Brandywine Operating Partnership 10-Q 5 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	3 Months Ended
	Mar. 31, 2014	Apr. 30, 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	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	157,037,189
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	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
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 $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Real estate investments:	'	'
Operating properties	$4,701,289	$4,669,289
Accumulated depreciation	-1,019,306	-983,808
Operating real estate investments, net	3,681,983	3,685,481
Construction-in-progress	90,140	74,174
Land inventory	96,427	93,351
Total real estate investments, net	3,868,550	3,853,006
Cash and cash equivalents	236,291	263,207
Accounts receivable, net	23,123	17,389
Accrued rent receivable, net	128,331	126,295
Investment in real estate ventures, at equity	180,237	180,512
Deferred costs, net	123,216	122,954
Intangible assets, net	125,162	132,329
Other assets	75,138	69,403
Total assets	4,760,048	4,765,095
LIABILITIES AND BENEFICIARIES’ EQUITY	'	'
Mortgage notes payable	666,305	670,151
Unsecured term loans	450,000	450,000
Unsecured senior notes, net of discounts	1,475,501	1,475,230
Accounts payable and accrued expenses	106,963	83,693
Distributions payable	25,604	25,584
Deferred income, gains and rent	72,937	71,635
Acquired lease intangibles, net	32,229	34,444
Other liabilities	35,357	32,923
Total liabilities	2,864,896	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 200,000,000; 156,916,901 and 156,731,993 issued and outstanding in 2014 and 2013, respectively	1,567	1,566
Additional paid-in capital	2,974,094	2,971,596
Deferred compensation payable in common shares	6,267	5,407
Common shares in grantor trust, 384,571 in 2014 and 312,279 in 2013	-6,267	-5,407
Cumulative earnings	520,322	522,528
Accumulated other comprehensive loss	-3,905	-2,995
Cumulative distributions	1,617,878	1,592,515
Total equity, excluding non-controlling interest	1,874,240	1,900,220
Non-controlling interests	20,912	21,215
Total beneficiaries' equity	1,895,152	1,921,435
Total liabilities and beneficiaries' equity	4,760,048	4,765,095
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Real estate investments:	'	'
Operating properties	4,701,289	4,669,289
Accumulated depreciation	-1,019,306	-983,808
Operating real estate investments, net	3,681,983	3,685,481
Construction-in-progress	90,140	74,174
Land inventory	96,427	93,351
Total real estate investments, net	3,868,550	3,853,006
Cash and cash equivalents	236,291	263,207
Accounts receivable, net	23,123	17,389
Accrued rent receivable, net	128,331	126,295
Investment in real estate ventures, at equity	180,237	180,512
Deferred costs, net	123,216	122,954
Intangible assets, net	125,162	132,329
Other assets	75,138	69,403
Total assets	4,760,048	4,765,095
LIABILITIES AND BENEFICIARIES’ EQUITY	'	'
Mortgage notes payable	666,305	670,151
Unsecured term loans	450,000	450,000
Unsecured senior notes, net of discounts	1,475,501	1,475,230
Accounts payable and accrued expenses	106,963	83,693
Distributions payable	25,604	25,584
Deferred income, gains and rent	72,937	71,635
Acquired lease intangibles, net	32,229	34,444
Other liabilities	35,357	32,923
Total liabilities	2,864,896	2,843,660
Commitments and contingencies (Note 16)	'	'
Redeemable limited partnership units at redemption value;	'	'
Redeemable limited partnership units at redemption value; 1,763,739 issued and outstanding in 2014 and 2013, respectively	26,691	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, 156,916,901 and 156,731,993 units issued and outstanding in 2014 and 2013, respectively	1,774,950	1,800,530
Accumulated other comprehensive loss	-4,297	-3,377
Total equity, excluding non-controlling interest	1,867,503	1,894,003
Non-controlling interests	958	946
Total beneficiaries' equity	1,868,461	1,894,949
Total liabilities and beneficiaries' equity	4,760,048	4,765,095
Series E Preferred Stock [Member]	'	'
Equity:	'	'
Total beneficiaries' equity	$40	$40

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 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	200,000,000	200,000,000
Common Stock, Shares, Issued	156,916,901	156,731,993
Common Stock, Shares, Outstanding	156,916,901	156,731,993
Common shares in grantor trust	384,571	312,279
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	1,763,739	1,763,739
Redeemable Limited Partnership Units Outstanding	1,763,739	1,763,739
General Partners' Capital Account, Units Issued	156,916,901	156,731,993
General Partners' Capital Account, Units Outstanding	156,916,901	156,731,993

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Revenue:	'	'
Rents	$121,671	$114,608
Tenant reimbursements	23,460	20,341
Termination fees	2,203	496
Third party management fees, labor reimbursement and leasing	4,150	3,236
Other	630	873
Total revenue	152,114	139,554
Expenses:	'	'
Property operating expenses	46,801	39,349
Real estate taxes	13,457	14,295
Third party management expenses	1,716	1,425
Depreciation and amortization	52,570	49,476
General and administrative expenses	8,181	6,551
Total operating expenses	122,725	111,096
Operating Income	29,389	28,458
Other income (expense):	'	'
Interest income	385	58
Interest expense	-31,844	-30,914
Interest expense — amortization of deferred financing costs	-1,189	-1,161
Interest expense — financing obligation	-272	-218
Equity in income of real estate ventures	242	1,535
Net Gain (Loss) On Real Estate Venture Transactions, including real estate venture formation	-135	0
Gain on sale of undepreciated real estate	1,187	0
Loss on early extinguishment of debt	0	-3
Loss from continuing operations	-2,237	-2,245
Discontinued operations:	'	'
Income (Loss) from discontinued operations	-8	860
Net gain on disposition of discontinued operations	0	5,304
Total discontinued operations	-8	6,164
Net income (loss)	-2,245	3,919
Discontinued operations attributable to non-controlling interests, Basic	0	-78
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-12	0
Net (income) loss attributable to non-controlling interests — LP units	44	50
Net (income) loss attributable to non-controlling interests	32	-28
Net income (loss) attributable to Brandywine Realty Trust	-2,213	3,891
Distribution to Preferred Shares	-1,725	-1,725
Nonforfeitable dividends allocated to unvested restricted shareholders	-103	-108
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	-4,041	2,058
Basic income (loss) per Common Share:	'	'
Continuing operations	($0.03)	($0.03)
Discontinued operations	$0	$0.04
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.03)	$0.01
Diluted income (loss) per Common Share:	'	'
Continuing operations	($0.03)	($0.03)
Discontinued operations	$0	$0.04
Net income attributable to common shareholders/unitholders, Diluted	($0.03)	$0.01
Weighted Average Number of Shares Outstanding, Basic	156,794,019	143,605,659
Weighted Average Number of Shares Outstanding, Diluted	156,794,019	143,605,659
Net income (loss) attributable to Brandywine Realty Trust	'	'
Total continuing operations	-2,205	-2,195
Total discontinued operations	-8	6,086
Net income	-2,245	3,919
Net income (Loss) attributable to Brandywine Realty Trust	-2,213	3,891
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Revenue:	'	'
Rents	121,671	114,608
Tenant reimbursements	23,460	20,341
Termination fees	2,203	496
Third party management fees, labor reimbursement and leasing	4,150	3,236
Other	630	873
Total revenue	152,114	139,554
Expenses:	'	'
Property operating expenses	46,801	39,349
Real estate taxes	13,457	14,295
Third party management expenses	1,716	1,425
Depreciation and amortization	52,570	49,476
General and administrative expenses	8,181	6,551
Total operating expenses	122,725	111,096
Operating Income	29,389	28,458
Other income (expense):	'	'
Interest income	385	58
Interest expense	-31,844	-30,914
Interest expense — amortization of deferred financing costs	-1,189	-1,161
Interest expense — financing obligation	-272	-218
Equity in income of real estate ventures	242	1,535
Net Gain (Loss) On Real Estate Venture Transactions, including real estate venture formation	-135	0
Gain on sale of undepreciated real estate	1,187	0
Loss on early extinguishment of debt	0	-3
Loss from continuing operations	-2,237	-2,245
Discontinued operations:	'	'
Income (Loss) from discontinued operations	-8	860
Net gain on disposition of discontinued operations	0	5,304
Total discontinued operations	-8	6,164
Net income (loss)	-2,245	3,919
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-12	0
Net income (loss) attributable to Brandywine Realty Trust	-2,257	3,919
Distribution to Preferred Shares	-1,725	-1,725
Nonforfeitable dividends allocated to unvested restricted shareholders	-103	-108
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	-4,085	2,086
Basic income (loss) per Common Share:	'	'
Continuing operations	($0.03)	($0.03)
Discontinued operations	$0	$0.04
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.03)	$0.01
Diluted income (loss) per Common Share:	'	'
Continuing operations	($0.03)	($0.03)
Discontinued operations	$0	$0.04
Net income attributable to common shareholders/unitholders, Diluted	($0.03)	$0.01
Weighted Average Number of Shares Outstanding, Basic	158,557,758	145,451,396
Weighted Average Number of Shares Outstanding, Diluted	158,557,758	145,451,396
Net income (loss) attributable to Brandywine Realty Trust	'	'
Total continuing operations	-2,249	-2,245
Total discontinued operations	-8	6,164
Net income	-2,245	3,919
Net income (Loss) attributable to Brandywine Realty Trust	($2,257)	$3,919

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income Statement (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Net income (loss)	($2,245)	$3,919
Comprehensive Income (Loss)	'	'
Unrealized gain (loss) on derivative financial instruments	-980	1,845
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	60	48
Total comprehensive income (loss)	-920	1,893
Comprehensive Income	-3,165	5,812
Comprehensive (income) loss attributable to non-controlling interest	42	-52
Comprehensive income (loss) attributable to Brandywine Realty Trust	-3,123	5,760
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Net income (loss)	-2,245	3,919
Comprehensive Income (Loss)	'	'
Unrealized gain (loss) on derivative financial instruments	-980	1,845
Reclassification of realized (gains)/losses on derivative financial instruments to operations, net	60	48
Total comprehensive income (loss)	-920	1,893
Comprehensive Income	($3,165)	$5,812

Consolidated_Statements_of_Ben

Consolidated Statements of Beneficiaries' Equity (USD $)	Total	Series E Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Deferred Compensation, Share-based Payments [Member]	Common Stock In Grantor Trust [Member]	Cumulative Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Distributions [Member]	Noncontrolling Interest [Member]
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 (loss)	3,919	'	'	'	'	'	3,891	'	'	28
Comprehensive Income (Loss)	1,893	'	'	'	'	'	'	1,870	'	23
Equity Issuance Costs	-61	'	'	-61	'	'	'	'	'	'
Bonus Share Issuance, Shares	'	'	27,918	'	'	'	'	'	'	'
Bonus Share Issuance, Value	361	'	'	361	'	'	'	'	'	'
Share Based Compensation Activity, Shares	'	'	123,523	'	7,050	'	'	'	'	'
Share Based Compensation Activity, Value	2,666	'	1	2,655	'	'	10	'	'	'
Share Issuance from/to Deferred Compensation Plan, Shares	'	'	22,404	'	17,958	'	'	'	'	'
Share issuance from/to Deferred Compensation Plan, Value	0	'	'	'	164	-164	'	'	'	'
Adjustments to Non-controlling Interest	0	'	'	-19	'	'	'	'	'	19
Preferred Share distributions	-1,725	'	'	'	'	'	'	'	-1,725	'
Distributions declared ($0.15 per share)	-21,936	'	'	'	'	'	'	'	-21,660	-276
Ending Balance at Mar. 31, 2013	1,758,633	40	1,435	2,783,130	5,516	-5,516	483,635	-14,048	-1,516,591	21,032
Ending Balance, Shares at Mar. 31, 2013	'	4,000,000	143,712,578	'	315,753	'	'	'	'	'
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	'	312,279	'	'	'	'	'
Net income (loss)	-2,245	'	'	'	'	'	-2,213	'	'	-32
Comprehensive Income (Loss)	-920	'	'	'	'	'	'	-910	'	-10
Equity Issuance Costs	-52	'	'	-52	'	'	'	'	'	'
Share Based Compensation Activity, Shares	'	'	108,347	'	'	'	'	'	'	'
Share Based Compensation Activity, Value	2,651	'	1	2,643	'	'	7	'	'	'
Share Issuance from/to Deferred Compensation Plan, Shares	'	'	76,561	'	72,292	'	'	'	'	'
Share issuance from/to Deferred Compensation Plan, Value	-89	'	'	-89	860	-860	'	'	'	'
Adjustments to Non-controlling Interest	0	'	'	-4	'	'	'	'	'	4
Preferred Share distributions	-1,725	'	'	'	'	'	'	'	-1,725	'
Distributions declared ($0.15 per share)	-23,903	'	'	'	'	'	'	'	-23,638	-265
Ending Balance at Mar. 31, 2014	$1,895,152	$40	$1,567	$2,974,094	$6,267	($6,267)	$520,322	($3,905)	($1,617,878)	$20,912
Ending Balance, Shares at Mar. 31, 2014	'	4,000,000	156,916,901	'	384,571	'	'	'	'	'

Consolidated_Statements_of_Ben1

Consolidated Statements of Beneficiaries' Equity (Parantheticals) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cumulative Distributions [Member]	'	'
Common Stock, Dividends, Per Share, Declared	$0.15	$0.15
Noncontrolling Interest [Member]	'	'
Common Stock, Dividends, Per Share, Declared	$0.15	$0.15

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Net income (loss)	($2,245)	$3,919
Adjustments to reconcile net income (loss) to net cash from operating activities:	'	'
Depreciation and amortization	52,570	50,304
Amortization of deferred financing costs	1,189	1,161
Amortization of debt discount/(premium), net	-162	366
Amortization of stock compensation costs	3,048	2,097
Share-based compensation expense relating to awards withheld for employee taxes upon vesting of share awards	-531	-245
Straight-line rent income	-3,592	-5,514
Amortization of acquired above (below) market leases, net	-1,957	-1,771
Straight-line ground rent expense	22	474
Provision for doubtful accounts	897	505
Loss on real estate venture transactions	135	0
Loss on early extinguishment of debt	0	3
Real estate venture income in excess of distributions	-123	-358
Deferred financing obligation	-272	-452
Changes in assets and liabilities:	'	'
Accounts receivable	-5,759	-1,321
Other assets	-7,508	-4,352
Accounts payable and accrued expenses	14,400	10,793
Increase (Decrease) in Leasing Receivables	1,714	46
Other liabilities	-199	-88
Net cash from operating activities	50,440	50,263
Cash flows from investing activities:	'	'
Acquisition of properties	-13,972	0
Sales of properties, net	3,350	112,863
Proceeds from Sale of Equity Method Investments	0	16,963
Proceeds from repayment of mortgage notes receivable	1,200	200
Capital expenditures for tenant improvements	-36,222	-24,215
Capital expenditures for redevelopments	-1,031	-2,427
Capital expenditures for developments	-1,851	-82
Reimbursement from real estate venture for pre-formation development costs	0	1,976
Advances for purchase of tenant assets, net of repayments	94	-375
Investment in unconsolidated Real Estate Ventures	-808	-7,039
Escrowed cash	1,636	-420
Cash distributions from unconsolidated Real Estate Ventures in excess of cumulative equity income	2,828	1,357
Leasing costs	-3,589	-8,250
Net cash from (used in) investing activities	-48,365	90,551
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	-3,349	-2,765
Deferred financing obligation interest expense	0	234
Debt financing costs	-35	0
Exercise of stock options	0	672
Distributions paid to shareholders	-25,330	-23,353
Distributions to noncontrolling interest	-277	-277
Net cash used in financing activities	-28,991	-94,489
Increase (Decrease) in cash and cash equivalents	-26,916	46,325
Cash and cash equivalents at beginning of period	263,207	1,549
Cash and cash equivalents at end of period	236,291	47,874
Supplemental disclosure:	'	'
Cash paid for interest, net of capitalized interest during the three months ended March 31, 2014 and 2013 of $1,230 and $625, respectively	19,213	11,367
Supplemental disclosure of non-cash activity:	'	'
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	8,228	-1,701
Change in capital expenditures financed through retention payable at period end	538	-697
Change in unfunded tenant allowance	-43	-64
Gain (Loss) on Sale of Properties	1,187	5,304
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Net income (loss)	-2,245	3,919
Adjustments to reconcile net income (loss) to net cash from operating activities:	'	'
Depreciation and amortization	52,570	50,304
Amortization of deferred financing costs	1,189	1,161
Amortization of debt discount/(premium), net	-162	366
Amortization of stock compensation costs	3,048	2,097
Share-based compensation expense relating to awards withheld for employee taxes upon vesting of share awards	-531	-245
Straight-line rent income	-3,592	-5,514
Amortization of acquired above (below) market leases, net	-1,957	-1,771
Straight-line ground rent expense	22	474
Provision for doubtful accounts	897	505
Loss on real estate venture transactions	135	0
Loss on early extinguishment of debt	0	3
Real estate venture income in excess of distributions	-123	-358
Deferred financing obligation	-272	-452
Changes in assets and liabilities:	'	'
Accounts receivable	-5,759	-1,321
Other assets	-7,508	-4,352
Accounts payable and accrued expenses	14,400	10,793
Increase (Decrease) in Leasing Receivables	1,714	46
Other liabilities	-199	-88
Net cash from operating activities	50,440	50,263
Cash flows from investing activities:	'	'
Acquisition of properties	-13,972	0
Sales of properties, net	3,350	112,863
Proceeds from Sale of Equity Method Investments	0	16,963
Proceeds from repayment of mortgage notes receivable	1,200	200
Capital expenditures for tenant improvements	-36,222	-24,215
Capital expenditures for redevelopments	-1,031	-2,427
Capital expenditures for developments	-1,851	-82
Reimbursement from real estate venture for pre-formation development costs	0	1,976
Advances for purchase of tenant assets, net of repayments	94	-375
Investment in unconsolidated Real Estate Ventures	-808	-7,039
Escrowed cash	1,636	-420
Cash distributions from unconsolidated Real Estate Ventures in excess of cumulative equity income	2,828	1,357
Leasing costs	-3,589	-8,250
Net cash from (used in) investing activities	-48,365	90,551
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	-3,349	-2,765
Deferred financing obligation interest expense	0	234
Debt financing costs	-35	0
Exercise of stock options	0	672
Distributions paid to shareholders	-25,607	-23,630
Net cash used in financing activities	-28,991	-94,489
Increase (Decrease) in cash and cash equivalents	-26,916	46,325
Cash and cash equivalents at beginning of period	263,207	1,549
Cash and cash equivalents at end of period	236,291	47,874
Supplemental disclosure:	'	'
Cash paid for interest, net of capitalized interest during the three months ended March 31, 2014 and 2013 of $1,230 and $625, respectively	19,213	11,367
Supplemental disclosure of non-cash activity:	'	'
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	8,228	-1,701
Change in capital expenditures financed through retention payable at period end	538	-697
Change in unfunded tenant allowance	-43	-64
Gain (Loss) on Sale of Properties	$1,187	$5,304

Consolidated_Statement_of_Cash

Consolidated Statement of Cash Flows (Parentheticals) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Supplemental Cash Flow Information [Abstract]	'	'
Capitalized interest	$1,230	$625
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Supplemental Cash Flow Information [Abstract]	'	'
Capitalized interest	$1,230	$625

Organization_of_the_Parent_Com

Organization of the Parent Company and The Operating Partnership	3 Months Ended
	Mar. 31, 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 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 March 31, 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 March 31, 2014, the Company owned 205 properties, consisting of 175 office properties, 20 industrial facilities, five mixed-use properties (200 core properties), two development properties, two redevelopment properties and one re-entitlement property (collectively, the “Properties”) containing an aggregate of approximately 24.9 million net rentable square feet. In addition, as of March 31, 2014, the Company owned economic interests in 17 unconsolidated real estate ventures that own properties containing an aggregate of approximately 5.7 million net rentable square feet (collectively, the “Real Estate Ventures”). As of March 31, 2014, the Company also owned 450 acres of undeveloped land, and held options to purchase approximately 50 additional acres of undeveloped land. As of March 31, 2014, these land parcels could support, under current zoning and entitlements, approximately 6.2 million square feet of development. 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 March 31, 2014, the management company subsidiaries were managing properties containing an aggregate of approximately 32.8 million net rentable square feet, of which approximately 24.9 million net rentable square feet related to Properties owned by the Company and approximately 7.9 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	3 Months Ended
	Mar. 31, 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 March 31, 2014, the results of its operations for the three-month periods ended March 31, 2014 and 2013 and its cash flows for the three-month periods ended March 31, 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. All other reclassifications are related to the treatment of sold properties as discontinued operations on the statement of operations for all periods presented.
	Recent Accounting Pronouncements
	In March 2014, the Financial Accounting Standards Board (FASB) issued an accounting standard update communicating technical corrections and improvements related to glossary terms within the codification. The update provides further clarification for certain of the terms currently codified and removed certain other terms used, though not otherwise defined. The update had no impact on our accounting policies, 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. As there were no dispositions for the quarter ended March 31, 2014 and guidance is applied prospectively, there was no impact to the Company’s statements of income or financial position.

Real_Estate_Investments

Real Estate Investments	3 Months Ended
	Mar. 31, 2014
Real Estate [Abstract]	'
Real Estate Disclosure [Text Block]	'
	As of March 31, 2014 and December 31, 2013, the gross carrying value of the Company’s Properties was as follows (in thousands):
		March 31,		December 31,
		2014		2013
	Land	$	680,695	$	680,513
	Building and improvements	3,508,570		3,504,060
	Tenant improvements	512,024		484,716
		$	4,701,289	$	4,669,289
	Acquisition
	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 for $1.0 million. The net assets were purchased using available corporate funds.
	One of the two potential office buildings at Encino Trace is currently in development with with $14.6 million funded through March 31, 2014. Project costs on the first building will be funded over the remaining construction period, which is scheduled to be completed during the second quarter of 2015.
	Disposition
	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.

Investment_in_Unconsolidated_V

Investment in Unconsolidated Ventures	3 Months Ended
	Mar. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investments and Joint Ventures Disclosure [Text Block]	'
	INVESTMENT IN UNCONSOLIDATED VENTURES
	As of March 31, 2014, the Company had an aggregate investment of approximately $180.2 million in 17 unconsolidated Real Estate Ventures. The Company formed or acquired interests in these ventures with unaffiliated third parties to develop or manage office properties or to acquire land in anticipation of possible development of office or residential properties. As of March 31, 2014, 11 of the Real Estate Ventures owned 55 office buildings that contain an aggregate of approximately 5.7 million net rentable square feet; two Real Estate Ventures owned 3.8 acres of undeveloped parcels of land; three Real Estate Venture owned 22.5-acres of land under active development 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 the Real Estate Ventures in excess of its investment balance unless the Company is liable for the obligations of the Real Estate Venture or is otherwise committed to provide financial support to the Real Estate Venture.
	The following is a summary of the financial position of the Real Estate Ventures as of March 31, 2014 and December 31, 2013 (in thousands):
		March 31,				December 31,
		2014				2013
	Net property	$	988,378			$	965,475
	Other assets	144,871				164,152
	Other liabilities	45,126				49,442
	Debt	720,609				699,860
	Equity	367,514				380,325
	Company’s share of equity (Company’s basis) (a)	180,237			(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 March 31, 2014, which was included in other liabilities.
	The Company held interests in 17 Real Estate Ventures containing an aggregate of approximately 5.7 million net rentable square feet and 19 Real Estate Ventures containing an aggregate of approximately 6.4 million net rentable square feet as of the three-month periods ended March 31, 2014 and 2013, respectively. 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 March 31,
		2014				2013
	Revenue	$	34,385			$	40,889
	Operating expenses	13,982				18,266
	Interest expense, net	8,100				9,772
	Depreciation and amortization	13,598				12,906
	Net loss	(1,295		)		(55		)
	Company’s share of income (Company’s basis)	242				1,535
	Guarantees
	As of March 31, 2014, the Company had provided guarantees on behalf of certain real estate ventures, consisting of (i) a $24.7 million payment guaranty on the construction loan for the project being undertaken by evo at Cira; (ii) a $3.2 million payment guarantee on the construction loan for 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	3 Months Ended
	Mar. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Deferred Costs [Text Block]	'
	DEFERRED COSTS
	As of March 31, 2014 and December 31, 2013, the Company’s deferred costs were comprised of the following (in thousands):
		March 31, 2014
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	159,517	$	(60,985	)	$	98,532
	Financing Costs	40,315		(15,631		)	24,684
	Total	$	199,832	$	(76,616	)	$	123,216
		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-month periods ended March 31, 2014 and 2013, the Company capitalized internal direct leasing costs of $2.1 million, in accordance with the accounting standard for the capitalization of leasing costs.
Components Of Deferred Costs Net [Table Text Block]	'
	As of March 31, 2014 and December 31, 2013, the Company’s deferred costs were comprised of the following (in thousands):
		March 31, 2014
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	159,517	$	(60,985	)	$	98,532
	Financing Costs	40,315		(15,631		)	24,684
	Total	$	199,832	$	(76,616	)	$	123,216
		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	3 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Intangible Assets Disclosure [Text Block]	'
	INTANGIBLE ASSETS AND LIABILITIES
	As of March 31, 2014 and December 31, 2013, the Company’s intangible assets/liabilities were comprised of the following (in thousands):
		March 31, 2014
		Total Cost		Accumulated			Intangible assets/liabilities, net
				Amortization
	Intangible assets, net:
	In-place lease value	$	147,606	$	(38,327	)	$	109,279
	Tenant relationship value	37,671		(26,858		)	10,813
	Above market leases acquired	6,661		(1,591		)	5,070
	Total intangible assets, net	$	191,938	$	(66,776	)	$	125,162
	Acquired lease intangibles, net:
	Below market leases acquired	$	81,847	$	(49,618	)	$	32,229
		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 March 31, 2014, the Company’s annual amortization for its intangible assets/liabilities were as follows (in thousands, and assuming no early lease terminations):
		Assets		Liabilities
	2014 (nine months remaining)	$	19,879	$	5,401
	2015	23,314		5,455
	2016	18,573		3,486
	2017	16,573		2,890
	2018	12,161		2,353
	Thereafter	34,662		12,644
	Total	$	125,162	$	32,229

Debt_Obligations

Debt Obligations	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Debt Disclosure [Text Block]	'
	DEBT OBLIGATIONS
	The following table sets forth information regarding the Company’s consolidated debt obligations at March 31, 2014 and December 31, 2013 (in thousands):
	Property / Location	March 31, 2014			31-Dec-13			Effective			Maturity
								Interest			Date
								Rate
	MORTGAGE DEBT:
	Tysons Corner	$	90,918		$	91,395		5.36	%	(a)	15-Aug
	One Commerce Square	124,604			125,089			3.68	%	(a)	16-Jan
	Two Logan Square	88,362			88,583			7.57	%		16-Apr
	Fairview Eleven Tower	21,566			21,630			4.25	%	(b)	17-Jan
	Two Commerce Square	112,000			112,000			4.51	%	(a)	23-Apr
	Cira Square (GSA Philadelphia Campus)	189,370			190,964			7	%		30-Sep
	Cira Centre South Garage	39,530			40,101			7.12	%		30-Sep
	Principal balance outstanding	666,350			669,762
	Plus: fair market value premiums (discounts), net	(45		)	389
	Total mortgage indebtedness	$	666,305		$	670,151
	UNSECURED DEBT:
	Three-Year Term Loan - Swapped to fixed	$	150,000		$	150,000		2.6	%		15-Feb
	Four-Year Term Loan	100,000			100,000			LIBOR + 1.75%		(c)	16-Feb
	Seven-Year Term Loan - Swapped to fixed	200,000			200,000			3.62	%		19-Feb
	$250.0M 5.400% Guaranteed Notes due 2014	218,549			218,549			5.53	%		14-Nov
	$250.0M 7.500% Guaranteed Notes due 2015	157,625			157,625			7.76	%		15-May
	$250.0M 6.000% Guaranteed Notes due 2016	149,919			149,919			5.95	%		16-Apr
	$300.0M 5.700% Guaranteed Notes due 2017	300,000			300,000			5.68	%		17-May
	$325.0M 4.950% Guaranteed Notes due 2018	325,000			325,000			5.13	%		18-Apr
	$250.0M 3.950% Guaranteed Notes due 2023	250,000			250,000			4.02	%		23-Feb
	Indenture IA (Preferred Trust I)	27,062			27,062			2.75	%		Mar-35
	Indenture IB (Preferred Trust I)	25,774			25,774			3.3	%		Apr-35
	Indenture II (Preferred Trust II)	25,774			25,774			3.09	%		Jul-35
	Principal balance outstanding	1,929,703			1,929,703
	Plus: original issue premiums (discounts), net	(4,202		)	(4,473		)
	Total unsecured indebtedness	$	1,925,501		$	1,925,230
	Total Debt Obligations	$	2,591,806		$	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 joint venture in which the Company holds a 50% interest.
	(c)	London Interbank Offered Rate (“LIBOR”).
	During the three-month periods ended March 31, 2014 and 2013, the Company’s weighted-average effective interest rate on its mortgage notes payable was 5.73% and 6.65%, respectively.
	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 March 31, 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 March 31, 2014, the Company did not have any outstanding borrowings on its Credit Facility, with $1.7 million in letters of credit outstanding, leaving $598.3 million of unused availability under the Credit Facility. During each of the three-month periods ended March 31, 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, the $150.0 million three-year term loan, and the $100.0 million four-year term loan by an aggregate of $200.0 million, subject to customary conditions and limitations, by obtaining additional commitments from the current lenders and other financial institutions. The Company also has the option to extend the maturity dates of each of the Credit Facility, the $150.0 million three-year term loan and the $100.0 million four-year term loan by one year, subject to payment of an extension fee and other customary conditions and limitations. The Company may repay the $150.0 million three-year term loan and the $100.0 million four-year term loan at any time without penalty. The $200.0 million seven-year term loan is subject to a 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 term loans depends on the Company's unsecured senior debt credit rating. Based on the Company's current credit rating, the spread for such loans will be 150 basis points under the Credit Facility, 175 basis points under both the $150.0 million three-year term loan and the $100.0 million four-year term loan and 190 basis points under the $200.0 million seven-year term loan. At the Company's option, advances under the Credit Facility and term loans may also bear interest at a per annum floating rate equal to the higher of the prime rate or the federal funds rate plus 0.50% per annum. The Credit Facility contains a competitive bid option that allows banks that are part of the lender consortium to bid to make loans to the Company at a reduced rate.
	The Company executed hedging transactions that fix the rate on the $200.0 million seven-year term loan at a 3.623% average rate for its full term, and the rate on the $150.0 million three-year term loan at a 2.596% average rate for periods of three to four years. All hedges commenced on February 1, 2012 and the rates are inclusive of the LIBOR spread based on the Company's current investment grade rating. See Note 9 for details of the interest rate swaps entered into as of March 31, 2014.
	The Credit Facility and term loans contain financial and operating covenants and restrictions. The Company was in compliance with all such restrictions and financial covenants as of March 31, 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 March 31, 2014, the Company’s aggregate scheduled principal payments on debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
	2014 (nine months remaining)	$	228,964
	2015	409,655
	2016	467,703
	2017	330,323
	2018	336,954
	Thereafter	822,454
	Total principal payments	2,596,053
	Net unamortized premiums/(discounts)	(4,247		)
	Outstanding indebtedness	$	2,591,806

Fair_Value_of_Financial_Instru

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 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 March 31, 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 March 31, 2014 and December 31, 2013 approximate the fair values for cash and cash equivalents, accounts receivable, other assets, accounts payable and accrued expenses.
	The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands):
		March 31, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Mortgage notes payable	$	666,305	$	705,244	$	670,151	$	715,244
	Unsecured notes payable	$	1,396,891	$	1,477,304	$	1,396,620	$	1,471,041
	Variable rate debt	$	528,610	$	526,693	$	528,610	$	526,693
	Notes receivable	$	5,826	$	6,795	$	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 March 31, 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 March 31, 2014 was 3.514%. 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 14.63% for the notes receivable as of March 31, 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 March 31, 2014 and December 31, 2013. Although management is not aware of any factors that would significantly affect the fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since March 31, 2014, and current estimates of fair value may differ from the amounts presented herein.

Risk_Management_and_Use_of_Fin

Risk Management and Use of Financial Instruments	3 Months Ended
	Mar. 31, 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 March 31, 2014 and December 31, 2013. The notional amounts provide an indication of the extent of the Company's involvement in these instruments at that time, but do not represent exposure to credit, interest rate or market risks (amounts presented in thousands and included in other liabilities on the Company's consolidated balance sheets).
	Hedge Product	Hedge Type	Designation		Notional Amount				Strike		Trade Date	Maturity Date	Fair value
					3/31/14		12/31/13						3/31/14			12/31/13
	Assets:
	Swap	Interest Rate	Cash Flow	(a)	$	25,774	$	25,774	3.3	%	December 22, 2011	January 30, 2021	$	252		$	549
	Swap	Interest Rate	Cash Flow	(a)	25,774		25,774		3.09	%	6-Jan-12	30-Oct-19	63			218
					$	51,548	$	51,548					$	315		$	767
	Liabilities:
	Swap	Interest Rate	Cash Flow	(a)	$	200,000	$	200,000	3.623	%	December 6-13, 2011	February 1, 2019	$	(1,195	)	$	(545	)
	Swap	Interest Rate	Cash Flow	(a)	77,000		77,000		2.703	%	December 9-13, 2011	February 1, 2016	(825		)	(887		)
	Swap	Interest Rate	Cash Flow	(a)	50,000		50,000		2.47	%	December 13, 2011	February 1, 2015	(250		)	(283		)
	Swap	Interest Rate	Cash Flow	(a)	23,000		23,000		2.513	%	December 7-12, 2011	May 1, 2015	(150		)	(162		)
	Swap	Interest Rate	Cash Flow	(a)	27,062		27,062		2.75	%	December 21, 2011	September 30, 2017	(296		)	(311		)
					$	377,062	$	377,062					$	(2,716	)	$	(2,188	)
	(a) Hedging unsecured variable rate debt.
	The Company measures its derivative instruments at fair value and records them in the balance sheet as either an asset or liability. As of March 31, 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	3 Months Ended
	Mar. 31, 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 months ended March 31, 2014.
	For the three-month period ended March 31, 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-month period ended March 31, 2013 (in thousands):
		Three-month period ended March 31, 2013
	Revenue:
	Rents	$	3,763
	Tenant reimbursements	338
	Termination fees	—
	Other	114
	Total revenue	4,215
	Expenses:
	Property operating expenses	1,382
	Real estate taxes	466
	Depreciation and amortization	1,507
	Total operating expenses	3,355
	Other income:
	Interest income	—
	Income from discontinued operations before gain on sale of interests in real estate	860
	Net gain on disposition of discontinued operations	5,304
	Income from discontinued operations	$	6,164
	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	3 Months Ended
	Mar. 31, 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 March 31, 2014 and December 31, 2013 was $20.0 million and $20.3 million, respectively. The Parent Company believes that the aggregate settlement value of these interests (based on the number of units outstanding and the closing price of the common shares on the balance sheet date) was approximately $25.5 million and $24.8 million, respectively, as of March 31, 2014 and December 31, 2013.

Beneficiaries_Equity_of_the_Pa

Beneficiaries Equity of the Parent Company	3 Months Ended
	Mar. 31, 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 March 31,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Loss from continuing operations	$	(2,237	)	$	(2,237	)	$	(2,245	)	$	(2,245	)
	Loss from continuing operations attributable to non-controlling interests	44			44			50			50
	Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	(12		)	(12		)	—			—
	Nonforfeitable dividends allocated to unvested restricted shareholders	(103		)	(103		)	(108		)	(108		)
	Preferred share dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Loss from continuing operations available to common shareholders	(4,033		)	(4,033		)	(4,028		)	(4,028		)
	Income (Loss) from discontinued operations	(8		)	(8		)	6,164			6,164
	Discontinued operations attributable to non-controlling interests	—			—			(78		)	(78		)
	Discontinued operations attributable to common shareholders	(8		)	(8		)	6,086			6,086
	Net income (loss) attributable to common shareholders	$	(4,041	)	$	(4,041	)	$	2,058		$	2,058
	Denominator
	Weighted-average shares outstanding	156,794,019			156,794,019			143,605,659			143,605,659
	Earnings per Common Share:
	Loss from continuing operations attributable to common shareholders	$	(0.03	)	$	(0.03	)	$	(0.03	)	$	(0.03	)
	Discontinued operations attributable to common shareholders	—			—			0.04			0.04
	Net income (loss) attributable to common shareholders	$	(0.03	)	$	(0.03	)	$	0.01		$	0.01
	Redeemable common limited partnership units totaling 1,763,739 as of March 31, 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 months ended March 31, 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 March 12, 2014, the Parent Company declared a distribution of $0.15 per common share, totaling $23.6 million, which was paid on April 17, 2014 to shareholders of record as of April 3, 2014. On March 12, 2014, the Parent Company declared distributions on its Series E Preferred Shares to holders of record as of March 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 April 15, 2014 to holders of Series E Preferred Shares totaled $1.7 million.
	On November 5, 2013, the Parent Company commenced a continuous equity offering program (the “Offering Program”), under which it may sell, in at-the-market offerings, up to an aggregate amount of 16,000,000 common shares until November 5, 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 of beneficial interest and determinations by the Parent Company of the appropriate sources of funding. In conjunction with the Offering Program, the Parent Company engages sales agents who receive compensation, in aggregate, of up to 2% of the gross sales price per share sold. From inception of the Offering Program through March 31, 2014, the Parent Company has not sold any shares under the program, resulting in 16,000,000 remaining shares available for sale.
	On April 10, 2013, the Parent Company closed a public offering of 12,650,000 common shares, inclusive of 1,650,000 common shares issued upon exercise by the underwriters of the option granted to them to purchase additional shares. The Parent Company contributed the net proceeds from the sale of shares, amounting to $181.5 million after deducting underwriting discounts and commissions and other offering expenses, to the Operating Partnership in exchange for partnership units of the Operating Partnership. The Operating Partnership continues to use the net proceeds for working capital, capital expenditures and other general corporate purposes, which may include acquisitions, developments and the repayment, repurchase and refinancing of debt.
	Common Share Repurchases
	The Parent Company maintains a share repurchase program under which it may repurchase its common shares from time to time in accordance with limits set by the Board of Trustees.
	The Parent Company did not repurchase any shares under the share repurchase program during the three-month periods ended March 31, 2014 and 2013. As of March 31, 2014, the Parent Company may purchase an additional 539,200 shares under the program.
	Repurchases may be made from time to time in the open market or in privately negotiated transactions, subject to market conditions and compliance with legal requirements. The share repurchase program does not contain any time limitation and does not obligate the Parent Company to repurchase any shares. The Parent Company may discontinue the program at any time.

Partners_Equity_of_the_Operati

Partners Equity of the Operating Partnership	3 Months Ended
	Mar. 31, 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 March 31,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Loss from continuing operations	$	(2,237	)	$	(2,237	)	$	(2,245	)	$	(2,245	)
	Nonforfeitable dividends allocated to unvested restricted unitholders	(103		)	(103		)	(108		)	(108		)
	Preferred unit dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Net income attributable to non-controlling interests	(12		)	(12		)	—			—
	Loss from continuing operations available to common unitholders	(4,077		)	(4,077		)	(4,078		)	(4,078		)
	Discontinued operations attributable to common unitholders	(8		)	(8		)	6,164			6,164
	Net income (loss) attributable to common unitholders	$	(4,085	)	$	(4,085	)	$	2,086		$	2,086
	Denominator
	Weighted-average units outstanding	158,557,758			158,557,758			145,451,396			145,451,396
	Earnings per Common Partnership Unit:
	Loss from continuing operations attributable to common unitholders	$	(0.03	)	$	(0.03	)	$	(0.03	)	$	(0.03	)
	Discontinued operations attributable to common unitholders	—			—			0.04			0.04
	Net income (loss) attributable to common unitholders	$	(0.03	)	$	(0.03	)	$	0.01		$	0.01
	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 months ended March 31, 2014 and 2013, earnings representing nonforfeitable dividends as noted in the table above were allocated to the unvested restricted units.
	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 March 12, 2014, the Operating Partnership declared a distribution of $0.15 per common partnership unit, totaling $23.6 million, which was paid on April 17, 2014 to unitholders of record as of April 3, 2014. On March 12, 2014, the Operating Partnership declared distributions on its Series E-Linked Preferred Mirror Units to holders of record as of March 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 April 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 three-month periods ended March 31, 2014 and 2013 and accordingly, during the three-month periods ended March 31, 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	3 Months Ended
	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
SHARE BASED AND DEFERRED COMPENSATION	'
	SHARE BASED COMPENSATION
	Stock Options
	At March 31, 2014, options exercisable for 2,983,569 common shares were outstanding under the Parent Company's shareholder approved equity incentive plan (referred to as the "Equity Incentive Plan"). The Company recognized a nominal amount of compensation expense related to unvested options during the three-month period ended March 31, 2014. During the three-month period ended March 31, 2013 the Company recognized $0.3 million of compensation expense related to unvested options.
	Option activity as of March 31, 2014 and changes during the three months ended March 31, 2014 were as follows:
		Shares		Weighted				Weighted Average		Aggregate Intrinsic
				Average				Remaining Contractual		Value
				Exercise Price				Term (in years)
	Outstanding at January 1, 2014	2,983,569		$	15.5			4.92		$	—
	Granted	—		$	—			—		—
	Exercised	—		$	—			—
	Canceled	—		$	—
	Outstanding at March 31, 2014	2,983,569		$	15.5			4.92		$	—
	Vested/Exercisable at March 31, 2014	2,983,569		$	15.5			4.92		$	—
	Restricted Share Awards
	As of March 31, 2014, 687,904 restricted shares were outstanding under the Equity Incentive Plan and vest over three years from the initial grant date. The remaining compensation expense to be recognized at March 31, 2014 was approximately $3.3 million, and is expected to be recognized over a weighted average remaining vesting period of 1.7 years. During the three-month periods ended March 31, 2014 and 2013 the Company recognized compensation expense related to outstanding restricted shares of $1.4 million and $0.9 million, of which $0.2 million was capitalized in each of these periods, consistent with the Company’s review of employee salaries eligible for capitalization.
	The following table summarizes the Company’s restricted share activity for the three months ended March 31, 2014:
		Shares		Weighted
				Average Grant
				Date Fair value
	Non-vested at January 1, 2014	563,713		$	12.56
	Granted	201,435		14.37
	Vested	(70,548	)	16.82
	Forfeited	(6,696	)	11.84
	Non-vested at March 31, 2014	687,904		$	12.66
	On March 11, 2014 and March 12, 2014 the Compensation Committee of the Company’s Board of Trustees awarded restricted shares of which 131,641 cliff vest after three years from the grant date and 69,794 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 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 granted share-based awards to the Parent Company's officers referred to as Restricted Performance Share Units , or RPSU's, in accordance with the following schedule;
	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) Units were issued in accordance with our qualifying retirement provision, meaning the recipient’s voluntary termination of employment after reaching age 57 and accumulating at least 15 years of service with the Company. Of the 14,742 shares originally granted, 563 dividend equivalent rights were accrued at the time of retirement and 30,610 shares were issued based on our TSR (Total Shareholder Return) Percentile at October 31, 2012 of 200%.
	The RPSUs represent the right to earn common shares. The number of common shares, if any, deliverable to award recipients depends on the Company’s performance based on its total return to shareholders during the three years measurement period, or, if earlier, the date of a change in control. The Company's performance is compared to the shareholder return of REITs within an index ("Index Companies") over the measurement period for 50% of the RPSUs awarded on that date, with the remaining 50% being compared to the total shareholder return of REITs within the Company's proxy peer group ("Peer Group") over such period. The vesting of RPSUs is contingent upon the continued employment of the participants through the performance periods (with exceptions for death, disability and qualifying retirement). If the Company's total return to shareholders over the measurement period places it below the 25th percentile of the Index Companies or the components in the Peer Group, as applicable, then no shares will be earned under the related RSPUs. If the Company's total return to shareholders over the measurement period places the Company at or above the 25th percentile of the Index Companies or the components of in the Peer Group, as applicable, then a percentage of the awards ranging from 50% to 200% will be earned. Dividends are deemed credited to the performance units accounts and are applied to “acquire” additional RPSUs for the account of the unit holder at the price per common share on the dividend payment date. If earned, RPSUs will be settled in common shares in an amount that reflects the number of RPSUs in the holder’s account at the end of the applicable measurement period.
	On the date of each grant, the RPSUs were valued 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-month period ended March 31, 2014, the Company recognized total compensation expense for the 2014, 2013 and 2012 RPSU awards of $1.7 million, of which $0.4 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the three-month period ended March 31, 2013, the Company recognized total compensation expense for the 2013, 2012 and 2011 RPSU awards of $1.2 million, of which $0.3 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation.
	A total of 150,829 common shares vested on March 1, 2014 and were delivered to holders in settlement of the RPSUs awarded on March 2, 2011 (with a three-year measurement period ended December 31, 2013). Holders of these RPSUs also received a cash dividend for these common shares on February 7, 2014.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	SEGMENT INFORMATION
	During the quarter ended March 31, 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 segment includes properties in Chester, Delaware, and Montgomery counties in the Philadelphia suburbs. The Philadelphia CBD segment includes properties located in the City of Philadelphia in Pennsylvania. The Metropolitan Washington, D.C. segment includes properties in Northern Virginia and southern Maryland. The New Jersey/Delaware segment includes properties in Burlington and Camden counties in New Jersey and in New Castle county in the state of Delaware. The Richmond, Virginia segment includes properties primarily in Albemarle, Chesterfield, Goochland and Henrico counties and one property in Durham, North Carolina. The Austin, Texas segment includes properties in Austin. 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.
	Segment information is as follows (in thousands):
		Pennsylvania			Philadelphia			Metropolitan Washington, D.C.		New Jersey/Delaware		Richmond,			Austin, Texas		California		Corporate			Total
		Suburbs			CBD							Virginia
	As of March 31, 2014:
	Real estate investments, at cost:
	Operating properties	$	1,209,328		$	1,318,170		$	1,219,542	$	414,353	$	310,465		$	36,480	$	192,951	$	—		$	4,701,289
	Construction-in-progress																		90,140			90,140
	Land inventory																		96,427			96,427
	Investment in real estate ventures, at equity (a)	$	17,379		$	20,131		$	59,847	$	—	$	1,355		$	81,525	$	—	$	—		$	180,237
	As of December 31, 2013:
	Real estate investments, at cost:
	Operating properties	$	1,199,105		$	1,300,666		$	1,214,965	$	414,716	$	310,397		$	36,856	$	192,584	$	—		$	4,669,289
	Construction-in-progress																		74,174			74,174
	Land inventory																		93,351			93,351
	Investment in real estate ventures, at equity	$	17,272		$	19,975		$	59,905	$	—	$	1,400		$	81,960	$	—	$	—		$	180,512
	For the three-month period ended March 31, 2014:
	Total revenue	$	40,574		$	49,414		$	30,690	$	15,625	$	8,867		$	2,081	$	4,602	$	261		$	152,114
	Property operating expenses, real estate taxes and third party management expenses	14,687			18,443			11,957		8,692		4,340			1,176		2,409		270			61,974
	Net operating income	$	25,887		$	30,971		$	18,733	$	6,933	$	4,527		$	905	$	2,193	$	(9	)	$	90,140
	Equity in income of real estate ventures	$	32		$	(21	)	$	67	$	18	$	(45	)	$	191	$	—	$	—		$	242
	For the three-month period ended March 31, 2013:
	Total revenue	$	37,916		$	35,925		$	27,785	$	14,919	$	8,765		$	9,257	$	4,605	$	382		$	139,554
	Property operating expenses, real estate taxes and third party management expenses	14,436			13,534			10,763		7,031		3,683			3,958		2,160		(496		)	55,069
	Net operating income	$	23,480		$	22,391		$	17,022	$	7,888	$	5,082		$	5,299	$	2,445	$	878		$	84,485
	Equity in income of real estate ventures	$	31		$	566		$	16	$	908	$	(8	)	$	22	$	—	$	—		$	1,535
	(a) Does not include the negative investment balance of one real estate venture totaling $1.2 million as of March 31, 2014, which was included in other liabilities.
	Net operating income (“NOI”) is defined as total revenue less property operating expenses, real estate taxes and third party management expenses. Segment NOI includes revenue, real estate taxes and property operating expenses directly related to operation and management of the properties owned and managed within the respective geographical region. Segment NOI excludes property level depreciation and amortization, revenue and expenses directly associated with third party real estate management services, expenses associated with corporate administrative support services, and inter-company eliminations. NOI also does not reflect general and administrative expenses, interest expenses, real estate impairment losses, depreciation and amortization costs, capital expenditures and leasing costs. Trends in development and construction activities that could materially impact the Company’s results from operations are also not reflected in NOI. All companies may not calculate NOI in the same manner. NOI is the measure that is used by the Company to evaluate the operating performance of its real estate assets by segment. The Company also believes that NOI provides useful information to investors regarding its financial condition and results of operations because it reflects only those income and expenses recorded at the property level. The Company believes that net income, as defined by GAAP, is the most appropriate earnings measure. The following is a reconciliation of consolidated NOI to consolidated net income (loss), as defined by GAAP:
		Three month periods ended March 31,
		2014			2013
		(amounts in thousands)
	Consolidated net operating income	$	90,140		$	84,485
	Less:
	Interest expense	(31,844		)	(30,914		)
	Interest expense - amortization of deferred financing costs	(1,189		)	(1,161		)
	Interest expense - financing obligation	(272		)	(218		)
	Depreciation and amortization	(52,570		)	(49,476		)
	General and administrative expenses	(8,181		)	(6,551		)
	Loss on real estate venture transactions	(135		)	—
	Loss on early extinguishment of debt	—			(3		)
	Plus:
	Interest income	385			58
	Equity in income of real estate ventures	242			1,535
	Gain on sale of undepreciated real estate	1,187			—
	Loss from continuing operations	(2,237		)	(2,245		)
	Income (loss) from discontinued operations	(8		)	6,164
	Net income (loss)	$	(2,245	)	$	3,919

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 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 we determine that the likelihood of an unfavorable outcome is probable and when the amount of loss is reasonably estimable. The Company does not expect that the liabilities, if any, that may ultimately result from such legal actions will have a material adverse effect on the consolidated financial position, results of operations or cash flows of the Company.
	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 15 to 75 years. Minimum future rental payments on non-cancelable leases at March 31, 2014 are as follows (in thousands):
	2014 (nine months remaining)	$	1,062
	2015	1,415
	2016	1,415
	2017	1,415
	2018	1,415
	Thereafter	61,666
	Total	$	68,388
	The Company obtained ground tenancy rights related to two properties in Philadelphia, Pennsylvania, which provide for contingent rent participation by the lessor in certain capital transactions and net operating cash flows of the properties after certain returns are achieved by the Company. Such amounts, if any, will be reflected as contingent rent when incurred. The leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate taxes. The above schedule of future minimum rental payments does not include any contingent rent amounts or any reimbursed expenses. 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	3 Months Ended
	Mar. 31, 2014
Subsequent Events [Abstract]	'
Subsequent Events [Text Block]	'
	SUBSEQUENT EVENTS
	Four Points Centre Venture
	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 property 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 currently estimates a $0.2 million loss on the contribution, driven primarily by closing costs.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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 March 31, 2014, the results of its operations for the three-month periods ended March 31, 2014 and 2013 and its cash flows for the three-month periods ended March 31, 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. All other reclassifications are related to the treatment of sold properties as discontinued operations on the statement of operations for all periods presented.
Recent Accounting Pronouncement [Policy Text Block]	'
	Recent Accounting Pronouncements
	In March 2014, the Financial Accounting Standards Board (FASB) issued an accounting standard update communicating technical corrections and improvements related to glossary terms within the codification. The update provides further clarification for certain of the terms currently codified and removed certain other terms used, though not otherwise defined. The update had no impact on our accounting policies, 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. As there were no dispositions for the quarter ended March 31, 2014 and guidance is applied prospectively, there was no impact to the Company’s statements of income or financial position.

Real_Estate_Investments_Tables

Real Estate Investments (Tables)	3 Months Ended
	Mar. 31, 2014
Real Estate [Abstract]	'
Gross Carrying Value Of Company's Properties [Table Text Block]	'
	As of March 31, 2014 and December 31, 2013, the gross carrying value of the Company’s Properties was as follows (in thousands):
		March 31,		December 31,
		2014		2013
	Land	$	680,695	$	680,513
	Building and improvements	3,508,570		3,504,060
	Tenant improvements	512,024		484,716
		$	4,701,289	$	4,669,289

Investment_in_Unconsolidated_V1

Investment in Unconsolidated Ventures (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2014 and December 31, 2013 (in thousands):
		March 31,				December 31,
		2014				2013
	Net property	$	988,378			$	965,475
	Other assets	144,871				164,152
	Other liabilities	45,126				49,442
	Debt	720,609				699,860
	Equity	367,514				380,325
	Company’s share of equity (Company’s basis) (a)	180,237			(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 March 31, 2014, which was 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 March 31,
		2014				2013
	Revenue	$	34,385			$	40,889
	Operating expenses	13,982				18,266
	Interest expense, net	8,100				9,772
	Depreciation and amortization	13,598				12,906
	Net loss	(1,295		)		(55		)
	Company’s share of income (Company’s basis)	242				1,535

Deferred_Costs_Tables

Deferred Costs (Tables)	3 Months Ended
	Mar. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Components Of Deferred Costs Net [Table Text Block]	'
	As of March 31, 2014 and December 31, 2013, the Company’s deferred costs were comprised of the following (in thousands):
		March 31, 2014
		Total Cost		Accumulated			Deferred Costs,
				Amortization			net
	Leasing Costs	$	159,517	$	(60,985	)	$	98,532
	Financing Costs	40,315		(15,631		)	24,684
	Total	$	199,832	$	(76,616	)	$	123,216
		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)	3 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Intangible Assets [Table Text Block]	'
	As of March 31, 2014 and December 31, 2013, the Company’s intangible assets/liabilities were comprised of the following (in thousands):
		March 31, 2014
		Total Cost		Accumulated			Intangible assets/liabilities, net
				Amortization
	Intangible assets, net:
	In-place lease value	$	147,606	$	(38,327	)	$	109,279
	Tenant relationship value	37,671		(26,858		)	10,813
	Above market leases acquired	6,661		(1,591		)	5,070
	Total intangible assets, net	$	191,938	$	(66,776	)	$	125,162
	Acquired lease intangibles, net:
	Below market leases acquired	$	81,847	$	(49,618	)	$	32,229
		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 March 31, 2014, the Company’s annual amortization for its intangible assets/liabilities were as follows (in thousands, and assuming no early lease terminations):
		Assets		Liabilities
	2014 (nine months remaining)	$	19,879	$	5,401
	2015	23,314		5,455
	2016	18,573		3,486
	2017	16,573		2,890
	2018	12,161		2,353
	Thereafter	34,662		12,644
	Total	$	125,162	$	32,229

Debt_Obligations_Tables

Debt Obligations (Tables)	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Consolidated Debt Obligations [Table Text Block]	'
	The following table sets forth information regarding the Company’s consolidated debt obligations at March 31, 2014 and December 31, 2013 (in thousands):
	Property / Location	March 31, 2014			31-Dec-13			Effective			Maturity
								Interest			Date
								Rate
	MORTGAGE DEBT:
	Tysons Corner	$	90,918		$	91,395		5.36	%	(a)	15-Aug
	One Commerce Square	124,604			125,089			3.68	%	(a)	16-Jan
	Two Logan Square	88,362			88,583			7.57	%		16-Apr
	Fairview Eleven Tower	21,566			21,630			4.25	%	(b)	17-Jan
	Two Commerce Square	112,000			112,000			4.51	%	(a)	23-Apr
	Cira Square (GSA Philadelphia Campus)	189,370			190,964			7	%		30-Sep
	Cira Centre South Garage	39,530			40,101			7.12	%		30-Sep
	Principal balance outstanding	666,350			669,762
	Plus: fair market value premiums (discounts), net	(45		)	389
	Total mortgage indebtedness	$	666,305		$	670,151
	UNSECURED DEBT:
	Three-Year Term Loan - Swapped to fixed	$	150,000		$	150,000		2.6	%		15-Feb
	Four-Year Term Loan	100,000			100,000			LIBOR + 1.75%		(c)	16-Feb
	Seven-Year Term Loan - Swapped to fixed	200,000			200,000			3.62	%		19-Feb
	$250.0M 5.400% Guaranteed Notes due 2014	218,549			218,549			5.53	%		14-Nov
	$250.0M 7.500% Guaranteed Notes due 2015	157,625			157,625			7.76	%		15-May
	$250.0M 6.000% Guaranteed Notes due 2016	149,919			149,919			5.95	%		16-Apr
	$300.0M 5.700% Guaranteed Notes due 2017	300,000			300,000			5.68	%		17-May
	$325.0M 4.950% Guaranteed Notes due 2018	325,000			325,000			5.13	%		18-Apr
	$250.0M 3.950% Guaranteed Notes due 2023	250,000			250,000			4.02	%		23-Feb
	Indenture IA (Preferred Trust I)	27,062			27,062			2.75	%		Mar-35
	Indenture IB (Preferred Trust I)	25,774			25,774			3.3	%		Apr-35
	Indenture II (Preferred Trust II)	25,774			25,774			3.09	%		Jul-35
	Principal balance outstanding	1,929,703			1,929,703
	Plus: original issue premiums (discounts), net	(4,202		)	(4,473		)
	Total unsecured indebtedness	$	1,925,501		$	1,925,230
	Total Debt Obligations	$	2,591,806		$	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 joint venture in which the Company holds a 50% interest.
	(c)	London Interbank Offered Rate (“LIBOR”).
Schedule of Maturities of Long-term Debt [Table Text Block]	'
	As of March 31, 2014, the Company’s aggregate scheduled principal payments on debt obligations, excluding amortization of discounts and premiums, were as follows (in thousands):
	2014 (nine months remaining)	$	228,964
	2015	409,655
	2016	467,703
	2017	330,323
	2018	336,954
	Thereafter	822,454
	Total principal payments	2,596,053
	Net unamortized premiums/(discounts)	(4,247		)
	Outstanding indebtedness	$	2,591,806

Fair_Value_of_Financial_Instru1

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 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):
		March 31, 2014				December 31, 2013
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
	Mortgage notes payable	$	666,305	$	705,244	$	670,151	$	715,244
	Unsecured notes payable	$	1,396,891	$	1,477,304	$	1,396,620	$	1,471,041
	Variable rate debt	$	528,610	$	526,693	$	528,610	$	526,693
	Notes receivable	$	5,826	$	6,795	$	7,026	$	7,759

Risk_Management_and_Use_of_Fin1

Risk Management and Use of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 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
					3/31/14		12/31/13						3/31/14			12/31/13
	Assets:
	Swap	Interest Rate	Cash Flow	(a)	$	25,774	$	25,774	3.3	%	December 22, 2011	January 30, 2021	$	252		$	549
	Swap	Interest Rate	Cash Flow	(a)	25,774		25,774		3.09	%	6-Jan-12	30-Oct-19	63			218
					$	51,548	$	51,548					$	315		$	767
	Liabilities:
	Swap	Interest Rate	Cash Flow	(a)	$	200,000	$	200,000	3.623	%	December 6-13, 2011	February 1, 2019	$	(1,195	)	$	(545	)
	Swap	Interest Rate	Cash Flow	(a)	77,000		77,000		2.703	%	December 9-13, 2011	February 1, 2016	(825		)	(887		)
	Swap	Interest Rate	Cash Flow	(a)	50,000		50,000		2.47	%	December 13, 2011	February 1, 2015	(250		)	(283		)
	Swap	Interest Rate	Cash Flow	(a)	23,000		23,000		2.513	%	December 7-12, 2011	May 1, 2015	(150		)	(162		)
	Swap	Interest Rate	Cash Flow	(a)	27,062		27,062		2.75	%	December 21, 2011	September 30, 2017	(296		)	(311		)
					$	377,062	$	377,062					$	(2,716	)	$	(2,188	)
	(a) Hedging unsecured variable rate debt.

Discontinued_Operations_Tables

Discontinued Operations (Tables)	3 Months Ended
	Mar. 31, 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-month period ended March 31, 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-month period ended March 31, 2013 (in thousands):
		Three-month period ended March 31, 2013
	Revenue:
	Rents	$	3,763
	Tenant reimbursements	338
	Termination fees	—
	Other	114
	Total revenue	4,215
	Expenses:
	Property operating expenses	1,382
	Real estate taxes	466
	Depreciation and amortization	1,507
	Total operating expenses	3,355
	Other income:
	Interest income	—
	Income from discontinued operations before gain on sale of interests in real estate	860
	Net gain on disposition of discontinued operations	5,304
	Income from discontinued operations	$	6,164

Beneficiaries_Equity_of_the_Pa1

Beneficiaries Equity of the Parent Company (Tables)	3 Months Ended
	Mar. 31, 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 March 31,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Loss from continuing operations	$	(2,237	)	$	(2,237	)	$	(2,245	)	$	(2,245	)
	Loss from continuing operations attributable to non-controlling interests	44			44			50			50
	Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	(12		)	(12		)	—			—
	Nonforfeitable dividends allocated to unvested restricted shareholders	(103		)	(103		)	(108		)	(108		)
	Preferred share dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Loss from continuing operations available to common shareholders	(4,033		)	(4,033		)	(4,028		)	(4,028		)
	Income (Loss) from discontinued operations	(8		)	(8		)	6,164			6,164
	Discontinued operations attributable to non-controlling interests	—			—			(78		)	(78		)
	Discontinued operations attributable to common shareholders	(8		)	(8		)	6,086			6,086
	Net income (loss) attributable to common shareholders	$	(4,041	)	$	(4,041	)	$	2,058		$	2,058
	Denominator
	Weighted-average shares outstanding	156,794,019			156,794,019			143,605,659			143,605,659
	Earnings per Common Share:
	Loss from continuing operations attributable to common shareholders	$	(0.03	)	$	(0.03	)	$	(0.03	)	$	(0.03	)
	Discontinued operations attributable to common shareholders	—			—			0.04			0.04
	Net income (loss) attributable to common shareholders	$	(0.03	)	$	(0.03	)	$	0.01		$	0.01

Partners_Equity_of_the_Operati1

Partners Equity of the Operating Partnership (Tables)	3 Months Ended
	Mar. 31, 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 March 31,
		2014						2013
		Basic			Diluted			Basic			Diluted
	Numerator
	Loss from continuing operations	$	(2,237	)	$	(2,237	)	$	(2,245	)	$	(2,245	)
	Nonforfeitable dividends allocated to unvested restricted unitholders	(103		)	(103		)	(108		)	(108		)
	Preferred unit dividends	(1,725		)	(1,725		)	(1,725		)	(1,725		)
	Net income attributable to non-controlling interests	(12		)	(12		)	—			—
	Loss from continuing operations available to common unitholders	(4,077		)	(4,077		)	(4,078		)	(4,078		)
	Discontinued operations attributable to common unitholders	(8		)	(8		)	6,164			6,164
	Net income (loss) attributable to common unitholders	$	(4,085	)	$	(4,085	)	$	2,086		$	2,086
	Denominator
	Weighted-average units outstanding	158,557,758			158,557,758			145,451,396			145,451,396
	Earnings per Common Partnership Unit:
	Loss from continuing operations attributable to common unitholders	$	(0.03	)	$	(0.03	)	$	(0.03	)	$	(0.03	)
	Discontinued operations attributable to common unitholders	—			—			0.04			0.04
	Net income (loss) attributable to common unitholders	$	(0.03	)	$	(0.03	)	$	0.01		$	0.01

Share_Based_and_Deferred_Compe1

Share Based and Deferred Compensation (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	'
	The Compensation Committee of the Parent Company’s Board of Trustees granted share-based awards to the Parent Company's officers referred to as Restricted Performance Share Units , or RPSU's, in accordance with the following schedule;
	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) Units were issued in accordance with our qualifying retirement provision, meaning the recipient’s voluntary termination of employment after reaching age 57 and accumulating at least 15 years of service with the Company. Of the 14,742 shares originally granted, 563 dividend equivalent rights were accrued at the time of retirement and 30,610 shares were issued based on our TSR (Total Shareholder Return) Percentile at October 31, 2012 of 200%.
Options Activity [Table Text Block]	'
	Option activity as of March 31, 2014 and changes during the three months ended March 31, 2014 were as follows:
		Shares		Weighted				Weighted Average		Aggregate Intrinsic
				Average				Remaining Contractual		Value
				Exercise Price				Term (in years)
	Outstanding at January 1, 2014	2,983,569		$	15.5			4.92		$	—
	Granted	—		$	—			—		—
	Exercised	—		$	—			—
	Canceled	—		$	—
	Outstanding at March 31, 2014	2,983,569		$	15.5			4.92		$	—
	Vested/Exercisable at March 31, 2014	2,983,569		$	15.5			4.92		$	—
Company's Restricted Share Activity [Table Text Block]	'
	The following table summarizes the Company’s restricted share activity for the three months ended March 31, 2014:
		Shares		Weighted
				Average Grant
				Date Fair value
	Non-vested at January 1, 2014	563,713		$	12.56
	Granted	201,435		14.37
	Vested	(70,548	)	16.82
	Forfeited	(6,696	)	11.84
	Non-vested at March 31, 2014	687,904		$	12.66

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
	Segment information is as follows (in thousands):
		Pennsylvania			Philadelphia			Metropolitan Washington, D.C.		New Jersey/Delaware		Richmond,			Austin, Texas		California		Corporate			Total
		Suburbs			CBD							Virginia
	As of March 31, 2014:
	Real estate investments, at cost:
	Operating properties	$	1,209,328		$	1,318,170		$	1,219,542	$	414,353	$	310,465		$	36,480	$	192,951	$	—		$	4,701,289
	Construction-in-progress																		90,140			90,140
	Land inventory																		96,427			96,427
	Investment in real estate ventures, at equity (a)	$	17,379		$	20,131		$	59,847	$	—	$	1,355		$	81,525	$	—	$	—		$	180,237
	As of December 31, 2013:
	Real estate investments, at cost:
	Operating properties	$	1,199,105		$	1,300,666		$	1,214,965	$	414,716	$	310,397		$	36,856	$	192,584	$	—		$	4,669,289
	Construction-in-progress																		74,174			74,174
	Land inventory																		93,351			93,351
	Investment in real estate ventures, at equity	$	17,272		$	19,975		$	59,905	$	—	$	1,400		$	81,960	$	—	$	—		$	180,512
	For the three-month period ended March 31, 2014:
	Total revenue	$	40,574		$	49,414		$	30,690	$	15,625	$	8,867		$	2,081	$	4,602	$	261		$	152,114
	Property operating expenses, real estate taxes and third party management expenses	14,687			18,443			11,957		8,692		4,340			1,176		2,409		270			61,974
	Net operating income	$	25,887		$	30,971		$	18,733	$	6,933	$	4,527		$	905	$	2,193	$	(9	)	$	90,140
	Equity in income of real estate ventures	$	32		$	(21	)	$	67	$	18	$	(45	)	$	191	$	—	$	—		$	242
	For the three-month period ended March 31, 2013:
	Total revenue	$	37,916		$	35,925		$	27,785	$	14,919	$	8,765		$	9,257	$	4,605	$	382		$	139,554
	Property operating expenses, real estate taxes and third party management expenses	14,436			13,534			10,763		7,031		3,683			3,958		2,160		(496		)	55,069
	Net operating income	$	23,480		$	22,391		$	17,022	$	7,888	$	5,082		$	5,299	$	2,445	$	878		$	84,485
	Equity in income of real estate ventures	$	31		$	566		$	16	$	908	$	(8	)	$	22	$	—	$	—		$	1,535
	(a) Does not include the negative investment balance of one real estate venture totaling $1.2 million as of March 31, 2014, which was included in other liabilities.
Reconciliation Of Consolidated Net Operating Income [Table Text Block]	'
		Three month periods ended March 31,
		2014			2013
		(amounts in thousands)
	Consolidated net operating income	$	90,140		$	84,485
	Less:
	Interest expense	(31,844		)	(30,914		)
	Interest expense - amortization of deferred financing costs	(1,189		)	(1,161		)
	Interest expense - financing obligation	(272		)	(218		)
	Depreciation and amortization	(52,570		)	(49,476		)
	General and administrative expenses	(8,181		)	(6,551		)
	Loss on real estate venture transactions	(135		)	—
	Loss on early extinguishment of debt	—			(3		)
	Plus:
	Interest income	385			58
	Equity in income of real estate ventures	242			1,535
	Gain on sale of undepreciated real estate	1,187			—
	Loss from continuing operations	(2,237		)	(2,245		)
	Income (loss) from discontinued operations	(8		)	6,164
	Net income (loss)	$	(2,245	)	$	3,919

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 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 15 to 75 years. Minimum future rental payments on non-cancelable leases at March 31, 2014 are as follows (in thousands):
	2014 (nine months remaining)	$	1,062
	2015	1,415
	2016	1,415
	2017	1,415
	2018	1,415
	Thereafter	61,666
	Total	$	68,388

Organization_of_the_Parent_Com1

Organization of the Parent Company and The Operating Partnership (Details)	Mar. 31, 2014	Mar. 13, 2013
	Real_Estate_Investments	sqft
	sqft
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	24,900,000	'
Area Owned by Company of Undeveloped Parcels Of Land	450	'
Area Of Additional Undeveloped Parcels Of Land With Option to Purchase	50	'
Total potential development capacity	6,200,000	'
Unconsolidated Real Estate Ventures [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Net rentable square feet	5,700,000	6,400,000
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	32,800,000	'
Third Parties and Real Estate Ventures [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Net rentable square feet	7,900,000	'
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	175	'
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	'
Core Properties [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	200	'
Development Property [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	2	'
Redevelopment Property [Member]	'	'
Organization of The Parent Company and The Operating Partnership [Line Items]	'	'
Number of Real Estate Properties	2	'
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 $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment, Gross [Abstract]	'	'
Land	$680,695	$680,513
Buildings and Improvements, Gross	3,508,570	3,504,060
Leasehold Improvements, Gross	512,024	484,716
Real Estate Investments	$4,701,289	$4,669,289

Real_Estate_Investments_Acquis

Real Estate Investments Acquisitions and Dispositions (Details) (USD $)	3 Months Ended			0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 27, 2014	Feb. 19, 2014	Mar. 31, 2014
				Rob Roy - Land [Member]	Encino Trace - Land [Member]	Encino Trace - Building I [Member]
				acre	Properties
					sqft
					Storey
					acre
Significant Acquisitions and Disposals [Line Items]	'	'	'	'	'	'
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	'	'	'	'	4	'
Area of Land	'	'	'	16.8	'	'
Business Combination, Consideration Transferred	'	'	'	'	$14,000,000	'
Construction in Progress, Gross	'	'	'	'	8,400,000	'
Land	680,695,000	'	680,513,000	'	4,600,000	'
Escrow Deposit	'	'	'	'	1,000,000	'
Construction-in-progress	90,140,000	'	74,174,000	'	'	14,600,000
Land Sales	'	'	'	3,500,000	'	'
Gain on sale of undepreciated real estate	$1,187,000	$0	'	$1,200,000	'	'

Investment_in_Unconsolidated_V2

Investment in Unconsolidated Ventures (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 13, 2013
	sqft			Real_Estate_Ventures
	Room
	Buildings
	Real_Estate_Ventures
	acre
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Company's share of equity (Company's Basis)	$180,237,000	'	$180,512,000	'
Loss on real estate venture transactions	-135,000	0	'	'
Number of unconsolidated investments in Real Estate Ventures	17	'	'	19
Number of real estate ventures that owns buildings	11	'	'	'
Number of office buildings in Real Estate Ventures	55	'	'	'
Aggregate Approximate Area Of Office Buildings	5,700,000	'	'	'
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	808,000	7,039,000	'	'
Number of real estate ventures that owns land under development	3	'	'	'
Area Owned By Real Estate Venture in Parcels Of Land Under Development	22.5	'	'	'
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%	'	'	'
TB-BDN Plymouth Apartments [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Guarantor Obligations, Current Carrying Value	3,200,000	'	'	'
Unconsolidated Real Estate Ventures [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Net rentable square feet	5,700,000	'	'	6,400,000
The Grove at Cira Centre South [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Guarantor Obligations, Current Carrying Value	24,700,000	'	'	'
PJP VII [Member]	'	'	'	'
Schedule of Equity Method Investments [Line Items]	'	'	'	'
Guarantor Obligations, Current Carrying Value	$500,000	'	'	'

Investment_in_Unconsolidated_V3

Investment in Unconsolidated Ventures (Summary of Results of Operations of Unconsolidated Ventures) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Schedule of Equity Method Investments [Line Items]	'	'
Company's share of income (Company's basis)	$242	$1,535
Unconsolidated Real Estate Ventures [Member]	'	'
Schedule of Equity Method Investments [Line Items]	'	'
Revenue	34,385	40,889
Operating expenses	13,982	18,266
Interest expense, net	8,100	9,772
Depreciation and amortization	13,598	12,906
Net loss	-1,295	-55
Company's share of income (Company's basis)	$242	$1,535

Investment_in_Unconsolidated_V4

Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Equity Method Investments [Line Items]	'		'
Company's share of equity (Company's Basis)	$180,237		$180,512
Austin Joint Venture [Member]	'		'
Schedule of Equity Method Investments [Line Items]	'		'
Company's share of equity (Company's Basis)	-1,200		'
Unconsolidated Real Estate Ventures [Member]	'		'
Schedule of Equity Method Investments [Line Items]	'		'
Net property	988,378		965,475
Other assets	144,871		164,152
Other liabilities	45,126		49,442
Debt	720,609		699,860
Equity	367,514		380,325
Company's share of equity (Company's Basis)	$180,237	[1],[2]	$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.
[2]	(b) Does not include the negative investment balance of one real estate venture totaling $1.2 million as of March 31, 2014, which was included in other liabilities.

Deferred_Costs_Details

Deferred Costs (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Components of Deferred Costs Net [Abstract]	'	'
Leasing Costs, Total Cost	$159,517	$155,885
Financing Costs, Total Cost	40,315	40,317
Total Cost	199,832	196,202
Leasing Costs, Accumulated Amortization	-60,985	-58,805
Financing Costs, Accumulated Amortization	-15,631	-14,443
Total, Accumulated Amortization	-76,616	-73,248
Leasing, Deferred Costs, Net	98,532	97,080
Financing Costs, Deferred Costs, Net	24,684	25,874
Deferred Costs, Net	$123,216	$122,954

Deferred_Costs_Details_Textual

Deferred Costs (Details Textuals) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Deferred Costs (Textuals) [Abstract]	'	'
Capitalized Internal Direct Leasing Costs	$2.10	$2.10

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Intangible Assets [Line Items]	'	'
Total Cost	$191,938	$196,147
Accumulated Amortization	-66,776	-63,818
Intangible Assets, net	125,162	132,329
In-place lease value	'	'
Intangible Assets [Line Items]	'	'
Total Cost	147,606	150,782
Accumulated Amortization	-38,327	-35,607
Intangible Assets, net	109,279	115,175
Tenant relationship value	'	'
Intangible Assets [Line Items]	'	'
Total Cost	37,671	38,692
Accumulated Amortization	-26,858	-26,868
Intangible Assets, net	10,813	11,824
Above market leases acquired	'	'
Intangible Assets [Line Items]	'	'
Total Cost	6,661	6,673
Accumulated Amortization	-1,591	-1,343
Intangible Assets, net	5,070	5,330
Below Market Leases Acquired [Member]	'	'
Intangible Assets [Line Items]	'	'
Total Cost	-81,847	-81,991
Accumulated Amortization	49,618	47,547
Intangible Assets, net	($32,229)	($34,444)

Intangible_Assets_Annual_Amort

Intangible Assets Annual Amortization of Intangible Assets (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Annual amortization of intangible assets and liabilities	'	'
Intangible Assets, net	($125,162)	($132,329)
Assets [Member]	'	'
Annual amortization of intangible assets and liabilities	'	'
2013	19,879	'
2014	23,314	'
2015	18,573	'
2016	16,573	'
2017	12,161	'
Thereafter	34,662	'
Intangible Assets, net	-125,162	'
Liabilities [Member]	'	'
Annual amortization of intangible assets and liabilities	'	'
2013	-5,401	'
2014	-5,455	'
2015	-3,486	'
2016	-2,890	'
2017	-2,353	'
Thereafter	-12,644	'
Intangible Assets, net	$32,229	'

Debt_Obligations_Consolidated_

Debt Obligations (Consolidated Debt Obligations Outstanding) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]	'		'
Net unamortized premiums/(discounts)	($4,247)		'
Total mortgage indebtedness	666,305		670,151
Total Debt Obligations	2,591,806		2,595,381
Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	666,350		669,762
Net unamortized premiums/(discounts)	-45		389
Total mortgage indebtedness	666,305		670,151
Unsecured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	1,929,703		1,929,703
Net unamortized premiums/(discounts)	-4,202		-4,473
Total unsecured indebtedness	1,925,501		1,925,230
Unsecured Debt [Member] | Three Year Term Loan [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	150,000		150,000
Debt Instrument, Interest Rate, Effective Percentage	2.60%		'
Debt Instrument Maturity Dates	'Feb-15		'
Unsecured Debt [Member] | Four-Year Term Loan - Variable [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	100,000		100,000
Debt Instrument, Interest Rate Terms	'LIBOR + 1.75%	[1]	'
Debt Instrument Maturity Dates	'Feb-16		'
Unsecured Debt [Member] | Seven Year Term Loan [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	200,000		200,000
Debt Instrument, Interest Rate, Effective Percentage	3.62%		'
Debt Instrument Maturity Dates	'Feb-19		'
Unsecured Debt [Member] | 2014 5.400% Notes	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	218,549		218,549
Debt Instrument, Interest Rate, Effective Percentage	5.53%		'
Debt Instrument Maturity Dates	'Nov-14		'
Unsecured Debt [Member] | $250.0M 7.500% Guaranteed Notes due 2015	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	157,625		157,625
Debt Instrument, Interest Rate, Effective Percentage	7.76%		'
Debt Instrument Maturity Dates	'May-15		'
Unsecured Debt [Member] | $250.0M 6.000% Guranteed Notes due 2016 [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	149,919		149,919
Debt Instrument, Interest Rate, Effective Percentage	5.95%		'
Debt Instrument Maturity Dates	'Apr-16		'
Unsecured Debt [Member] | $300.0M 5.700% Guaranteed Notes due 2017	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	300,000		300,000
Debt Instrument, Interest Rate, Effective Percentage	5.68%		'
Debt Instrument Maturity Dates	'May-17		'
Unsecured Debt [Member] | $325.0M 4.950% Guaranteed Notes due 2018	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	325,000		325,000
Debt Instrument, Interest Rate, Effective Percentage	5.13%		'
Debt Instrument Maturity Dates	'Apr-18		'
Unsecured Debt [Member] | $250.0M 3.950% Guaranteed Notes due 2023	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	250,000		250,000
Debt Instrument, Interest Rate, Effective Percentage	4.02%		'
Debt Instrument Maturity Dates	'Feb-23		'
Unsecured Debt [Member] | Indenture IA (Preferred Trust I) [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	27,062		27,062
Debt Instrument, Interest Rate, Effective Percentage	2.75%		'
Debt Instrument Maturity Dates	'Mar-35		'
Unsecured Debt [Member] | Indenture IB (Preferred Trust I) [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	25,774		25,774
Debt Instrument, Interest Rate, Effective Percentage	3.30%		'
Debt Instrument Maturity Dates	'Apr-35		'
Unsecured Debt [Member] | Indenture II (Preferred Trust II) [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	25,774		25,774
Debt Instrument, Interest Rate, Effective Percentage	3.09%		'
Debt Instrument Maturity Dates	'Jul-35		'
Tysons Corner [Member] | Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	90,918		91,395
Debt Instrument, Interest Rate, Effective Percentage	5.36%	[2]	'
Debt Instrument Maturity Dates	'Aug-15		'
One Commerce Square [Member] | Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	124,604		125,089
Debt Instrument, Interest Rate, Effective Percentage	3.68%	[2]	'
Debt Instrument Maturity Dates	'Jan-16		'
Two Logan Square [Member] | Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	88,362		88,583
Debt Instrument, Interest Rate, Effective Percentage	7.57%		'
Debt Instrument Maturity Dates	'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	21,566		21,630
Debt Instrument, Interest Rate, Effective Percentage	4.25%	[3]	'
Debt Instrument Maturity Dates	'Jan-17		'
Two Commerce Square [Member] | Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	112,000		112,000
Debt Instrument, Interest Rate, Effective Percentage	4.51%	[2]	'
Debt Instrument Maturity Dates	'Apr-23		'
IRS Philadelphia Campus [Member] | Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	189,370		190,964
Debt Instrument, Interest Rate, Effective Percentage	7.00%		'
Debt Instrument Maturity Dates	'Sep-30		'
Cira South Garage [Member] | Secured Debt [Member]	'		'
Debt Instrument [Line Items]	'		'
Long-term Debt, Gross	$39,530		$40,101
Debt Instrument, Interest Rate, Effective Percentage	7.12%		'
Debt Instrument Maturity Dates	'Sep-30		'
[1]	(c)London Interbank Offered Rate (“LIBOR”).
[2]	(a)These loans were assumed upon acquisition of the related properties. The interest rate reflects the market rate at the time of acquisition.
[3]	(b)Represents the full debt amount secured by a property owned by a consolidated joint venture in which the Company holds a 50% interest.

Debt_Obligations_Aggregate_Sch

Debt Obligations (Aggregate Scheduled Principal Payments of Debt Obligation, Excluding Amortization of Discounts and Premiums) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Extinguishment of Debt [Line Items]	'	'
2013	$228,964	'
2014	409,655	'
2015	467,703	'
2016	330,323	'
2017	336,954	'
Thereafter	822,454	'
Total principal payments	2,596,053	'
Net unamortized premiums/(discounts)	-4,247	'
Total Debt Obligations	$2,591,806	$2,595,381

Debt_Obligations_Details_Textu

Debt Obligations (Details Textuals) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
In Millions, unless otherwise specified	Secured Debt [Member]	Secured Debt [Member]	Unsecured Debt [Member]	Unsecured Debt [Member]	Unsecured Debt [Member]	Unsecured Debt [Member]	Unsecured Debt [Member]
			Three Year Term Loan [Member]	Letter of Credit [Member]	Line of Credit [Member]	Four Year Term Loan [Member]	Seven Year Term Loan [Member]
Debt Instrument [Line Items]	'	'	'	'	'	'	'
Long-term Debt, Weighted Average Interest Rate	5.73%	6.65%	'	'	'	'	'
Debt Instrument, Basis Spread on Variable Rate	'	'	1.75%	1.50%	'	'	1.90%
Letters of Credit Outstanding, Amount	'	'	'	$1.70	'	'	'
Line of Credit Facility, Remaining Borrowing Capacity	'	'	'	'	598.3	'	'
Debt Instrument, Face Amount	'	'	150	'	'	250	200
Line of Credit Facility, Option for Additional Borrowing Capacity subject to customary conditions and limitations	'	'	'	'	$200	'	'
Declining prepayment penalty after Three Years	'	'	'	'	'	'	1.00%
Derivative, Average Fixed Interest Rate	'	'	2.60%	'	'	'	3.62%

Debt_Obligations_Details_Textu1

Debt Obligations (Details Textuals 2) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 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, Face Amount	150
Debt Instrument Term	'3 years
Option to Extend Term Loan	'1 year
Debt Instrument, Basis Spread on Variable Rate	1.75%
Unsecured Debt [Member] | Four-Year Term Loan - Variable [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Face Amount	100
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
Debt Instrument, Basis Spread on Variable Rate	1.90%
Senior notes 5.400 Percent due 2014 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	5.40%
Senior Notes Due2015 [Member]	'
Debt Instrument [Line Items]	'
Debt Instrument, Interest Rate, Stated Percentage	7.50%

Fair_Value_of_Financial_Instru2

Fair Value of Financial Instruments (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Company's estimates of fair value differ from the carrying amounts	'	'
Mortgage notes payable	$666,305	$670,151
Mortgage notes payable, Fair Value	705,244	715,244
Unsecured Notes Payable, Carrying Amount	1,396,891	1,396,620
Unsecured Notes Payable, Fair Value	1,477,304	1,471,041
Variable Rate Debt, Carrying Amount	528,610	528,610
Variable Rate Debt, Fair Value	526,693	526,693
Notes Receivable, Carrying Amount	5,826	7,026
Notes Receivable, Fair Value	$6,795	$7,759

Fair_Value_of_Financial_Instru3

Fair Value of Financial Instruments (Details Textuals) (Details)	3 Months Ended
	Mar. 31, 2014
Notes Receivable [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Fair Value Inputs, Discount Rate	14.63%
Variable rate and mortgage debt [Member]	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'
Fair Value Inputs, Discount Rate	3.51%

Risk_Management_and_Use_of_Fin2

Risk Management and Use of Financial Instruments (Fair Values of Derivative Financial Instruments) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Assets [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	$51,548	$51,548
Derivative, Fair Value, Net	315	767
Other Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	377,062	377,062
Derivative, Fair Value, Net	-2,716	-2,188
3.300% Interest Rate Swap Maturing January 30, 2021 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Assets [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	25,774	25,774
Derivative, Fixed Interest Rate	3.30%	'
Derivative, Fair Value, Net	252	549
3.090% Interest Rate Swap Maturing October 30, 2019 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Assets [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	25,774	25,774
Derivative, Fixed Interest Rate	3.09%	'
Derivative, Fair Value, Net	63	218
3.623% Interest Rate Swap Maturing February 1, 2019 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	200,000	200,000
Derivative, Fixed Interest Rate	3.62%	'
Derivative, Fair Value, Net	-1,195	-545
2.703% Interest Rate Swap Maturing February 1, 2016 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	77,000	77,000
Derivative, Fixed Interest Rate	2.70%	'
Derivative, Fair Value, Net	-825	-887
2.470% Interest Rate Swap Maturing February 1, 2015 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	50,000	50,000
Derivative, Fixed Interest Rate	2.47%	'
Derivative, Fair Value, Net	-250	-283
2.513% Interest Rate Swap Maturing May 1, 2015 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	23,000	23,000
Derivative, Fixed Interest Rate	2.51%	'
Derivative, Fair Value, Net	-150	-162
2.750% Interest Rate Swap Maturing September 30, 2017 [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Derivative, Notional Amount	27,062	27,062
Derivative, Fixed Interest Rate	2.75%	'
Derivative, Fair Value, Net	($296)	($311)

Discontinued_Operations_Detail

Discontinued Operations (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Revenue:	'	'
Rents	$121,671	$114,608
Other Real Estate Revenue	630	873
Tenant reimbursements	23,460	20,341
Total revenue	152,114	139,554
Expenses:	'	'
Property operating expenses	46,801	39,349
Real estate taxes	13,457	14,295
Depreciation and amortization	52,570	49,476
Total operating expenses	122,725	111,096
Interest income	385	58
Income from discontinued operations before gain on sale of interests in real estate	-8	860
Net gain on disposition of discontinued operations	0	5,304
Income (Loss) from discontinued operations	-8	6,164
Discontinued Operations [Member]	'	'
Revenue:	'	'
Rents	'	3,763
Termination fees	'	0
Other Real Estate Revenue	'	114
Tenant reimbursements	'	338
Total revenue	'	4,215
Expenses:	'	'
Property operating expenses	'	1,382
Real estate taxes	'	466
Depreciation and amortization	'	1,507
Total operating expenses	'	3,355
Interest income	'	0
Income from discontinued operations before gain on sale of interests in real estate	'	860
Net gain on disposition of discontinued operations	'	5,304
Income (Loss) from discontinued operations	'	$6,164

Discontinued_Operations_Detail1

Discontinued Operations (Details Textuals) (Details) (Discontinued Operations [Member])	12 Months Ended
	Dec. 31, 2013
	Properties
Discontinued Operations [Member]	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'
Number of properties sold	14

Non_Controlling_Interests_In_t1

Non Controlling Interests In the Parent Company (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Noncontrolling Interest [Abstract]	'	'
Aggregate amount related to non-controlling interests classified within equity	$20	$20.30
Settlement Value Of Non Controlling Interest In Operating Partnership	$25.50	$24.80

Beneficiaries_Equity_of_the_Pa2

Beneficiaries Equity of the Parent Company (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Numerator	'	'
Income (Loss) from Continuing Operations, Basic	($2,237)	($2,245)
Income (Loss) From Continuing Operations, Diluted	-2,237	-2,245
Net Income (Loss) From Continuing Operations Attributable to Non controlling interests, Basic	44	50
Net Income (Loss) From Continuing Operations Attributable To Non Controlling Interests, Diluted	44	50
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-12	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted	12	0
Amount allocated to unvested restricted shareholders/unitholders, Basic	-103	-108
Amount allocated to unvested restricted shareholders/unitholders, Diluted	-103	-108
Preferred share/unit dividends, Basic	-1,725	-1,725
Preferred share/unit dividends, Diluted	-1,725	-1,725
Income (Loss) from Continuing Operations Available to Common Shareholders/unitholders, Basic	-4,033	-4,028
Income (Loss) from Continuing Operations Available to Common Shareholders/unitholders, Diluted	-4,033	-4,028
Income (Loss) from Discontinued Operations	-8	6,164
Income (Loss) From Discontinued Operations, Diluted	-8	6,164
Discontinued operations attributable to non-controlling interests, Basic	0	-78
Discontinued Operations Attributable to Noncontrolling Interests- Diluted	0	-78
Discontinued operations attributable to common shareholders, Basic	-8	6,086
Discontinued operations attributable to common shareholders, Diluted	-8	6,086
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	-4,041	2,058
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	($4,041)	$2,058
Denominator	'	'
Weighted Average Number of Shares Outstanding, Basic	156,794,019	143,605,659
Weighted Average Number of Shares Outstanding, Diluted	156,794,019	143,605,659
Earnings per common share from continuing operations Abstract	'	'
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	($0.03)	($0.03)
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	($0.03)	($0.03)
Discontinued Operations attributable to common shareholders/unitholders, Basic	$0	$0.04
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$0	$0.04
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.03)	$0.01
Net income attributable to common shareholders/unitholders, Diluted	($0.03)	$0.01

Beneficiaries_Equity_of_the_Pa3

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

0 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

0 Months Ended

3 Months Ended

12 Months Ended

Apr. 10, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Nov. 05, 2013

Apr. 17, 2014

Apr. 17, 2014

Apr. 15, 2014

Mar. 31, 2014

Dec. 31, 2013

Apr. 17, 2014

Class A Units [Member]

Series E Preferred Stock [Member]

Offering Program [Member]

Dividend Declared [Member]

Dividend Paid [Member]

Dividend Paid [Member]

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]

'

'

'

'

'

'

'

'

'

'

'

'

'

Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount

'

'

'

'

1,763,739

'

'

'

'

'

'

'

'

Stock Issued During Period, Shares, New Issues

12,650,000

'

'

'

'

'

'

'

'

'

'

'

'

Additional shares granted under option to purchase in public offering

1,650,000

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Issuance of Common Stock

$181,500,000

'

'

'

'

'

'

'

'

'

'

'

'

Dividends Payable, Amount Per Share

'

'

'

'

'

'

'

$0.15

'

'

'

'

$0.15

Distributions payable

'

25,604,000

'

25,584,000

'

'

'

'

23,600,000

'

25,604,000

25,584,000

23,600,000

Preferred Stock, Shares Issued

'

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

'

$1,725,000

$1,725,000

'

'

'

'

'

'

$1,700,000

'

'

'

Shares Authorized For Equity Offering Program

'

'

'

'

'

'

16,000,000

'

'

'

'

'

'

Remaining Shares Available For Sales

'

'

'

'

'

'

16,000,000

'

'

'

'

'

'

Common Stock, Shares Authorized

'

200,000,000

'

200,000,000

'

'

'

'

'

'

'

'

'

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

'

539,200

'

'

'

'

'

'

'

'

'

'

'

Partners_Equity_of_the_Operati2

Partners Equity of the Operating Partnership (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Numerator	'	'
Income (Loss) from Continuing Operations, Basic	($2,237)	($2,245)
Income (Loss) From Continuing Operations, Diluted	-2,237	-2,245
Amount allocated to unvested restricted shareholders/unitholders, Basic	-103	-108
Amount allocated to unvested restricted shareholders/unitholders, Diluted	-103	-108
Preferred share/unit dividends, Basic	-1,725	-1,725
Preferred share/unit dividends, Diluted	-1,725	-1,725
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-12	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted	12	0
Income (Loss) from Discontinued Operations	-8	6,164
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	-4,041	2,058
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	-4,041	2,058
Denominator	'	'
Weighted-average units outstanding, Basic	156,794,019	143,605,659
Weighted Average Number of Shares Outstanding, Diluted	156,794,019	143,605,659
Earnings per Common Partnership Unit [Abstract]	'	'
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	($0.03)	($0.03)
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	($0.03)	($0.03)
Discontinued Operations attributable to common shareholders/unitholders, Basic	$0	$0.04
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$0	$0.04
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.03)	$0.01
Net income attributable to common shareholders/unitholders, Diluted	($0.03)	$0.01
BRANDYWINE OPERATING PARTNERSHIP, L.P.	'	'
Numerator	'	'
Income (Loss) from Continuing Operations, Basic	-2,237	-2,245
Income (Loss) From Continuing Operations, Diluted	-2,237	-2,245
Amount allocated to unvested restricted shareholders/unitholders, Basic	-103	-108
Amount allocated to unvested restricted shareholders/unitholders, Diluted	-103	-108
Preferred share/unit dividends, Basic	-1,725	-1,725
Preferred share/unit dividends, Diluted	-1,725	-1,725
Net income attributable to non-controlling interest — partners' share of consolidated real estate ventures	-12	0
Noncontrolling Interest in Net Income (Loss) Joint Venture Partners, Redeemable, Diluted	12	0
Income (Loss) from continuing operations available to common unitholders, Basic	-4,077	-4,078
Income (Loss) from continuing operations available to common unitholders, Diluted	-4,077	-4,078
Income (Loss) from Discontinued Operations	-8	6,164
Income (Loss) From Discontinued Operations, Diluted	-8	6,164
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	-4,085	2,086
Net Income (Loss) Available to Common Shareholders/unitholders, Diluted	($4,085)	$2,086
Denominator	'	'
Weighted-average units outstanding, Basic	158,557,758	145,451,396
Weighted Average Number of Shares Outstanding, Diluted	158,557,758	145,451,396
Earnings per Common Partnership Unit [Abstract]	'	'
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Basic Share	($0.03)	($0.03)
Income (Loss) from Continuing Operations Attributable to Common Shareholders/unitholders, Per Diluted Share	($0.03)	($0.03)
Discontinued Operations attributable to common shareholders/unitholders, Basic	$0	$0.04
Discontinued Operations attributable to common shareholders/unitholders, Diluted	$0	$0.04
Net income (loss) attributable to common shareholders/unitholders, Basic	($0.03)	$0.01
Net income attributable to common shareholders/unitholders, Diluted	($0.03)	$0.01

Partners_Equity_of_the_Operati3

Partners Equity of the Operating Partnership (Details Textuals) (Details) (USD $)	0 Months Ended	3 Months Ended		12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended			0 Months Ended
	Apr. 10, 2013	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Apr. 17, 2014	Apr. 17, 2014	Apr. 15, 2014
					BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P.	6.90% Series E-linked Preferred Units [Member]	Dividend Paid [Member]	Dividend Paid [Member]	Dividend Paid [Member]
							BRANDYWINE OPERATING PARTNERSHIP, L.P.		BRANDYWINE OPERATING PARTNERSHIP, L.P.	6.90% Series E-linked Preferred Units [Member]
										BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings per Common Partnership Unit [Line Items]	'	'	'	'	'	'	'	'	'	'
Dividends Payable, Amount Per Share	'	'	'	'	'	'	'	'	$0.15	'
Stock Issued During Period, Shares, New Issues	12,650,000	'	'	'	'	'	'	'	'	'
Additional shares granted under option to purchase in public offering	1,650,000	'	'	'	'	'	'	'	'	'
Proceeds from Issuance of Common Stock	$181,500,000	'	'	'	'	'	'	'	'	'
Distributions payable	'	25,604,000	'	25,584,000	25,604,000	25,584,000	'	23,600,000	23,600,000	'
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	'	$1,725,000	$1,725,000	'	'	'	'	'	'	$1,700,000

Share_Based_and_Deferred_Compe2

Share Based and Deferred Compensation (Option Activity) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	'4 years 11 months 0 days	'4 years 11 months 0 days
Share Based Compensation Arrangement By Share Based Payment Award Option Activity [Abstract]	'	'
Outstanding at the beginning of year, shares	2,983,569	'
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	$0	'
Exercised in Period, Shares	0	'
Exercises in Period, Weighted Average Grant Date Fair Value	$0	'
Forfeited, shares	0	'
Forfeited, Weighted Average Grant Date Fair Value	$0	'
Outstanding at the end of year, shares	2,983,569	2,983,569
Outstanding at end of year, Weighted Average Exercise Price	$15.50	$15.50
Outstanding at end of year, Aggregate Intrinsic Value	0	0
Vested/Exerciseable, shares	2,983,569	'
Vested/Exerciseable at end of period, Weigted Average Exercise Price	$15.50	'
Vested/Exerciseable at end of period, Weighted Average Remaining Contractual Term (in years)	'4 years 11 months 0 days	'
Vested/Exercisable at end of year, Aggregate Intrinsic Value	$0	'
Stock Option [Member]	'	'
Share Based Compensation Arrangement By Share Based Payment Award Option Activity [Abstract]	'	'
Outstanding at the end of year, shares	2,983,569	'

Share_Based_and_Deferred_Compe3

Share Based and Deferred Compensation (Restricted Share Activity) (Details) (Restricted Stock [Member], USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 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]	'	'	'	'	'
Allocated Share-based Compensation Expense	$1.40	$0.90	'	'	'
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, Shares	201,435	'	'	'	'
Granted, Weighted Average Grant Date Fair Value	$14.37	'	'	'	'
Vested, shares	-70,548	'	'	'	'
Vested, Weighted Average Grant Date Fair Value	$16.82	'	'	'	'
Forfeited, shares	-6,696	'	'	'	'
Forfeited, Weighted Average Grant Date Fair Value	$11.84	'	'	'	'
Non-vested at June 30, 2013, shares	687,904	'	'	'	'
Non-vested at June 30, 2013, Weighted Average Grant Date Fair Value	$12.66	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount	$0.20	$0.20	'	'	'

Share_Based_and_Deferred_Compe4

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

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

0 Months Ended

12 Months Ended

Mar. 31, 2014

Dec. 31, 2011

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 11, 2014

Mar. 12, 2014

Mar. 01, 2012

Feb. 25, 2014

Feb. 25, 2013

Stock Option [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]

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 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]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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 date

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

687,904

'

563,713

'

'

'

'

'

134,284

61,720

211,521

'

203,395

Vested/Exerciseable, shares

2,983,569

'

'

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

'1 year 8 months 12 days

'

'

'

'

'

'

'

'

'

'

'

'

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

'

'

3,300,000

'

'

'

'

'

'

'

'

'

'

'

'

Allocated Share-based Compensation Expense

'

300,000

1,400,000

900,000

'

'

'

1,700,000

1,200,000

'

'

'

'

'

'

Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount

'

'

$200,000

$200,000

'

'

'

$400,000

$300,000

'

'

'

'

'

'

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

'

'

70,548

'

'

'

'

'

150,829

'

'

'

'

'

'

Age Limit Of Voluntary Termination Of Employment

'

'

'

'

'

'

'

'

'

57

'

'

'

'

'

Share_Based_and_Deferred_Compe5

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

3 Months Ended

0 Months Ended

12 Months Ended

3 Months Ended

0 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Mar. 11, 2014

Mar. 12, 2014

Oct. 31, 2012

Mar. 01, 2012

Feb. 25, 2014

Feb. 25, 2013

Mar. 31, 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]

Executive Officer [Member]

Rate

Original Grant [Member]

Dividend equivalent shares vested [Member]

Total vested [Member]

Rate

Rate

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

$1,700,000

$1,200,000

'

'

'

'

'

'

'

'

'

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]

'

'

Unvested Balance

'

'

134,284

61,720

'

211,521

'

203,395

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate

'

'

'

'

200.00%

'

'

'

'

56300.00%

3061000.00%

[1]

(a) Units were issued in accordance with our qualifying retirement provision, meaning the recipient’s voluntary termination of employment after reaching age 57 and accumulating at least 15 years of service with the Company. Of the 14,742 shares originally granted, 563 dividend equivalent rights were accrued at the time of retirement and 30,610 shares were issued based on our TSR (Total Shareholder Return) Percentile at October 31, 2012 of 200%.

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Real Estate Investments At Cost [Abstract]	'		'	'
Net gain on sale of interests in real estate	($1,187)		($5,304)	'
Operating properties	4,701,289		'	4,669,289
Construction-in-progress	90,140		'	74,174
Land inventory	96,427		'	93,351
Investment in real estate ventures, at equity	180,237		'	180,512
Total revenue	152,114		139,554	'
Property operating expenses	-61,974		-55,069	'
Gross Profit	90,140		84,485	'
Equity in income of real estate ventures	242		1,535	'
Interest Expense, Debt	31,844		30,914	'
Amortization of deferred financing costs	1,189		1,161	'
Interest Expense, Other	272		218	'
Depreciation and amortization	52,570		49,476	'
General and administrative expenses	8,181		6,551	'
Loss on early extinguishment of debt	0		-3	'
Interest income	385		58	'
Gain on sale of undepreciated real estate	1,187		0	'
Income (Loss) from Continuing Operations, Basic	-2,237		-2,245	'
Income (Loss) from Discontinued Operations	-8		6,164	'
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	-2,245		3,919	'
Pennsylvania [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	1,209,328		'	1,199,105
Investment in real estate ventures, at equity	17,379		'	17,272
Total revenue	40,574		37,916	'
Property operating expenses	-14,687		-14,436	'
Gross Profit	25,887		23,480	'
Equity in income of real estate ventures	32		31	'
Philadelphia CBD [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	1,318,170		'	1,300,666
Investment in real estate ventures, at equity	20,131		'	19,975
Total revenue	49,414		35,925	'
Property operating expenses	-18,443		-13,534	'
Gross Profit	30,971		22,391	'
Equity in income of real estate ventures	-21		566	'
Metropolitan Dc [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	1,219,542		'	1,214,965
Investment in real estate ventures, at equity	59,847		'	59,905
Total revenue	30,690		27,785	'
Property operating expenses	-11,957		-10,763	'
Gross Profit	18,733		17,022	'
Equity in income of real estate ventures	67		16	'
New Jersey/ Delaware [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	414,353		'	414,716
Investment in real estate ventures, at equity	0		'	0
Total revenue	15,625		14,919	'
Property operating expenses	-8,692		-7,031	'
Gross Profit	6,933		7,888	'
Equity in income of real estate ventures	18		908	'
Richmond, Virginia [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	310,465		'	310,397
Investment in real estate ventures, at equity	1,355		'	1,400
Total revenue	8,867		8,765	'
Property operating expenses	-4,340		-3,683	'
Gross Profit	4,527		5,082	'
Equity in income of real estate ventures	-45		-8	'
Austin, Texas [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	36,480		'	36,856
Investment in real estate ventures, at equity	81,525	[1]	'	81,960
Total revenue	2,081		9,257	'
Property operating expenses	-1,176		-3,958	'
Gross Profit	905		5,299	'
Equity in income of real estate ventures	191		22	'
California	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	192,951		'	192,584
Investment in real estate ventures, at equity	0		'	0
Total revenue	4,602		4,605	'
Property operating expenses	-2,409		-2,160	'
Gross Profit	2,193		2,445	'
Equity in income of real estate ventures	0		0	'
Corporate [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Operating properties	0		'	0
Construction-in-progress	90,140		'	74,174
Land inventory	96,427		'	93,351
Investment in real estate ventures, at equity	0		'	0
Total revenue	261		382	'
Property operating expenses	-270		496	'
Gross Profit	-9		878	'
Equity in income of real estate ventures	0		0	'
Austin Joint Venture [Member]	'		'	'
Real Estate Investments At Cost [Abstract]	'		'	'
Investment in real estate ventures, at equity	($1,200)		'	'
[1]	(a) Does not include the negative investment balance of one real estate venture totaling $1.2 million as of March 31, 2014, which was included in other liabilities.

Segment_Information_Reconcilia

Segment Information (Reconciliation of Consolidated Net Operating Income) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
	Reportable_Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'	'
Consolidated net operating income	$90,140	$84,485
Less:	'	'
Interest expense	-31,844	-30,914
Interest expense — amortization of deferred financing costs	-1,189	-1,161
Interest expense — financing obligation	-272	-218
Depreciation and amortization	-52,570	-49,476
General and administrative expenses	-8,181	-6,551
Net Gain (Loss) On Real Estate Venture Transactions, including real estate venture formation	-135	0
Loss on early extinguishment of debt	0	-3
Plus:	'	'
Interest income	385	58
Equity in income of real estate ventures	242	1,535
Net gain (loss) on sale of undepreciated real estate	1,187	0
Loss from continuing operations	-2,237	-2,245
Income (Loss) from Discontinued Operations	-8	6,164
Net income	($2,245)	$3,919
Number of Reportable Segments	7	'

Commitments_and_Contingencies_1

Commitments and Contingencies (Details)	Mar. 31, 2014
	Y
Long-term Purchase Commitment [Line Items]	'
Minimum remaining lease period	15
Maximum remaining lease period	75

Commitments_and_Contingencies_2

Commitments and Contingencies (Ground Rent) (Details) (Ground Rent [Member], USD $)	Mar. 31, 2014
In Thousands, unless otherwise specified
Ground Rent [Member]	'
Long-term Purchase Commitment [Line Items]	'
2014 (nine months remaining)	$1,062
2014	1,415
2015	1,415
2016	1,415
2017	1,415
Thereafter	61,666
Operating Leases, Future Minimum Payments Due	$68,388

Subsequent_Events_Details

Subsequent Events (Details) (USD $)	3 Months Ended				0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Apr. 03, 2014	Apr. 03, 2014	Apr. 03, 2014	Apr. 03, 2014
			Four Points Centre [Member]	Austin Joint Venture [Member]	Austin Joint Venture [Member]	Austin Joint Venture [Member]
			Properties	Four Points Centre [Member]	Brandywine Realty Trust [Member]	DRA Advisors LLC [Member]
			Storey		Four Points Centre [Member]	Four Points Centre [Member]
			sqft
Subsequent Event [Line Items]	'	'	'	'	'	'
Number of Real Estate Properties	'	'	2	'	'	'
Number of floors of a building	'	'	3	'	'	'
Net Rentable Space	'	'	192,396	'	'	'
Aggregate gross sales price of a joint venture	'	'	'	'	$41,500,000	'
Non-Recourse Debt	'	'	'	29,000,000	'	'
Amount Of Participant Contribution	'	'	'	'	'	5,900,000
Proceeds from Equity Method Investment, Dividends or Distributions	2,828,000	1,357,000	'	'	34,400,000	'
Payments to Acquire Equity Method Investments	'	'	'	'	5,900,000	'
Loss On Real Estate Venture Transactions, including real estate venture formation	($135,000)	$0	'	'	($200,000)	'