	20,086	20,323
Total operating expenses	115,747	113,142	354,771	335,788
Operating Income	30,811	30,212	94,401	87,764
Other income (expense):	'	'	'	'
Interest income	528	268	1,298	448
Historic tax credit transaction income	11,853	11,853	11,853	11,853
Interest expense	-31,481	-30,338	-94,837	-91,689
Amortization of deferred financing costs	-1,566	-1,158	-3,952	-3,502
Interest expense — financing obligation	-273	-264	-861	-693
Recognized hedge activity	-828	0	-828	0
Equity in income (loss) of real estate ventures	-486	714	-733	3,757
Net gain on disposition of real estate	4,698	0	4,698	0
Net gain (loss) on sale of undepreciated real estate	0	-129	1,184	-129
Net gain from remeasurement of investment in RE ventures	0	0	458	7,847
Net gain (loss) on real estate venture transactions	0	0	-417	3,683
Loss on early extinguishment of debt	-2,606	-11	-2,606	-1,127
Provision for impairment on assets held for sale	-1,765	0	-1,765	0
Income from continuing operations	8,885	11,147	7,893	18,212
Discontinued operations:	'	'	'	'
Income (loss) from discontinued operations	0	-43	18	946
Net gain (loss) on disposition of discontinued operations	-3	-16	900	3,029
Total discontinued operations	-3	-59	918	3,975
Net income	8,882	11,088	8,811	22,187
Net (income) loss from discontinued operations attributable to non-controlling interests — LP units	0	1	-10	-52
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-24	0	-12	0
Net income attributable to non-controlling interests — LP units	-84	-106	-35	-143
Net income attributable to non-controlling interests	-108	-105	-57	-195
Net income attributable to Brandywine Realty Trust	8,774	10,983	8,754	21,992
Distribution to Preferred Shares	-1,725	-1,725	-5,175	-5,175
Nonforfeitable dividends allocated to unvested restricted shareholders	-82	-85	-268	-278
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	6,967	9,173	3,311	16,539
Basic income per Common Share:	'	'	'	'
Continuing operations	$0.04	$0.06	$0.01	$0.08
Discontinued operations	$0	$0	$0.01	$0.03
Net income (loss) attributable to common shareholders/unitholders, Basic	$0.04	$0.06	$0.02	$0.11
Diluted income per Common Share:	'	'	'	'
Continuing operations	$0.04	$0.06	$0.01	$0.08
Discontinued operations	$0	$0	$0.01	$0.03
Net income attributable to common shareholders/unitholders, Diluted	$0.04	$0.06	$0.02	$0.11
Weighted Average Number of Shares Outstanding, Basic	171,606,722	156,703,348	161,866,955	151,933,441
Weighted Average Number of Shares Outstanding, Diluted	173,193,870	157,992,082	163,353,970	153,142,825
Net income attributable to Brandywine Realty Trust	'	'	'	'
Total continuing operations	8,777	11,041	7,846	18,069
Total discontinued operations	-3	-58	908	3,923
Net income	8,882	11,088	8,811	22,187
Net income (Loss) attributable to Brandywine Realty Trust	8,774	10,983	8,754	21,992
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'	'	'
Revenue:	'	'	'	'
Rents	120,288	116,382	363,581	347,054
Tenant reimbursements	20,095	20,694	64,057	60,595
Termination fees	1,418	2,040	6,970	2,946
Third party management fees, labor reimbursement and leasing	3,932	3,263	12,269	9,652
Other	825	975	2,295	3,305
Total revenue	146,558	143,354	449,172	423,552
Expenses:	'	'	'	'
Property operating expenses	42,675	40,639	132,612	119,421
Real estate taxes	12,869	14,167	39,167	42,639
Third party management expenses	1,687	1,317	5,133	4,105
Depreciation and amortization	52,616	50,583	157,773	149,300
General and administrative expenses	5,900	6,436	20,086	20,323
Total operating expenses	115,747	113,142	354,771	335,788
Operating Income	30,811	30,212	94,401	87,764
Other income (expense):	'	'	'	'
Interest income	528	268	1,298	448
Historic tax credit transaction income	11,853	11,853	11,853	11,853
Interest expense	-31,481	-30,338	-94,837	-91,689
Amortization of deferred financing costs	-1,566	-1,158	-3,952	-3,502
Interest expense — financing obligation	-273	-264	-861	-693
Recognized hedge activity	-828	0	-828	0
Equity in income (loss) of real estate ventures	-486	714	-733	3,757
Net gain on disposition of real estate	4,698	0	4,698	0
Net gain (loss) on sale of undepreciated real estate	0	-129	1,184	-129
Net gain from remeasurement of investment in RE ventures	0	0	458	7,847
Net gain (loss) on real estate venture transactions	0	0	-417	3,683
Loss on early extinguishment of debt	-2,606	-11	-2,606	-1,127
Provision for impairment on assets held for sale	-1,765	0	-1,765	0
Income from continuing operations	8,885	11,147	7,893	18,212
Discontinued operations:	'	'	'	'
Income (loss) from discontinued operations	0	-43	18	946
Net gain (loss) on disposition of discontinued operations	-3	-16	900	3,029
Total discontinued operations	-3	-59	918	3,975
Net income	8,882	11,088	8,811	22,187
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-24	0	-12	0
Net income attributable to Brandywine Realty Trust	8,858	11,088	8,799	22,187
Distribution to Preferred Shares	-1,725	-1,725	-5,175	-5,175
Nonforfeitable dividends allocated to unvested restricted shareholders	-82	-85	-268	-278
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	7,051	9,278	3,356	16,734
Basic income per Common Share:	'	'	'	'
Continuing operations	$0.04	$0.06	$0.01	$0.08
Discontinued operations	$0	$0	$0.01	$0.03
Net income (loss) attributable to common shareholders/unitholders, Basic	$0.04	$0.06	$0.02	$0.11
Diluted income per Common Share:	'	'	'	'
Continuing operations	$0.04	$0.06	$0.01	$0.08
Discontinued operations	$0	$0	$0.01	$0.03
Net income attributable to common shareholders/unitholders, Diluted	$0.04	$0.06	$0.02	$0.11
Weighted Average Number of Shares Outstanding, Basic	173,341,782	158,467,087	163,620,963	153,731,070
Weighted Average Number of Shares Outstanding, Diluted	174,928,930	159,755,821	165,107,978	154,940,454
Net income attributable to Brandywine Realty Trust	'	'	'	'
Total continuing operations	8,861	11,147	7,881	18,212
Total discontinued operations	-3	-59	918	3,975
Net income	8,882	11,088	8,811	22,187
Net income (Loss) attributable to Brandywine Realty Trust	$8,858	$11,088	$8,799	$22,187

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income Statement (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net income	$8,882	$11,088	$8,811	$22,187
Comprehensive Income (Loss)	'	'	'	'
Unrealized gain (loss) on derivative financial instruments	4,232	-1,302	967	9,978
Recognized hedge activity	-828	0	-828	0
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	76	64	196	232
Other comprehensive income (loss)	'	'	335	10,210
Comprehensive Income	12,362	9,850	9,146	32,397
Comprehensive income attributable to non-controlling interest	-141	-91	-55	-312
Comprehensive income attributable to Brandywine Realty Trust	12,221	9,759	9,091	32,085
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'	'	'
Net income	8,882	11,088	8,811	22,187
Comprehensive Income (Loss)	'	'	'	'
Unrealized gain (loss) on derivative financial instruments	4,232	-1,302	967	9,978
Recognized hedge activity	-828	0	-828	0
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	76	64	196	232
Other comprehensive income (loss)	3,480	-1,238	335	10,210
Comprehensive Income	$12,362	$9,850	$9,146	$32,397

Consolidated_Statements_of_Ben

Consolidated Statements of Beneficiaries' Equity (USD $)	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Deferred Compensation, Share-based Payments [Member]	Common Stock In Grantor Trust [Member]	Cumulative Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Distributions [Member]	Noncontrolling Interest [Member]
In Thousands, except Share data
Beginning Balance at Dec. 31, 2012	$1,773,516	$40	$1,434	$2,780,194	$5,352	($5,352)	$479,734	($15,918)	($1,493,206)	$21,238
Beginning Balance, Shares at Dec. 31, 2012	'	4,000,000	143,538,733	'	290,745	'	'	'	'	'
Net income	22,187	'	'	'	'	'	21,992	'	'	195
Comprehensive Income (Loss)	10,210	'	'	'	'	'	'	10,093	'	117
Stock Issued During Period, Shares, New Issues	'	'	12,650,000	'	'	'	'	'	'	'
Stock Issued During Period, Value, New Issues	182,034	'	127	181,907	'	'	'	'	'	'
Equity Issuance Costs	-382	'	'	-382	'	'	'	'	'	'
Conversion of LP Units to Common Shares	'	'	81,998	'	'	'	'	'	'	'
Bonus Share Issuance, Shares	'	'	27,918	'	'	'	'	'	'	'
Stock Issued During Period, Value, Conversion of Units	0	'	1	1,240	'	'	'	'	'	-1,241
Bonus Share Issuance, Value	361	'	'	361	'	'	'	'	'	'
Share Based Compensation Activity, Shares	'	'	409,979	'	34,117	'	'	'	'	'
Share Based Compensation Activity, Value	8,034	'	3	8,022	'	'	9	'	'	'
Share Issuance from/to Deferred Compensation Plan, Shares	'	'	-4,838	'	-11,839	'	'	'	'	'
Share issuance from/to Deferred Compensation Plan, Value	0	'	'	'	79	-79	'	'	'	'
Adjustments to Non-controlling Interest	0	'	'	-766	'	'	'	'	'	766
Preferred Share distributions	-5,175	'	'	'	'	'	'	'	-5,175	'
Distributions declared ($0.45 per share)	-69,627	'	'	'	'	'	'	'	-68,821	-806
Ending Balance at Sep. 30, 2013	1,921,158	40	1,565	2,970,576	5,431	-5,431	501,735	-5,825	-1,567,202	20,269
Ending Balance, Shares at Sep. 30, 2013	'	4,000,000	156,703,790	'	313,023	'	'	'	'	'
Beginning Balance at Dec. 31, 2013	1,921,435	40	1,566	2,971,596	5,407	-5,407	522,528	-2,995	-1,592,515	21,215
Beginning Balance, Shares at Dec. 31, 2013	'	4,000,000	156,731,993	'	312,280	'	'	'	'	'
Net income	8,811	'	'	'	'	'	8,754	'	'	57
Comprehensive Income (Loss)	335	'	'	'	'	'	'	337	'	-2
Common Stock, Shares, Issued	178,982,369	'	'	'	'	'	'	'	'	'
Stock Issued During Period, Shares, New Issues	21,850,000	'	21,850,000	'	'	'	'	'	'	'
Stock Issued During Period, Value, New Issues	335,398	'	219	335,179	'	'	'	'	'	'
Equity Issuance Costs	-452	'	'	-452	'	'	'	'	'	'
Conversion of LP Units to Common Shares	'	'	41,734	'	'	'	'	'	'	'
Stock Issued During Period, Value, Conversion of Units	0	'	'	655	'	'	'	'	'	-655
Share Based Compensation Activity, Shares	'	'	279,913	'	'	'	'	'	'	'
Share Based Compensation Activity, Value	4,614	'	5	4,597	'	'	12	'	'	'
Share Issuance from/to Deferred Compensation Plan, Shares	'	'	78,729	'	72,256	'	'	'	'	'
Share issuance from/to Deferred Compensation Plan, Value	-90	'	'	-90	812	-812	'	'	'	'
Adjustments to Non-controlling Interest	0	'	'	-1,172	'	'	'	'	'	1,172
Preferred Share distributions	-5,175	'	'	'	'	'	'	'	-5,175	'
Distributions declared ($0.45 per share)	-74,986	'	'	'	'	'	'	'	-74,198	-788
Ending Balance at Sep. 30, 2014	$2,189,890	$40	$1,790	$3,310,313	$6,219	($6,219)	$531,294	($2,658)	($1,671,888)	$20,999
Ending Balance, Shares at Sep. 30, 2014	'	4,000,000	178,982,369	'	384,536	'	'	'	'	'

Consolidated_Statements_of_Ben1

Consolidated Statements of Beneficiaries' Equity (Parantheticals) (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cumulative Distributions [Member]	'	'
Common Stock, Dividends, Per Share, Declared	$0.45	$0.45
Noncontrolling Interest [Member]	'	'
Common Stock, Dividends, Per Share, Declared	$0.45	$0.45

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Net income	$8,811	$22,187
Adjustments to reconcile net income (loss) to net cash from operating activities:	'	'
Depreciation and amortization	157,773	151,066
Amortization of deferred financing costs	3,952	3,502
Amortization of debt discount/(premium), net	-455	1,112
Amortization of stock compensation costs	3,622	5,510
Shares used for employee taxes upon vesting of share awards	-1,263	-1,062
Recognized hedge activity	828	0
Straight-line rent income	-11,416	-16,337
Amortization of acquired above (below) market leases, net	-5,206	-5,372
Straight-line ground rent expense	66	1,286
Provision for doubtful accounts	1,687	1,777
Net (gain) loss on real estate venture transactions	417	-3,683
Net gain on sale of interests in real estate	-5,882	-3,044
Net gain from remeasurement of investment in a real estate venture	-458	-7,847
Historic tax credit transaction income	-11,853	-11,853
Loss on early extinguishment of debt	2,606	1,127
Provision for impairment on assets held for sale	1,765	0
Real estate venture income in excess of distributions	659	-2,371
Deferred financing obligation	-864	-1,392
Changes in assets and liabilities:	'	'
Accounts receivable	-4,586	-287
Other assets	-10,317	-6,660
Accounts payable and accrued expenses	9,304	14,684
Deferred income, gains and rent	-4,430	1,265
Other liabilities	-1,760	1,718
Net cash from operating activities	133,000	145,326
Cash flows from investing activities:	'	'
Acquisition of properties	-12,405	-20,758
Sales of properties, net	81,625	145,931
Distribution of sales proceeds from real estate venture	0	16,963
Proceeds from repayment of mortgage notes receivable	5,125	200
Capital expenditures for tenant improvements	-85,698	-64,481
Capital expenditures for redevelopments	-10,195	-5,288
Capital expenditures for developments	-48,057	-5,399
Reimbursement from real estate venture for pre-formation development costs	0	1,976
Advances for purchase of tenant assets, net of repayments	-212	-420
Investment in unconsolidated Real Estate Ventures	-16,330	-30,142
Escrowed cash	1,076	902
Cash distributions from unconsolidated Real Estate Ventures in excess of cumulative equity income	7,341	3,661
Leasing costs	-17,018	-25,704
Net cash from (used in) investing activities	-94,748	17,441
Cash flows from financing activities:	'	'
Proceeds from Credit Facility borrowings	0	186,000
Repayments of Credit Facility borrowings	0	-255,000
Repayments of mortgage notes payable	-9,994	-8,351
Repayments of unsecured term loans	-250,828	0
Proceeds from unsecured notes	496,459	0
Deferred financing obligation interest expense	0	697
Net proceeds from issuance of common shares	335,016	181,527
Repayments of unsecured notes	-120,361	-13,027
Debt financing costs	-3,630	-6
Exercise of stock options	709	2,240
Distributions paid to shareholders	-76,081	-72,061
Distributions to noncontrolling interest	-806	-818
Net cash from financing activities	370,484	21,201
Increase in cash and cash equivalents	408,736	183,968
Cash and cash equivalents at beginning of period	263,207	1,549
Cash and cash equivalents at end of period	671,943	185,517
Supplemental disclosure:	'	'
Cash paid for interest, net of capitalized interest during the nine months ended September 30, 2014 and 2013 of $4,466 and $2,012, respectively	92,196	76,528
Supplemental disclosure of non-cash activity:	'	'
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
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 disposition of property	-5,897	0
Change in investments in joint venture related to non-cash acquisition of property	0	13,040
Change in operating real estate related to non-cash adjustment to land	0	-4,386
Change in receivable from settlement of acquisitions	619	0
Change in investments in real estate ventures related to a contribution of land	0	-6,058
Change in capital expenditures financed through accounts payable at period end	4,415	1,210
Change in capital expenditures financed through retention payable at period end	3,479	-736
Change in unfunded tenant allowance	-327	-811
Conversion of LP Units to Common Shares	655	1,241
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Net income	8,811	22,187
Adjustments to reconcile net income (loss) to net cash from operating activities:	'	'
Depreciation and amortization	157,773	151,066
Amortization of deferred financing costs	3,952	3,502
Amortization of debt discount/(premium), net	-455	1,112
Amortization of stock compensation costs	3,622	5,510
Shares used for employee taxes upon vesting of share awards	-1,263	-1,062
Recognized hedge activity	828	0
Straight-line rent income	-11,416	-16,337
Amortization of acquired above (below) market leases, net	-5,206	-5,372
Straight-line ground rent expense	66	1,286
Provision for doubtful accounts	1,687	1,777
Net (gain) loss on real estate venture transactions	417	-3,683
Net gain on sale of interests in real estate	-5,882	-3,044
Net gain from remeasurement of investment in a real estate venture	-458	-7,847
Historic tax credit transaction income	-11,853	-11,853
Loss on early extinguishment of debt	2,606	1,127
Provision for impairment on assets held for sale	1,765	0
Real estate venture income in excess of distributions	659	-2,371
Deferred financing obligation	-864	-1,392
Changes in assets and liabilities:	'	'
Accounts receivable	-4,586	-287
Other assets	-10,317	-6,660
Accounts payable and accrued expenses	9,304	14,684
Deferred income, gains and rent	-4,430	1,265
Other liabilities	-1,760	1,718
Net cash from operating activities	133,000	145,326
Cash flows from investing activities:	'	'
Acquisition of properties	-12,405	-20,758
Sales of properties, net	81,625	145,931
Distribution of sales proceeds from real estate venture	0	16,963
Proceeds from repayment of mortgage notes receivable	5,125	200
Capital expenditures for tenant improvements	-85,698	-64,481
Capital expenditures for redevelopments	-10,195	-5,288
Capital expenditures for developments	-48,057	-5,399
Reimbursement from real estate venture for pre-formation development costs	0	1,976
Advances for purchase of tenant assets, net of repayments	-212	-420
Investment in unconsolidated Real Estate Ventures	-16,330	-30,142
Escrowed cash	1,076	902
Cash distributions from unconsolidated Real Estate Ventures in excess of cumulative equity income	7,341	3,661
Leasing costs	-17,018	-25,704
Net cash from (used in) investing activities	-94,748	17,441
Cash flows from financing activities:	'	'
Proceeds from Credit Facility borrowings	0	186,000
Repayments of Credit Facility borrowings	0	-255,000
Repayments of mortgage notes payable	-9,994	-8,351
Repayments of unsecured term loans	-250,828	0
Proceeds from unsecured notes	496,459	0
Deferred financing obligation interest expense	0	697
Net proceeds from issuance of common shares	335,016	181,527
Repayments of unsecured notes	-120,361	-13,027
Debt financing costs	-3,630	-6
Exercise of stock options	709	2,240
Distributions paid to shareholders	-76,887	-72,879
Net cash from financing activities	370,484	21,201
Increase in cash and cash equivalents	408,736	183,968
Cash and cash equivalents at beginning of period	263,207	1,549
Cash and cash equivalents at end of period	671,943	185,517
Supplemental disclosure:	'	'
Cash paid for interest, net of capitalized interest during the nine months ended September 30, 2014 and 2013 of $4,466 and $2,012, respectively	92,196	76,528
Supplemental disclosure of non-cash activity:	'	'
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
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 disposition of property	-5,897	0
Change in investments in joint venture related to non-cash acquisition of property	0	13,040
Change in operating real estate related to non-cash adjustment to land	0	-4,386
Change in receivable from settlement of acquisitions	619	0
Change in investments in real estate ventures related to a contribution of land	0	-6,058
Change in capital expenditures financed through accounts payable at period end	4,415	1,210
Change in capital expenditures financed through retention payable at period end	3,479	-736
Change in unfunded tenant allowance	-327	-811
Conversion of LP Units to Common Shares	$655	$1,241

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (Parentheticals) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Supplemental Cash Flow Information [Abstract]	'	'
Capitalized interest	$4,466	$2,012
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Supplemental Cash Flow Information [Abstract]	'	'
Capitalized interest	$4,466	$2,012

Organization_of_the_Parent_Com

Organization of the Parent Company and The Operating Partnership	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP [Text Block]	'
	ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP
	The Parent Company is a self-administered and self-managed real estate investment trust (“REIT”) that provides leasing, property management, development, redevelopment, acquisition and other tenant-related services for a portfolio of office, industrial, retail and mixed-use 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 September 30, 2014, owned a 98.9% 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 September 30, 2014, the Company owned 205 properties, consisting of 169 office properties, 20 industrial facilities, five mixed-use properties, one retail property (195 core properties), five properties classified as held for sale, three development properties, one redevelopment property and one re-entitlement property (collectively, the “Properties”) containing an aggregate of approximately 25.4 million net rentable square feet. In addition, as of September 30, 2014, the Company owned economic interests in 17 unconsolidated real estate ventures that own properties containing an aggregate of approximately 6.1 million net rentable square feet (collectively, the “Real Estate Ventures”). As of September 30, 2014, the Company also owned 415 acres of undeveloped land, and held options to purchase approximately 50 additional acres of undeveloped land. As of September 30, 2014, these land parcels could support, under current zoning and entitlements, approximately 5.7 million square feet of development inclusive of options to purchase approximately 50 additional acres of undeveloped land. The Properties and the properties owned by the Real Estate Ventures are located in or near Philadelphia, Pennsylvania; Metropolitan Washington, D.C.; Southern New Jersey; Richmond, Virginia; Wilmington, Delaware; Austin, Texas and Oakland, Concord and Carlsbad, California.
	The Company conducts its third-party real estate management services business primarily through wholly-owned management company subsidiaries. As of September 30, 2014, the management company subsidiaries were managing properties containing an aggregate of approximately 33.7 million net rentable square feet, of which approximately 25.4 million net rentable square feet related to Properties owned by the Company and approximately 8.3 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.
	Unless otherwise indicated, all references in this Form 10-Q to square feet represent net rentable area.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Text Block]	'
	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Basis of Presentation
	The consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments (consisting solely of normal recurring matters) for a fair statement of the financial position of the Company as of September 30, 2014, the results of its operations for the three and nine-month periods ended September 30, 2014 and 2013 and its cash flows for the nine-month periods ended September 30, 2014 and 2013 have been included. The results of operations for such interim periods are not necessarily indicative of the results for a full year. These consolidated financial statements should be read in conjunction with the Parent Company’s and the Operating Partnership’s consolidated financial statements and footnotes included in their combined 2013 Annual Report on Form 10-K filed with the SEC on February 25, 2014.
	Reclassifications
	Certain amounts have been reclassified in prior years to conform to the current year presentation, including the reclassification of notes receivable to other assets within the balance sheets and the reclassification of changes in escrow balances from operating cash flows to investing cash flows in the statements of cash flows. All other 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.
	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	9 Months Ended
	Sep. 30, 2014
Real Estate [Abstract]	'
Real Estate Disclosure [Text Block]	'
	REAL ESTATE INVESTMENTS
	As of September 30, 2014 and December 31, 2013, the gross carrying value of the Company’s Properties was as follows (in thousands):
		September 30,		December 31,
		2014		2013
	Land	$	675,109	$	680,513
	Building and improvements	3,419,903		3,504,060
	Tenant improvements	513,883		484,716
		$	4,608,895	$	4,669,289
	Acquisitions
	During the nine months ended September 30, 2014, the Company recorded a $0.5 million gain on remeasurement of its investment in partnerships with Parkway Properties, Inc. On December 19, 2013, the Company increased its equity ownership interest from 25% to 99% in each of the two partnerships that own One and Two Commerce Square, two 41-story trophy-class office towers in Philadelphia, Pennsylvania. As of December 31, 2013, the Company had recorded a $1.6 million net receivable balance from its former partner. This receivable balance represented the former partner's estimated portion of the net current assets pursuant to the terms of the agreement (the "Redemption Agreement") that provided for the forgoing transaction. In accordance with settlement procedures provided for in the Redemption Agreement, the Company and Parkway finalized the purchase accounting based on facts and circumstances that existed at the date of the acquisition but that were not fully known at such time. During the nine months ended September 30, 2014, $2.1 million of consideration was received from the former partner in full settlement of the aforementioned provision and a measurement period adjustment was made to adjust the fair value of the Company's previously held equity investment, resulting in a gain on remeasurement of the Company's investment in the partnerships of $0.5 million. For additional information related to this transaction, see the audited financial statements included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2013.
	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, which was placed into construction in progress. As such, the Company has treated this transaction as a business combination and allocated the purchase price to the tangible and intangible assets. 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 net assets were purchased using available corporate funds.
	As of September 30, 2014, each of the two office buildings at Encino Trace were in development, and the Company had funded, through such date, $28.7 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. Additional project costs will be funded over the remaining construction period.
	Dispositions
	On September 30, 2014, the Company sold an office building containing 172,943 rentable square feet at 1880 Campus Commons Drive in Reston, Virginia commonly known as Campus Pointe for a sales price of $42.5 million resulting in a gain on sale of $4.7 million after closing and other transaction related costs. The disposal of Campus Pointe does not represent a strategic shift that has a major effect on the Company's operations and financial results. Accordingly, the property remains classified within continuing operations for all periods presented.
	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 7, 2014, the Company received $0.9 million from an escrow account that was established in connection with the sale of eight office properties containing 800,546 square feet in Lawrenceville, New Jersey, known as Princeton Pike Corporate Center. The sale of Princeton Pike Corporate Center was completed on February 25, 2013 for an aggregate sales price of $121.0 million and resulted in a $5.3 million gain on sale after closing and other transaction related costs. The escrow account was funded with $2.0 million at closing and was established for use by the buyer to fund certain tenant improvement projects with any unused portion to be returned to the Company. The unused amount received from the escrow account was recognized as a gain on sale during the period ended September 30, 2014. The aforementioned gain was recognized within discontinued operations which is consistent with the accounting classification of the assets that were disposed of on February 25, 2013.
	On April 3, 2014, the Company contributed two 3-story, Class A office buildings, containing an aggregate of approximately 192,396 net rentable square feet known as Four Points Centre 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) the DRA member 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. The disposal of Four Points Centre does not represent a strategic shift that has a major effect on the Company's operations and financial results. Accordingly, the property remains classified within continuing operations for all periods presented.
	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
	On October 24, 2014, the Company sold its Valleybrooke Office Park, comprised of five properties consisting of 279,934 rentable square feet, located in Malvern, Pennsylvania for a sale price of $37.9 million. As of September 30, 2014, the Company categorized its Valleybooke portfolio as held for sale on its consolidated balance sheet. The carrying value of the property exceeds the fair value less the costs of sale. As a result, the Company recognized an impairment loss totaling approximately $1.8 million during the three months ended September 30, 2014. The disposal of the Valleybrooke Office Park does not represent a strategic shift that has a major effect on the Company's operations and financial results. Accordingly, the impairment loss and operating results of this property remain classified within continuing operations for all periods presented.

Investment_in_Unconsolidated_V

Investment in Unconsolidated Ventures	9 Months Ended
	Sep. 30, 2014
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investments and Joint Ventures Disclosure [Text Block]	'
	INVESTMENT IN UNCONSOLIDATED VENTURES
	As of September 30, 2014, the Company held ownership interests in 17 unconsolidated Real Estate Ventures, of which $197.5 million is included in assets and $1.2 million is included in other liabilities relating to the negative investment balance of one real estate venture. The Company formed or acquired interests in these ventures with unaffiliated third parties to develop or manage office properties or to acquire land in anticipation of possible development of office or residential properties. As of September 30, 2014, 11 of the Real Estate Ventures owned 58 office buildings that contain an aggregate of approximately 6.1 million net rentable square feet; two Real Estate Ventures owned 3.8 acres of undeveloped parcels of land; three Real Estate Venture owned 21.8 acres of land under development; one Real Estate Venture owned a residential tower that contains 345 apartment units and one Real Estate Venture owned 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 a Real Estate Venture in excess of its investment balance unless the Company is liable for the obligations of the Real Estate Venture or is otherwise committed to provide financial support to the Real Estate Venture.
	The following is a summary of the financial position of the Real Estate Ventures as of September 30, 2014 and December 31, 2013 (in thousands):
		September 30,				December 31,
		2014				2013
	Net property	$	1,140,798			$	965,475
	Other assets	166,020				164,152
	Other liabilities	59,690				49,442
	Debt	852,636				699,860
	Equity	394,492				380,325
	Company’s share of equity (Company’s basis) (a)	197,539			(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 September 30, 2014, which is included in other liabilities.
	The Company held interests in 17 Real Estate Ventures containing an aggregate of approximately 6.1 million net rentable square feet as of the three and nine-month periods ended September 30, 2014 and 17 Real Estate Ventures containing an aggregate of approximately 6.2 million net rentable square feet as of the three and nine-month periods ended September 30, 2013. The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests during these periods (in thousands):
		Three-month periods ended September 30,							Nine-month periods ended September 30,
		2014				2013			2014			2013
	Revenue	$	37,446			$	30,684		$	106,905		$	108,500
	Operating expenses	(15,433		)		(13,199		)	(44,257		)	(48,671		)
	Interest expense, net	(9,245		)		(9,223		)	(26,234		)	(28,167		)
	Depreciation and amortization	(13,552		)		(9,893		)	(40,423		)	(33,778		)
	Net loss	(784		)		(1,631		)	(4,009		)	(2,116		)
	Company’s share of income (loss) (Company’s basis)	(486		)		714			(733		)	3,757
	Austin Venture - The Crossings
	On July 31, 2014, the Austin Venture completed the acquisition of the Crossings at Lakeline, comprised of two 3-story buildings containing 232,274 rentable square feet located in Austin, TX for $48.2 million. The transaction was funded with $34.5 million of mortgage loan proceeds and $12.8 million (net of $0.9 million in purchase adjustments) of cash contributions, with $6.4 million from each of DRA and the Company. The fixed rate mortgage loan was financed through a non-affiliated third party. The Austin Venture incurred approximately $0.1 million of transaction costs to acquire the property. The Austin Venture expensed the acquisition costs and allocated the purchase price of the property, net of $0.6 million credit from the seller.
	Based on the facts and circumstances of this acquisition, the consummation of the acquisition did not cause the Austin Venture to become a VIE to the Company. Accordingly, the Company continues to assess the consolidation of the Austin Venture under the voting interest model and its investment continues to be accounted for under the equity method of accounting.
	Austin Venture - Four Points Centre
	On April 3, 2014, the Company contributed two 3-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 for further information on the contribution.
	Guarantees
	As of September 30, 2014, the Company had provided guarantees on behalf of certain real estate ventures, consisting of (i) a $24.7 million payment guarantee 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 the development 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 has provided and expects to continue to provide cost overrun and completion guarantees, with rights of contribution among partners in the real estate venture, as well as customary environmental indemnities and guarantees of customary exceptions to nonrecourse provisions in loan agreements. For additional information regarding these real estate ventures, see "Investments in Unconsolidated Ventures" in notes to the audited financial statements included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2013.

Deferred_Costs

Deferred Costs	9 Months Ended
	Sep. 30, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Deferred Costs [Text Block]	'
	DEFERRED COSTS
	As of September 30, 2014 and December 31, 2013, the Company’s deferred costs were comprised of the following (in thousands):
		September 30, 2014
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	159,744	$	(63,136	)	$	96,608
	Financing Costs	42,265		(15,992		)	26,273
	Total	$	202,009	$	(79,128	)	$	122,881
		December 31, 2013
		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 each of the three and nine-month periods ended September 30, 2014, the Company capitalized internal direct leasing costs of $1.6 million and $5.6 million, respectively, and $1.8 million and $5.8 million during the three and nine-month periods ended September 30, 2013 in accordance with the accounting standard for the capitalization of leasing costs.
Components Of Deferred Costs Net [Table Text Block]	'
	As of September 30, 2014 and December 31, 2013, the Company’s deferred costs were comprised of the following (in thousands):
		September 30, 2014
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	159,744	$	(63,136	)	$	96,608
	Financing Costs	42,265		(15,992		)	26,273
	Total	$	202,009	$	(79,128	)	$	122,881
		December 31, 2013
		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

Intangible_Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Intangible Assets Disclosure [Text Block]	'
	INTANGIBLE ASSETS AND LIABILITIES
	As of September 30, 2014 and December 31, 2013, the Company’s intangible assets/liabilities were comprised of the following (in thousands):
		September 30, 2014
		Total Cost		Accumulated			Intangible assets/liabilities, net
				Amortization
	Intangible assets, net:
	In-place lease value	$	130,594	$	(38,403	)	$	92,191
	Tenant relationship value	35,186		(26,517		)	8,669
	Above market leases acquired	5,715		(1,275		)	4,440
	Total intangible assets, net	$	171,495	$	(66,195	)	$	105,300
	Acquired lease intangibles, net:
	Below market leases acquired	$	53,049	$	(25,661	)	$	27,388
		December 31, 2013
		Total Cost		Accumulated			Intangible assets/liabilities, net
				Amortization
	Intangible assets, 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 intangible assets, net	$	196,147	$	(63,818	)	$	132,329
	Acquired lease intangibles, net:
	Below market leases acquired	$	81,991	$	(47,547	)	$	34,444
	As of September 30, 2014, the Company’s annual amortization for its intangible assets/liabilities were as follows (in thousands, and assuming no prospective early lease terminations):
		Assets		Liabilities
	2014 (three months remaining)	$	5,892	$	1,378
	2015	21,363		5,212
	2016	16,898		3,253
	2017	15,148		2,664
	2018	11,399		2,241
	Thereafter	34,600		12,640
	Total	$	105,300	$	27,388

Debt_Obligations

Debt Obligations	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Debt Disclosure [Text Block]	'
	DEBT OBLIGATIONS
	The following table sets forth information regarding the Company’s consolidated debt obligations at September 30, 2014 and December 31, 2013 (in thousands):
	Property / Location	September 30, 2014				31-Dec-13			Effective			Maturity
									Interest			Date
									Rate
	MORTGAGE DEBT:
	Tysons Corner	$	89,995			$	91,395		5.36%		(a)	Aug-15
	One Commerce Square	123,691				125,089			3.68%		(a)	Jan-16
	Two Logan Square	87,982				88,583			7.57%			Apr-16
	Fairview Eleven Tower	21,373				21,630			4.25%		(b)	Jan-17
	Two Commerce Square	112,000				112,000			4.51%		(a)	Apr-23
	Cira Square (GSA Philadelphia Campus)	186,109				190,964			7.00%			Sep-30
	Cira Centre South Garage	38,362				40,101			7.12%			Sep-30
	Principal balance outstanding	659,512				669,762
	Plus: fair market value premiums (discounts), net	(911		)		389
	Total mortgage indebtedness	$	658,601			$	670,151
	UNSECURED DEBT:
	Three-Year Term Loan - Swapped to fixed	$	—			$	150,000		2.60%		(d)	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 5.400% Guaranteed Notes due 2014	143,500				218,549			5.53%		(e)	Nov-14
	$250.0M 7.500% Guaranteed Notes due 2015	114,919				157,625			7.76%		(e)	May-15
	$250.0M 6.000% Guaranteed Notes due 2016	149,919				149,919			5.95%			Apr-16
	$300.0M 5.700% Guaranteed Notes due 2017	300,000				300,000			5.68%			May-17
	$325.0M 4.950% Guaranteed Notes due 2018	325,000				325,000			5.13%			Apr-18
	$250.0M 3.950% Guaranteed Notes due 2023	250,000				250,000			4.02%			Feb-23
	$250.0M 4.100% Guaranteed Notes due 2024	250,000				—			4.23%		(e)	Oct-24
	$250.0M 4.550% Guaranteed Notes due 2029	250,000				—			4.60%		(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			3.30%			Apr-35
	Indenture II (Preferred Trust II)	25,774				25,774			3.09%			Jul-35
	Principal balance outstanding	2,061,948				1,929,703
	Plus: original issue premiums (discounts), net	(7,169		)		(4,473		)
	Total unsecured indebtedness	$	2,054,779			$	1,925,230
	Total Debt Obligations	$	2,713,380			$	2,595,381
	(a)	These loans were assumed upon acquisition of the related properties. The interest rate reflects the market rate at the time of acquisition.
	(b)	Represents the full debt amount secured by a property owned by a consolidated real estate venture in which the Company holds a 50% interest.
	(c)	London Interbank Offered Rate (“LIBOR”).
	(d)	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.
	(e)	On September 16, 2014, the Company closed on an underwritten offering of $250 million 4.10% Guaranteed Notes due 2024 (the "2-24 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 a portion 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 the nine-month periods ended September 30, 2014 and 2013, the Company’s weighted-average effective interest rate on its mortgage notes payable was 5.73% and 6.64%, 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 discount of $1.5 million and $2.0 million, respectively, in the consolidated balance sheet as of September 30, 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. Please refer to Footnote 9 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 following table provides additional information on the Company’s repurchase of $117.8 million in aggregate principal amount of its outstanding unsecured notes (consisting of a portion of the 2014 Notes and 2015 Notes, as indicated above) during the nine-month period ended September 30, 2014 (in thousands):
	Notes	Repurchase				Principal			Loss			Deferred Financing
		Amount										Amortization
	2014 5.400% Notes	$	75,531			$	75,049		$	(527	)	$	5
	2015 7.500% Notes	44,593				42,706			(2,079		)	41
		$	120,124			$	117,755		$	(2,606	)	$	46
	The Parent Company unconditionally guarantees the unsecured debt obligations of the Operating Partnership (or is a co-borrower with the Operating Partnership) but does not by itself incur unsecured indebtedness. The Parent Company has no material assets other than its investment in the Operating Partnership.
	The Company utilizes its unsecured revolving credit facility (the "Credit Facility") for general business purposes, including funding costs of acquisitions, developments and redevelopments and repayment of other debt. The scheduled maturity date of the Credit Facility in place at September 30, 2014 is February 1, 2016. The per annum variable interest rate on balances outstanding under the Credit Facility is LIBOR plus 1.50%. The interest rate and facility fee are subject to adjustment upon a change in the Company’s unsecured debt ratings. As of September 30, 2014, the Company did not have any outstanding borrowings on its Credit Facility, with $2.8 million in letters of credit outstanding, leaving $597.2 million of unused availability under the Credit Facility. During each of the three and nine-month periods ended September 30, 2014 and 2013, there were no weighted-average interest rates associated with the Credit Facility because there were no borrowings outstanding under the Credit Facility during either period.
	The Company has the option to increase the amounts available to be advanced under the Credit Facility, 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 by one year the maturity dates of the Credit Facility, subject to payment of an extension fee and other customary conditions and limitations. The $200.0 million seven-year 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 and under the $200.0 million seven-year term loan depends on the Company's 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. At the Company's 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 on loans to the Company at a reduced rate.
	The Company executed hedging transactions that fix the rate on the $200.0 million seven-year term loan at a 3.623% average rate for its full term. All hedges commenced on February 1, 2012 and the rates are inclusive of the LIBOR spread based on the Company's current investment grade rating. See Note 9 for details of the interest rate swaps entered into as of September 30, 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 September 30, 2014. In the event of a default related to the financing and operating covenants, the Company's dividend distributions are limited 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 September 30, 2014, the Company’s aggregate scheduled principal payments on debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
	2014 (three months remaining)	$	261,996		(a)
	2015	102,030
	2016	367,703
	2017	330,323
	2018	336,954
Thereafter	1,322,454
Total principal payments	2,721,460
Net unamortized premiums/(discounts)	(8,080		)
Outstanding indebtedness	$	2,713,380
(a)	The Company completed the redemption of the 5.40% Guaranteed Notes due November 1, 2014 and 7.50% Guaranteed Notes due May 15, 2015 through a tender offer on October 16, 2014. See Note 17 - Subsequent Events, for discussion of redemption.

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Disclosures [Text Block]	'
	FAIR VALUE OF FINANCIAL INSTRUMENTS
	The Company determined the fair values disclosed below using available market information and discounted cash flow analyses as of September 30, 2014 and December 31, 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 estimates and valuation methodologies may have a material effect on the fair value amounts shown. The Company believes that the carrying amounts reflected in the consolidated balance sheets at September 30, 2014 and December 31, 2013 approximate the fair values for cash and cash equivalents, accounts receivable, other assets (excluding notes receivable), 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):
		September 30, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Unsecured notes payable	$	1,776,169	$	1,848,107	$	1,396,620	$	1,471,041
	Variable rate debt	$	278,610	$	257,212	$	528,610	$	526,693
	Mortgage notes payable	$	658,601	$	691,022	$	670,151	$	715,244
	Notes receivable	$	1,901	$	3,517	$	7,026	$	7,759
	The fair value of the Company's unsecured notes payable are categorized as Level 2 (as provided by the accounting standard for Fair Value Measurements and Disclosures), as these instruments are valued using quoted market prices as of September 30, 2014 and December 31, 2013.
	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 fully secured loans with similar terms and maturities. The weighted average discount rate for the combined variable rate debt and mortgage loans as of September 30, 2014 was 4.01%. The fair value of the notes receivable was estimated 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. The Company used a discount rate of 14.66% for the notes receivable as of September 30, 2014. The Company applies its knowledge of the debt markets to determine appropriate discount rates to utilize in the discounted cash flow models. As these inputs are unobservable, the Company has categorized the valuation of mortgage notes payable, variable rate debt and notes receivable as Level 3 (as provided by the accounting standard for Fair Value Measurements and Disclosures).
	Disclosure about the fair value of financial instruments is based upon pertinent information available to management as of September 30, 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 September 30, 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	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS [Text Block]	'
	FAIR VALUE OF DERIVATIVE FINANCIAL INSTRUMENTS
	The following table summarizes the terms and fair values of the Company's derivative financial instruments as of September 30, 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).
	Hedge Product		Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
						9/30/14		12/31/13						9/30/14			12/31/13
	Assets:
	Swap		Interest Rate	Cash Flow	(a)	$	25,774	$	25,774	3.3	%	December 22, 2011	January 30, 2021	$	68		$	549
	Swap		Interest Rate	Cash Flow	(a)	25,774		25,774		3.09	%	6-Jan-12	30-Oct-19	23			218
						$	51,548	$	51,548					$	91		$	767
	Liabilities:
	Swap		Interest Rate	Cash Flow	(a)	$	200,000	$	200,000	3.623	%	December 6-13, 2011	February 1, 2019	$	(1,243	)	$	(545	)
	Swap		Interest Rate	Cash Flow	(a)	27,062		27,062		2.75	%	December 21, 2011	September 30, 2017	(181		)	(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		)
						$	227,062	$	377,062					$	(1,424	)	$	(2,188	)
	(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 (refer to Note 7), 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 September 30, 2014, two interest rate swaps held an asset position and were included in other assets on the Company's consolidated balance sheet. The remaining 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.

Discontinued_Operations

Discontinued Operations	9 Months Ended
	Sep. 30, 2014
Discontinued Operations and Disposal Groups [Abstract]	'
DISCONTINUED OPERATIONS [Text Block]	'
	DISCONTINUED OPERATIONS
	The Company had no property dispositions classified as discontinued operations during the three and nine months ended September 30, 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. See Note 3 for further information.
	For the three and nine-month periods ended September 30, 2013, income from discontinued operations relates to the 14 properties sold by the Company from January 1, 2013 through December 31, 2013. The following table summarizes the revenue and expense information for properties classified as discontinued operations for the three and nine-month periods ended September 30, 2013 (in thousands):
		Three-month period ended September 30, 2013			Nine-month period ended
					30-Sep-13
	Revenue:
	Rents	$	96		$	4,754
	Tenant reimbursements	10			355
	Termination fees	—			—
	Other	—			123
	Total revenue	106			5,232
	Expenses:
	Property operating expenses	62			1,773
	Real estate taxes	39			623
	Depreciation and amortization	48			1,893
	Total operating expenses	149			4,289
	Other income:
	Interest income	—			3
	Income from discontinued operations before gain on sale of interests in real estate	(43		)	946
	Net gain on disposition of discontinued operations	(16		)	3,029
	Income from discontinued operations	$	(59	)	$	3,975
	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	9 Months Ended
	Sep. 30, 2014
Noncontrolling Interest [Abstract]	'
NON-CONTROLLING INTERESTS IN THE PARENT COMPANY [Text Block]	'
	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 in the accompanying consolidated balance sheet of the Parent Company as of September 30, 2014 and December 31, 2013 was $19.9 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 $24.2 million and $24.8 million, respectively, as of September 30, 2014 and December 31, 2013.

Beneficiaries_Equity_of_the_Pa

Beneficiaries Equity of the Parent Company	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
BENEFICIARIES' EQUITY OF THE PARENT COMPANY [Text Block]	'
	BENEFICIARIES’ EQUITY OF THE PARENT COMPANY
	Earnings per Share (EPS)
	The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding):
		Three-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	8,885		$	8,885		$	11,147		$	11,147
	Loss from continuing operations attributable to non-controlling interests	(84		)	(84		)	(106		)	(106		)
	Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	(24		)	(24		)	—			—
	Nonforfeitable dividends allocated to unvested restricted shareholders	(82		)	(82		)	(85		)	(85		)
	Preferred share dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Income from continuing operations available to common shareholders	6,970			6,970			9,231			9,231
	Loss from discontinued operations	(3		)	(3		)	(59		)	(59		)
	Discontinued operations attributable to non-controlling interests	—			—			1			1
	Discontinued operations attributable to common shareholders	(3		)	(3		)	(58		)	(58		)
	Net income attributable to common shareholders	$	6,967		$	6,967		$	9,173		$	9,173
	Denominator
	Weighted-average shares outstanding	171,606,722			171,606,722			156,703,348			156,703,348
	Contingent securities/Share based compensation	—			1,587,148			—			1,288,734
	Weighted-average shares outstanding	171,606,722			173,193,870			156,703,348			157,992,082
	Earnings per Common Share:
	Income from continuing operations attributable to common shareholders	$	0.04		$	0.04		$	0.06		$	0.06
	Discontinued operations attributable to common shareholders	—			—			—			—
	Net income attributable to common shareholders	$	0.04		$	0.04		$	0.06		$	0.06
		Nine-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	7,893		$	7,893		$	18,212		$	18,212
	Income from continuing operations attributable to non-controlling interests	(35		)	(35		)	(143		)	(143		)
	Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	(12		)	(12		)	—			—
	Nonforfeitable dividends allocated to unvested restricted shareholders	(268		)	(268		)	(278		)	(278		)
	Preferred share dividends	(5,175		)	(5,175		)	(5,175		)	(5,175		)
	Income from continuing operations available to common shareholders	2,403			2,403			12,616			12,616
	Income from discontinued operations	918			918			3,975			3,975
	Discontinued operations attributable to non-controlling interests	(10		)	(10		)	(52		)	(52		)
	Discontinued operations attributable to common shareholders	908			908			3,923			3,923
	Net income attributable to common shareholders	$	3,311		$	3,311		$	16,539		$	16,539
	Denominator
	Weighted-average shares outstanding	161,866,955			161,866,955			151,933,441			151,933,441
	Contingent securities/Share based compensation	—			1,487,015			—			1,209,384
	Weighted-average shares outstanding	161,866,955			163,353,970			151,933,441			153,142,825
	Earnings per Common Share:
	Income from continuing operations attributable to common shareholders	$	0.01		$	0.01		$	0.08		$	0.08
	Discontinued operations attributable to common shareholders	0.01			0.01			0.03			0.03
	Net income attributable to common shareholders	$	0.02		$	0.02		$	0.11		$	0.11
	Redeemable common limited partnership units totaling 1,721,905 and 1,763,739 as of September 30, 2014 and 2013, respectively, 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 three and nine-month periods ended September 30, 2014 and 2013, earnings representing nonforfeitable dividends as noted in the table above were allocated to the unvested restricted shares issued to the Company’s executives and other employees under the Company's shareholder-approved long-term incentive plan.
	Common and Preferred Shares
	On September 10, 2014, the Parent Company declared a distribution of $0.15 per common share, totaling $27.2 million, which was paid on October 20, 2014 to shareholders of record as of October 6, 2014. In addition, the Parent Company declared distributions on its Series E Preferred Shares to holders of record as of September 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 October 15, 2014 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 May 15, 2014, the Company amended its Amended and Restated Declaration of Trust to increase the Company’s total number of shares of beneficial interest from 220,000,000 to 420,000,000 shares, with the number of authorized common shares of beneficial interest increased from 200,000,000 to 400,000,000 and the number of authorized preferred shares of beneficial interest remaining unchanged at 20,000,000.
	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. 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 and determinations by the Parent Company of the appropriate sources of funding. Sales agents engaged by the Parent Company under the Offering Program are entitled to receive, as compensation and in aggregate, up to 2% of the gross sales price per share sold under the Offering Program. From inception of the Offering Program through September 30, 2014, the Parent Company had not sold any shares under the program, leaving 16,000,000 remaining shares available for sale.
	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 nine-month periods ended September 30, 2014 and 2013. As of September 30, 2014, the Parent Company may purchase up to 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	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Partners Equity of Operating Partnership [Text Block]	'
	PARTNERS’ EQUITY OF THE OPERATING PARTNERSHIP
	Earnings per Common Partnership Unit
	The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding):
		Three-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	8,885		$	8,885		$	11,147		$	11,147
	Nonforfeitable dividends allocated to unvested restricted unitholders	(82		)	(82		)	(85		)	(85		)
	Preferred unit dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Net income attributable to non-controlling interests	(24		)	(24		)	—			—
	Income from continuing operations available to common unitholders	7,054			7,054			9,337			9,337
	Discontinued operations attributable to common unitholders	(3		)	(3		)	(59		)	(59		)
	Net income attributable to common unitholders	$	7,051		$	7,051		$	9,278		$	9,278
	Denominator
	Weighted-average units outstanding	173,341,782			173,341,782			158,467,087			158,467,087
	Contingent securities/Share based compensation	—			1,587,148			—			1,288,734
	Total weighted-average units outstanding	173,341,782			174,928,930			158,467,087			159,755,821
	Earnings per Common Partnership Unit:
	Income from continuing operations attributable to common unitholders	$	0.04		$	0.04		$	0.06		$	0.06
	Discontinued operations attributable to common unitholders	—			—			—			—
	Net income attributable to common unitholders	$	0.04		$	0.04		$	0.06		$	0.06
		Nine-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	7,893		$	7,893		$	18,212		$	18,212
	Amount allocable to unvested restricted unitholders	(268		)	(268		)	(278		)	(278		)
	Preferred unit dividends	(5,175		)	(5,175		)	(5,175		)	(5,175		)
	Net income attributable to non-controlling interests	(12		)	(12		)	—			—
	Income from continuing operations available to common unitholders	2,438			2,438			12,759			12,759
	Discontinued operations attributable to common unitholders	918			918			3,975			3,975
	Net income attributable to common unitholders	$	3,356		$	3,356		$	16,734		$	16,734
	Denominator
	Weighted-average units outstanding	163,620,963			163,620,963			153,731,070			153,731,070
	Contingent securities/Share based compensation	—			1,487,015			—			1,209,384
	Total weighted-average units outstanding	163,620,963			165,107,978			153,731,070			154,940,454
	Earnings per Common Partnership Unit:
	Income from continuing operations attributable to common unitholders	$	0.01		$	0.01		$	0.08		$	0.08
	Discontinued operations attributable to common unitholders	0.01			0.01			0.03			0.03
	Net income attributable to common unitholders	$	0.02		$	0.02		$	0.11		$	0.11
	Unvested restricted units are considered participating securities which require the use of the two-class method for the computation of basic and diluted earnings per share. For the three and nine-month periods ended September 30, 2014 and 2013, earnings representing nonforfeitable dividends as noted in the table above 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 common partnership units not held by the Parent Company have the same economic characteristics as the Parent Company's common shares and share proportionately in the net income or loss and in any distributions of the Operating Partnership. The common partnership units not held by the Parent Company are redeemable at any time at the option of the holder, and the Parent Company, as the sole general partner of the Operating Partnership, may at its option elect to settle the redemption in cash or through the exchange on a one-for-one basis with common shares of the Parent Company. Similarly, the Series E-Linked Preferred Mirror Units of the Operating Partnership have the same economic characteristics as the Series E Preferred Shares of the Parent Company. Whenever the Parent Company issues common shares or preferred shares, it contributes the net proceeds to the Operating Partnership in exchange for, as applicable, an equal number of common partnership units or preferred units that mirror the economic terms of the preferred shares.
	On September 10, 2014, the Operating Partnership declared a distribution of $0.15 per common partnership unit, totaling $27.2 million, which was paid on October 20, 2014 to unitholders of record as of October 6, 2014. On September 10, 2014, the Operating Partnership declared distributions on its Series E-Linked Preferred Mirror Units to holders of record as of September 30, 2014. These units are entitled to a preferential return of 6.90% per annum on the $25.00 per unit liquidation preference. Distributions paid on October 15, 2014 to holders of Series E-Linked Preferred Mirror Units totaled $1.7 million.
	Common Unit Repurchases
	The Parent Company did not repurchase any shares under its share repurchase program in either of the nine-month periods ended September 30, 2014 and 2013 and accordingly, during the nine-month periods ended September 30, 2014 and 2013, 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	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
SHARE BASED AND DEFERRED COMPENSATION	'
	SHARE BASED COMPENSATION
	Stock Options
	At September 30, 2014, options exercisable for 2,808,784 common shares were outstanding under the Parent Company's shareholder approved equity incentive plan (referred to as the "Equity Incentive Plan"). During the nine-month period ended September 30, 2014 the Company recognized a nominal amount of compensation expense related to unvested options. During the three and nine-month periods ended September 30, 2013 the Company recognized compensation expense related to unvested options of $0.2 million and $0.6 million, of which a nominal amount and $0.1 million, respectively, were capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation.
	Option activity as of September 30, 2014 and changes during the nine months ended September 30, 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		$	—
	Granted	—
	Exercised	(60,127	)	$	11.8			—		$	182,101
	Canceled	(114,658	)	$	20.61
	Outstanding at September 30, 2014	2,808,784		$	15.37			4.42		$	—
	Vested/Exercisable at September 30, 2014	2,808,784		$	15.37			4.42		$	—
	Restricted Share Awards
	As of September 30, 2014, 549,175 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 September 30, 2014 was approximately $2.5 million, and is expected to be recognized over a weighted average remaining vesting period of 1.7 years. During the three and nine-month periods ended September 30, 2014, the Company recognized compensation expense related to outstanding restricted shares of $0.4 million and $2.3 million, of which $0.1 million and $0.5 million, respectively, were capitalized as part of the Company’s review of employee salaries eligible for capitalization. During the three and nine-month periods ended September 30, 2013, the Company recognized compensation expense related to outstanding restricted shares of $0.9 million and $2.6 million, of which $0.1 million and $0.4 million, respectively, were capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation.
	The following table summarizes the Company’s restricted share activity for the nine months ended September 30, 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	(9,488	)	12.57
	Non-vested at September 30, 2014	549,175		$	12.22
	On March 11, 2014 and March 12, 2014 the Compensation Committee of the Parent Company’s Board of Trustees awarded restricted shares of which 131,641 cliff vest after three years from the grant date and 69,794 vest ratably over three years, of which 2,792 were canceled, leaving 67,002 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.
	Grant Date		Measurement Period Commencement Date	Measurement Period End Date		Fair Value of Units on Grant Date (in thousands)			Units Granted			Units Canceled		Units		Unvested Balance
														Vested (a)
	3/1/12		1/1/12	12/31/14		$	4,273		265,222			(38,959	)	(14,742	)	211,521
	2/25/13		1/1/13	12/31/15		4,137			231,093			(27,698	)			203,395
	3/11/14		1/1/14	12/31/16		2,624			134,284							134,284
	3/12/14		1/1/14	12/31/16		1,225			61,720							61,720
	(a) These RPSUs were settled upon the holder’s qualifying retirement in October 2012 after reaching age 57 and accumulating at least 15 years of service with the Company. Of the 14,742 RPSU's originally granted, 563 dividend equivalent rights had accrued at the time of qualifying retirement. In accordance with the pay-out formula in the award agreement, on October 31, 2012, the Company issued 30,610 common shares in settlement of the RPSU's based on the Company’s total shareholder return relative to the comparator groups.
	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 three and nine-month periods ended September 30, 2014, the Company recognized total compensation expense for the 2014, 2013 and 2012 RPSU awards of $0.5 million and $2.8 million, of which $0.2 million and $0.9 million, respectively, were capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the three and nine-month periods ended September 30, 2013, the Company recognized total compensation expense for the 2013, 2012 and 2011 RPSU awards of $1.3 million and $3.7 million, of which $0.2 million and $0.6 million, respectively, were capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation.
	The remaining compensation expense to be recognized at September 30, 2014 was approximately $2.7 million, and is expected to be recognized over a weighted average remaining vesting period of 1.2 years.
	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.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	SEGMENT INFORMATION
	During the quarter ended September 30, 2014, the Company was managing its portfolio within seven segments: (1) Pennsylvania Suburbs, (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 Suburbs 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 the City of Austin, Texas. 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.
	The following tables provide selected asset information and results of operations of the Company's reportable segments (in thousands):
	Real estate investments, at cost:
			30-Sep-14				31-Dec-13
	Philadelphia CBD		$	1,327,288			$	1,300,666
	Pennsylvania Suburbs		1,230,785				1,199,105
	Metropolitan Washington, D.C.		1,178,942				1,214,965
	New Jersey/Delaware		418,419				414,716
	Richmond, Virginia		311,350				310,397
	California		193,080				192,584
	Austin, Texas (a)		—				36,856
			$	4,659,864			$	4,669,289
	Less: Assets held for sale (b)		(50,969		)		—
	Operating Properties		$	4,608,895			$	4,669,289
	Corporate
	Construction-in-progress		$	140,456			$	74,174
	Land inventory		$	90,842			$	93,351
	(a)	On April 3, 2014, the Company contributed Four Points Centre to an unconsolidated joint venture. See Note 3 for further information on the contribution. Following this contribution, the Company has no wholly-owned properties in the Austin, Texas segment.
	(b)	On September 30, 2014, the Company was actively marketing for sale of its Valleybrooke Office Park, comprised of five properties located in the Pennsylvania Suburbs segment. As of September 30, 2014 the properties were classified as held for sale on the consolidated balance sheet. The sale is not classified as a significant disposition under the accounting guidance for discontinued operations. Accordingly, the real estate investments remained in the Pennsylvania Suburbs segment as of September 30, 2014.
	Net operating income:
		Three-month periods ended
		September 30,
		2014										2013
		Total revenue				Operating expenses (b)			Net operating income			Total revenue			Operating expenses (b)			Net operating income
	Philadelphia CBD	$	49,469			$	(18,168	)	$	31,301		$	35,891		$	(13,704	)	$	22,187
	Pennsylvania Suburbs	39,996				(13,409		)	26,587			39,167			(13,884		)	25,283
	Metropolitan Washington, D.C.	27,764				(10,672		)	17,092			29,321			(10,321		)	19,000
	New Jersey/Delaware	14,975				(7,506		)	7,469			15,330			(8,203		)	7,127
	Richmond, Virginia	8,354				(3,724		)	4,630			8,640			(3,734		)	4,906
	California	4,902				(2,711		)	2,191			4,632			(2,531		)	2,101
	Austin, Texas (a)	843				(569		)	274			9,938			(3,958		)	5,980
	Corporate	255				(472		)	(217		)	435			212			647
	Operating Properties	$	146,558			$	(57,231	)	$	89,327		$	143,354		$	(56,123	)	$	87,231
		Nine-month periods ended
		September 30,
		2014										2013
		Total revenue				Operating expenses (b)			Net operating income			Total revenue			Operating expenses (b)			Net operating income
	Philadelphia CBD	$	150,303			$	(55,399	)	$	94,904		$	107,957		$	(40,825	)	$	67,132
	Pennsylvania Suburbs	121,313				(41,542		)	79,771			114,085			(42,536		)	71,549
	Metropolitan Washington, D.C.	87,403				(33,134		)	54,269			85,889			(31,856		)	54,033
	New Jersey/Delaware	45,440				(23,728		)	21,712			45,273			(22,105		)	23,168
	Richmond, Virginia	25,543				(11,629		)	13,914			26,359			(11,017		)	15,342
	California	14,399				(7,634		)	6,765			13,773			(7,029		)	6,744
	Austin, Texas (a)	3,900				(2,362		)	1,538			29,067			(12,123		)	16,944
	Corporate	871				(1,484		)	(613		)	1,149			1,326			2,475
	Operating Properties	$	449,172			$	(176,912	)	$	272,260		$	423,552		$	(166,165	)	$	257,387
	(a)	On April 3, 2014, the Company contributed Four Points Centre to an unconsolidated real estate venture. See Note 3 for further information on the contribution. On October 16, 2013, the Company contributed seven properties in the Austin portfolio to an unconsolidated real estate venture. Following the contribution of these properties, there are no wholly owned properties in the Austin, Texas segment.
	(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							Three-month periods ended September 30,						Nine-month periods ended September 30,
		30-Sep-14				31-Dec-13			2014			2013			2014			2013
	Philadelphia CBD	$	20,779			$	19,975		$	32		$	405		$	13		$	1,548
	Pennsylvania Suburbs	17,739				17,272			(578		)	55			(937		)	643
	Metropolitan Washington, D.C.	67,800				59,905			(142		)	60			(117		)	41
	New Jersey/Delaware	—				—			82			79			204			1,154
	Richmond, Virginia	1,478				1,400			184			108			253			344
	Austin, Texas (a)	89,743				81,960			(64		)	7			(149		)	27
	Total	$	197,539			$	180,512		$	(486	)	$	714		$	(733	)	$	3,757
	(a)	Investment in real estate ventures does not include the $1.2 million negative investment balance in one real estate venture as of September 30, 2014, which is included in other liabilities.
	Net operating income (“NOI”) is a non-GAAP measure that 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:
		Three-month periods ended September 30,							Nine-month periods ended September 30,
	2014				2013			2014			2013
	(amounts in thousands)							(amounts in thousands)
Consolidated net operating income	$	89,327			$	87,231		$	272,260		$	257,387
Other income (expense):
Depreciation and amortization	(52,616		)		(50,583		)	(157,773		)	(149,300		)
General and administrative expenses	(5,900		)		(6,436		)	(20,086		)	(20,323		)
Interest income	528				268			1,298			448
Interest expense	(31,481		)		(30,338		)	(94,837		)	(91,689		)
Recognized hedge activity	(828		)		—			(828		)	—
Amortization of deferred financing costs	(1,566		)		(1,158		)	(3,952		)	(3,502		)
Interest expense - financing obligation	(273		)		(264		)	(861		)	(693		)
Equity in income (loss) of real estate ventures	(486		)		714			(733		)	3,757
Net gain on disposition of real estate	4,698				—			4,698			—
Gain (Loss) on sale of undepreciated real estate	—				(129		)	1,184			(129		)
Gain from remeasurement of investment in a real estate venture	—				—			458			7,847
Gain (Loss) on real estate venture transactions	—				—			(417		)	3,683
Loss on early extinguishment of debt	(2,606		)		(11		)	(2,606		)	(1,127		)
Provision for impairment on assets held for sale	(1,765		)		—			(1,765		)	—
Historic tax credit transaction income	11,853				11,853			11,853			11,853
Income from continuing operations	8,885				11,147			7,893			18,212
Income (loss) from discontinued operations	(3		)		(59		)	918			3,975
Net income	$	8,882			$	11,088		$	8,811		$	22,187

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
COMMITMENTS AND CONTINGENCIES [Text Block]	'
	COMMITMENTS AND CONTINGENCIES
	Legal Proceedings
	The Company is involved from time to time in litigation on various matters, including disputes with tenants and disputes arising out of agreements to purchase or sell properties. Given the nature of the Company’s business activities, these lawsuits are considered routine to the conduct of its business. The result of any particular lawsuit cannot be predicted, because of the very nature of litigation, the litigation process and its adversarial nature, and the jury system. The Company will establish reserves for specific legal proceedings when it determines 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 any current legal actions will have a material adverse effect on the Company's consolidated financial position, results of operations or cash flows.
	Environmental
	As an owner of real estate, the Company is subject to various environmental laws of federal, state, and local governments. The Company’s compliance with existing laws has not had a material adverse effect on its financial condition and results of operations, and the Company does not believe it will have a material adverse effect in the future. However, the Company cannot predict the impact of unforeseen environmental contingencies or new or changed laws or regulations on its current Properties or on properties that the Company may acquire.
	Ground Rent
	Future minimum rental payments under the terms of all non-cancelable ground leases under which the Company is the lessee are expensed on a straight-line basis regardless of when payments are due. The Company’s ground leases have remaining lease terms ranging from 7 to 75 years. Minimum future rental payments on non-cancelable leases at September 30, 2014 are as follows (in thousands):
	2014 (three months remaining)	$	345
	2015	1,380
	2016	1,380
	2017	1,380
	2018	1,380
	Thereafter	58,515
	Total	$	64,380
	The Company obtained ground tenancy rights related to two properties in Philadelphia, Pennsylvania. One of these ground leases is currently held by a real estate venture. These ground leases 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 or real estate venture, as applicable. Such amounts, if any, will be reflected as contingent rent when incurred. The leases also provide for payment by the Company, or real estate venture, as applicable, 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. Reference is made in our Annual Report on Form 10-K for the year ended December 31, 2013 for further detail regarding commitments and contingencies.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events [Text Block]	'
	SUBSEQUENT EVENTS
	Valleybrooke Disposition
	On October 24, 2014, the Company sold its Valleybrooke office portfolio for a sale price of $37.9 million. (See Note 3 for discussion of impairment) The loss on sale, including closing costs of $1.8 million, approximated the impairment loss recorded as of September 30, 2014.
	1919 Market Street Venture
	On October 21, 2014, the Company formed a joint venture named 1919 Market Street Ventures ("1919 Ventures") with LCOR/CalSTRS ("LCOR"), a fully integrated commercial real estate company unaffiliated with the Company.  Each of the Company and LCOR owns a 50% interest in 1919 Ventures which, through wholly-owned subsidiaries, owns a one acre parcel of land in Philadelphia, Pennsylvania.  The Company and LCOR valued the land and improvements at $16.4 million and LCOR acquired its 50% interest in 1919 Ventures from the Company for $8.2 million.  After giving effect to cash contributions, distributions and credit to the Company for its pre-existing interest in the assets of 1919 Ventures, each of the Company and LCOR had made, as of the formation date, an additional $5.2 million capital contribution to 1919 Ventures for closing costs and development.
	River Place Acquisition
	On October 17, 2014, the Austin Venture acquired River Place, comprised of seven Class A office buildings containing 591,000 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 $20.0 million from each of DRA and the Company the Austin Venture. 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.
	Guaranteed Notes Redemption
	On October 16, 2014, in connection with the aforementioned offering, the Company redeemed for $143.5 million of its 5.40% Guaranteed Notes due November 1, 2014, and $114.9 million of its 7.50% Guaranteed Notes due May 15, 2015. The Company funded $270.3 million from net proceeds of the registered offering, as well as available cash balances, with the Company recognizing a $4.9 million loss on the early extinguishment of debt.
	The Company has evaluated subsequent events through the date the financial statements were issued.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2014
Accounting Policies [Abstract]	'
Basis of Accounting, Policy [Policy Text Block]	'
	Basis of Presentation
	The consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments (consisting solely of normal recurring matters) for a fair statement of the financial position of the Company as of September 30, 2014, the results of its operations for the three and nine-month periods ended September 30, 2014 and 2013 and its cash flows for the nine-month periods ended September 30, 2014 and 2013 have been included. The results of operations for such interim periods are not necessarily indicative of the results for a full year. These consolidated financial statements should be read in conjunction with the Parent Company’s and the Operating Partnership’s consolidated financial statements and footnotes included in their combined 2013 Annual Report on Form 10-K filed with the SEC on February 25, 2014.
Reclassification, Policy [Policy Text Block]	'
	Reclassifications
	Certain amounts have been reclassified in prior years to conform to the current year presentation, including the reclassification of notes receivable to other assets within the balance sheets and the reclassification of changes in escrow balances from operating cash flows to investing cash flows in the statements of cash flows. All other 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.
Recent Accounting Pronouncement [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.

Real_Estate_Investments_Tables

Real Estate Investments (Tables)	9 Months Ended
	Sep. 30, 2014
Real Estate [Abstract]	'
Gross Carrying Value Of Company's Properties [Table Text Block]	'
	As of September 30, 2014 and December 31, 2013, the gross carrying value of the Company’s Properties was as follows (in thousands):
		September 30,		December 31,
		2014		2013
	Land	$	675,109	$	680,513
	Building and improvements	3,419,903		3,504,060
	Tenant improvements	513,883		484,716
		$	4,608,895	$	4,669,289

Investment_in_Unconsolidated_V1

Investment in Unconsolidated Ventures (Tables)	9 Months Ended
	Sep. 30, 2014
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investment Summarized Financial Information [Table Text Block]	'
	The following is a summary of the financial position of the Real Estate Ventures as of September 30, 2014 and December 31, 2013 (in thousands):
		September 30,				December 31,
		2014				2013
	Net property	$	1,140,798			$	965,475
	Other assets	166,020				164,152
	Other liabilities	59,690				49,442
	Debt	852,636				699,860
	Equity	394,492				380,325
	Company’s share of equity (Company’s basis) (a)	197,539			(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 September 30, 2014, which is included in other liabilities.
Summary of results of operations of unconsolidated Real Estate Venture [Table Text Block]	'
	The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests during these periods (in thousands):
		Three-month periods ended September 30,							Nine-month periods ended September 30,
		2014				2013			2014			2013
	Revenue	$	37,446			$	30,684		$	106,905		$	108,500
	Operating expenses	(15,433		)		(13,199		)	(44,257		)	(48,671		)
	Interest expense, net	(9,245		)		(9,223		)	(26,234		)	(28,167		)
	Depreciation and amortization	(13,552		)		(9,893		)	(40,423		)	(33,778		)
	Net loss	(784		)		(1,631		)	(4,009		)	(2,116		)
	Company’s share of income (loss) (Company’s basis)	(486		)		714			(733		)	3,757

Deferred_Costs_Tables

Deferred Costs (Tables)	9 Months Ended
	Sep. 30, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Components Of Deferred Costs Net [Table Text Block]	'
	As of September 30, 2014 and December 31, 2013, the Company’s deferred costs were comprised of the following (in thousands):
		September 30, 2014
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	159,744	$	(63,136	)	$	96,608
	Financing Costs	42,265		(15,992		)	26,273
	Total	$	202,009	$	(79,128	)	$	122,881
		December 31, 2013
		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

Intangible_Assets_Tables

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Intangible Assets [Table Text Block]	'
	As of September 30, 2014 and December 31, 2013, the Company’s intangible assets/liabilities were comprised of the following (in thousands):
		September 30, 2014
		Total Cost		Accumulated			Intangible assets/liabilities, net
				Amortization
	Intangible assets, net:
	In-place lease value	$	130,594	$	(38,403	)	$	92,191
	Tenant relationship value	35,186		(26,517		)	8,669
	Above market leases acquired	5,715		(1,275		)	4,440
	Total intangible assets, net	$	171,495	$	(66,195	)	$	105,300
	Acquired lease intangibles, net:
	Below market leases acquired	$	53,049	$	(25,661	)	$	27,388
		December 31, 2013
		Total Cost		Accumulated			Intangible assets/liabilities, net
				Amortization
	Intangible assets, 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 intangible assets, net	$	196,147	$	(63,818	)	$	132,329
	Acquired lease intangibles, net:
	Below market leases acquired	$	81,991	$	(47,547	)	$	34,444
Annual Amortization For Its Intangible Assets Liabilities [Table Text Block]	'
	As of September 30, 2014, the Company’s annual amortization for its intangible assets/liabilities were as follows (in thousands, and assuming no prospective early lease terminations):
		Assets		Liabilities
	2014 (three months remaining)	$	5,892	$	1,378
	2015	21,363		5,212
	2016	16,898		3,253
	2017	15,148		2,664
	2018	11,399		2,241
	Thereafter	34,600		12,640
	Total	$	105,300	$	27,388

Debt_Obligations_Tables

Debt Obligations (Tables)	9 Months Ended
	Sep. 30, 2014
Debt Disclosure [Abstract]	'
Consolidated Debt Obligations [Table Text Block]	'
	The following table sets forth information regarding the Company’s consolidated debt obligations at September 30, 2014 and December 31, 2013 (in thousands):
	Property / Location	September 30, 2014				31-Dec-13			Effective			Maturity
									Interest			Date
									Rate
	MORTGAGE DEBT:
	Tysons Corner	$	89,995			$	91,395		5.36%		(a)	Aug-15
	One Commerce Square	123,691				125,089			3.68%		(a)	Jan-16
	Two Logan Square	87,982				88,583			7.57%			Apr-16
	Fairview Eleven Tower	21,373				21,630			4.25%		(b)	Jan-17
	Two Commerce Square	112,000				112,000			4.51%		(a)	Apr-23
	Cira Square (GSA Philadelphia Campus)	186,109				190,964			7.00%			Sep-30
	Cira Centre South Garage	38,362				40,101			7.12%			Sep-30
	Principal balance outstanding	659,512				669,762
	Plus: fair market value premiums (discounts), net	(911		)		389
	Total mortgage indebtedness	$	658,601			$	670,151
	UNSECURED DEBT:
	Three-Year Term Loan - Swapped to fixed	$	—			$	150,000		2.60%		(d)	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 5.400% Guaranteed Notes due 2014	143,500				218,549			5.53%		(e)	Nov-14
	$250.0M 7.500% Guaranteed Notes due 2015	114,919				157,625			7.76%		(e)	May-15
	$250.0M 6.000% Guaranteed Notes due 2016	149,919				149,919			5.95%			Apr-16
	$300.0M 5.700% Guaranteed Notes due 2017	300,000				300,000			5.68%			May-17
	$325.0M 4.950% Guaranteed Notes due 2018	325,000				325,000			5.13%			Apr-18
	$250.0M 3.950% Guaranteed Notes due 2023	250,000				250,000			4.02%			Feb-23
	$250.0M 4.100% Guaranteed Notes due 2024	250,000				—			4.23%		(e)	Oct-24
	$250.0M 4.550% Guaranteed Notes due 2029	250,000				—			4.60%		(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			3.30%			Apr-35
	Indenture II (Preferred Trust II)	25,774				25,774			3.09%			Jul-35
	Principal balance outstanding	2,061,948				1,929,703
	Plus: original issue premiums (discounts), net	(7,169		)		(4,473		)
	Total unsecured indebtedness	$	2,054,779			$	1,925,230
	Total Debt Obligations	$	2,713,380			$	2,595,381
	(a)	These loans were assumed upon acquisition of the related properties. The interest rate reflects the market rate at the time of acquisition.
	(b)	Represents the full debt amount secured by a property owned by a consolidated real estate venture in which the Company holds a 50% interest.
	(c)	London Interbank Offered Rate (“LIBOR”).
	(d)	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.
	(e)	On September 16, 2014, the Company closed on an underwritten offering of $250 million 4.10% Guaranteed Notes due 2024 (the "2-24 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 a portion 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 [Table Text Block]	'
	The following table provides additional information on the Company’s repurchase of $117.8 million in aggregate principal amount of its outstanding unsecured notes (consisting of a portion of the 2014 Notes and 2015 Notes, as indicated above) during the nine-month period ended September 30, 2014 (in thousands):
	Notes	Repurchase				Principal			Loss			Deferred Financing
		Amount										Amortization
	2014 5.400% Notes	$	75,531			$	75,049		$	(527	)	$	5
	2015 7.500% Notes	44,593				42,706			(2,079		)	41
		$	120,124			$	117,755		$	(2,606	)	$	46
Schedule of Maturities of Long-term Debt [Table Text Block]	'
	As of September 30, 2014, the Company’s aggregate scheduled principal payments on debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
	2014 (three months remaining)	$	261,996		(a)
	2015	102,030
	2016	367,703
	2017	330,323
	2018	336,954
	Thereafter	1,322,454
	Total principal payments	2,721,460
	Net unamortized premiums/(discounts)	(8,080		)
	Outstanding indebtedness	$	2,713,380
	(a)	The Company completed the redemption of the 5.40% Guaranteed Notes due November 1, 2014 and 7.50% Guaranteed Notes due May 15, 2015 through a tender offer on October 16, 2014. See Note 17 - Subsequent Events, for discussion of redemption.

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule Of Financial Instruments With Fair Values Different From Their Carrying Amount [Table Text Block]	'
	The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands):
		September 30, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Unsecured notes payable	$	1,776,169	$	1,848,107	$	1,396,620	$	1,471,041
	Variable rate debt	$	278,610	$	257,212	$	528,610	$	526,693
	Mortgage notes payable	$	658,601	$	691,022	$	670,151	$	715,244
	Notes receivable	$	1,901	$	3,517	$	7,026	$	7,759

Risk_Management_and_Use_of_Fin1

Risk Management and Use of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
Derivatives, Fair Value [Line Items]	'
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]	'
	Hedge Product		Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
						9/30/14		12/31/13						9/30/14			12/31/13
	Assets:
	Swap		Interest Rate	Cash Flow	(a)	$	25,774	$	25,774	3.3	%	December 22, 2011	January 30, 2021	$	68		$	549
	Swap		Interest Rate	Cash Flow	(a)	25,774		25,774		3.09	%	6-Jan-12	30-Oct-19	23			218
						$	51,548	$	51,548					$	91		$	767
	Liabilities:
	Swap		Interest Rate	Cash Flow	(a)	$	200,000	$	200,000	3.623	%	December 6-13, 2011	February 1, 2019	$	(1,243	)	$	(545	)
	Swap		Interest Rate	Cash Flow	(a)	27,062		27,062		2.75	%	December 21, 2011	September 30, 2017	(181		)	(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		)
						$	227,062	$	377,062					$	(1,424	)	$	(2,188	)
	(a)	Hedging unsecured variable rate debt.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	9 Months Ended
	Sep. 30, 2014
Long Lived Assets Held-for-sale [Line Items]	'
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]	'
	For the three and nine-month periods ended September 30, 2013, income from discontinued operations relates to the 14 properties sold by the Company from January 1, 2013 through December 31, 2013. The following table summarizes the revenue and expense information for properties classified as discontinued operations for the three and nine-month periods ended September 30, 2013 (in thousands):
		Three-month period ended September 30, 2013			Nine-month period ended
					30-Sep-13
	Revenue:
	Rents	$	96		$	4,754
	Tenant reimbursements	10			355
	Termination fees	—			—
	Other	—			123
	Total revenue	106			5,232
	Expenses:
	Property operating expenses	62			1,773
	Real estate taxes	39			623
	Depreciation and amortization	48			1,893
	Total operating expenses	149			4,289
	Other income:
	Interest income	—			3
	Income from discontinued operations before gain on sale of interests in real estate	(43		)	946
	Net gain on disposition of discontinued operations	(16		)	3,029
	Income from discontinued operations	$	(59	)	$	3,975

Beneficiaries_Equity_of_the_Pa1

Beneficiaries Equity of the Parent Company (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Earnings Per Share (EPS), Basic and Diluted	'
	Earnings per Share (EPS)
	The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding):
		Three-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	8,885		$	8,885		$	11,147		$	11,147
	Loss from continuing operations attributable to non-controlling interests	(84		)	(84		)	(106		)	(106		)
	Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	(24		)	(24		)	—			—
	Nonforfeitable dividends allocated to unvested restricted shareholders	(82		)	(82		)	(85		)	(85		)
	Preferred share dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Income from continuing operations available to common shareholders	6,970			6,970			9,231			9,231
	Loss from discontinued operations	(3		)	(3		)	(59		)	(59		)
	Discontinued operations attributable to non-controlling interests	—			—			1			1
	Discontinued operations attributable to common shareholders	(3		)	(3		)	(58		)	(58		)
	Net income attributable to common shareholders	$	6,967		$	6,967		$	9,173		$	9,173
	Denominator
	Weighted-average shares outstanding	171,606,722			171,606,722			156,703,348			156,703,348
	Contingent securities/Share based compensation	—			1,587,148			—			1,288,734
	Weighted-average shares outstanding	171,606,722			173,193,870			156,703,348			157,992,082
	Earnings per Common Share:
	Income from continuing operations attributable to common shareholders	$	0.04		$	0.04		$	0.06		$	0.06
	Discontinued operations attributable to common shareholders	—			—			—			—
	Net income attributable to common shareholders	$	0.04		$	0.04		$	0.06		$	0.06
		Nine-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	7,893		$	7,893		$	18,212		$	18,212
	Income from continuing operations attributable to non-controlling interests	(35		)	(35		)	(143		)	(143		)
	Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	(12		)	(12		)	—			—
	Nonforfeitable dividends allocated to unvested restricted shareholders	(268		)	(268		)	(278		)	(278		)
	Preferred share dividends	(5,175		)	(5,175		)	(5,175		)	(5,175		)
	Income from continuing operations available to common shareholders	2,403			2,403			12,616			12,616
	Income from discontinued operations	918			918			3,975			3,975
	Discontinued operations attributable to non-controlling interests	(10		)	(10		)	(52		)	(52		)
	Discontinued operations attributable to common shareholders	908			908			3,923			3,923
	Net income attributable to common shareholders	$	3,311		$	3,311		$	16,539		$	16,539
	Denominator
	Weighted-average shares outstanding	161,866,955			161,866,955			151,933,441			151,933,441
	Contingent securities/Share based compensation	—			1,487,015			—			1,209,384
	Weighted-average shares outstanding	161,866,955			163,353,970			151,933,441			153,142,825
	Earnings per Common Share:
	Income from continuing operations attributable to common shareholders	$	0.01		$	0.01		$	0.08		$	0.08
	Discontinued operations attributable to common shareholders	0.01			0.01			0.03			0.03
	Net income attributable to common shareholders	$	0.02		$	0.02		$	0.11		$	0.11

Partners_Equity_of_the_Operati1

Partners Equity of the Operating Partnership (Tables)	9 Months Ended
	Sep. 30, 2014
Equity [Abstract]	'
Earnings Per Common Partnership Unit [Table Text Block]	'
	Earnings per Common Partnership Unit
	The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding):
		Three-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	8,885		$	8,885		$	11,147		$	11,147
	Nonforfeitable dividends allocated to unvested restricted unitholders	(82		)	(82		)	(85		)	(85		)
	Preferred unit dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Net income attributable to non-controlling interests	(24		)	(24		)	—			—
	Income from continuing operations available to common unitholders	7,054			7,054			9,337			9,337
	Discontinued operations attributable to common unitholders	(3		)	(3		)	(59		)	(59		)
	Net income attributable to common unitholders	$	7,051		$	7,051		$	9,278		$	9,278
	Denominator
	Weighted-average units outstanding	173,341,782			173,341,782			158,467,087			158,467,087
	Contingent securities/Share based compensation	—			1,587,148			—			1,288,734
	Total weighted-average units outstanding	173,341,782			174,928,930			158,467,087			159,755,821
	Earnings per Common Partnership Unit:
	Income from continuing operations attributable to common unitholders	$	0.04		$	0.04		$	0.06		$	0.06
	Discontinued operations attributable to common unitholders	—			—			—			—
	Net income attributable to common unitholders	$	0.04		$	0.04		$	0.06		$	0.06
		Nine-month periods ended September 30,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Income from continuing operations	$	7,893		$	7,893		$	18,212		$	18,212
	Amount allocable to unvested restricted unitholders	(268		)	(268		)	(278		)	(278		)
	Preferred unit dividends	(5,175		)	(5,175		)	(5,175		)	(5,175		)
	Net income attributable to non-controlling interests	(12		)	(12		)	—			—
	Income from continuing operations available to common unitholders	2,438			2,438			12,759			12,759
	Discontinued operations attributable to common unitholders	918			918			3,975			3,975
	Net income attributable to common unitholders	$	3,356		$	3,356		$	16,734		$	16,734
	Denominator
	Weighted-average units outstanding	163,620,963			163,620,963			153,731,070			153,731,070
	Contingent securities/Share based compensation	—			1,487,015			—			1,209,384
	Total weighted-average units outstanding	163,620,963			165,107,978			153,731,070			154,940,454
	Earnings per Common Partnership Unit:
	Income from continuing operations attributable to common unitholders	$	0.01		$	0.01		$	0.08		$	0.08
	Discontinued operations attributable to common unitholders	0.01			0.01			0.03			0.03
	Net income attributable to common unitholders	$	0.02		$	0.02		$	0.11		$	0.11

Share_Based_and_Deferred_Compe1

Share Based and Deferred Compensation (Tables)	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Options Activity [Table Text Block]	'
	Option activity as of September 30, 2014 and changes during the nine months ended September 30, 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		$	—
	Granted	—
	Exercised	(60,127	)	$	11.8			—		$	182,101
	Canceled	(114,658	)	$	20.61
	Outstanding at September 30, 2014	2,808,784		$	15.37			4.42		$	—
	Vested/Exercisable at September 30, 2014	2,808,784		$	15.37			4.42		$	—
Company's Restricted Share Activity [Table Text Block]	'
	The following table summarizes the Company’s restricted share activity for the nine months ended September 30, 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	(9,488	)	12.57
	Non-vested at September 30, 2014	549,175		$	12.22
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	'
	Grant Date		Measurement Period Commencement Date	Measurement Period End Date		Fair Value of Units on Grant Date (in thousands)			Units Granted			Units Canceled		Units		Unvested Balance
														Vested (a)
	3/1/12		1/1/12	12/31/14		$	4,273		265,222			(38,959	)	(14,742	)	211,521
	2/25/13		1/1/13	12/31/15		4,137			231,093			(27,698	)			203,395
	3/11/14		1/1/14	12/31/16		2,624			134,284							134,284
	3/12/14		1/1/14	12/31/16		1,225			61,720							61,720
	(a) These RPSUs were settled upon the holder’s qualifying retirement in October 2012 after reaching age 57 and accumulating at least 15 years of service with the Company. Of the 14,742 RPSU's originally granted, 563 dividend equivalent rights had accrued at the time of qualifying retirement. In accordance with the pay-out formula in the award agreement, on October 31, 2012, the Company issued 30,610 common shares in settlement of the RPSU's based on the Company’s total shareholder return relative to the comparator groups.

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Schedule of Segment Real Estate Investments, by Segment [Table Text Block]	'
	Real estate investments, at cost:
			30-Sep-14				31-Dec-13
	Philadelphia CBD		$	1,327,288			$	1,300,666
	Pennsylvania Suburbs		1,230,785				1,199,105
	Metropolitan Washington, D.C.		1,178,942				1,214,965
	New Jersey/Delaware		418,419				414,716
	Richmond, Virginia		311,350				310,397
	California		193,080				192,584
	Austin, Texas (a)		—				36,856
			$	4,659,864			$	4,669,289
	Less: Assets held for sale (b)		(50,969		)		—
	Operating Properties		$	4,608,895			$	4,669,289
	Corporate
	Construction-in-progress		$	140,456			$	74,174
	Land inventory		$	90,842			$	93,351
Schedule of Segment Net Operating Income, by Segment [Table Text Block]	'
	Net operating income:
		Three-month periods ended
		September 30,
		2014										2013
		Total revenue				Operating expenses (b)			Net operating income			Total revenue			Operating expenses (b)			Net operating income
	Philadelphia CBD	$	49,469			$	(18,168	)	$	31,301		$	35,891		$	(13,704	)	$	22,187
	Pennsylvania Suburbs	39,996				(13,409		)	26,587			39,167			(13,884		)	25,283
	Metropolitan Washington, D.C.	27,764				(10,672		)	17,092			29,321			(10,321		)	19,000
	New Jersey/Delaware	14,975				(7,506		)	7,469			15,330			(8,203		)	7,127
	Richmond, Virginia	8,354				(3,724		)	4,630			8,640			(3,734		)	4,906
	California	4,902				(2,711		)	2,191			4,632			(2,531		)	2,101
	Austin, Texas (a)	843				(569		)	274			9,938			(3,958		)	5,980
	Corporate	255				(472		)	(217		)	435			212			647
	Operating Properties	$	146,558			$	(57,231	)	$	89,327		$	143,354		$	(56,123	)	$	87,231
		Nine-month periods ended
		September 30,
		2014										2013
		Total revenue				Operating expenses (b)			Net operating income			Total revenue			Operating expenses (b)			Net operating income
	Philadelphia CBD	$	150,303			$	(55,399	)	$	94,904		$	107,957		$	(40,825	)	$	67,132
	Pennsylvania Suburbs	121,313				(41,542		)	79,771			114,085			(42,536		)	71,549
	Metropolitan Washington, D.C.	87,403				(33,134		)	54,269			85,889			(31,856		)	54,033
	New Jersey/Delaware	45,440				(23,728		)	21,712			45,273			(22,105		)	23,168
	Richmond, Virginia	25,543				(11,629		)	13,914			26,359			(11,017		)	15,342
	California	14,399				(7,634		)	6,765			13,773			(7,029		)	6,744
	Austin, Texas (a)	3,900				(2,362		)	1,538			29,067			(12,123		)	16,944
	Corporate	871				(1,484		)	(613		)	1,149			1,326			2,475
	Operating Properties	$	449,172			$	(176,912	)	$	272,260		$	423,552		$	(166,165	)	$	257,387
	(a)	On April 3, 2014, the Company contributed Four Points Centre to an unconsolidated real estate venture. See Note 3 for further information on the contribution. On October 16, 2013, the Company contributed seven properties in the Austin portfolio to an unconsolidated real estate venture. Following the contribution of these properties, there are no wholly owned properties in the Austin, Texas segment.
	(b)	Includes property operating expense, real estate taxes and third party management expense.
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
	Unconsolidated real estate ventures:
		Investment in real estate ventures, at equity							Equity in income (loss) of real estate ventures
		As of							Three-month periods ended September 30,						Nine-month periods ended September 30,
		30-Sep-14				31-Dec-13			2014			2013			2014			2013
	Philadelphia CBD	$	20,779			$	19,975		$	32		$	405		$	13		$	1,548
	Pennsylvania Suburbs	17,739				17,272			(578		)	55			(937		)	643
	Metropolitan Washington, D.C.	67,800				59,905			(142		)	60			(117		)	41
	New Jersey/Delaware	—				—			82			79			204			1,154
	Richmond, Virginia	1,478				1,400			184			108			253			344
	Austin, Texas (a)	89,743				81,960			(64		)	7			(149		)	27
	Total	$	197,539			$	180,512		$	(486	)	$	714		$	(733	)	$	3,757
	(a)	Investment in real estate ventures does not include the $1.2 million negative investment balance in one real estate venture as of September 30, 2014, which is included in other liabilities.
Reconciliation Of Consolidated Net Operating Income [Table Text Block]	'
	Net operating income (“NOI”) is a non-GAAP measure that 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:
		Three-month periods ended September 30,							Nine-month periods ended September 30,
		2014				2013			2014			2013
		(amounts in thousands)							(amounts in thousands)
	Consolidated net operating income	$	89,327			$	87,231		$	272,260		$	257,387
	Other income (expense):
	Depreciation and amortization	(52,616		)		(50,583		)	(157,773		)	(149,300		)
	General and administrative expenses	(5,900		)		(6,436		)	(20,086		)	(20,323		)
	Interest income	528				268			1,298			448
	Interest expense	(31,481		)		(30,338		)	(94,837		)	(91,689		)
	Recognized hedge activity	(828		)		—			(828		)	—
	Amortization of deferred financing costs	(1,566		)		(1,158		)	(3,952		)	(3,502		)
	Interest expense - financing obligation	(273		)		(264		)	(861		)	(693		)
	Equity in income (loss) of real estate ventures	(486		)		714			(733		)	3,757
	Net gain on disposition of real estate	4,698				—			4,698			—
	Gain (Loss) on sale of undepreciated real estate	—				(129		)	1,184			(129		)
	Gain from remeasurement of investment in a real estate venture	—				—			458			7,847
	Gain (Loss) on real estate venture transactions	—				—			(417		)	3,683
	Loss on early extinguishment of debt	(2,606		)		(11		)	(2,606		)	(1,127		)
	Provision for impairment on assets held for sale	(1,765		)		—			(1,765		)	—
	Historic tax credit transaction income	11,853				11,853			11,853			11,853
	Income from continuing operations	8,885				11,147			7,893			18,212
	Income (loss) from discontinued operations	(3		)		(59		)	918			3,975
	Net income	$	8,882			$	11,088		$	8,811		$	22,187

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Operating Leases Future Minimum Payments Due [Table Text Block]	'
	Ground Rent
	Future minimum rental payments under the terms of all non-cancelable ground leases under which the Company is the lessee are expensed on a straight-line basis regardless of when payments are due. The Company’s ground leases have remaining lease terms ranging from 7 to 75 years. Minimum future rental payments on non-cancelable leases at September 30, 2014 are as follows (in thousands):
	2014 (three months remaining)	$	345
	2015	1,380
	2016	1,380
	2017	1,380
	2018	1,380
	Thereafter	58,515
	Total	$	64,380

Organization_of_the_Parent_Com1

Organization of the Parent Company and The Operating Partnership (Details)	Sep. 30, 2014	Sep. 30, 2013
	sqft	sqft
	Real_Estate_Investments
Parent Company [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Ownership in the Operating Partnership	98.90%	'
Net rentable square feet	25,400,000	'
Area Owned by Company of Undeveloped Parcels Of Land	415	'
Area Of Additional Undeveloped Parcels Of Land With Option to Purchase	50	'
Total potential development capacity	5,700,000	'
Unconsolidated Real Estate Ventures [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Net rentable square feet	6,100,000	6,200,000
Number Of Unconsolidated Real Estate Ventures	17	'
Wholly-owned Management Company Subsidiaries [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Net rentable square feet	33,700,000	'
Third Parties and Real Estate Ventures [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Net rentable square feet	8,300,000	'
Total Properties [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	205	'
Office Properties [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	169	'
Industrial Facilities [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	20	'
Mixed Use Properties [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	5	'
Retail Properties [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	1	'
Core Properties [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	195	'
Assets Held-for-sale [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	5	'
Development Property [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	3	'
Redevelopment Property [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	1	'
Re-entitlement Property [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	1	'

Real_Estate_Investments_Gross_

Real Estate Investments Gross Carrying Value of Company's Properties (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment, Gross [Abstract]	'	'
Land	$675,109	$680,513
Buildings and Improvements, Gross	3,419,903	3,504,060
Leasehold Improvements, Gross	513,883	484,716
Real Estate Investments	$4,608,895	$4,669,289

Real_Estate_Investments_Acquis

Real Estate Investments Acquisitions and Dispositions (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

0 Months Ended

9 Months Ended

0 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Apr. 16, 2014

Apr. 07, 2014

Feb. 25, 2014

Feb. 25, 2013

Apr. 03, 2014

Mar. 27, 2014

Apr. 03, 2014

Feb. 19, 2014

Sep. 30, 2014

Sep. 30, 2014

Dec. 31, 2013

Dec. 19, 2013

Apr. 03, 2014

Apr. 03, 2014

Campus Pointe [Member]

Valleybrooke Office Park [Member]

West Point II Land [Member]

Princeton Pike Corporate Center [Member]

Princeton Pike Corporate Center [Member]

Princeton Pike Corporate Center [Member]

Four Points Centre [Member]

Rob Roy - Land [Member]

Austin Joint Venture [Member]

Encino Trace - Land [Member]

Encino Trace - Building I [Member]

One and Two Commerce Square [Member]

One and Two Commerce Square [Member]

One and Two Commerce Square [Member]

DRA Advisors LLC [Member]

Brandywine Realty Trust [Member]

sqft

sqft

acre

Properties

Properties

acre

Four Points Centre [Member]

sqft

Storey

Austin Joint Venture [Member]

Austin Joint Venture [Member]

Properties

sqft

Storey

Properties

Four Points Centre [Member]

Four Points Centre [Member]

sqft

acre

Storey

Significant Acquisitions and Disposals [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate gross sales price of a joint venture

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$41,500,000

Net gain from remeasurement of investment in RE ventures

0

0

458,000

7,847,000

'

'

'

'

'

'

'

'

'

'

'

'

500,000

'

'

'

'

Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

'

'

Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

99.00%

'

'

Area Owned by Company of Undeveloped Parcels Of Land

'

'

'

'

'

'

'

'

'

'

'

'

'

'

54.1

'

'

'

'

'

'

Total potential development capacity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

320,000

'

'

'

'

'

'

Number of Real Estate Properties

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

Number of floors of a building

'

'

'

'

'

'

'

'

'

'

'

3

'

'

4

'

'

'

41

'

'

Business Acquisition, Transaction Costs

'

'

'

'

'

'

'

'

'

'

2,000,000

'

'

'

'

'

'

'

'

'

'

Net Rentable Space

'

'

'

'

'

'

'

'

'

'

'

192,396

'

'

'

'

'

'

'

'

'

Accounts receivable, net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,100,000

1,600,000

'

'

'

Area of Land

'

'

'

'

'

'

'

5.3

'

'

'

'

16.8

'

'

'

'

'

'

'

'

Business Combination, Consideration Transferred

'

'

'

'

'

'

'

'

'

'

'

'

'

'

14,000,000

'

'

'

'

'

'

Construction in Progress, Gross

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8,400,000

28,700,000

'

'

'

'

'

Land

675,109,000

'

675,109,000

'

680,513,000

'

'

'

'

'

'

'

'

'

4,600,000

'

'

'

'

'

'

Number of real estate properties sold

'

'

'

'

'

'

'

'

'

'

8

'

'

'

'

'

'

'

'

'

'

Net Rentable Space Sold

'

'

'

'

'

172,943

279,934

'

'

'

800,546

'

'

'

'

'

'

'

'

'

'

Escrow Deposit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

Sale Consideration Of Sold Property

'

'

'

'

'

42,500,000

37,900,000

1,600,000

'

'

121,000,000

'

3,500,000

'

'

'

'

'

'

'

'

Provision for impairment on assets held for sale

1,765,000

0

1,765,000

0

'

'

1,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net gain on disposition of real estate

4,698,000

0

4,698,000

0

'

4,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Disposal group, number of properties held for sale

'

'

'

'

'

'

5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net gain (loss) on disposition of discontinued operations

-3,000

-16,000

900,000

3,029,000

'

'

'

'

900,000

5,300,000

'

'

'

'

'

'

'

'

'

'

'

Number of Real Estate Properties

'

'

'

'

'

'

'

'

'

'

'

2

'

'

'

'

'

'

'

'

'

Gain (Loss) on sale of undepreciated real estate

0

-129,000

1,184,000

-129,000

'

'

'

'

'

'

'

'

1,200,000

'

'

'

'

'

'

'

'

Non-Recourse Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

29,000,000

'

'

'

'

'

'

'

Amount Of Participant Contribution

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,900,000

'

Proceeds from Equity Method Investment, Dividends or Distributions

'

'

7,341,000

3,661,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

34,400,000

Equity method investment, credit to capital contribution

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,900,000

Net gain (loss) on real estate venture transactions

$0

$0

($417,000)

$3,683,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

($200,000)

Investment_in_Unconsolidated_V2

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

9 Months Ended

0 Months Ended

0 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Jul. 31, 2014

Jul. 31, 2014

Sep. 30, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2014

Apr. 03, 2014

Jul. 31, 2014

Jul. 31, 2014

Buildings

Real_Estate_Ventures

Crossings at Lakeline [Member]

Crossings at Lakeline [Member]

TB-BDN Plymouth Apartments [Member]

Unconsolidated Real Estate Ventures [Member]

Unconsolidated Real Estate Ventures [Member]

The Grove at Cira Centre South [Member]

PJP VII [Member]

Four Points Centre [Member]

DRA Advisors LLC [Member]

Brandywine Realty Trust [Member]

acre

sqft

sqft

sqft

Storey

Crossings at Lakeline [Member]

Crossings at Lakeline [Member]

Real_Estate_Ventures

Storey

Properties

Room

Properties

sqft

ApartmentUnits

sqft

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity method investments, Cash contributions

'

'

'

$12,800,000

'

'

'

'

'

'

'

$6,400,000

$6,400,000

Equity method investments, Purchase adjustments

'

'

'

900,000

'

'

'

'

'

'

'

'

'

Equity method investments, Closing costs

'

'

'

'

100,000

'

'

'

'

'

'

'

'

Equity method investments, Credit from seller

'

'

'

600,000

'

'

'

'

'

'

'

'

'

Number of floors of a building

'

'

'

'

3

'

'

'

'

'

3

'

'

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

197,539,000

'

180,512,000

'

'

'

'

'

'

'

'

'

'

Number of unconsolidated investments in Real Estate Ventures

17

17

'

'

'

'

'

'

'

'

'

'

'

Net rentable square feet

'

'

'

'

'

'

6,100,000

6,200,000

'

'

'

'

'

Number of Real Estate Properties

'

'

'

'

2

'

'

'

'

'

2

'

'

Net Rentable Area

'

'

'

'

232,274

'

'

'

'

'

'

'

'

Equity method investment, Consideration transferred

'

'

'

48,200,000

'

'

'

'

'

'

'

'

'

Net Rentable Space

'

'

'

'

'

'

'

'

'

'

192,396

'

'

Number of real estate ventures that owns buildings

11

'

'

'

'

'

'

'

'

'

'

'

'

Number of office buildings in Real Estate Ventures

58

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate Approximate Area Of Office Buildings

6,100,000

'

'

'

'

'

'

'

'

'

'

'

'

Number of real estate ventures that owns undeveloped land

2

'

'

'

'

'

'

'

'

'

'

'

'

Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land

3.8

'

'

'

'

'

'

'

'

'

'

'

'

Payments to Acquire Equity Method Investments

16,330,000

30,142,000

'

'

'

'

'

'

'

'

'

'

'

Number of real estate ventures that owns land under development

3

'

'

'

'

'

'

'

'

'

'

'

'

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

21.8

'

'

'

'

'

'

'

'

'

'

'

'

Number of Real Estate Investments in residential towers

1

'

'

'

'

'

'

'

'

'

'

'

'

Number of apartment units in a Real Estate Venture

345

'

'

'

'

'

'

'

'

'

'

'

'

Number of real estate ventures developed hotel property

1

'

'

'

'

'

'

'

'

'

'

'

'

Number Of Rooms Contain In One Real Estate Venture Developed As Hotel Property

137

'

'

'

'

'

'

'

'

'

'

'

'

Minimum Percentage Of Unconsolidated Equity Method Investment Ownership

20.00%

'

'

'

'

'

'

'

'

'

'

'

'

Maximum Percentage Of Unconsolidated Equity Method Investment Ownership

65.00%

'

'

'

'

'

'

'

'

'

'

'

'

Guarantor Obligations, Current Carrying Value

'

'

'

'

'

$3,200,000

'

'

$24,700,000

$500,000

'

'

'

Investment_in_Unconsolidated_V3

Investment in Unconsolidated Ventures (Summary of Results of Operations of Unconsolidated Ventures) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Company's share of income (Company's basis)	($486)	$714	($733)	$3,757
Unconsolidated Real Estate Ventures [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Revenue	37,446	30,684	106,905	108,500
Operating expenses	-15,433	-13,199	-44,257	-48,671
Interest expense, net	-9,245	-9,223	-26,234	-28,167
Depreciation and amortization	-13,552	-9,893	-40,423	-33,778
Net loss	-784	-1,631	-4,009	-2,116
Company's share of income (Company's basis)	($486)	$714	($733)	$3,757

Investment_in_Unconsolidated_V4

Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2014		Dec. 31, 2013		Jul. 31, 2014
In Thousands, unless otherwise specified			Austin, Texas [Member]	Unconsolidated Real Estate Ventures [Member]		Unconsolidated Real Estate Ventures [Member]		Crossings at Lakeline [Member]
Schedule of Equity Method Investments [Line Items]	'	'	'	'		'		'
Net property	'	'	'	$1,140,798		$965,475		'
Other assets	'	'	'	166,020		164,152		'
Other liabilities	'	'	'	59,690		49,442		'
Debt	'	'	'	852,636		699,860		34,500
Equity	'	'	'	394,492		380,325		'
Company's share of equity (Company's Basis)	$197,539	$180,512	($1,200)	$197,539	[1]	$180,512	[1]	'
[1]	(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.

Deferred_Costs_Details

Deferred Costs (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Components of Deferred Costs Net [Abstract]	'	'
Leasing Costs, Total Cost	$159,744	$155,885
Financing Costs, Total Cost	42,265	40,317
Total Cost	202,009	196,202
Leasing Costs, Accumulated Amortization	-63,136	-58,805
Financing Costs, Accumulated Amortization	-15,992	-14,443
Total, Accumulated Amortization	-79,128	-73,248
Leasing, Deferred Costs, Net	96,608	97,080
Financing Costs, Deferred Costs, Net	26,273	25,874
Deferred Costs, Net	$122,881	$122,954

Deferred_Costs_Details_Textual

Deferred Costs (Details Textuals) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Deferred Costs (Textuals) [Abstract]	'	'	'	'
Capitalized Internal Direct Leasing Costs	$1.60	$1.80	$5.60	$5.80

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 16, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Intangible Assets [Line Items]	'	'	'	'	'	'
Recognized hedge activity	$800	($828)	$0	($828)	$0	'
Total Cost	'	171,495	'	171,495	'	196,147
Accumulated Amortization	'	-66,195	'	-66,195	'	-63,818
Intangible Assets, net	'	105,300	'	105,300	'	132,329
In-place lease value	'	'	'	'	'	'
Intangible Assets [Line Items]	'	'	'	'	'	'
Total Cost	'	130,594	'	130,594	'	150,782
Accumulated Amortization	'	-38,403	'	-38,403	'	-35,607
Intangible Assets, net	'	92,191	'	92,191	'	115,175
Tenant relationship value	'	'	'	'	'	'
Intangible Assets [Line Items]	'	'	'	'	'	'
Total Cost	'	35,186	'	35,186	'	38,692
Accumulated Amortization	'	-26,517	'	-26,517	'	-26,868
Intangible Assets, net	'	8,669	'	8,669	'	11,824
Above market leases acquired	'	'	'	'	'	'
Intangible Assets [Line Items]	'	'	'	'	'	'
Total Cost	'	5,715	'	5,715	'	6,673
Accumulated Amortization	'	-1,275	'	-1,275	'	-1,343
Intangible Assets, net	'	4,440	'	4,440	'	5,330
Below Market Leases Acquired [Member]	'	'	'	'	'	'
Intangible Assets [Line Items]	'	'	'	'	'	'
Total Cost	'	-53,049	'	-53,049	'	-81,991
Accumulated Amortization	'	25,661	'	25,661	'	47,547
Intangible Assets, net	'	($27,388)	'	($27,388)	'	($34,444)

Intangible_Assets_Annual_Amort

Intangible Assets Annual Amortization of Intangible Assets (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Annual amortization of intangible assets and liabilities	'	'
Intangible Assets, net	($105,300)	($132,329)
Assets [Member]	'	'
Annual amortization of intangible assets and liabilities	'	'
2013	5,892	'
2014	21,363	'
2015	16,898	'
2016	15,148	'
2017	11,399	'
Thereafter	34,600	'
Intangible Assets, net	-105,300	'
Liabilities [Member]	'	'
Annual amortization of intangible assets and liabilities	'	'
2013	-1,378	'
2014	-5,212	'
2015	-3,253	'
2016	-2,664	'
2017	-2,241	'
Thereafter	-12,640	'
Intangible Assets, net	$27,388	'

Debt_Obligations_Consolidated_

Debt Obligations (Consolidated Debt Obligations Outstanding) (Details) (USD $)	9 Months Ended
	Sep. 30, 2014		Sep. 16, 2014	Dec. 31, 2013
Debt Instrument [Line Items]	'		'	'
Net unamortized premiums/(discounts)	($8,080,000)		'	'
Total mortgage indebtedness	658,601,000		'	670,151,000
Total Debt Obligations	2,713,380,000		'	2,595,381,000
Line of Credit and Seven Year Term Loan [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
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.		'	'
Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	659,512,000		'	669,762,000
Net unamortized premiums/(discounts)	-911,000		'	389,000
Total mortgage indebtedness	658,601,000		'	670,151,000
Unsecured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	2,061,948,000		'	1,929,703,000
Net unamortized premiums/(discounts)	-7,169,000		'	-4,473,000
Total unsecured indebtedness	2,054,779,000		'	1,925,230,000
Unsecured Debt [Member] | Three Year Term Loan [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	0	[1]	'	150,000,000
Debt Instrument, Interest Rate, Effective Percentage	2.60%		'	'
Debt Instrument, Maturity Date	1-Feb-15		'	'
Debt Instrument, Repurchased Face Amount	'		150,000,000	'
Unsecured Debt [Member] | Four-Year Term Loan - Swapped to fixed [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Debt Instrument, Repurchased Face Amount	'		100,000,000	'
Unsecured Debt [Member] | Four-Year Term Loan - Variable [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	0	[1]	'	100,000,000
Debt Instrument, Interest Rate Terms	'LIBOR + 1.75%	[2]	'	'
Debt Instrument, Maturity Date	1-Feb-16		'	'
Unsecured Debt [Member] | Seven Year Term Loan [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	200,000,000		'	200,000,000
Debt Instrument, Face Amount	200,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	3.62%		'	'
Debt Instrument, Maturity Date	1-Feb-19		'	'
Unsecured Debt [Member] | 2014 5.400% Notes	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	143,500,000	[3]	'	218,549,000
Debt Instrument, Interest Rate, Stated Percentage	5.40%		'	'
Debt Instrument, Face Amount	250,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	5.53%		'	'
Debt Instrument, Maturity Date	1-Nov-14		'	'
Debt Instrument, Repurchased Face Amount	'		143,500,000	'
Unsecured Debt [Member] | $250.0M 7.500% Guaranteed Notes due 2015	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	114,919,000	[3]	'	157,625,000
Debt Instrument, Interest Rate, Stated Percentage	7.50%		'	'
Debt Instrument, Face Amount	250,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	7.76%		'	'
Debt Instrument, Maturity Date	15-May-15		'	'
Debt Instrument, Repurchased Face Amount	'		114,900,000	'
Unsecured Debt [Member] | $250.0M 6.000% Guranteed Notes due 2016 [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	149,919,000		'	149,919,000
Debt Instrument, Interest Rate, Stated Percentage	6.00%		'	'
Debt Instrument, Face Amount	250,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	5.95%		'	'
Debt Instrument, Maturity Date	1-Apr-16		'	'
Unsecured Debt [Member] | $300.0M 5.700% Guaranteed Notes due 2017	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	300,000,000		'	300,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.70%		'	'
Debt Instrument, Face Amount	300,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	5.68%		'	'
Debt Instrument, Maturity Date	1-May-17		'	'
Unsecured Debt [Member] | $325.0M 4.950% Guaranteed Notes due 2018	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	325,000,000		'	325,000,000
Debt Instrument, Interest Rate, Stated Percentage	4.95%		'	'
Debt Instrument, Face Amount	325,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	5.13%		'	'
Debt Instrument, Maturity Date	15-Apr-18		'	'
Unsecured Debt [Member] | $250.0M 3.950% Guaranteed Notes due 2023	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	250,000,000		'	250,000,000
Debt Instrument, Interest Rate, Effective Percentage	4.02%		'	'
Debt Instrument, Maturity Date	15-Feb-23		'	'
Unsecured Debt [Member] | Note 2024 [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	250,000,000	[3]	'	0
Debt Instrument, Interest Rate, Stated Percentage	4.10%		'	'
Debt Instrument, Face Amount	250,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	4.23%		'	'
Debt Instrument, Maturity Date	1-Oct-24		'	'
Unsecured Debt [Member] | Note 2029 [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	250,000,000	[3]	'	0
Debt Instrument, Interest Rate, Stated Percentage	4.60%		'	'
Debt Instrument, Face Amount	250,000,000		'	'
Debt Instrument, Interest Rate, Effective Percentage	4.60%		'	'
Debt Instrument, Maturity Date	1-Oct-29		'	'
Unsecured Debt [Member] | Indenture IA (Preferred Trust I) [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	27,062,000		'	27,062,000
Debt Instrument, Interest Rate, Effective Percentage	2.75%		'	'
Debt Instrument, Maturity Date	30-Mar-35		'	'
Unsecured Debt [Member] | Indenture IB (Preferred Trust I) [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	25,774,000		'	25,774,000
Debt Instrument, Interest Rate, Effective Percentage	3.30%		'	'
Debt Instrument, Maturity Date	30-Apr-35		'	'
Unsecured Debt [Member] | Indenture II (Preferred Trust II) [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	25,774,000		'	25,774,000
Debt Instrument, Interest Rate, Effective Percentage	3.09%		'	'
Debt Instrument, Maturity Date	30-Jul-35		'	'
Tysons Corner [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	89,995,000		'	91,395,000
Debt Instrument, Interest Rate, Effective Percentage	5.36%	[4]	'	'
Debt Instrument, Maturity Date	1-Aug-15		'	'
One Commerce Square [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	123,691,000		'	125,089,000
Debt Instrument, Interest Rate, Effective Percentage	3.68%	[4]	'	'
Debt Instrument, Maturity Date	6-Jan-16		'	'
Two Logan Square [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	87,982,000		'	88,583,000
Debt Instrument, Interest Rate, Effective Percentage	7.57%		'	'
Debt Instrument, Maturity Date	1-Apr-16		'	'
Fairview Eleven Tower [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Equity Method Investment, Ownership Percentage	50.00%		'	'
Fairview Eleven Tower [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	21,373,000		'	21,630,000
Debt Instrument, Interest Rate, Effective Percentage	4.25%	[5]	'	'
Debt Instrument, Maturity Date	1-Jan-17		'	'
Two Commerce Square [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	112,000,000		'	112,000,000
Debt Instrument, Interest Rate, Effective Percentage	4.51%	[4]	'	'
Debt Instrument, Maturity Date	5-Apr-23		'	'
IRS Philadelphia Campus [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	186,109,000		'	190,964,000
Debt Instrument, Interest Rate, Effective Percentage	7.00%		'	'
Debt Instrument, Maturity Date	10-Sep-30		'	'
Cira South Garage [Member] | Secured Debt [Member]	'		'	'
Debt Instrument [Line Items]	'		'	'
Long-term Debt, Gross	$38,362,000		'	$40,101,000
Debt Instrument, Interest Rate, Effective Percentage	7.12%		'	'
Debt Instrument, Maturity Date	10-Sep-30		'	'
[1]	(d)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.
[2]	(c)London Interbank Offered Rate (“LIBOR”).
[3]	(e)On September 16, 2014, the Company closed on an underwritten offering of $250 million 4.10% Guaranteed Notes due 2024 (the "2-24 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 a portion 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).
[4]	(a)These loans were assumed upon acquisition of the related properties. The interest rate reflects the market rate at the time of acquisition.
[5]	(b)Represents the full debt amount secured by a property owned by a consolidated real estate venture in which the Company holds a 50% interest.

Debt_Obligations_Outstanding_U

Debt Obligations (Outstanding Unsecured Notes in Series of Transactions) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Extinguishment of Debt [Line Items]	'	'
Repayments of unsecured notes	$120,361	$13,027
Extinguishment of Debt, Amount	117,755	'
2014 5.400% Notes	'	'
Extinguishment of Debt [Line Items]	'	'
Repayments of unsecured notes	75,531	'
Extinguishment of Debt, Amount	75,049	'
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	527	'
Write off of Deferred Debt Issuance Cost	5	'
2015 7.500% Notes	'	'
Extinguishment of Debt [Line Items]	'	'
Repayments of unsecured notes	44,593	'
Extinguishment of Debt, Amount	42,706	'
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	2,079	'
Write off of Deferred Debt Issuance Cost	41	'
Discharge of Debt [Member]	'	'
Extinguishment of Debt [Line Items]	'	'
Repayments of unsecured notes	120,124	'
Extinguishment of Debt, Amount	117,755	'
Gains (Losses) on Extinguishment of Debt, before Write off of Deferred Debt Issuance Cost	2,606	'
Write off of Deferred Debt Issuance Cost	$46	'

Debt_Obligations_Aggregate_Sch

Debt Obligations (Aggregate Scheduled Principal Payments of Debt Obligation, Excluding Amortization of Discounts and Premiums) (Details) (USD $)	Sep. 30, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Extinguishment of Debt [Line Items]	'		'
2013	$261,996	[1]	'
2014	102,030		'
2015	367,703		'
2016	330,323		'
2017	336,954		'
Thereafter	1,322,454		'
Total principal payments	2,721,460		'
Net unamortized premiums/(discounts)	-8,080		'
Total Debt Obligations	$2,713,380		$2,595,381
[1]	(a)The Company completed the redemption of the 5.40% Guaranteed Notes due November 1, 2014 and 7.50% Guaranteed Notes due May 15, 2015 through a tender offer on October 16, 2014. See Note 17 - Subsequent Events, for discussion of redemption.

Debt_Obligations_Details_Textu

Debt Obligations (Details Textuals) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended
	Sep. 16, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Debt Instrument [Line Items]	'	'	'	'	'
Extinguishment of Debt, Amount	'	'	'	$117,755,000	'
Loss on early extinguishment of debt	2,606,000	-2,606,000	-11,000	-2,606,000	-1,127,000
Secured Debt [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Long-term Debt, Weighted Average Interest Rate	'	5.73%	6.64%	5.73%	6.64%
Unsecured Debt [Member] | Three and Four Year Term Loan [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Write off of Deferred Debt Issuance Cost	300,000	'	'	'	'
Unsecured Debt [Member] | Note 2024 [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Debt Instrument, Face Amount	'	250,000,000	'	250,000,000	'
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%	'	'	'	'
Unsecured Debt [Member] | Note 2029 [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Debt Instrument, Face Amount	'	250,000,000	'	250,000,000	'
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%	'	'	'	'
Unsecured Debt [Member] | Notes 2024 and 2029 [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Proceeds from Notes Payable	492,900,000	'	'	'	'
Unsecured Debt [Member] | Three Year Term Loan [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Debt Instrument, Repurchased Face Amount	150,000,000	'	'	'	'
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	'	2,800,000	'	2,800,000	'
Unsecured Debt [Member] | Line of Credit [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Line of Credit Facility, Remaining Borrowing Capacity	'	597,200,000	'	597,200,000	'
Unsecured Debt [Member] | Four Year Term Loan [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Debt Instrument, Redemption, Description	'1,026.88 per $1,000	'	'	'	'
Extinguishment of Debt, Amount	75,100,000	'	'	'	'
Debt Instrument, Face Amount	'	250,000,000	'	250,000,000	'
Unsecured Debt [Member] | 2015 7.500% Notes	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Debt Instrument, Redemption, Description	'$1,070.24 per $1,000	'	'	'	'
Extinguishment of Debt, Amount	42,700,000	'	'	'	'
Debt Instrument, Face Amount	'	250,000,000	'	250,000,000	'
Unsecured Debt [Member] | Seven Year Term Loan [Member]	'	'	'	'	'
Debt Instrument [Line Items]	'	'	'	'	'
Debt Instrument, Face Amount	'	$200,000,000	'	$200,000,000	'
Declining prepayment penalty after Three Years	'	'	'	1.00%	'
Derivative, Average Fixed Interest Rate	'	3.62%	'	3.62%	'

Debt_Obligations_Details_Textu1

Debt Obligations (Details Textuals 2) (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2014
Unsecured Debt [Member] | Four Year Term Loan [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	250
Debt Instrument, Interest Rate, Stated Percentage	5.40%
Unsecured Debt [Member] | $250.0M 7.500% Guaranteed Notes due 2015	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	250
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Unsecured Debt [Member] | $250.0M 6.000% Guranteed Notes due 2016 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	250
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Unsecured Debt [Member] | $300.0M 5.700% Guaranteed Notes due 2017	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	300
Debt Instrument, Interest Rate, Stated Percentage	5.70%
Unsecured Debt [Member] | $325.0M 4.950% Guaranteed Notes due 2018	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	325
Debt Instrument, Interest Rate, Stated Percentage	4.95%
Unsecured Debt [Member] | $250.0M 3.950% Guaranteed Notes due 2023	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	250
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Unsecured Debt [Member] | Three Year Term Loan [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument Term	'3 years
Option to Extend Term Loan	'1 year
Unsecured Debt [Member] | Four-Year Term Loan - Variable [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument Term	'4 years
Option to Extend Term Loan	'1 year
Debt Instrument, Basis Spread on Variable Rate	1.75%
Unsecured Debt [Member] | Letter of Credit [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Basis Spread on Variable Rate	1.50%
Unsecured Debt [Member] | Three and Four Year Term Loan [Member]	'
Debt Instrument [Line Items]	'
Derivative, Lower Remaining Maturity Range	'3 years
Derivative, Higher Remaining Maturity Range	'4 years
Unsecured Debt [Member] | Seven Year Term Loan [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	200
Debt Instrument Term	'7 years
Unsecured Debt [Member] | Note 2024 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	250
Debt Instrument, Interest Rate, Stated Percentage	4.10%
Unsecured Debt [Member] | Note 2029 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	250
Senior notes 5.400 Percent due 2014 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	5.40%
Senior Notes Due2015 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	7.50%

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Company's estimates of fair value differ from the carrying amounts	'	'
Mortgage notes payable	$658,601	$670,151
Mortgage notes payable, Fair Value	691,022	715,244
Unsecured Notes Payable, Carrying Amount	1,776,169	1,396,620
Unsecured Notes Payable, Fair Value	1,848,107	1,471,041
Variable Rate Debt, Carrying Amount	278,610	528,610
Variable Rate Debt, Fair Value	257,212	526,693
Notes Receivable, Carrying Amount	1,901	7,026
Notes Receivable, Fair Value	$3,517	$7,759

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments (Details Textuals) (Details)	9 Months Ended
	Sep. 30, 2014
Notes Receivable [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Fair Value Inputs, Discount Rate	14.66%
Variable rate and mortgage debt [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Fair Value Inputs, Discount Rate	4.01%

Risk_Management_and_Use_of_Fin2

Risk Management and Use of Financial Instruments (Fair Values of Derivative Financial Instruments) (Details) (USD $)

0 Months Ended

3 Months Ended

9 Months Ended

In Thousands, unless otherwise specified

Sep. 16, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 16, 2014

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Sep. 30, 2014

Dec. 31, 2013

Other Assets [Member]

Other Assets [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

3.300% Interest Rate Swap Maturing January 30, 2021 [Member]

3.300% Interest Rate Swap Maturing January 30, 2021 [Member]

3.090% Interest Rate Swap Maturing October 30, 2019 [Member]

3.090% Interest Rate Swap Maturing October 30, 2019 [Member]

3.623% Interest Rate Swap Maturing February 1, 2019 [Member]

3.623% Interest Rate Swap Maturing February 1, 2019 [Member]

2.703% Interest Rate Swap Maturing February 1, 2016 [Member]

2.703% Interest Rate Swap Maturing February 1, 2016 [Member]

2.470% Interest Rate Swap Maturing February 1, 2015 [Member]

2.470% Interest Rate Swap Maturing February 1, 2015 [Member]

2.513% Interest Rate Swap Maturing May 1, 2015 [Member]

2.513% Interest Rate Swap Maturing May 1, 2015 [Member]

2.750% Interest Rate Swap Maturing September 30, 2017 [Member]

2.750% Interest Rate Swap Maturing September 30, 2017 [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Cash Flow Hedging [Member]

Other Assets [Member]

Other Assets [Member]

Other Liabilities [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Other Assets [Member]

Other Assets [Member]

Other Assets [Member]

Other Assets [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Other Liabilities [Member]

Derivatives, Fair Value [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Long Term Debt Maturities Repayments Of Principal

'

$2,721,460

'

$2,721,460

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Notional Amount

'

'

'

'

'

'

'

'

'

'

'

150,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Liability, Notional Amount

'

'

'

'

'

'

'

227,062

377,062

'

'

'

'

'

'

'

200,000

200,000

0

77,000

0

50,000

0

23,000

27,062

27,062

Derivative, Fixed Interest Rate

'

'

'

'

'

'

'

'

'

'

'

'

3.30%

'

3.09%

'

3.62%

'

2.70%

'

2.47%

'

2.51%

'

2.75%

'

Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement

'

'

'

'

'

'

'

'

'

91

767

'

68

549

23

218

'

'

'

'

'

'

'

'

'

'

Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-1,243

-545

0

-887

0

-283

0

-162

-181

-311

Derivative Asset, Notional Amount

'

'

'

'

'

51,548

51,548

'

'

'

'

'

25,774

25,774

25,774

25,774

'

'

'

'

'

'

'

'

'

'

Derivative, Fair Value, Net

'

'

'

'

'

'

'

-1,424

-2,188

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Recognized hedge activity

$800

($828)

$0

($828)

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Apr. 07, 2014	Feb. 25, 2014	Sep. 30, 2013	Sep. 30, 2013
					Princeton Pike Corporate Center [Member]	Princeton Pike Corporate Center [Member]	Discontinued Operations [Member]	Discontinued Operations [Member]
Revenue:	'	'	'	'	'	'	'	'
Rents	$120,288	$116,382	$363,581	$347,054	'	'	$96	$4,754
Termination fees	1,418	2,040	6,970	2,946	'	'	0	0
Other Real Estate Revenue	825	975	2,295	3,305	'	'	0	123
Tenant reimbursements	20,095	20,694	64,057	60,595	'	'	10	355
Total revenue	146,558	143,354	449,172	423,552	'	'	106	5,232
Expenses:	'	'	'	'	'	'	'	'
Property operating expenses	42,675	40,639	132,612	119,421	'	'	62	1,773
Real estate taxes	12,869	14,167	39,167	42,639	'	'	39	623
Depreciation and amortization	52,616	50,583	157,773	149,300	'	'	48	1,893
Total operating expenses	115,747	113,142	354,771	335,788	'	'	149	4,289
Interest income	528	268	1,298	448	'	'	0	3
Income from discontinued operations before gain on sale of interests in real estate	0	-43	18	946	'	'	-43	946
Net gain on disposition of discontinued operations	-3	-16	900	3,029	900	5,300	-16	3,029
Income (Loss) from discontinued operations	($3)	($59)	$918	$3,975	'	'	($59)	$3,975

Discontinued_Operations_Detail1

Discontinued Operations (Details Textuals) (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Apr. 07, 2014	Feb. 25, 2014	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2013
					Princeton Pike Corporate Center [Member]	Princeton Pike Corporate Center [Member]	Discontinued Operations [Member]	Discontinued Operations [Member]	Discontinued Operations [Member]
									Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'	'	'
Net gain on disposition of discontinued operations	($3)	($16)	$900	$3,029	$900	$5,300	($16)	$3,029	'
Number of properties sold	'	'	'	'	'	'	'	'	14

Non_Controlling_Interests_In_t1

Non Controlling Interests In the Parent Company (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Noncontrolling Interest [Abstract]	'	'
Aggregate amount related to non-controlling interests classified within equity	$19.90	$20.30
Settlement Value Of Non Controlling Interest In Operating Partnership	$24.20	$24.80

Beneficiaries_Equity_of_the_Pa2

Beneficiaries Equity of the Parent Company (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]	'	'	'	'
Stock Issued During Period, Shares, New Issues	'	'	21,850,000	'
Numerator	'	'	'	'
Income (Loss) from Continuing Operations, Basic	$8,885	$11,147	$7,893	$18,212
Income (Loss) From Continuing Operations, Diluted	8,885	11,147	7,893	18,212
Noncontrolling Interest in Net Income (Loss) Limited Partnerships, Redeemable	84	106	35	143
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-24	0	-12	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted	-24	0	-12	0
Nonfofeitbale dividends allocated to unvested restricted shareholders	82	85	268	278
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted	82	85	268	278
Preferred share/unit dividends, Basic	-1,725	-1,725	-5,175	-5,175
Preferred share/unit dividends, Diluted	-1,725	-1,725	-5,175	-5,175
Income (Loss) from continuing operations available to common unitholders, Basic	6,970	9,231	2,403	12,616
Income (Loss) from continuing operations available to common unitholders, Diluted	6,970	9,231	2,403	12,616
Income (Loss) from Discontinued Operations	-3	-59	918	3,975
Income (Loss) From Discontinued Operations, Diluted	-3	-59	918	3,975
Net (income) loss from discontinued operations attributable to non-controlling interests — LP units	0	1	-10	-52
Discontinued Operations Attributable to Noncontrolling Interests- Diluted	0	1	-10	-52
Discontinued operations attributable to common shareholders, Basic	-3	-58	908	3,923
Discontinued operations attributable to common shareholders, Diluted	-3	-58	908	3,923
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	6,967	9,173	3,311	16,539
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	$6,967	$9,173	$3,311	$16,539
Denominator	'	'	'	'
Weighted Average Number of Shares Outstanding, Basic	171,606,722	156,703,348	161,866,955	151,933,441
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,587,148	1,288,734	1,487,015	1,209,384
Weighted Average Number of Shares Outstanding, Diluted	173,193,870	157,992,082	163,353,970	153,142,825
Earnings per common share from continuing operations Abstract	'	'	'	'
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$0.04	$0.06	$0.01	$0.08
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	$0.04	$0.06	$0.01	$0.08
Discontinued Operations attributable to common shareholders/unitholders, Basic	$0	$0	$0.01	$0.03
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$0	$0	$0.01	$0.03
Net income (loss) attributable to common shareholders/unitholders, Basic	$0.04	$0.06	$0.02	$0.11
Net income attributable to common shareholders/unitholders, Diluted	$0.04	$0.06	$0.02	$0.11

Beneficiaries_Equity_of_the_Pa3

Beneficiaries Equity of the Parent Company (Details Textuals) (Details) (USD $)

3 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

In Thousands, except Share data, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

15-May-14

14-May-14

Sep. 30, 2014

Sep. 30, 2014

Nov. 05, 2013

Oct. 06, 2014

Oct. 15, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Oct. 06, 2014

Series E Preferred Stock [Member]

Offering Program [Member]

Offering Program [Member]

Dividend Paid [Member]

Dividend Paid [Member]

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.

Series E Preferred Stock [Member]

Dividend Paid [Member]

Class of Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share

$0.04

$0.06

$0.01

$0.08

'

'

'

'

'

'

'

'

$0.04

$0.06

$0.01

$0.08

'

'

Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share

$0.04

$0.06

$0.01

$0.08

'

'

'

'

'

'

'

'

$0.04

$0.06

$0.01

$0.08

'

'

Discontinued Operations attributable to common shareholders/unitholders, Basic

$0

$0

$0.01

$0.03

'

'

'

'

'

'

'

'

$0

$0

$0.01

$0.03

'

'

Stock Issued During Period, Shares, New Issues

'

'

21,850,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Issuance of Common Stock

'

'

$335,016

$181,527

'

'

'

'

'

'

'

'

'

'

$335,016

$181,527

'

'

Distributions payable

28,857

'

28,857

'

25,584

'

'

'

'

'

27,200

'

28,857

'

28,857

'

25,584

27,200

Preferred Stock, Shares Issued

4,000,000

'

4,000,000

'

4,000,000

'

'

'

'

'

'

'

4,000,000

'

4,000,000

'

4,000,000

'

Preferred Stock, Dividend Rate, Percentage

'

'

6.90%

'

6.90%

'

'

6.90%

'

'

'

'

'

'

6.90%

'

6.90%

'

Preferred Stock, Liquidation Preference Per Share

'

'

'

'

'

'

'

$25

'

'

'

'

'

'

'

'

'

'

Dividends, Preferred Stock, Cash

'

'

$5,175

$5,175

'

'

'

'

'

'

'

$1,700

'

'

'

'

'

'

Shares of Beneficial Interest, Shares Authorized

'

'

'

'

'

420,000,000

220,000,000

'

'

'

'

'

'

'

'

'

'

'

Shares Authorized For Equity Offering Program

'

'

'

'

'

'

'

'

'

16,000,000

'

'

'

'

'

'

'

'

Remaining Shares Available For Sales

'

'

'

'

'

'

'

'

16,000,000

'

'

'

'

'

'

'

'

'

Common Stock, Shares Authorized

400,000,000

'

400,000,000

'

200,000,000

400,000,000

200,000,000

'

'

'

'

'

'

'

'

'

'

'

Preferred Stock, Shares Authorized

20,000,000

'

20,000,000

'

20,000,000

20,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased

539,200

'

539,200

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Discontinued Operations attributable to common shareholders/unitholders, Diluted

$0

$0

$0.01

$0.03

'

'

'

'

'

'

'

'

$0

$0

$0.01

$0.03

'

'

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

$0.04

$0.06

$0.02

$0.11

'

'

'

'

'

'

'

'

$0.04

$0.06

$0.02

$0.11

'

'

Net income attributable to common shareholders/unitholders, Diluted

$0.04

$0.06

$0.02

$0.11

'

'

'

'

'

'

'

'

$0.04

$0.06

$0.02

$0.11

'

'

Partners_Equity_of_the_Operati2

Partners Equity of the Operating Partnership (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator	'	'	'	'
Income (Loss) from Continuing Operations, Basic	$8,885	$11,147	$7,893	$18,212
Income (Loss) From Continuing Operations, Diluted	8,885	11,147	7,893	18,212
Nonfofeitbale dividends allocated to unvested restricted shareholders	82	85	268	278
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted	82	85	268	278
Preferred share/unit dividends, Basic	-1,725	-1,725	-5,175	-5,175
Preferred share/unit dividends, Diluted	-1,725	-1,725	-5,175	-5,175
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-24	0	-12	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted	24	0	12	0
Income (Loss) from continuing operations available to common unitholders, Basic	6,970	9,231	2,403	12,616
Income (Loss) from continuing operations available to common unitholders, Diluted	6,970	9,231	2,403	12,616
Income (Loss) from Discontinued Operations	-3	-59	918	3,975
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	6,967	9,173	3,311	16,539
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	6,967	9,173	3,311	16,539
Denominator	'	'	'	'
Weighted-average units outstanding, Basic	171,606,722	156,703,348	161,866,955	151,933,441
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,587,148	1,288,734	1,487,015	1,209,384
Weighted Average Number of Shares Outstanding, Diluted	173,193,870	157,992,082	163,353,970	153,142,825
Earnings per Common Partnership Unit [Abstract]	'	'	'	'
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$0.04	$0.06	$0.01	$0.08
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	$0.04	$0.06	$0.01	$0.08
Discontinued Operations attributable to common shareholders/unitholders, Basic	$0	$0	$0.01	$0.03
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$0	$0	$0.01	$0.03
Net income (loss) attributable to common shareholders/unitholders, Basic	$0.04	$0.06	$0.02	$0.11
Net income attributable to common shareholders/unitholders, Diluted	$0.04	$0.06	$0.02	$0.11
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'	'	'
Numerator	'	'	'	'
Income (Loss) from Continuing Operations, Basic	8,885	11,147	7,893	18,212
Income (Loss) From Continuing Operations, Diluted	8,885	11,147	7,893	18,212
Nonfofeitbale dividends allocated to unvested restricted shareholders	82	85	268	278
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted	82	85	268	278
Preferred share/unit dividends, Basic	-1,725	-1,725	-5,175	-5,175
Preferred share/unit dividends, Diluted	-1,725	-1,725	-5,175	-5,175
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-24	0	-12	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted	24	0	12	0
Income (Loss) from continuing operations available to common unitholders, Basic	7,054	9,337	2,438	12,759
Income (Loss) from continuing operations available to common unitholders, Diluted	7,054	9,337	2,438	12,759
Income (Loss) from Discontinued Operations	-3	-59	918	3,975
Income (Loss) From Discontinued Operations, Diluted	-3	-59	918	3,975
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	7,051	9,278	3,356	16,734
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	$7,051	$9,278	$3,356	$16,734
Denominator	'	'	'	'
Weighted-average units outstanding, Basic	173,341,782	158,467,087	163,620,963	153,731,070
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	1,587,148	1,288,734	1,487,015	1,209,384
Weighted Average Number of Shares Outstanding, Diluted	174,928,930	159,755,821	165,107,978	154,940,454
Earnings per Common Partnership Unit [Abstract]	'	'	'	'
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	$0.04	$0.06	$0.01	$0.08
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	$0.04	$0.06	$0.01	$0.08
Discontinued Operations attributable to common shareholders/unitholders, Basic	$0	$0	$0.01	$0.03
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$0	$0	$0.01	$0.03
Net income (loss) attributable to common shareholders/unitholders, Basic	$0.04	$0.06	$0.02	$0.11
Net income attributable to common shareholders/unitholders, Diluted	$0.04	$0.06	$0.02	$0.11

Partners_Equity_of_the_Operati3

Partners Equity of the Operating Partnership (Details Textuals) (Details) (USD $)

9 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

9 Months Ended

0 Months Ended

In Thousands, except Share data, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Oct. 06, 2014

Oct. 06, 2014

Oct. 15, 2014

Sep. 10, 2014

Sep. 10, 2014

BRANDYWINE OPERATING PARTNERSHIP, L.P.

BRANDYWINE OPERATING PARTNERSHIP, L.P.

BRANDYWINE OPERATING PARTNERSHIP, L.P.

Class A Units [Member]

Class A Units [Member]

6.90% Series E-linked Preferred Units [Member]

Dividend Paid [Member]

Dividend Paid [Member]

Dividend Paid [Member]

Dividend Declared [Member]

Dividend Declared [Member]

BRANDYWINE OPERATING PARTNERSHIP, L.P.

BRANDYWINE OPERATING PARTNERSHIP, L.P.

6.90% Series E-linked Preferred Units [Member]

BRANDYWINE OPERATING PARTNERSHIP, L.P.

BRANDYWINE OPERATING PARTNERSHIP, L.P.

Earnings per Common Partnership Unit [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount

'

'

'

'

'

'

1,721,905

1,763,739

'

'

'

'

'

'

Dividends Payable, Amount Per Share

'

'

'

'

'

'

'

'

'

'

'

'

$0.15

$0.15

Stock Issued During Period, Shares, New Issues

21,850,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Issuance of Common Stock

$335,016

$181,527

'

$335,016

$181,527

'

'

'

'

'

'

'

'

'

Distributions payable

28,857

'

25,584

28,857

'

25,584

'

'

'

27,200

27,200

'

'

'

Preferred Stock, Dividend Rate, Percentage

6.90%

'

6.90%

6.90%

'

6.90%

'

'

6.90%

'

'

'

'

'

Preferred Stock, Liquidation Preference Per Share

'

'

'

'

'

'

'

'

$25

'

'

'

'

'

Dividends, Preferred Stock, Cash

$5,175

$5,175

'

'

'

'

'

'

'

'

'

$1,700

'

'

Share_Based_and_Deferred_Compe2

Share Based and Deferred Compensation (Option Activity) (Details) (USD $)	9 Months Ended	12 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2014
			Stock Option [Member]	Stock Option [Member]	Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'
Allocated Share-based Compensation Expense	'	'	$200,000	$600,000	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	'4 years 5 months 0 days	'5 years 1 month 25 days	'	'	'
Share Based Compensation Arrangement By Share Based Payment Award Option Activity [Abstract]	'	'	'	'	'
Outstanding at the beginning of year, shares	2,983,569	'	'	'	2,808,784
Outstanding at beginning of year, Weighted Average Exercise Price	$15.50	'	'	'	'
Outstanding at beginning of year, Aggregate Intrinsic Value	0	'	'	'	'
Granted, shares	0	'	'	'	'
Granted, Weighted Average Grant Date Fair Value	'	'	'	'	'
Exercised in Period, Shares	-60,127	'	'	'	'
Exercises in Period, Weighted Average Grant Date Fair Value	$11.80	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	182,101	'	'	'	'
Forfeited, shares	-114,658	'	'	'	'
Forfeited, Weighted Average Grant Date Fair Value	$20.61	'	'	'	'
Outstanding at the end of year, shares	2,808,784	2,983,569	'	'	2,808,784
Outstanding at end of year, Weighted Average Exercise Price	$15.37	$15.50	'	'	'
Outstanding at end of year, Aggregate Intrinsic Value	0	0	'	'	'
Vested/Exerciseable, shares	2,808,784	'	'	'	'
Vested/Exerciseable at end of period, Weigted Average Exercise Price	$15.37	'	'	'	'
Vested/Exerciseable at end of period, Weighted Average Remaining Contractual Term (in years)	'4 years 5 months 0 days	'	'	'	'
Vested/Exercisable at end of year, Aggregate Intrinsic Value	0	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	'	'	'	$100,000	'

Share_Based_and_Deferred_Compe3

Share Based and Deferred Compensation (Restricted Share Activity) (Details) (Restricted Stock [Member], USD $)	0 Months Ended	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	29-May-14	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Mar. 12, 2014	Mar. 11, 2014
						Executive Officer [Member]	Executive Officer [Member]	Executive Officer [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	'	'	'	'	'	67,002	'	'
Allocated Share-based Compensation Expense	'	$0.40	$0.90	$2.30	$2.60	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	'	$0.10	$0.10	$0.50	$0.40	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	'	'	'	'	'	'	69,794	131,641
Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period	'	'	'	'	'	'15 years	'	'
Non-vested at January 1, 2013, shares	'	'	'	563,713	'	'	'	'
Non-vested at January 1, 2013, Weighted Average Grant Date Fair Value	'	'	'	$12.56	'	'	'	'
Granted, Equity Instruments Other than Options, Grants in Period	27,684	'	'	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	'	'	'	-9,488	'	'	'	'
Forfeited, Weighted Average Grant Date Fair Value	'	'	'	$12.57	'	'	'	'
Non-vested at June 30, 2013, shares	'	549,175	'	549,175	'	'	'	'
Non-vested at June 30, 2013, Weighted Average Grant Date Fair Value	'	$12.22	'	$12.22	'	'	'	'

Share_Based_and_Deferred_Compe4

Share Based and Deferred Compensation (Details Textuals) (Details) (USD $)

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

0 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

0 Months Ended

12 Months Ended

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2014

Sep. 30, 2014

Mar. 01, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Feb. 07, 2014

Sep. 30, 2014

Mar. 12, 2014

Mar. 11, 2014

Mar. 11, 2014

Mar. 12, 2014

Mar. 01, 2012

Feb. 25, 2014

Feb. 25, 2013

Stock Option [Member]

Stock Option [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Minimum [Member]

Maximum [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Stock [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [Member]

Restricted Performance Share Units Plan [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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

69,794

131,641

134,284

61,720

265,222

'

231,093

Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,792

'

'

'

'

'

'

'

Voluntary Termination Of Employment Terms

'

'

'

'

'

'after reaching age 57 and accumulating at least 15 years of service with the Company

'

'

'

'

'

'

'

'after reaching age 57 and accumulating at least 15 years of service with the Company

'

'

'

'

'

'

'

'

'

'

Accumulated Service Period For Voluntary Termination

'

'

'

'

'

'15 years

'

'

'

'

'

'

'

'15 years

'

'

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Term, Minimum

'3 years

'

'

'

'

'3 years

'

'

'3 years

'7 years

'

'

'

'3 years

'

'

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

'

'

'

'

'

'three years from the initial grant dates

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Maximum Percentage Of Participants Base Units

'

'

'

'

'

'

'

'

'

'

'

'

'

200.00%

'

'

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$2,624,000

$1,225,000

$4,273,000

$4,137,000

'

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number

'

'

'

549,175

'

549,175

'

563,713

'

'

'

'

'

'

'

'

'

'

'

134,284

61,720

211,521

'

203,395

Vested/Exerciseable, shares

2,808,784

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition

'

'

'

'

'

'1 year 8 months 2 days

'

'

'

'

'

'

'

'1 year 2 months 2 days

'

'

'

'

'

'

'

'

'

'

Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized

'

'

'

2,500,000

'

2,500,000

'

'

'

'

'

2,700,000

'

2,700,000

'

'

'

'

'

'

'

'

'

'

Allocated Share-based Compensation Expense

'

200,000

600,000

400,000

900,000

2,300,000

2,600,000

'

'

'

'

500,000

1,300,000

2,800,000

3,700,000

'

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period

'

'

'

'

'

234,169

'

'

'

'

150,829

'

'

'

'

'

'

'

'

'

'

'

'

'

Age Limit Of Voluntary Termination Of Employment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

57

'

'

'

'

'

'

'

Dividends Payable, Amount Per Share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$0.15

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost

'

'

$100,000

$100,000

$100,000

$500,000

$400,000

'

'

'

'

$200,000

$200,000

$900,000

$600,000

'

'

'

'

'

'

'

'

'

Share_Based_and_Deferred_Compe5

Share Based and Deferred Compensation Restricted Performance Share Units (Details) (Restricted Performance Share Units Plan [Member], USD $)

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

12 Months Ended

9 Months Ended

0 Months Ended

Mar. 01, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Mar. 11, 2014

Mar. 12, 2014

Mar. 01, 2012

Feb. 25, 2014

Feb. 25, 2013

Sep. 30, 2014

Oct. 31, 2012

Oct. 31, 2012

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Executive Officer [Member]

Original Grant [Member]

Dividend equivalent shares vested [Member]

Total vested [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Age Limit Of Voluntary Termination Of Employment

'

'

'

'

'

'

'

'

'

'

57

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Award Requisite Service Period

'

'

'

'

'

'

'

'

'

'

'15 years

'

'

Allocated Share-based Compensation Expense

'

$500,000

$1,300,000

$2,800,000

$3,700,000

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost

'

200,000

200,000

900,000

600,000

'

'

'

'

'

'

'

'

Fair Value of Units on Grant Date

'

'

'

'

'

2,624,000

1,225,000

4,273,000

4,137,000

'

'

'

'

Units Granted

'

'

'

'

'

134,284

61,720

265,222

'

231,093

'

'

'

Units Canceled

'

'

'

'

'

'

'

38,959

27,698

'

'

'

'

Units Vested

-150,829

'

'

'

'

'

'

'

'

'

-14,742

[1]

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period

'

'

'

'

'

'

'

'

'

'

'

563

30,610

Unvested Balance

'

'

'

'

'

134,284

61,720

211,521

'

203,395

'

'

'

Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized

'

$2,700,000

'

$2,700,000

'

'

'

'

'

'

'

'

'

Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition

'

'

'

'1 year 2 months 2 days

'

'

'

'

'

'

'

'

'

[1]

(a) These RPSUs were settled upon the holder’s qualifying retirement in October 2012 after reaching age 57 and accumulating at least 15 years of service with the Company. Of the 14,742 RPSU's originally granted, 563 dividend equivalent rights had accrued at the time of qualifying retirement. In accordance with the pay-out formula in the award agreement, on October 31, 2012, the Company issued 30,610 common shares in settlement of the RPSU's based on the Company’s total shareholder return relative to the comparator groups.

Segment_Information_Details

Segment Information (Details) (USD $)	0 Months Ended	3 Months Ended			9 Months Ended
In Thousands, unless otherwise specified	Sep. 16, 2014	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Net gain on sale of interests in real estate	'	'		'	($5,882)		($3,044)	'
Operating properties	'	-4,608,895		'	-4,608,895		'	-4,669,289
Construction-in-progress	'	140,456		'	140,456		'	74,174
Land inventory	'	90,842		'	90,842		'	93,351
Investment in real estate ventures, at equity	'	197,539		'	197,539		'	180,512
Total revenue	'	146,558		143,354	449,172		423,552	'
Property operating expenses	'	-57,231		-56,123	-176,912		-166,165	'
Gross Profit	'	89,327		87,231	272,260		257,387	'
Equity in income (loss) of real estate ventures	'	-486		714	-733		3,757	'
Depreciation and amortization	'	52,616		50,583	157,773		149,300	'
General and administrative expenses	'	5,900		6,436	20,086		20,323	'
Interest Expense, Debt	'	31,481		30,338	94,837		91,689	'
Amortization of deferred financing costs	'	1,566		1,158	3,952		3,502	'
Interest Expense, Other	'	273		264	861		693	'
Loss on early extinguishment of debt	2,606	-2,606		-11	-2,606		-1,127	'
Gain (Loss) on sale of undepreciated real estate	'	0		-129	1,184		-129	'
Income (Loss) from Continuing Operations, Basic	'	8,885		11,147	7,893		18,212	'
Income (Loss) from Discontinued Operations	'	-3		-59	918		3,975	'
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	'	8,882		11,088	8,811		22,187	'
Philadelphia CBD [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-1,327,288		'	-1,327,288		'	-1,300,666
Investment in real estate ventures, at equity	'	20,779		'	20,779		'	19,975
Total revenue	'	49,469		35,891	150,303		107,957	'
Property operating expenses	'	-18,168		-13,704	-55,399		-40,825	'
Gross Profit	'	31,301		22,187	94,904		67,132	'
Equity in income (loss) of real estate ventures	'	32		405	13		1,548	'
Pennsylvania [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-1,230,785		'	-1,230,785		'	-1,199,105
Investment in real estate ventures, at equity	'	17,739		'	17,739		'	17,272
Total revenue	'	39,996		39,167	121,313		114,085	'
Property operating expenses	'	-13,409		-13,884	-41,542		-42,536	'
Gross Profit	'	26,587		25,283	79,771		71,549	'
Equity in income (loss) of real estate ventures	'	-578		55	-937		643	'
Metropolitan Dc [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-1,178,942		'	-1,178,942		'	-1,214,965
Investment in real estate ventures, at equity	'	67,800		'	67,800		'	59,905
Total revenue	'	27,764		29,321	87,403		85,889	'
Property operating expenses	'	-10,672		-10,321	-33,134		-31,856	'
Gross Profit	'	17,092		19,000	54,269		54,033	'
Equity in income (loss) of real estate ventures	'	-142		60	-117		41	'
New Jersey/ Delaware [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-418,419		'	-418,419		'	-414,716
Investment in real estate ventures, at equity	'	0		'	0		'	0
Total revenue	'	14,975		15,330	45,440		45,273	'
Property operating expenses	'	-7,506		-8,203	-23,728		-22,105	'
Gross Profit	'	7,469		7,127	21,712		23,168	'
Equity in income (loss) of real estate ventures	'	82		79	204		1,154	'
Richmond, Virginia [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-311,350		'	-311,350		'	-310,397
Investment in real estate ventures, at equity	'	1,478		'	1,478		'	1,400
Total revenue	'	8,354		8,640	25,543		26,359	'
Property operating expenses	'	-3,724		-3,734	-11,629		-11,017	'
Gross Profit	'	4,630		4,906	13,914		15,342	'
Equity in income (loss) of real estate ventures	'	184		108	253		344	'
Austin, Texas [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	0	[1]	'	0	[1]	'	-36,856
Investment in real estate ventures, at equity	'	89,743		'	89,743		'	81,960
Total revenue	'	843		9,938	3,900		29,067	'
Property operating expenses	'	-569		-3,958	-2,362		-12,123	'
Gross Profit	'	274		5,980	1,538		16,944	'
Equity in income (loss) of real estate ventures	'	-64		7	-149		27	'
Operating Segments [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-4,659,864		'	-4,659,864		'	-4,669,289
Assets Held-for-sale [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-50,969	[2]	'	-50,969	[2]	'	0
California	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Operating properties	'	-193,080		'	-193,080		'	-192,584
Total revenue	'	4,902		4,632	14,399		13,773	'
Property operating expenses	'	-2,711		-2,531	-7,634		-7,029	'
Gross Profit	'	2,191		2,101	6,765		6,744	'
Corporate [Member]	'	'		'	'		'	'
Real Estate Investments At Cost [Abstract]	'	'		'	'		'	'
Construction-in-progress	'	140,456		'	140,456		'	74,174
Land inventory	'	90,842		'	90,842		'	93,351
Total revenue	'	255		435	871		1,149	'
Property operating expenses	'	-472		212	-1,484		1,326	'
Gross Profit	'	($217)		$647	($613)		$2,475	'
Durham, NC [Member]	'	'		'	'		'	'
Segment Reporting Information [Line Items]	'	'		'	'		'	'
Number of Real Estate Properties	'	1		'	1		'	'
[1]	(a)On April 3, 2014, the Company contributed Four Points Centre to an unconsolidated joint venture. See Note 3 for further information on the contribution. Following this contribution, the Company has no wholly-owned properties in the Austin, Texas segment.
[2]	(b)On September 30, 2014, the Company was actively marketing for sale of its Valleybrooke Office Park, comprised of five properties located in the Pennsylvania Suburbs segment. As of September 30, 2014 the properties were classified as held for sale on the consolidated balance sheet. The sale is not classified as a significant disposition under the accounting guidance for discontinued operations. Accordingly, the real estate investments remained in the Pennsylvania Suburbs segment as of September 30, 2014.

Segment_Information_Reconcilia

Segment Information (Reconciliation of Consolidated Net Operating Income) (Details) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 16, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
				Reportable_Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'	'	'	'
Consolidated net operating income	'	$89,327	$87,231	$272,260	$257,387
Other income (expense):	'	'	'	'	'
Depreciation and amortization	'	-52,616	-50,583	-157,773	-149,300
General and administrative expenses	'	-5,900	-6,436	-20,086	-20,323
Interest income	'	528	268	1,298	448
Interest expense	'	-31,481	-30,338	-94,837	-91,689
Recognized hedge activity	800	-828	0	-828	0
Amortization of deferred financing costs	'	-1,566	-1,158	-3,952	-3,502
Interest expense — financing obligation	'	-273	-264	-861	-693
Equity in income (loss) of real estate ventures	'	-486	714	-733	3,757
Net gain on disposition of real estate	'	4,698	0	4,698	0
Gain (Loss) on sale of undepreciated real estate	'	0	-129	1,184	-129
Net gain from remeasurement of investment in RE ventures	'	0	0	458	7,847
Net gain (loss) on real estate venture transactions	'	0	0	-417	3,683
Loss on early extinguishment of debt	2,606	-2,606	-11	-2,606	-1,127
Provision for impairment on assets held for sale	'	-1,765	0	-1,765	0
Historic tax credit transaction income	'	-11,853	-11,853	-11,853	-11,853
Discontinued Operations attributable to common shareholders/unitholders, Basic	'	$0	$0	$0.01	$0.03
Income from continuing operations	'	8,885	11,147	7,893	18,212
Income (Loss) from Discontinued Operations	'	-3	-59	918	3,975
Net income	'	$8,882	$11,088	$8,811	$22,187
Number of Reportable Segments	'	'	'	7	'

Commitments_and_Contingencies_1

Commitments and Contingencies (Details)	Sep. 30, 2014
	Y
Long-term Purchase Commitment [Line Items]	'
Minimum remaining lease period	7
Maximum remaining lease period	75

Commitments_and_Contingencies_2

Commitments and Contingencies (Ground Rent) (Details) (Ground Rent [Member], USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified
Ground Rent [Member]	'
Long-term Purchase Commitment [Line Items]	'
2014 (three months remaining)	$345
2014	1,380
2015	1,380
2016	1,380
2017	1,380
Thereafter	58,515
Operating Leases, Future Minimum Payments Due	$64,380

Subsequent_Events_Details

Subsequent Events (Details) (USD $)

0 Months Ended

3 Months Ended

9 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

Sep. 16, 2014

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Oct. 24, 2014

Oct. 21, 2014

Oct. 17, 2014

Oct. 17, 2014

Oct. 21, 2014

Oct. 17, 2014

Oct. 21, 2014

Oct. 17, 2014

Oct. 16, 2014

Oct. 16, 2014

Oct. 16, 2014

Valleybrooke Office Park [Member]

Valleybrooke Office Park [Member]

1919 Venture [Member]

River Place [Member]

River Place [Member]

Brandywine Realty Trust [Member]

Brandywine Realty Trust [Member]

LCOR/Calstrs [Member]

DRA Advisors LLC [Member]

2014 5.400% Notes

2015 7.500% Notes

Note Four and Five [Member]

sqft

1919 Venture [Member]

River Place [Member]

1919 Venture [Member]

River Place [Member]

Debt Instrument, Redemption [Member]

Debt Instrument, Redemption [Member]

Debt Instrument, Redemption [Member]

Real_Estate_Investments

Subsequent Event [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sale Consideration Of Sold Property

'

'

'

'

'

'

$37,900,000

'

'

'

'

'

'

'

'

'

'

Provision for impairment on assets held for sale

'

1,765,000

0

1,765,000

0

1,765,000

'

'

'

'

'

'

'

'

'

'

'

Equity Method Investment, Ownership Percentage

'

'

'

'

'

'

'

50.00%

'

'

'

'

'

'

'

'

'

Amount Of Participant Contribution

'

'

'

'

'

'

'

'

'

'

'

'

8,200,000

'

'

'

'

General Partners' Contributed Capital

'

'

'

'

'

'

'

'

'

'

5,200,000

'

'

'

'

'

'

Aggregate gross sales price of a joint venture

'

'

'

'

'

'

'

16,400,000

'

'

'

'

'

'

'

'

'

Equity Method Investment, Short-term Loan

'

'

'

'

'

'

'

'

88,000,000

'

'

'

'

'

'

'

'

Number of Real Estate Properties

'

'

'

'

'

'

'

'

'

7

'

'

'

'

'

'

'

Net Rentable Space

'

'

'

'

'

'

'

'

'

591,000

'

'

'

'

'

'

'

Equity method investment, Consideration transferred

'

'

'

'

'

'

'

'

128,100,000

'

'

'

'

'

'

'

'

Equity method investments, Cash contributions

'

'

'

'

'

'

'

'

'

'

'

20,000,000

'

20,000,000

'

'

'

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.

'

'

'

'

'

'

'

'

Long-term Debt, Gross

'

'

'

'

'

'

'

'

'

'

'

'

'

'

143,500,000

114,900,000

'

Debt Instrument, Interest Rate, Stated Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5.40%

7.50%

'

Repayments of Notes Payable

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

270,300,000

Loss on early extinguishment of debt

$2,606,000

($2,606,000)

($11,000)

($2,606,000)

($1,127,000)

'

'

'

'

'

'

'

'

'

'

'

$4,900,000