Brandywine Realty Trust (BDN) 10-K 24 Feb 21 2020 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 18, 2021	Jun. 30, 2020
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	Brandywine Realty Trust
Entity Central Index Key	0000790816
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Incorporation, State or Country Code	MD
Entity File Number	001-9106
Entity Tax Identification Number	23-2413352
Entity Address, Address Line One	2929 Walnut Street
Entity Address, Address Line Two	Suite 1700
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19104
City Area Code	610
Local Phone Number	325-5600
Title of 12(b) Security	Common Shares of Beneficial Interest
Trading Symbol	BDN
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1,811,989,986
Entity Common Stock, Shares Outstanding		170,637,419
Documents Incorporated by Reference	Portions of the proxy statement for the 2021 Annual Meeting of Shareholders of Brandywine Realty Trust are incorporated by reference into Part III of this Form 10-K.
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Document Information [Line Items]
Entity Registrant Name	Brandywine Operating Partnership, L.P.
Entity Central Index Key	0001060386
Entity Incorporation, State or Country Code	DE
Entity File Number	000-24407
Entity Tax Identification Number	23-2862640
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Real estate investments:
Operating properties	$ 3,474,109	$ 4,006,459
Accumulated depreciation	(896,561)	(973,318)
Right of use asset - operating leases, net	20,977	21,656
Operating real estate investments, net	2,598,525	3,054,797
Construction-in-progress	210,311	180,718
Land held for development	117,984	96,124
Prepaid leasehold interests in land held for development, net	39,185	39,592
Total real estate investments, net	2,966,005	3,371,231
Assets held for sale, net	7,349	7,349
Cash and cash equivalents	46,344	90,499
Accounts receivable, net of allowance of $0 and $284 as of December 31, 2020 and December 31, 2019, respectively	13,536	16,363
Accrued rent receivable, net of allowance of $5,086 and $7,691 as of December 31, 2020 and December 31, 2019, respectively	155,372	174,144
Investment in Real Estate Ventures, equity method	401,327	120,294
Deferred costs, net	84,856	95,560
Intangible assets, net	48,570	84,851
Other assets	176,747	115,678
Total assets	3,900,106	4,075,969
LIABILITIES AND BENEFICIARIES' EQUITY
Mortgage notes payable, net	0	313,812
Unsecured term loan, net	249,084	248,561
Unsecured senior notes, net	1,581,511	1,582,045
Accounts payable and accrued expenses	121,982	113,347
Distributions payable	32,706	33,815
Deferred income, gains and rent	21,396	35,284
Intangible liabilities, net	18,448	22,263
Lease Liability - operating leases	22,758	22,554
Other liabilities	47,573	15,985
Total liabilities	2,095,458	2,387,666
Commitments and contingencies (See Note 20)
Equity:
Common Shares of Brandywine Realty Trust's beneficial interest, $0.01 par value; shares authorized 400,000,000; 170,572,964 and 176,480,095 issued and outstanding as of December 31, 2020 and December 31, 2019, respectively	1,707	1,766
Additional paid-in-capital	3,138,152	3,192,158
Deferred compensation payable in common shares	17,516	16,216
Common shares in grantor trust, 1,160,494 and 1,105,542 issued and outstanding as of December 31, 2020 and December 31, 2019, respectively	(17,516)	(16,216)
Cumulative earnings	1,110,083	804,556
Accumulated other comprehensive loss	(7,561)	(2,370)
Cumulative distributions	(2,448,238)	(2,318,233)
Total Brandywine Realty Trust's equity	1,794,143	1,677,877
Noncontrolling interests	10,505	10,426
Total beneficiaries' equity	1,804,648	1,688,303
Total liabilities and partners' equity	3,900,106	4,075,969
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real estate investments:
Operating properties	3,474,109	4,006,459
Accumulated depreciation	(896,561)	(973,318)
Right of use asset - operating leases, net	20,977	21,656
Operating real estate investments, net	2,598,525	3,054,797
Construction-in-progress	210,311	180,718
Land held for development	117,984	96,124
Prepaid leasehold interests in land held for development, net	39,185	39,592
Total real estate investments, net	2,966,005	3,371,231
Assets held for sale, net	7,349	7,349
Cash and cash equivalents	46,344	90,499
Accounts receivable, net of allowance of $0 and $284 as of December 31, 2020 and December 31, 2019, respectively	13,536	16,363
Accrued rent receivable, net of allowance of $5,086 and $7,691 as of December 31, 2020 and December 31, 2019, respectively	155,372	174,144
Investment in Real Estate Ventures, equity method	401,327	120,294
Deferred costs, net	84,856	95,560
Intangible assets, net	48,570	84,851
Other assets	176,747	115,678
Total assets	3,900,106	4,075,969
LIABILITIES AND BENEFICIARIES' EQUITY
Mortgage notes payable, net	0	313,812
Unsecured term loan, net	249,084	248,561
Unsecured senior notes, net	1,581,511	1,582,045
Accounts payable and accrued expenses	121,982	113,347
Distributions payable	32,706	33,815
Deferred income, gains and rent	21,396	35,284
Intangible liabilities, net	18,448	22,263
Lease Liability - operating leases	22,758	22,554
Other liabilities	47,573	15,985
Total liabilities	2,095,458	2,387,666
Commitments and contingencies (See Note 20)
Redeemable limited partnership units at redemption value; 981,634 issued and outstanding as of December 31, 2020 and December 31, 2019	11,566	15,388
Equity:
General Partnership Capital; 170,572,964 and 176,480,095 units issued and outstanding as of December 31, 2020 and December 31, 2019, respectively	1,800,945	1,674,539
Accumulated other comprehensive loss	(7,935)	(2,715)
Total Brandywine Operating Partnership, L.P.'s equity	1,793,010	1,671,824
Noncontrolling interest - consolidated real estate ventures	72	1,091
Total partners' equity	1,793,082	1,672,915
Total liabilities and partners' equity	$ 3,900,106	$ 4,075,969

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Common stock, par or stated value per share (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares, issued (in shares)	170,572,964	176,480,095
Common stock, shares, outstanding (in shares)	170,572,964	176,480,095
Common shares in grantor trust, issued and outstanding (in shares)	1,160,494	1,105,542
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Accounts receivable, allowance for credit loss	$ 0	$ 284
Accrued rent receivable, allowance for credit loss	$ 5,086	$ 7,691
Redeemable limited partnership units issued (in units)	981,634	981,634
Redeemable limited partnership units outstanding (in units)	981,634	981,634
General Partners' Capital, units issued (in units)	170,572,964	176,480,095
General Partners' Capital, units outstanding (in units)	170,572,964	176,480,095

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Total revenue	$ 534,852	$ 580,417	$ 544,345
Operating expenses
Property operating expenses	132,172	154,361	154,848
Real estate taxes	63,032	62,237	51,341
Third party management expenses	10,252	9,248	11,910
Depreciation and amortization	188,283	210,005	176,000
General and administrative expenses	30,288	32,156	27,802
Provision for impairment	0	0	71,707
Total operating expenses	424,027	468,007	493,608
Gain on sale of real estate
Net gain on disposition of real estate	289,461	356	2,932
Net gain on sale of undepreciated real estate	201	2,020	3,040
Total gain on sale of real estate	289,662	2,376	5,972
Operating income	400,487	114,786	56,709
Other income (expense):
Interest income	1,939	2,318	4,703
Interest expense	(73,911)	(81,512)	(78,199)
Interest expense - amortization of deferred financing costs	(2,904)	(2,768)	(2,498)
Equity in loss of Real Estate Ventures	(18,584)	(9,922)	(15,231)
Net gain on real estate venture transactions	75	11,639	142,233
Gain on promoted interest in unconsolidated real estate venture	0	0	28,283
Loss on early extinguishment of debt	0	0	(105)
Net income before income taxes	307,102	34,541	135,895
Income tax (provision) benefit	224	(12)	(423)
Net income	307,326	34,529	135,472
Net income attributable to noncontrolling interests	(1,799)	(262)	(954)
Net income attributable to Brandywine Realty Trust	305,527	34,267	134,518
Nonforfeitable dividends allocated to unvested restricted shareholders	(410)	(396)	(369)
Net income attributable to Common Shareholders/ Unitholders of Brandywine Realty Trust	$ 305,117	$ 33,871	$ 134,149
Basic income per Common Share (in dollars per shares)	$ 1.77	$ 0.19	$ 0.75
Diluted income per Common Share (in dollars per share)	$ 1.77	$ 0.19	$ 0.75
Basic weighted average shares outstanding (in shares)	171,926,079	176,132,941	178,519,748
Diluted weighted average shares outstanding (in shares)	172,317,076	176,686,813	179,641,492
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Total revenue	$ 534,852	$ 580,417	$ 544,345
Operating expenses
Property operating expenses	132,172	154,361	154,848
Real estate taxes	63,032	62,237	51,341
Third party management expenses	10,252	9,248	11,910
Depreciation and amortization	188,283	210,005	176,000
General and administrative expenses	30,288	32,156	27,802
Provision for impairment	0	0	71,707
Total operating expenses	424,027	468,007	493,608
Gain on sale of real estate
Net gain on disposition of real estate	289,461	356	2,932
Net gain on sale of undepreciated real estate	201	2,020	3,040
Total gain on sale of real estate	289,662	2,376	5,972
Operating income	400,487	114,786	56,709
Other income (expense):
Interest income	1,939	2,318	4,703
Interest expense	(73,911)	(81,512)	(78,199)
Interest expense - amortization of deferred financing costs	(2,904)	(2,768)	(2,498)
Equity in loss of Real Estate Ventures	(18,584)	(9,922)	(15,231)
Net gain on real estate venture transactions	75	11,639	142,233
Gain on promoted interest in unconsolidated real estate venture	0	0	28,283
Loss on early extinguishment of debt	0	0	(105)
Net income before income taxes	307,102	34,541	135,895
Income tax (provision) benefit	224	(12)	(423)
Net income	307,326	34,529	135,472
Net income attributable to noncontrolling interests - consolidated real estate ventures	(20)	(69)	(55)
Net income attributable to Brandywine Operating Partnership	307,306	34,460	135,417
Nonforfeitable dividends allocated to unvested restricted shareholders	(410)	(396)	(369)
Net income attributable to Common Shareholders/ Unitholders of Brandywine Realty Trust	$ 306,896	$ 34,064	$ 135,048
Basic income per Common Share (in dollars per shares)	$ 1.77	$ 0.19	$ 0.75
Diluted income per Common Share (in dollars per share)	$ 1.77	$ 0.19	$ 0.75
Basic weighted average shares outstanding (in shares)	172,907,713	177,114,932	179,959,370
Diluted weighted average shares outstanding (in shares)	173,298,710	177,668,804	181,081,114
Rents
Revenue
Total revenue	$ 513,504	$ 554,665	$ 515,044
Rents | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Total revenue	513,504	554,665	515,044
Third party management fees, labor reimbursement and leasing
Revenue
Total revenue	18,580	19,626	22,557
Third party management fees, labor reimbursement and leasing | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Total revenue	18,580	19,626	22,557
Other
Revenue
Total revenue	2,768	6,126	6,744
Other | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Total revenue	$ 2,768	$ 6,126	$ 6,744

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income		$ 307,326	$ 34,529	$ 135,472
Comprehensive income (loss):
Unrealized gain (loss) on derivative financial instruments		(5,972)	(8,210)	1,478
Amortization of interest rate contracts	[1]	752	770	1,191
Total comprehensive income (loss)		(5,220)	(7,440)	2,669
Comprehensive income		302,106	27,089	138,141
Comprehensive income attributable to noncontrolling interest		(1,770)	(221)	(993)
Comprehensive income attributable to Brandywine Realty Trust/Brandywine Operating Partnership		300,336	26,868	137,148
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Net income		307,326	34,529	135,472
Comprehensive income (loss):
Unrealized gain (loss) on derivative financial instruments		(5,972)	(8,210)	1,478
Amortization of interest rate contracts	[1]	752	770	1,191
Total comprehensive income (loss)		(5,220)	(7,440)	2,669
Comprehensive income		302,106	27,089	138,141
Comprehensive income attributable to noncontrolling interest		(20)	(69)	(55)
Comprehensive income attributable to Brandywine Realty Trust/Brandywine Operating Partnership		$ 302,086	$ 27,020	$ 138,086
[1]	Amounts reclassified from comprehensive income to interest expense within the Consolidated Statements of Operations.

Consolidated Statements of Bene

Consolidated Statements of Beneficiaries' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Deferred Compensation Payable in Common Shares	Additional Paid-in Capital	Common Shares in Grantor Trust	Cumulative Earnings	Cumulative EarningsCumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Cumulative Distributions	Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2017			178,285,236	894,736
Beneficiaries' Equity, beginning balance at Dec. 31, 2017	$ 1,826,870		$ 1,784	$ 12,445	$ 3,218,077	$ (12,445)	$ 641,093		$ 2,399	$ (2,053,741)	$ 17,258
Net income	135,472						134,518				954
Other comprehensive income	2,669								2,630		39
Issuance of Common Shares of Beneficial Interest (in shares)			23,311
Issuance of Common Shares of Beneficial Interest	$ 416				416
Repurchase and retirement of Common Shares of Beneficial Interest (in shares)	(1,729,278)		(1,729,278)
Repurchase and retirement of Common Shares of Beneficial Interest	$ (21,858)		$ (17)		(21,841)
Issuance of partnership interest in consolidated real estate venture	16										16
Distributions from consolidated real estate venture	(94)										(94)
Share Choice Plan Issuance (in shares)			(1,285)
Redemption of LP Units	(7,043)										(7,043)
Share-based compensation activity (in shares)			196,151
Share-based compensation activity	5,845		$ 2		5,829		14
Share Issuance from/(to) Deferred Compensation Plan (in shares)			99,189	82,384
Share Issuance from/(to) Deferred Compensation Plan	(111)		$ 1	$ 1,576	(112)	(1,576)
Reallocation of Noncontrolling Interest	0				(2,057)						2,057
Distributions declared	(131,154)									(130,168)	(986)
Ending balance (in shares) at Dec. 31, 2018			176,873,324	977,120
Beneficiaries' Equity, ending balance at Dec. 31, 2018	1,811,028	$ (5,336)	$ 1,770	$ 14,021	3,200,312	(14,021)	775,625	$ (5,336)	5,029	(2,183,909)	12,201
Net income	34,529						34,267				262
Other comprehensive income	$ (7,440)								(7,399)		(41)
Repurchase and retirement of Common Shares of Beneficial Interest (in shares)	(1,337,169)		(1,337,169)
Repurchase and retirement of Common Shares of Beneficial Interest	$ (17,281)		$ (13)		(17,268)
Issuance of partnership interest in consolidated real estate venture	27										27
Purchase of partnership interest in consolidated real estate venture	(2,180)				(983)						(1,197)
Redemption of LP Units (in shares)			1,245
Redemption of LP Units	0				16						(16)
Share-based compensation activity (in shares)			845,210	41,342
Share-based compensation activity	10,027		$ 9		10,018
Share Issuance from/(to) Deferred Compensation Plan (in shares)			97,485	87,080
Share Issuance from/(to) Deferred Compensation Plan	0			$ 2,195		(2,195)
Reallocation of Noncontrolling Interest	0				63						(63)
Distributions declared	(135,071)									(134,324)	(747)
Ending balance (in shares) at Dec. 31, 2019			176,480,095	1,105,542
Beneficiaries' Equity, ending balance at Dec. 31, 2019	1,688,303		$ 1,766	$ 16,216	3,192,158	(16,216)	804,556		(2,370)	(2,318,233)	10,426
Net income	307,326						305,527				1,799
Other comprehensive income	$ (5,220)								(5,191)		(29)
Repurchase and retirement of Common Shares of Beneficial Interest (in shares)	(6,248,483)		(6,248,483)
Repurchase and retirement of Common Shares of Beneficial Interest	$ (59,999)		$ (62)		(59,937)
Sale of partnership interest to consolidated real estate venture	(1,017)
Distributions from consolidated real estate venture	(22)
Share-based compensation activity (in shares)			309,096	50,967
Share-based compensation activity	6,236		$ 3		6,233
Share Issuance from/(to) Deferred Compensation Plan (in shares)			32,256	3,985
Share Issuance from/(to) Deferred Compensation Plan	(206)			$ 1,300	(206)	(1,300)
Reallocation of Noncontrolling Interest	0				(96)						96
Distributions declared	(130,753)									(130,005)	(748)
Ending balance (in shares) at Dec. 31, 2020			170,572,964	1,160,494
Beneficiaries' Equity, ending balance at Dec. 31, 2020	$ 1,804,648		$ 1,707	$ 17,516	$ 3,138,152	$ (17,516)	$ 1,110,083		$ (7,561)	$ (2,448,238)	$ 10,505

Consolidated Statements of Be_2

Consolidated Statements of Beneficiaries' Equity (Parenthetical) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Statement of Stockholders' Equity [Abstract]
Distributions declared per Common Share (in dollars per share)	$ 0.73	$ 0.76	$ 0.76

Consolidated Statements of Part

Consolidated Statements of Partners' Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P.Cumulative Effect, Period of Adoption, Adjustment	BRANDYWINE OPERATING PARTNERSHIP, L.P.Accumulated Other Comprehensive Income (Loss)	BRANDYWINE OPERATING PARTNERSHIP, L.P.Noncontrolling Interests	BRANDYWINE OPERATING PARTNERSHIP, L.P.General Partner Capital	BRANDYWINE OPERATING PARTNERSHIP, L.P.General Partner CapitalCumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 31, 2017								178,285,236
Partners' Equity, beginning balance at Dec. 31, 2017				$ 1,799,955		$ 2,056	$ 2,215	$ 1,795,684
Net income	$ 135,472		$ 954	135,472			55	$ 135,417
Other comprehensive income	2,669	$ 2,630	39	2,669		2,669
Deferred compensation obligation (in shares)								99,189
Deferred compensation obligation	(111)			(111)				$ (111)
Issuance of LP Units (in shares)								23,311
Issuance of LP Units				416				$ 416
Repurchase and retirement of LP units (in shares)								(1,729,278)
Repurchase and retirement of LP units				(21,858)				$ (21,858)
Issuance of partnership interest in consolidated real estate venture	16		16	16			16
Distributions from consolidated real estate venture	(94)		(94)	(94)			(94)
Share Choice Plan Issuance (in shares)								(1,285)
Share-based compensation activity (in shares)								196,151
Share-based compensation activity	5,845			5,848				$ 5,848
Redemption value of limited partnership units				6,363				6,363
Distributions declared to general partnership unitholders				(130,168)				$ (130,168)
Ending balance (in shares) at Dec. 31, 2018								176,873,324
Partners' Equity, ending balance at Dec. 31, 2018				1,798,508	$ (5,336)	4,725	2,192	$ 1,791,591	$ (5,336)
Net income	34,529		262	34,529			69	$ 34,460
Other comprehensive income	(7,440)	(7,399)	(41)	(7,440)		(7,440)
Deferred compensation obligation (in shares)								97,485
Deferred compensation obligation	0
Conversion of LP Units to common shares (in shares)								1,245
Conversion of LP Units to common shares				16				$ 16
Repurchase and retirement of LP units (in shares)								(1,337,169)
Repurchase and retirement of LP units				(17,297)				$ (17,297)
Issuance of partnership interest in consolidated real estate venture	27		27	27			27
Share-based compensation activity (in shares)								845,210
Share-based compensation activity	10,027			10,027				$ 10,027
Purchase of partnership interest in consolidated real estate venture	(2,180)		(1,197)				(1,197)	(983)
Adjustment of redeemable partnership units to liquidation value at period end				(3,615)				(3,615)
Distributions declared to general partnership unitholders				(134,324)				$ (134,324)
Ending balance (in shares) at Dec. 31, 2019								176,480,095
Partners' Equity, ending balance at Dec. 31, 2019				1,672,915		(2,715)	1,091	$ 1,674,539
Net income	307,326		1,799	307,326			20	$ 307,306
Other comprehensive income	(5,220)	$ (5,191)	$ (29)	(5,220)		(5,220)
Deferred compensation obligation (in shares)								32,256
Deferred compensation obligation	(206)			(206)				$ (206)
Repurchase and retirement of LP units (in shares)								(6,248,483)
Repurchase and retirement of LP units				(59,999)				$ (59,999)
Distributions from consolidated real estate venture	(22)			(22)			(22)
Share-based compensation activity (in shares)								309,096
Share-based compensation activity	6,236			6,236				$ 6,236
Sale of partnership interest to consolidated real estate venture	$ (1,017)
Adjustment of redeemable partnership units to liquidation value at period end				3,074				3,074
Distributions declared to general partnership unitholders				(130,005)				$ (130,005)
Ending balance (in shares) at Dec. 31, 2020								170,572,964
Partners' Equity, ending balance at Dec. 31, 2020				$ 1,793,082		$ (7,935)	$ 72	$ 1,800,945

Consolidated Statements of Pa_2

Consolidated Statements of Partners' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
BRANDYWINE OPERATING PARTNERSHIP, L.P. | General Partner Capital
Distributions to general partnership unitholders (USD per share)	$ 0.76	$ 0.76	$ 0.73

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 307,326	$ 34,529	$ 135,472
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	188,283	210,005	176,000
Amortization of deferred financing costs	2,904	2,768	2,498
Amortization of debt discount/(premium), net	(568)	189	702
Amortization of stock compensation costs	6,627	6,876	5,716
Straight-line rent income	(14,743)	(11,369)	(12,283)
Amortization of acquired above (below) market leases, net	(4,867)	(8,857)	(3,344)
Ground rent expense	1,455	1,470	431
Provision for doubtful accounts	1,049	(1,345)	1,775
Net gain on real estate venture transactions	(75)	(11,639)	(142,233)
Gain on promoted interest in unconsolidated real estate venture	0	0	(28,283)
Net gain on sale of interests in real estate	(289,662)	(2,376)	(5,972)
Loss on early extinguishment of debt	0	0	105
Provision for impairment	0	0	71,707
Other than temporary impairment	0	0	4,076
Loss from Real Estate Ventures, net of distributions	18,584	10,242	12,871
Income tax provision (benefit)	(224)	12	423
Changes in assets and liabilities:
Accounts receivable	(2,031)	(248)	3,524
Other assets	(5,034)	9,368	(14,334)
Accounts payable and accrued expenses	14,374	(5,599)	12,579
Deferred income, gains and rent	(12,149)	9,319	3,017
Other liabilities	14,557	(9,115)	2,902
Net cash provided by operating activities	225,806	234,230	227,349
Cash flows from investing activities:
Acquisition of properties	(41,950)	0	(196,625)
Acquisition of partners interest in consolidated real estate venture	0	(2,181)	0
Proceeds from the sale of properties	278,114	41,795	324,090
Proceeds from real estate venture sales	0	9,730	60,346
Issuance of note receivable	(50,000)	0	0
Issuance of mortgage note receivable	0	0	(175,172)
Proceeds from repayment of mortgage notes receivable	0	3,341	192
Proceeds from repayment of a capital lease	0	0	181
Capital expenditures for tenant improvements	(73,166)	(67,258)	(65,264)
Capital expenditures for redevelopments	(21,664)	(53,846)	(48,231)
Capital expenditures for developments	(65,420)	(77,192)	(99,104)
Advances for the purchase of tenant assets, net of repayments	1,488	(1,035)	410
Investment in unconsolidated Real Estate Ventures	(719)	(253)	(908)
Deposits for real estate	0	(4,181)	(8,234)
Escrowed cash	0	0	5,694
Capital distributions from Real Estate Ventures	9,001	35,906	6,526
Leasing costs paid	(17,394)	(15,485)	(18,407)
Net cash provided by (used in) investing activities	18,290	(130,659)	(214,506)
Cash flows from financing activities:
Repayments of mortgage notes payable	(94,993)	(7,595)	(122,180)
Proceeds from credit facility borrowings	318,000	348,500	455,500
Repayments of credit facility borrowings	(318,000)	(441,000)	(363,000)
Proceeds from unsecured notes	0	216,373	0
Debt financing costs paid	0	(1,965)	(3,430)
Proceeds from the exercise of stock options	47	3,771	0
Proceeds from the issuance of common shares	0	0	416
Shares used for employee taxes upon vesting of share awards	(1,346)	(1,554)	(1,494)
Partner contributions to consolidated real estate venture	0	27	16
Partner distributions from consolidated real estate venture	0	0	(94)
Repurchase and retirement of common shares	(60,000)	(17,282)	(21,841)
Redemption of limited partnership units	0	0	(7,043)
Distributions paid to shareholders	(131,150)	(134,140)	(128,859)
Distributions to noncontrolling interest	(747)	(747)	(1,065)
Net cash used in financing activities	(288,189)	(35,612)	(193,074)
Increase/(Decrease) in cash and cash equivalents and restricted cash	(44,093)	67,959	(180,231)
Cash and cash equivalents, beginning of period	90,499	22,842	202,179
Restricted cash, beginning of period	671	369	1,263
Cash and cash equivalents and restricted cash at beginning of year	91,170	23,211	203,442
Cash and cash equivalents, end of period	46,344	90,499	22,842
Restricted cash, end of period	733	671	369
Cash and cash equivalents and restricted cash at end of period	47,077	91,170	23,211
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the years ended December 31, 2020, 2019 and 2018 of $4,650, $2,246 and $3,586 respectively	79,498	66,508	76,858
Cash paid for income taxes	688	1,385	405
Supplemental disclosure of non-cash activity:
Dividends and distributions declared but not paid	32,706	33,815	33,632
Change in construction-in-progress related to non-cash disposition of land	0	0	27,231
Change in deferred income, gains and rent to the non-cash disposition of land	0	0	(29,780)
Change in investment in real estate ventures as a result of dispositions	0	1,806	14,169
Change in Notes receivable as a result of a noncash acquisition of an operating property	0	0	130,742
Change in real estate ventures as a result of other than temporary impairment	0	0	(4,076)
Change in operating real estate related to a non-cash acquisition of an operating property	0	0	(20,653)
Change in intangible assets, net related to non-cash acquisition of an operating property	0	0	(3,144)
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	0	0	182
Change in investments in joint venture related to non-cash acquisition of property	0	0	(16,832)
Change in mortgage notes payable related to acquisition of an operating property	0	0	9,940
Change in operating real estate from deconsolidation of operating properties	(427,710)	0	0
Change in investment in real estate ventures from deconsolidation of operating properties	(296,262)	0	0
Change in mortgage notes payable from deconsolidation of operating properties	(220,271)	0	0
Change in capital expenditures financed through accounts payable at period end	(9,949)	(10,618)	8,784
Change in other assets as a result of deconsolidation of operating properties	1,471	0	0
Change in capital expenditures financed through retention payable at period end	284	(946)	(2,912)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Cash flows from operating activities:
Net income	307,326	34,529	135,472
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	188,283	210,005	176,000
Amortization of deferred financing costs	2,904	2,768	2,498
Amortization of debt discount/(premium), net	(568)	189	702
Amortization of stock compensation costs	6,627	6,876	5,716
Straight-line rent income	(14,743)	(11,369)	(12,283)
Amortization of acquired above (below) market leases, net	(4,867)	(8,857)	(3,344)
Ground rent expense	1,455	1,470	431
Provision for doubtful accounts	1,049	(1,345)	1,775
Net gain on real estate venture transactions	(75)	(11,639)	(142,233)
Gain on promoted interest in unconsolidated real estate venture	0	0	(28,283)
Net gain on sale of interests in real estate	(289,662)	(2,376)	(5,972)
Loss on early extinguishment of debt	0	0	105
Provision for impairment	0	0	71,707
Other than temporary impairment	0	0	4,076
Loss from Real Estate Ventures, net of distributions	18,584	10,242	12,871
Income tax provision (benefit)	(224)	12	423
Changes in assets and liabilities:
Accounts receivable	(2,031)	(248)	3,524
Other assets	(5,034)	9,368	(14,334)
Accounts payable and accrued expenses	14,374	(5,599)	12,579
Deferred income, gains and rent	(12,149)	9,319	3,017
Other liabilities	14,557	(9,115)	2,902
Net cash provided by operating activities	225,806	234,230	227,349
Cash flows from investing activities:
Acquisition of properties	(41,950)	0	(196,625)
Acquisition of partners interest in consolidated real estate venture	0	(2,181)	0
Proceeds from the sale of properties	278,114	41,795	324,090
Proceeds from real estate venture sales	0	9,730	60,346
Issuance of note receivable	(50,000)	0	0
Issuance of mortgage note receivable	0	0	(175,172)
Proceeds from repayment of mortgage notes receivable	0	3,341	192
Proceeds from repayment of a capital lease	0	0	181
Capital expenditures for tenant improvements	(73,166)	(67,258)	(65,264)
Capital expenditures for redevelopments	(21,664)	(53,846)	(48,231)
Capital expenditures for developments	(65,420)	(77,192)	(99,104)
Advances for the purchase of tenant assets, net of repayments	1,488	(1,035)	410
Investment in unconsolidated Real Estate Ventures	(719)	(253)	(908)
Deposits for real estate	0	(4,181)	(8,234)
Escrowed cash	0	0	5,694
Capital distributions from Real Estate Ventures	9,001	35,906	6,526
Leasing costs paid	(17,394)	(15,485)	(18,407)
Net cash provided by (used in) investing activities	18,290	(130,659)	(214,506)
Cash flows from financing activities:
Repayments of mortgage notes payable	(94,993)	(7,595)	(122,180)
Proceeds from credit facility borrowings	318,000	348,500	455,500
Repayments of credit facility borrowings	(318,000)	(441,000)	(363,000)
Proceeds from unsecured notes	0	216,373	0
Debt financing costs paid	0	(1,965)	(3,430)
Proceeds from the exercise of stock options	47	3,771	0
Proceeds from the issuance of common shares	0	0	416
Shares used for employee taxes upon vesting of share awards	(1,346)	(1,554)	(1,494)
Partner contributions to consolidated real estate venture	0	27	16
Partner distributions from consolidated real estate venture	0	0	(94)
Repurchase and retirement of common shares	(60,000)	(17,282)	(21,841)
Redemption of limited partnership units	0	0	(7,043)
Distributions paid to shareholders	(131,897)	(134,887)	(129,924)
Net cash used in financing activities	(288,189)	(35,612)	(193,074)
Increase/(Decrease) in cash and cash equivalents and restricted cash	(44,093)	67,959	(180,231)
Cash and cash equivalents, beginning of period	90,499	22,842	202,179
Restricted cash, beginning of period	671	369	1,263
Cash and cash equivalents and restricted cash at beginning of year	91,170	23,211	203,442
Cash and cash equivalents, end of period	46,344	90,499	22,842
Restricted cash, end of period	733	671	369
Cash and cash equivalents and restricted cash at end of period	47,077	91,170	23,211
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the years ended December 31, 2020, 2019 and 2018 of $4,650, $2,246 and $3,586 respectively	79,498	66,508	76,858
Cash paid for income taxes	688	1,385	405
Supplemental disclosure of non-cash activity:
Dividends and distributions declared but not paid	32,706	33,815	33,632
Change in construction-in-progress related to non-cash disposition of land	0	0	27,231
Change in deferred income, gains and rent to the non-cash disposition of land	0	0	(29,780)
Change in investment in real estate ventures as a result of dispositions	0	1,806	14,169
Change in Notes receivable as a result of a noncash acquisition of an operating property	0	0	130,742
Change in real estate ventures as a result of other than temporary impairment	0	0	(4,076)
Change in operating real estate related to a non-cash acquisition of an operating property	0	0
Change in intangible assets, net related to non-cash acquisition of an operating property	0	0	(3,144)
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	0	0	182
Change in investments in joint venture related to non-cash acquisition of property	0	0	(16,832)
Change in mortgage notes payable related to acquisition of an operating property	0	0	9,940
Change in operating real estate from deconsolidation of operating properties			(20,653)
Change in capital expenditures financed through accounts payable at period end	(9,949)	(10,618)	8,784
Change in other assets as a result of deconsolidation of operating properties	1,471	0	0
Change in capital expenditures financed through retention payable at period end	$ 284	$ (946)	$ (2,912)

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental disclosure:
Capitalized interest	$ 4,650	$ 2,246	$ 3,586
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Supplemental disclosure:
Capitalized interest	$ 4,650	$ 2,246	$ 3,586

ORGANIZATION OF THE PARENT COMP

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP	1. ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP Brandywine Realty Trust (the "Parent Company") is a self-administered and self-managed real estate investment trust (“REIT”) engaged in the acquisition, development, redevelopment, ownership, management, and operation of a portfolio of office and mixed-use properties. The Parent Company owns its assets and conducts its operations through Brandywine Operating Partnership, L.P. (the "Operating Partnership") and subsidiaries of the Operating Partnership. The Parent Company is the sole general partner of the Operating Partnership and, as of December 31, 2020, owned a 99.4% 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.” The Parent Company, the Operating Partnership, and their consolidated subsidiaries are collectively referred to as the "Company." As of December 31, 2020, the Company owned 82 properties that contained an aggregate of approximately 13.9 million net rentable square feet (collectively, the “Properties”). The Company’s core portfolio of operating properties (the “Core Properties”) excludes development properties, redevelopment properties, and properties held for sale. The Properties were comprised of the following as of December 31, 2020: Number of Properties Rentable Square Feet Office properties 73 12,470,257 Mixed-use properties 5 942,334 Core Properties 78 13,412,591 Development property 1 205,803 Redevelopment properties 3 234,070 The Properties 82 13,852,464 In addition to the Properties, as of December 31, 2020, the Company owned 228.5 acres of land held for development, of which 35.2 acres were held for sale. The Company also held leasehold interests in two land parcels totaling 1.8 acres, each acquired through prepaid 99-year ground leases, and held options to purchase approximately 55.5 additional acres of undeveloped land. As of December 31, 2020, the total potential development that this inventory of land could support under current zoning and entitlements, including the parcels under option, amounted to an estimated 14.2 million square feet, of which 0.2 million square feet relates to 35.2 acres held for sale. As of December 31, 2020, the Company also owned economic interests in nine unconsolidated real estate ventures (collectively, the “Real Estate Ventures”) (see Note 4, ''Investment in Unconsolidated Real Estate Ventures ” for further information). The Properties and the properties owned by the Real Estate Ventures are located in or near Philadelphia, Pennsylvania; Austin, Texas; Metropolitan Washington, D.C.; Southern New Jersey; and Wilmington, Delaware. All references to building square footage, rentable square feet, acres, occupancy percentage, the number of buildings, and tax basis are unaudited. The Company conducts its third-party real estate management services business primarily through seven management companies (collectively, the “Management Companies”): Brandywine Realty Services Corporation (“BRSCO”), BDN Management Inc. (“BMI”), Brandywine Properties I Limited, Inc. (“BPI”), BDN Brokerage, LLC (“BBL”), Brandywine Properties Management, L.P. (“BPM”), Brandywine Brokerage Services, LLC (“BBS”), and BDN GC Services LLC ("BGCS"). BRSCO, BMI and BPI are each a taxable REIT subsidiary. BBS, BBL, BPM, and BGCS are tax disregarded entities wholly owned by the taxable REIT subsidiary entities. As of December 31, 2020, the Operating Partnership owned, directly and indirectly, 100% of each of BRSCO, BMI, BPI, BBL, BPM, BBS, and BGCS. As of December 31, 2020, the Management Company subsidiaries were managing properties containing an aggregate of approximately 24.7 million net rentable square feet, of which approximately 13.9 million net rentable square feet related to Properties owned by the Company and approximately 10.8 million net rentable square feet related to properties owned by third parties and Real Estate Ventures.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Principles of Consolidation The Company consolidates variable interest entities (“VIEs”) in which it is considered to be the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. The primary beneficiary is defined by the entity having both of the following characteristics: (i) the power to direct those matters that most significantly impact the activities of the VIE and (ii) the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. For entities that the Company has the obligations to fund losses, its maximum exposure to loss is not limited to the carrying amount of its investments. The Company continuously assesses its determination of the primary beneficiary for each entity and assesses reconsideration events that may cause a change in the original determinations. As of December 31, 2020 and 2019, the Company included in its consolidated balance sheets consolidated VIEs having total assets of $49.2 million and $392.0 million, respectively, and total liabilities of $21.6 million and $255.6 million, respectively. When an entity is not deemed to be a VIE, the Company consolidates entities for which it has significant decision making control over the entity’s operations. The Company’s judgment with respect to its level of influence or control of an entity involves consideration of various factors including the form of the Company’s ownership interest, its representation in the entity’s governance, the size of its investment (including loans), estimates of future cash flows, its ability to participate in policy making decisions and the rights of the other investors to participate in the decision making process and to replace the Company as manager and/or liquidate the venture, if applicable. The Company’s assessment of its influence or control over an entity affects the presentation of these investments in the Company’s consolidated financial statements. In addition to evaluating control rights, the Company consolidates entities in which the outside partner has no substantive kick-out rights to remove the Company as managing member. The portion of the consolidated entities that are not owned by the Company is presented as noncontrolling interest as of and during the periods consolidated. All intercompany transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("US GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates. Operating Properties Operating properties are carried at historical cost less accumulated depreciation and impairment losses. The value of operating properties reflects their purchase price or development cost. Acquisition costs related to business combinations are expensed as incurred, whereas the costs related to asset acquisitions are capitalized as incurred. Costs incurred for the renovation and betterment of an operating property are capitalized to the Company’s investment in that property. Ordinary repairs and maintenance are expensed as incurred. Purchase Price Allocation For acquisitions of real estate or in-substance real estate that are accounted for as business combinations, we recognize the assets acquired (including the intangible value of acquired above- or below-market leases, acquired in-place leases and tenant relationship values), liabilities assumed, noncontrolling interests, and previously existing ownership interests at fair value as of the acquisition date. Any excess (deficit) of the consideration transferred relative to the fair value of the net assets acquired is accounted for as goodwill (bargain purchase gain). Acquisition costs related to business combinations are expensed as incurred. Acquisitions of real estate and in-substance real estate that do not meet the definition of a business are accounted for as asset acquisitions. The Company generally expects that acquisitions of real estate or in-substance real estate will not meet the definition of business and therefore are accounted for as asset acquisitions, unless specifically noted otherwise. The accounting model for asset acquisitions is similar to the accounting model for business combinations except that the acquisition consideration (including acquisition costs) is allocated to the individual assets acquired and liabilities assumed on a relative fair value basis. As a result, asset acquisitions do not result in recognition of goodwill or a bargain purchase gain. Additionally, because the accounting model for asset acquisitions is a cost accumulation model, preexisting interests in the acquired assets, if any, are not remeasured to fair value but continue to be accounted for at their historical cost. Direct acquisition costs are capitalized if an asset acquisition is probable. If we determine that an asset acquisition is no longer probable, no new costs are capitalized and all capitalized costs that are not recoverable are written off. The purchase price is allocated to the acquired assets and assumed liabilities, including land and buildings, as if vacant based on highest and best use for the acquired assets. The Company assesses and considers fair value of the operating properties based on estimated cash flow projections that utilize discount and/or capitalization rates that it deems appropriate, as well as available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known and anticipated trends, and market and economic conditions. The Company allocates the purchase price of properties considered to be business combinations and asset acquisitions to net tangible and identified intangible assets acquired based on fair values. Above-market and below-market in-place lease values for acquired properties are recorded based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) the Company’s estimate of the fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining noncancellable term of the lease (including the below market fixed renewal periods that are considered probable, if applicable). Capitalized above-market lease values are amortized as a reduction of rental income over the remaining noncancellable terms of the respective leases. Capitalized below-market lease values are amortized as an increase to rental income over the remaining noncancellable terms of the respective leases, including any below market fixed-rate renewal option periods that are considered probable. Other intangible assets also include in-place leases based on the Company’s evaluation of the specific characteristics of each tenant’s lease and the Company’s overall relationship with the respective tenant. The Company estimates the cost to execute leases with terms similar to the remaining lease terms of the in-place leases, including leasing commissions, legal and other related expenses. This intangible asset is amortized to expense over the remaining term of the respective leases and any fixed-rate bargain renewal periods. Factors considered by the Company in this analysis include an estimate of the carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance, and other operating expenses, and estimates of lost rents at market rates during the expected lease-up periods, which primarily range from four In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) are recorded to revenue. Depreciation and Amortization The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements (5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset (1 to 16 years) or (ii) the lease term). Construction-in-Progress Project costs directly associated with the development and construction of a real estate project are capitalized as construction-in-progress. Construction-in-progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes, and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. Interest expense is capitalized using the Company’s weighted average interest rate. Internal direct costs are capitalized to projects in which qualifying expenditures are being incurred. See Note 3, ''Real Estate Investments," for more information related to the capitalization of project costs. Ground Leases The Company is the lessee under long-term ground leases classified as operating leases. The Company makes significant assumptions and judgments when determining the discount rate for the lease to calculate the present value of the lease payments. As the rate implicit in the lease is not readily determinable, the Company estimates the incremental borrowing rate (“IBR”) that it would need to pay to borrow, on a collateralized basis, an amount equal to the lease payments in a similar economic environment, over a similar lease term. The Company utilizes a market-based approach to estimate the IBR for each individual lease. The base IBR is estimated utilizing observable mortgage and corporate bond rates, which are then adjusted to account for considerations related to the Company’s credit rating and the lease term to select an incremental borrowing rate for each lease. The right of use assets and lease liabilities are presented as “Right of use asset - operating leases, net” and “Lease liability - operating leases”, respectively, on the consolidated balance sheet as of December 31, 2020. The lease liabilities and right of use assets are amortized on a straight-line basis over the lease term with the corresponding expense classified in “Property operating expenses” on the consolidated statements of operations. The most recent CPI adjustment is used to determine the present value of the lease payments for an indexed lease and ultimately the right of use asset and corresponding lease liability. Rent payments for amounts in excess of this estimated growth rate will be expensed on a cash basis as incurred and are considered variable lease costs. Impairment of Real Estate Investments The Company reviews its real estate investments for impairment following the end of each quarter for each of its real estate investments where events or changes in circumstances indicate that the carrying amounts may not be recoverable. The Company updates leasing and other assumptions regularly, paying particular attention to real estate investments where there is an event or change in circumstances that indicates an impairment in value. Additionally, the Company considers strategic decisions regarding the future development plans for real estate investment under development and other market factors. For real estate investments to be held and used, the Company analyzes recoverability based on the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over, in most cases, a 10-year hold period. If there is significant possibility that the Company will dispose of assets earlier, it analyzes the recoverability using a probability weighted analysis of the undiscounted future cash flows expected to be generated from the operations and eventual disposition of each asset using various probable hold periods. If the recoverability analysis indicates that the carrying value of the tested real estate investment is not recoverable, the real estate investment is written down to its fair value and an impairment is recognized in the amount of the excess of the carrying amount of the asset over its fair value. If and when the Company’s plans change, it revises its recoverability analysis to use cash flows expected from operations and eventual disposition of each asset using hold periods that are consistent with its revised plans. Estimated future cash flows used in such analysis are based on the Company’s plans for the real estate investment and its views of market economic conditions. The estimates consider assumptions, including but not limited to market rental rates, capitalization rates, and recent sales data for comparable real estate investments. Future cash flows are discounted when determining fair value of an asset. Most of these assumptions are influenced by our direct experience with the real estate investments and their markets as well as market data obtained from real estate leasing and brokerage firms. Assets Held for Sale The Company generally reclassifies assets to held for sale when the transaction has been approved by its Board of Trustees, or by officers vested with authority to approve the transaction, and there are no known significant contingencies relating to the sale of the real estate investment within one year of the consideration date and the consummation of the transaction is otherwise considered probable. When a real estate investment is designated as held for sale, the Company stops depreciating the real estate investment and estimates the real estate investment’s fair value, net of selling costs. If the determination is made that the estimated fair value, net of selling costs, is less than the net carrying value of the real estate investment, an impairment is recognized, reducing the net carrying value of the real estate investment to estimated fair value less selling costs. For periods in which a real estate investment is classified as held for sale, the Company classifies the assets and liabilities, as applicable, of the real estate investment as held for sale on the consolidated balance sheet for such periods. Impairment of Land Held for Development When demand for build-to-suit properties declines and the ability to sell land held for development deteriorates, or other market factors indicate possible impairment in the recoverability of land held for development, it is reviewed for impairment by comparing its fair value to its carrying value. If the estimated sales value is less than the carrying value, the carrying value is written down to its estimated fair value. Estimated fair value is generally determined using a market valuation approach, comparing the subject property to recent comparable market transactions in a similar location; or using estimated cash flows. Cash and Cash Equivalents Cash and cash equivalents are highly-liquid investments with original maturities of three months or less. The Company maintains cash equivalents in money market accounts with financial institutions in excess of insured limits, but believes this risk is mitigated by only investing in or through major financial institutions. The Company does not invest its available cash balances in money market funds. As such, available cash balances are appropriately reflected as cash and cash equivalents on the consolidated balance sheets. Restricted Cash Restricted cash consists of cash held as collateral to provide credit enhancement for the Company’s mortgage debt, cash for property taxes, capital expenditures and tenant improvements. Restricted cash also includes cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties. Restricted cash is included in “Other assets” in the consolidated balance sheets. Accounts Receivable and Accrued Rent Receivable Generally, leases with tenants are accounted for as operating leases. Minimum lease payments under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payment terms are recorded as “Accrued rent receivable, net” on the consolidated balance sheets. Included in current tenant receivables are tenant reimbursements which are comprised of amounts recoverable from tenants for common area maintenance expenses and certain other recoverable expenses that are recognized as revenue in the period in which the related expenses are incurred. Tenant receivables and accrued rent receivables are carried net of the allowances for doubtful accounts. The allowance for doubtful accounts is an estimate based on the Company's experience of the probability of future events confirming a loss and represents the estimated probable losses. For tenant receivables, the allowance is calculated by applying a range of loss percentages to receivable aging categories. For accrued rent receivables, the allowance is generally calculated by assigning risk factors by industry which are primarily based on the Company's historical collection and charge-off experience adjusted for current market conditions, which requires management's judgment. Investments in Unconsolidated Real Estate Ventures Under the equity method, investments in real estate ventures are recorded initially at cost and subsequently adjusted for equity in earnings, contributions, distributions, and impairments. For real estate ventures that are constructing assets to commence planned principal operations, the Company capitalizes interest expense to the extent that it is recoverable using the Company’s weighted average interest rate of consolidated debt and its investment balance as a basis. Planned principal operations commence when a property is available to lease and at that point in time, the Company ceases capitalizing interest to its investment basis. At least quarterly, management assesses whether there are any other than temporary impairment indicators of the Company’s investments in real estate ventures. An investment is other than temporarily impaired only if the fair value of the investment in a real estate venture, as estimated by management, is less than the carrying value and the decline is other than temporary. To the extent that an other than temporary impairment has occurred, an impairment charge is recorded in the amount of the excess of the carrying amount of the investment over the estimated fair value. Management is required to make significant judgments about the estimated fair value of its investments to determine if an impairment exists. Fair value is generally determined through income valuation approaches, including discounted cash flows and direct capitalization models. When the Company acquires an interest in or contributes assets to a real estate venture project, the difference between the Company’s cost basis in the investment and the value of the real estate venture or asset contributed is amortized over the life of the related assets, intangibles, and liabilities and such adjustment is included in the Company’s share of equity in income of unconsolidated Real Estate Ventures. Deferred Costs Certain costs incurred in connection with property leasing are capitalized as deferred leasing costs. Deferred leasing costs consist primarily of third-party and internal leasing commissions that are amortized using the straight-line method over the life of the respective lease which generally ranges from 1 to 16 years. Management re-evaluates the remaining useful lives of leasing costs in conjunction with changes in the respective lease term. Notes Receivable The Company accounts for notes receivable on its balance sheet at amortized cost, net of allowance for loan losses. Interest income is recognized over the term of the notes receivable and is calculated based on the contractual terms of each note agreement. At inception and on a quarterly basis, the Company evaluates notes receivable for the current estimate of expected credit losses over the contractual term using a probability-of-default method and reports in net income (as a credit loss expense) the amount necessary to adjust the allowance for credit losses to reflect management's current estimate. Management considers performance and/or value of the underlying collateral property as well as the financial and operating capability of the borrower/sponsor in its evaluation. Notes receivable are placed on nonaccrual status when management determines, after considering economic and business conditions and collection efforts, that the loans are impaired, or collection of interest is doubtful. Uncollectible interest previously accrued is recognized as bad debt expense. Interest income on nonaccrual loans is recognized only to the extent that cash payments are received. Deferred Financing Costs Costs incurred in connection with debt financing are capitalized as a direct deduction from the carrying value of the debt, except for costs capitalized related to the Company’s revolving credit facility, which are capitalized within the “Deferred costs, net” caption on the accompanying consolidated balance sheets. Deferred financing costs are charged to interest expense over the terms of the related debt agreements. Deferred financing costs consist primarily of loan fees which are amortized over the related loan term on a basis that approximates the effective interest method. Deferred financing costs are accelerated, when debt is extinguished, as part of the “Interest expense-amortization of deferred financing costs” caption within the Company’s consolidated statements of operations. Original issue discounts are recognized as part of the gain or loss on extinguishment of debt, as appropriate. Revenue Recognition Rental Revenue The Company generates revenue under leases with tenants occupying the Properties. Generally, leases with tenants are accounted for as operating leases. As of December 31, 2020 and 2019, the Company does not have any leases classified as direct-financing or sales-type leases. The operating leases have various expiration dates. Fixed lease payments under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payments are recorded as “Accrued rent receivable” on the consolidated balance sheets. Variable lease payments are recognized as lease revenue in the period in which changes occur in facts and circumstances on which the variable lease payments are based. Topic 842 requires a binary approach to evaluating leases for collectability. Lessors are required to determine if it is probable that substantially all of the lease payments will be collected from the tenant over the lease term. Should the lessor determine that it is not probable that substantially all of the lease payments will be collected, the standard requires that the lessor write off any accrued rent receivable and begin recognizing lease payments on a cash basis. The Company’s lease revenue is impacted by the Company’s determination of whether improvements to the property, whether made by the Company or by the tenant, are landlord assets. The determination of whether an improvement is a landlord asset requires judgment. In making this judgment, the Company’s primary consideration is whether an improvement would be utilizable by another tenant upon the then-existing tenant vacating the improved space. If the Company has funded an improvement that it determines not to be landlord assets, then it treats the cost of the improvement as a lease incentive. If the tenant has funded an improvement that the Company determines to be landlord assets, then the Company treats the costs of the improvement as deferred revenue and amortizes these costs into revenue over the lease term. For certain leases, the Company also makes significant assumptions and judgments in determining the lease term, including assumptions when the lease provides the tenant with an early termination option or purchase option. The lease term impacts the period over which the Company determines and records lease payments and also impacts the period over which it amortizes lease-related costs. The Company considers all relevant factors that create an economic incentive for the lessee and uses judgment to determine if those factors, considered together, signify that the lessee is reasonably certain to exercise the option. For leases where a tenant executes a lease termination, termination fees are recognized over the modified term of the lease as rental income. Additionally, any deferred rents receivable are accelerated over the modified lease term. The Company’s leases also typically provide for tenant reimbursement of a portion of common area maintenance expenses and other operating expenses to the extent that a tenant’s pro rata share of expenses exceeds a base year level set in the lease or to the extent that the tenant has a lease on a triple net basis. As the timing and pattern of revenue recognition is the same, rents and tenant reimbursements are treated as a combined lease component and included in the "Rents" caption within the Company's consolidated statements of operations. Fixed lease payments include contractual rents under lease agreements with tenants recognized on a straight-line basis over the lease term, including amortization of lease incentives and above or below market rent intangibles, and parking income that is fixed under a long-term contract. Variable lease payments include reimbursements billed to tenants, termination fees, bad debt expense, and parking income that is not fixed under a long-term contract. Point of Sale Revenue Point of sale revenue consists of parking, restaurant, and flexible stay revenue from the Company’s hotel operations. Point of sale service obligations are performed daily, and the customer obtains control of those services simultaneously as they are performed. Accordingly, revenue is recorded on an accrual basis as it is earned, coinciding with the services that are provided to the Company’s customers. Parking and flexible stay revenue is recognized within rents and restaurant income is recognized within other income on the consolidated statements of operations. Third party management fees, labor reimbursement, and leasing The Company performs property management services for third-party property owners of real estate that consist of: (i) providing leasing services, (ii) property inspections, (iii) repairs and maintenance monitoring, and (iv) financial and accounting oversight. For these services, the Company earns management fees monthly, which are based on a fixed percentage of each managed property’s financial results, and is reimbursed for the labor costs incurred by its property management employees as services are rendered to the property owners. The Company determined that control over the services is passed to its customers simultaneously as performance occurs. Accordingly, management fee revenue is earned as the services are provided to the Company’s customers. Lease commissions are earned when the Company, as a broker for the third party property owner, executes a lease agreement with a tenant. Based on the terms of the Company’s lease commission contracts, the Company's performance obligation to the customer has been completed upon execution of each lease agreement. The Company’s lease commissions are earned based on a fixed percentage of rental income generated for each executed lease agreement and there is no variable income component. Development fee revenue is earned through two different sources: (i) the Company performs development services for third parties as an agent and earns fixed development fees based on a percentage of construction costs incurred over the construction period, and (ii) the Company acts as a general contractor on behalf of one of its managed real estate ventures. The Company acts as the principal construction company for the real estate ventures and records gross revenue as it provides construction services based on the quantifiable construction outputs. In applying the cost based output method of revenue recognition, the Company uses the actual costs incurred relative to the total estimated costs to determine its progress towards contract completion and to calculate the corresponding gross revenue and gross profit to recognize. For any costs that do not contribute to satisfying the Company’s performance obligations, it excludes such costs from its output methods of revenue recognition as the amounts are not reflective of transferring control of the outputs to the customer. The use of estimates in this calculation involves significant judgment. The following is a summary of revenue earned by the Company’s reportable segments (see Note 19, ''Segment Information,” for further information) during the year ended December 31, 2020 (in thousands): Philadelphia CBD Pennsylvania Suburbs Austin, Texas Metropolitan Washington, D.C. Other Corporate (a) Total Fixed rent $ 166,286 $ 128,044 $ 63,366 $ 29,830 $ 8,064 $ (2,412) $ 393,178 Variable rent 51,410 12,951 35,123 3,544 2,401 (1,343) 104,086 Total lease revenue 217,696 140,995 98,489 33,374 10,465 (3,755) 497,264 Amortization of deferred market rents 1,146 (12) 3,531 — 203 — 4,868 Daily parking & hotel flexible stay 10,777 179 49 135 232 — 11,372 Total rents 229,619 141,162 102,069 33,509 10,900 (3,755) 513,504 Third party management fees, labor reimbursement and leasing 927 39 689 6,541 2,560 7,824 18,580 Other income 1,482 412 224 173 9 468 2,768 Total revenue $ 232,028 $ 141,613 $ 102,982 $ 40,223 $ 13,469 $ 4,537 $ 534,852 The following is a summary of revenue earned by the Company’s reportable segments (see Note 19, ''Segment Information,” for further information) during the year ended December 31, 2019 (in thousands): Philadelphia CBD Pennsylvania Suburbs Austin, Texas Metropolitan Washington, D.C. Other Corporate (a) Total Fixed rent $ 178,481 $ 125,969 $ 62,232 $ 39,420 $ 7,834 $ (2,412) $ 411,524 Variable rent 58,580 14,282 34,748 4,029 3,080 (495) 114,224 Total lease revenue 237,061 140,251 96,980 43,449 10,914 (2,907) 525,748 Amortization of deferred market rents 3,745 (12) 4,638 — 486 — 8,857 Daily parking & hotel flexible stay 18,665 174 165 824 232 — 20,060 Total rents 259,471 140,413 101,783 44,273 11,632 (2,907) 554,665 Third party management fees, labor reimbursement and leasing 876 43 1,956 6,922 2,915 6,914 19,626 Other income 3,422 628 418 303 11 1,344 6,126 Total revenue $ 263,769 $ 141,084 $ 104,157 $ 51,498 $ 14,558 $ 5,351 $ 580,417 (a) Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals. Income Taxes Parent Company The Parent Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the “Code”). In order to continue to qualify as a REIT, the Parent Company is required to, among other things, distribute at least 90% of its annual REIT taxable income to its shareholders and meet certain tests regarding the nature of its income and assets. As a REIT, the Parent Company is not subject to federal and state (in states that follow federal rules) income taxes with respect to the portion of its income that meets certain criteria and is distributed annually to its shareholders. Accordingly, a nominal provision for federal and state (as applicable) income taxes is included in the accompanying consolidated financial statements with respect to the operations of the Parent Company. The Parent Company intends to continue to operate in a manner that allows it to meet the requirements for taxation as a REIT. If the Parent Company fails to qualify as a REIT in any taxable year, it will be subject to federal and state (as applicable) income taxes and may not be able to qualify as a REIT for the four subsequent tax years. The Par

REAL ESTATE INVESTMENTS

REAL ESTATE INVESTMENTS	12 Months Ended
	Dec. 31, 2020
Real Estate [Abstract]
REAL ESTATE INVESTMENTS	3. REAL ESTATE INVESTMENTS As of December 31, 2020 and 2019, the gross carrying value of the operating properties was as follows (in thousands): December 31, 2020 December 31, 2019 Land $ 407,514 $ 489,702 Building and improvements 2,665,232 3,049,395 Tenant improvements 401,363 467,362 Total $ 3,474,109 $ 4,006,459 Construction-in-Progress Internal direct construction costs totaling $8.4 million in 2020, $7.4 million in 2019, and $7.0 million in 2018 and interest totaling $4.6 million in 2020, $3.2 million in 2019, and $3.6 million in 2018 were capitalized related to the development of certain properties and land holdings. During the years ended December 31, 2020, 2019 and 2018, the Company’s internal direct construction costs are comprised entirely of capitalized salaries. The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands): December 31, 2020 2019 2018 Development $ 4,802 $ 3,047 $ 3,185 Redevelopment 543 775 968 Tenant Improvements 3,021 3,609 2,811 Total $ 8,366 $ 7,431 $ 6,964 2020 Acquisitions The following table summarizes the property acquisitions during the year ended December 31, 2020 (dollars in thousands): Property/Portfolio Name Acquisition Date Location Property Type Rentable Square Feet/Acres Purchase Price (a) 145 King of Prussia Road February 27, 2020 Radnor, PA Land 7.75 acres $ 11,250 1505-11 Race Street November 5, 2020 Philadelphia, PA Office 119,763 $ 9,700 250 King of Prussia Road (b) November 30, 2020 Radnor, PA Office 169,843 $ 20,250 (a) Exclusive of transaction costs and price adjustments. See purchase price allocation table below for a breakout of the net purchase price for wholly owned properties. (b) This property was placed into redevelopment and is therefore included within Construction-in-progress on the consolidated balance sheets. The Company accounted for the acquisition of 1501-11 Race Street as an asset acquisition and therefore capitalized $0.3 million of acquisition related costs. The Company utilized a number of sources in making estimates of fair value (including comparative sales transactions and market leasing assumptions) for purposes of allocating the purchase price to tangible and intangible assets acquired The acquisition values have been allocated as follows (in thousands): 1505-11 Race Street Building, land and improvements $ 9,723 Intangible assets acquired 2,422 Below market lease liabilities assumed (2,193) Total unencumbered acquisition value 9,952 Amortization period of intangible assets 1.5 years Amortization period of below market liabilities assumed 1.5 years 2019 Acquisitions During the year ended December 31, 2019, the Company did not acquire any properties from a third party. 2018 Acquisitions On December 19, 2018, the Company acquired an office property containing 120,559 rentable square feet located at 4516 Seton Center Parkway in Austin, Texas, known as Quarry Lake II, for a gross purchase price of $39.5 million. On December 11, 2018, the Company acquired from DRA Advisors (“DRA”), its 50% ownership interest in the G&I Austin Office LLC real estate venture (the "Austin Venture”) for an aggregate purchase price of $535.1 million. The Austin Venture owned twelve office properties (“the Austin Venture Portfolio”) containing an aggregate 1,570,123 square feet located in Austin, Texas. As a result of the acquisition, the Company acquired complete ownership of the Austin Venture Portfolio. The aggregate purchase price reflects the sum of: (i) the amount of such investment plus (ii) a $103.8 million non-cash accounting remeasurement gain related to the Company’s original investment in the Austin Venture Portfolio, reflected in the “Net gain on real estate venture transactions” in the consolidated statements of operations plus (iii) $28.3 million on account of the value of the Company’s promoted interest in the Austin Venture plus (iv) $14.6 million on account of the carrying amount of the Company’s original investment in the Austin Venture Portfolio. At settlement, the Company assumed $115.5 million of mortgage debt and received a credit at settlement of $130.7 million for a note receivable provided to the Austin Venture on November 1, 2018. This note receivable was used to repay one of Austin Venture’s mortgage loans prior to the December 11, 2018 acquisition date. The Company also obtained working capital of $24.9 million. Subsequent to receiving cash proceeds for its promoted interest in the Austin Venture and recognizing a remeasurement gain, the Company funded the acquisition with an aggregate cash payment of $117.3 million. Additionally, the assumed mortgage debt of $115.5 million was repaid at settlement. Both cash payments were funded through borrowings under the Company’s unsecured credit facility. The Company recognized a $28.3 million gain on its promoted interest in the Austin Venture, reflected in the caption “Gain on promoted interest in unconsolidated real estate venture” in the consolidated statements of operations. The gain on promoted interest was based off of the returns earned over the duration of the Austin Venture and the returns were determined based on operating results and real estate valuation of the venture. The Company previously accounted for its 50% non-controlling interest in the Austin Venture under the equity method of accounting. As a result of the Company’s acquisition of DRA’s 50% ownership interest in the Austin Venture, the Company obtained control of Austin Venture and the Company’s existing investment balance was remeasured based on the fair value of the underlying properties acquired and the existing distribution provisions under the relevant partnership agreement, including the Company’s entitlement to a distribution on account of its promoted interest. On June 29, 2018, the Company acquired, through a 99-year ground lease, the leasehold interest in a one-acre land parcel, located at 3025 JFK Boulevard, in Philadelphia, Pennsylvania. The Company prepaid $15.0 million of ground lease rent and, in accordance with ASC 840, capitalized $0.3 million of costs related to entering the lease. Additionally, the ground lease required the Company to pay $5.6 million for a leasehold valuation credit, which can be applied to increase the density of the projects subject to the Schuylkill Yards Project master development agreement. Of this credit, $2.4 million will be applied to the development of 3001-3003 and 3025 JFK Boulevard if the Company constructs a minimum of 1.2 million square feet of floor area ratio (“FAR”) on these land parcels. The remaining credit of $3.2 million can be used for development in excess of 1.2 million FAR at 3001-3003 and 3025 JFK Boulevard or toward future ground lease takedowns at the Schuylkill Yards Development Site. This $3.2 million credit is reimbursed if the master development agreement is terminated by the landowner. Based on the Company’s evaluation under ASC 840, the ground lease is classified as an operating lease. The ground lease and credit are included in the “Prepaid leasehold interests in land held for development, net” and “Other assets” captions, respectively, in the consolidated balance sheets. On March 22, 2018, the Company acquired, through a 99-year ground lease, the leasehold interest in a one-acre land parcel, located at 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania. The Company prepaid $24.6 million of ground lease rent and capitalized $0.3 million of costs related to entering the lease. The ground lease is classified as an operating lease and included in the “Prepaid leasehold interests in land held for development, net,” caption in the consolidated balance sheets. On January 5, 2018, the Company acquired, from its then partner in each of the Four Tower Bridge real estate venture and the Seven Tower Bridge real estate venture, the partner’s 35% ownership interest in the Four Tower Bridge real estate venture in exchange for the Company's 20% ownership interest in the Seven Tower Bridge real estate venture. As a result of this non-monetary exchange, the Company acquired 100% of the Four Tower Bridge real estate venture, which owns an office property containing 86,021 square feet, in Conshohocken, Pennsylvania, encumbered with $9.7 million in debt. The Company previously accounted for its noncontrolling interest in Four Tower Bridge using the equity method. As a result of the exchange transaction, the Company obtained control of the Four Tower Bridge property. The Company’s acquisition of the 35% ownership interest in Four Tower Bridge from its former partner resulted in the consolidation of the property. The unencumbered acquisition value of $23.6 million was determined under the comparative sales approach, which utilized observable transactions within the Conshohocken submarket. The acquisition values have been allocated as follows (in thousands): Quarry Lake II Austin Venture Portfolio Four Tower Bridge Acquisition Date 12/19/2018 12/11/2018 1/5/2018 Building, land and improvements $ 35,120 $ 457,390 $ 20,734 Intangible assets acquired 5,809 76,925 3,144 Below market lease liabilities assumed (1,524) (13,769) (182) Deferred gain (a) — 14,594 — Total unencumbered acquisition value $ 39,405 $ 535,140 $ 23,696 Mortgage debt assumed - at fair value (b) — — (9,940) Total encumbered acquisition value $ 39,405 $ 535,140 $ 13,756 Total unencumbered acquisition value 39,405 535,140 23,696 Mortgage debt assumed - at fair value (b) — — (9,940) Mortgage debt repaid at settlement (c) — (115,461) — Investment in unconsolidated real estate ventures — (14,594) (3,502) Gain on promoted interest in unconsolidated real estate venture — (28,283) — Gain on real estate venture transactions — (103,847) (11,633) Purchase price reduction for note receivable (d) — (130,742) — Net working capital assumed (368) (24,865) 1,379 Total cash payment at settlement $ 39,037 $ 117,348 $ — Weighted average amortization period of intangible assets 0 5.5 years 4.1 years Weighted average amortization period of below market liabilities assumed 3.0 years 4.6 years 4.8 years (a) Represents a deferred gain recognized at settlement, which resulted in a reduction of the acquisition value. (b) The outstanding principal balance on mortgage debt for Four Tower Bridge, assumed on January 5, 2018, was $9.7 million. (c) On December 11, 2018, the Company assumed $115.5 million of mortgage debt which was repaid in full at settlement. (d) Represents a note receivable due from the DRA Austin Venture that represents a purchase price reduction. Quarry Lake II contributed approximately $0.1 million of revenue and $0.1 million of net income, included in the Company’s consolidated statements of operations, for the twelve-month period ended December 31, 2018. Austin Venture Portfolio contributed approximately $3.4 million of revenue and $1.3 million of net loss, included in the Company’s consolidated statements of operations, for the twelve-month period ended December 31, 2018. Four Tower Bridge contributed approximately $2.8 million of revenue and $0.3 million of net income, included in the Company’s consolidated statements of operations, for the twelve-month period ended December 31, 2018. The unaudited pro forma information below summarizes the Company’s combined results of operations for the years ended December 31, 2018 and December 31, 2017, respectively, as though the acquisition of the Austin Venture Portfolio was completed on January 1, 2017. The supplemental pro forma operating data is not necessarily indicative of what the actual results of operations would have been assuming the transaction had been completed as set forth above, nor do they purport to represent the Company’s results of operations for future periods (in thousands). December 31, 2018 2017 Pro forma revenue $ 602,713 $ 582,244 Pro forma net income 134,142 115,475 Pro forma net income available to common shareholders 134,142 115,475 Dispositions The following table summarizes the property dispositions during the years ended December 31, 2020, 2019 and 2018 (dollars in thousands): Property/Portfolio Name Disposition Date Location Property Type Rentable Square Feet/Acres Sales Price Gain/(Loss) on Sale (a) Mid-Atlantic Office Portfolio (b) (g) December 21, 2020 Various Office 1,128,645 $ 192,943 $ 15,164 One and Two Commerce Square (c) July 21, 2020 Philadelphia, PA Office 1,896,142 $ 115,000 $ 271,905 Keith Valley June 15, 2020 Horsham, PA Land 14.0 Acres $ 4,000 $ 201 52 East Swedesford Road March 19, 2020 Malvern, PA Office 131,077 $ 18,000 $ 2,336 1900 Gallows Rd September 11, 2019 Vienna, VA Office 210,632 $ 36,400 $ (367) 9 Presidential Boulevard March 15, 2019 Bala Cynwyd, PA Land 2.7 Acres $ 5,325 $ 751 Subaru National Training Center (d) December 21, 2018 Camden, NJ Mixed-use 83,000 $ 45,300 $ 2,570 Rockpoint Portfolio (e) December 20, 2018 Herndon, VA Office 1,293,197 $ 312,000 $ 397 20 East Clementon Road June 21, 2018 Gibbsboro, NJ Office 38,260 $ 2,000 $ (35) Garza Ranch - Office (f) March 16, 2018 Austin, TX Land 6.6 acres $ 14,571 $ 1,515 Westpark Land January 10, 2018 Durham, NC Land 13.1 acres $ 485 $ 22 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) The Company sold a 60% equity interest in a portfolio of twelve suburban office properties containing an aggregate of 1.1 million square feet ("Mid-Atlantic Office Portfolio"), nine of which are located in the Pennsylvania suburbs and three of which are located in Maryland, to an unrelated third party for a gross sales price of $192.9 million. The transaction resulted in deconsolidation of the properties and formation of PA/MD NNN Office JV, LLC ("Mid-Atlantic Office JV"). The Company recorded its investment at fair value and recognized a gain of $15.2 million in "Net gain on disposition of real estate" on the Consolidated Statements of Operations. See Note 4, ''Investment in Unconsolidated Real Estate Ventures," for further information. (c) The Company sold a 30% preferred equity interest in two office buildings located in Philadelphia, Pennsylvania, to an unrelated third party for $115.0 million (the "Commerce Square Venture Transaction"), which resulted in deconsolidation of the properties and formation of Brandywine Commerce I LP and Brandywine Commerce II LP (collectively, the "Commerce Square Venture"). The transaction valued the properties at $600.0 million. The Company recorded its investment at fair value and recognized a gain of $271.9 million in "Net gain on disposition of real estate" on the Consolidated Statements of Operations. See Note 4, ''Investment in Unconsolidated Real Estate Ventures," for further information. (d) During the third quarter of 2018, the tenant, Subaru, exercised its purchase option for the Subaru National Training Center Development. The lease with Subaru was classified as a direct finance lease within "Other assets" on the consolidated balance sheets. In connection with the lease, the Company recognized $1.6 million in interest income during the twelve months ended December 31, 2018, in accordance with accounting guidance for direct finance leases under ASC 840. (e) For information related to this transaction, see the “Herndon Innovation Center Metro Portfolio Venture, LLC” section in Note 4, “Investment in Unconsolidated Real Estate Ventures.” (f) The Company had continuing involvement in this property through a completion guaranty, which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcel. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the consolidated balance sheet. The Company subsequently recognized the land sale and the $3.0 million gain on sale during the twelve months ended December 31, 2018 upon substantial completion of the infrastructure improvements and transfer of control to the buyer. (g) The sales price includes $4.1 million of variable consideration held in escrow that will be released to the Company over a six During the year ended December 31, 2019, the Company also recorded a $1.0 million gain related to contingent consideration received related to a land sale that closed in a prior period in the Other segment. The Company also received additional proceeds from a sale that closed in a prior year related to a property in the Metropolitan Washington, D.C. segment resulting in $0.7 million of additional gain on sale. Held for Use Impairment As of December 31, 2020 and 2019, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment. Based on the analysis, no impairments were identified during the twelve months ended December 31, 2020 and 2019. As of December 31, 2018, the Company evaluated the recoverability of the carrying values of certain properties that triggered an assessment under the undiscounted cash flow model. Based on its evaluation, the Company determined it would not recover the carrying value of one property in its Other segment, 1900 Gallows Road, located in Vienna, Virginia, due to a reduction in the intended hold period. Accordingly, the Company recorded an impairment of $14.8 million at December 31, 2018, reflected in the results for the twelve months ended December 31, 2018, which reduced the carrying value of the property from $52.8 million to its estimated fair value of $38.0 million. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of ten years and a residual capitalization rate and discount rate of 7.5% and 9.5%, respectively. The result was comparable to indicative pricing in the market. Held for Sale As of both December 31, 2020 and 2019, the Company determined that the sale of two parcels of land within the Other segment totaling 35.2 acres was probable and classified these properties as held for sale. As such, $7.3 million was classified as “Assets held for sale, net” on the consolidated balance sheets as of December 31, 2020 and 2019. As of December 31, 2020 and 2019, the fair value less the anticipated costs of sale of the properties exceeded the carrying values. The fair value of the properties is based on the pricing in the purchase and sale agreement. Held for Sale Impairment During the year ended December 31, 2018, the Company determined that the sale of eight office properties, known as the Rockpoint Portfolio, containing 1,293,197 rentable square feet, in the Metropolitan Washington, D.C. segment, was probable and classified these properties as held for sale and, as a result, recognized an impairment of $56.9 million. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of ten years and residual capitalization rates and discount rates of 7.47% and 8.60%, respectively. The results were comparable to indicative pricing in the market. The Rockpoint Portfolio was sold during the fourth quarter of 2018. See the “Dispositions” section above for further information relating to this sale.

INVESTMENT IN UNCONSOLIDATED RE

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES	12 Months Ended
	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES	4. INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES As of December 31, 2020, the Company held ownership interests in nine unconsolidated real estate ventures for an aggregate investment balance of $389.8 million, which includes a negative investment balance in one unconsolidated real estate venture of $11.5 million, reflected within 'Other liabilities' on the consolidated balance sheets. The Company formed or acquired interests in the Real Estate Ventures with unaffiliated third parties to develop or manage office, residential and/or mixed-use properties or to acquire land in anticipation of possible development of office, residential and/or mixed-use properties. As of December 31, 2020, five of the real estate ventures owned properties that contained an aggregate of approximately 8.4 million net rentable square feet of office space; two real estate ventures owned 1.4 acres of land held for development; one real estate venture owned 1.3 acres of land in active development; and one real estate venture owned a residential tower that contains 321 apartment units. The Company accounts for its interests in the Real Estate Ventures, which range from 15% to 70%, using the equity method. Certain of the Real Estate Ventures are subject to specified priority allocations of distributable cash. The Company earned management fees from the Real Estate Ventures of $4.7 million, $4.3 million and $6.3 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company earned leasing commission income from the Real Estate Ventures of $1.1 million, $1.7 million and $2.5 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company has outstanding accounts receivable balances from the Real Estate Ventures of $1.2 million and $0.8 million as of December 31, 2020 and 2019, respectively. The amounts reflected in the following tables (except for the Company’s share of equity in income) are based on the historical financial information of the individual real estate ventures. The Company records operating losses of a real estate venture in excess of its investment balance if the Company is liable for the obligations of the real estate venture or is otherwise committed to provide financial support to the real estate venture. The Company’s investment in the Real Estate Ventures as of December 31, 2020 and 2019, and the Company’s share of the Real Estate Ventures’ income (loss) for the years ended December 31, 2020 and 2019 was as follows (in thousands): Ownership Percentage Carrying Amount Company's Share of Real Estate Venture Income (Loss) Real Estate Venture Debt at 100%, gross 2020 2019 2020 2019 2020 2019 Office Properties Commerce Square Venture 70% (a) $ 253,128 $ — $ (9,150) $ — $ 219,168 $ — Mid-Atlantic Office Venture 40% (a) 32,996 — 96 — 120,831 — Brandywine - AI Venture LLC 50% 10,302 10,116 185 (2,800) — — Herndon Innovation Center Metro Portfolio Venture, LLC 15% 16,019 16,446 (358) (498) 207,302 207,302 MAP Venture 50% (11,516) (70) (6,570) (6,102) 185,000 185,000 PJP VII 25% (b) — — — 190 — — PJP II 30% (b) — — — 81 — — PJP VI 25% (b) — — — (185) — — Other 1919 Venture 50% 15,434 17,524 59 328 88,860 88,860 Development Properties 4040 Wilson Venture (c) 50% 34,454 37,002 (2,162) (368) 141,857 114,845 JBG - 51 N Street (c) 70% 21,237 21,531 (457) (313) — — JBG - 1250 First Street Office (c) 70% 17,757 17,745 (227) (255) — — $ 389,811 $ 120,294 $ (18,584) $ (9,922) $ 963,018 $ 596,007 (a) Ownership percentage represents the Company’s combined interest including preferred and common equity holdings. See "Commerce Square Venture" and "Mid-Atlantic Office JV" sections below for more information. (b) On October 29, 2019, the Company sold its interest in PJP II, PJP VI and PJP VII. See "PJP Ventures" section below for more information on the disposal. (c) This entity is a VIE. The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2020 and December 31, 2019 (in thousands): December 31, 2020 December 31, 2019 Net property $ 1,520,804 $ 834,367 Other assets 488,805 342,002 Other liabilities 333,049 290,071 Debt, net 956,688 585,068 Equity (a) 719,872 301,230 (a) This amount does not include 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. The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests during the twelve-month periods ended December 31, 2020, 2019 and 2018 (in thousands): Year Ended December 31, 2020 2019 2018 Revenue $ 150,276 $ 132,358 $ 165,326 Operating expenses (85,812) (71,784) (82,035) Interest expense, net (22,661) (21,908) (29,774) Depreciation and amortization (70,805) (53,331) (53,826) Provision for impairment — (5,664) (20,832) Loss on extinguishment of debt — (1,231) (1,385) Net loss $ (29,002) $ (21,560) $ (22,526) Ownership interest % Various Various Various Company's share of net loss $ (18,540) $ (9,865) $ (11,924) Other-than-temporary impairment — — (4,076) Basis adjustments and other (44) (57) 769 Equity in loss of Real Estate Ventures $ (18,584) $ (9,922) $ (15,231) As of December 31, 2020, the aggregate principal payments of the Real Estate Ventures recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2021 $ 148,693 2022 8,543 2023 477,649 2024 328,133 2025 — Thereafter — Total principal payments 963,018 Net deferred financing costs (8,224) Net original issue premium 1,894 Outstanding indebtedness $ 956,688 Mid-Atlantic Office JV On December 21, 2020, the Company contributed a portfolio of twelve properties containing an aggregate of 1,128,645 square feet, nine of which are located in the Pennsylvania suburbs segment and three located in the Metropolitan Washington, D.C segment, to the Mid-Atlantic Office JV, for a gross sales price of $192.9 million. After the transaction, the Company owns approximately 25% of the equity interest in the Mid-Atlantic Office JV through a $20.0 million preferred equity holding and approximately 15% of the equity interest through a common equity interest (representing 20% of the total common equity), for a combined approximately 40% equity interest in the venture. On the closing date, Mid-Atlantic Office JV also obtained $147.4 million of third-party debt financing secured by the twelve properties within the venture, with an initial advance of $120.8 million. The loan bears interest at LIBOR + 3.15% capped at a total maximum interest rate of 5.6% and matures on January 9, 2024. Based on the facts and circumstances at the formation of the Mid-Atlantic Office JV, the Company determined that the venture is not a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the voting interest model under the accounting standard for consolidation in order to determine whether to consolidate the Mid-Atlantic Office JV. Based upon each member's substantive participating rights over the activities of the Mid-Atlantic Office JV under the operating and related agreements of the Mid-Atlantic Office JV, it is not consolidated by the Company, and is accounted for under the equity method of accounting. As a result, the Company measured its equity interest at fair value based on the fair value of the Mid-Atlantic Office JV properties and the distribution provisions of the real estate venture agreement. Since the Company retains a non-controlling interest in the Mid-Atlantic Office JV and there are no other facts and circumstances that preclude the consummation of a sale, the contribution qualifies as a sale of a nonfinancial asset under the relevant guidance. Commerce Square Venture On July 21, 2020, the Company sold a 30% preferred equity interest in the entities that own One Commerce Square and Two Commerce Square. After the transaction, the Company owns approximately 32% of the equity interest in Commerce Square Venture through preferred equity interest holdings and approximately 38% of the equity interest in Commerce Square Venture as the sole common equity holder, for a combined approximately 70% equity interest in the venture. The properties held by the venture remain encumbered by the existing mortgages, which had a $222.1 million principal balance outstanding on the transaction date. Based on the facts and circumstances at the formation of the Commerce Square Venture, the Company determined that the venture is not a VIE. As a result, the Company used the voting interest model under the accounting standard for consolidation in order to determine whether to consolidate the Commerce Square Venture. Based upon each member's substantive participating rights over the activities of the Commerce Square Venture under the operating and related agreements of the Commerce Square Venture, the Company does not have a controlling interest in the properties as the third party investor holds substantive participating rights in the properties. Therefore, the Company deconsolidated the properties and the venture is accounted for under the equity method of accounting. As a result, the Company measured its equity interest at fair value based on the fair value of the Commerce Square Venture properties and the distribution provisions of the real estate venture agreement. Since the Company retains a non-controlling interest in the Commerce Square Venture and there are no other facts and circumstances that preclude sale recognition, the contribution qualifies as the sale of a nonfinancial asset under the relevant guidance. Under the conventional approach of accounting for equity method investments, an investor applies its percentage ownership interest to the venture’s net income or loss to determine the investor’s share of the earnings or losses of the venture. This approach is inappropriate if the venture’s capital structure gives different rights and priorities to its investors. Therefore, the Company follows the hypothetical liquidation at book value (“HLBV”) method in determining its share of the Commerce Square Venture’s earnings or losses for the reporting period as this method better reflects the Company’s claim on the venture’s book value at the end of each reporting period. Earnings for this equity method investment are recognized in accordance with the real estate venture agreement and, where applicable, based upon the allocation of the investment’s net assets at book value as if the investment was hypothetically liquidated at the end of each reporting period. PJP Ventures On October 29, 2019, PJP II, PJP VII and PJP VI, three real estate ventures in which the Company owned a 25%-30% interest, each sold its sole operating office property, totaling 204,347 rentable square feet in Charlottesville, Virginia, at an aggregate sales price of $51.0 million. The Company received cash proceeds of $9.1 million after closing costs and related debt payoffs. The Company recorded an $8.0 million gain within the caption "Net gains on real estate venture transactions" within its consolidated statements of operations for the year ended December 31, 2019. Herndon Innovation Center Metro Portfolio Venture, LLC On December 20, 2018, the Company contributed a portfolio of eight properties containing an aggregate of 1,293,197 square feet, located in its Metropolitan Washington, D.C. segment, to a newly-formed joint venture, known as the Herndon Innovation Center Metro Portfolio Venture, LLC (“Herndon Innovation Center”), for a gross sales price of $312.0 million. The Company and its partner own 15% and 85% interests in the Herndon Innovation Center, respectively. The Herndon Innovation Center funded the acquisition with $265.2 million of cash, which was distributed to the Company at closing. After funding its share of closing costs and working capital contributions of $2.2 million and $0.6 million, respectively, the Company received $262.4 million of cash proceeds at settlement and was given a $47.7 million capital credit for its share of the fair value of the Herndon Innovation Center. The Company recorded an impairment charge of $56.9 million for the Herndon Innovation Center during the third quarter of 2018. The Company recorded a $0.4 million gain on sale, which represents an adjustment to estimated closing costs used to determine the impairment charge in the third quarter of 2018. As part of the transaction, the Company’s subsidiary management company executed an agreement with the Herndon Innovation Center to provide property management and leasing services to the Herndon Innovation Center. On March 29, 2019, Herndon Innovation Center obtained $134.1 million of third-party debt financing, secured by four properties within the venture, with an initial advance of $113.1 million. The remaining funds available under the loan have not yet been drawn. The Company received $16.7 million for its share of the cash proceeds on April 12, 2019. The loan bears interest at LIBOR + 1.95% capped at a total maximum interest rate of 5.45% - 6.45% over the term of the loan and matures on March 29, 2024. On April 11, 2019, the venture obtained an additional $115.3 million of third-party debt financing secured by the remaining four properties within the venture, with an initial advance of $94.2 million. The remaining funds available under the loan have not yet been drawn. The loan bears interest at LIBOR + 1.80% capped at a total maximum interest rate of 6.3% and matures on April 11, 2024. On April 12, 2019, the Company received $13.8 million for its share of the cash proceeds from the financing. Austin Venture The Austin Venture owned twelve office properties containing an aggregate 1,570,123 square feet located in Austin, Texas. On October 16, 2013, the Company contributed a portfolio of seven office properties containing an aggregate of 1,398,826 rentable square feet located in Austin, Texas (the “Austin Properties”) to a newly-formed joint venture with G&I VII Austin Office LLC (“DRA”). DRA and the Company agreed to an aggregate gross sales price of $330.0 million subject to an obligation on the Company’s part to fund the first $5.2 million of post-closing capital expenditures, of which $0.8 million was funded by the Company during 2013 and the remaining $4.4 million was funded by the Company during the twelve months ended December 31, 2014. DRA owned a 50% interest in the Austin Venture and the Company owned a 50% interest in the Austin Venture, subject to the Company’s right to receive up to an additional 10% of distributions. The Company measured its equity interest at fair value based on the fair value of the Austin Properties and the distribution provisions of the real estate venture agreement. Since the Company retained a noncontrolling interest in the Austin Properties and there were no other facts and circumstances that precluded the consummation of a sale, the contribution qualified as a partial sale of real estate under the relevant guidance for sales of real estate. On December 11, 2018, the Company acquired DRA’s 50% ownership interest in the Austin Venture for an aggregate purchase price of $535.1 million. On the sale date, the Austin Venture owned twelve office properties containing an aggregate 1,570,123 square feet, located in Austin, Texas. See Note 3, ''Real Estate Investments," for further information. Brandywine - AI Venture As of December 31, 2020 Brandywine - AI Venture (BDN - AI Venture) consists of one office property located in Metropolitan D.C. segment located at 3141 Fairview Park Drive. During 2019, BDN AI Venture recorded a $5.6 million held for use impairment charge related to 3141 Fairview Park Drive. The Company’s share of the impairment charge was $2.8 million which is reflected in “Equity in loss of Real Estate Ventures” in the consolidated statements of operations for the year ended December 31, 2019. During 2019, BDN - AI Venture transferred an office building located in Falls Church, Virginia containing 180,659 rentable square feet to the mortgage lender in full satisfaction of the lender’s outstanding $26.0 million mortgage loan. The mortgage loan was nonrecourse to the Company. The Company recognized its $2.2 million share of the gain on debt forgiveness in "Net gain on real estate venture transactions" in the consolidated statements of operations for the year ended December 31, 2019. During 2018, BDN - AI Venture sold three office properties containing 510,202 rentable square feet located in Silver Spring, MD (“Station Square”) for a gross sales price of $107.0 million. At the time of sale, the properties were encumbered by a mortgage of $66.5 million, which was repaid in full at closing, resulting in a debt prepayment penalty of $0.7 million. After mortgage payoff and closing costs, BDN - AI Venture received cash proceeds of $34.8 million, of which, the Company received $17.4 million and recognized a $1.5 million gain on the sale. Additionally, in 2018, BDN - AI Venture recorded a $20.8 million held for use impairment charge related to 3141 Fairview Park Drive and 3130 Fairview Park Drive, the two then-remaining properties held by the venture. The Company’s share of the impairment charge was $10.4 million which was recognized in “Equity in loss of Real Estate Ventures” in the consolidated statements of operations for the year ended December 31, 2018. Based on the Company’s evaluation of the fair value of its investment in BDN - AI Venture subsequent to the disposition of Station Square, the Company determined that a persistent weak demand for office space and intense competition for tenants at the two remaining properties had reduced the fair value of the investment below the carrying value. As a result, the Company recorded an other than temporary impairment of $4.1 million which was recognized in “Equity in Loss of Real Estate Ventures” in the consolidated statements of operations for the year ended December 31, 2018. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years, a residual capitalization rate of 8.0% and discount rates ranging from 9.0% to 9.5%. MAP Venture The MAP Venture owns 58 office properties that contain an aggregate of 3,924,783 square feet located in the Pennsylvania Suburbs, New Jersey/Delaware, Metropolitan Washington, D.C. and Richmond, Virginia ("MAP Venture"). The MAP Venture was formed as a limited liability company in which the Company has been designated as the Managing Member. In addition, through an affiliate, the Company provides property management services at the Buildings on behalf of the MAP Venture for a market based management fee. The MAP Venture leases the land parcels under the 58 office properties through a ground lease that extends through February 2115. Annual payments by the MAP Venture, as tenant under the ground leases, initially total $11.9 million and increase 2.5% annually through November 2025. Thereafter, annual rental payments increase by 2.5% or CPI at the discretion of the lessor. Upon adoption of Topic 842, Leases, on January 1, 2019, the MAP Venture determined that the carrying amount of the right of use asset was greater than the fair value of the underlying right of use asset. The fair value of the underlying right of use asset was determined using the purchase price paid by a third-party to acquire the ground lease. As a result, MAP Venture recorded a $9.2 million cumulative effect of accounting change adjustment simultaneously with the recording of the right of use asset to reduce the value of the right of use asset to its estimated fair value. The Company recorded its $4.6 million proportionate share of the cumulative effect of accounting change adjustment through "Cumulative earnings” on its consolidated balance sheets. On August 1, 2018, MAP Venture refinanced its $180.8 million third party debt financing, secured by the buildings of MAP Venture and maturing February 9, 2019, with $185.0 million third party debt financing, also secured by the buildings, bearing interest at LIBOR + 2.45% and maturing on August 1, 2023. The interest rate is swapped to a fixed rate of 2.66% through the maturity date. 1919 Venture 1919 Venture owns a 29-story, 455,000 square foot mixed-use tower consisting of 321 luxury apartments, 24,000 square feet of commercial space and a 215-car structured parking facility. See to Note 5, "Investment in Unconsolidated Real Estate Ventures" for additional information regarding the related-party note receivable with 1919 Venture. Four Tower Bridge Acquisition During 2018, the Company acquired, from its then partner in each of the Four Tower Bridge real estate venture and the Seven Tower Bridge real estate venture, the partner’s remaining 35% ownership interest in the Four Tower Bridge real estate venture in exchange for the Company's 20% ownership interest in the Seven Tower Bridge real estate venture. The Four Tower Bridge real estate venture owned an office property containing 86,021 square feet in Conshohocken, Pennsylvania encumbered with $9.7 million in debt. The Company previously accounted for its noncontrolling interest in Four Tower Bridge using the equity method. As a result of the exchange transaction, the Company obtained control of the Four Tower Bridge property and recognized a gain of $11.6 million. For further information regarding the accounting of the transaction, see Note 3, ''Real Estate Investments . ” evo at Cira Centre South Venture On January 10, 2018, evo at Cira, a real estate venture in which the Company held a 50% interest, sold its sole asset, a 345-unit student housing tower, at a gross sales value of $197.5 million. The student housing tower, located in Philadelphia, Pennsylvania, was encumbered by a secured loan with a principal balance of $110.9 million at the time of sale, which was repaid in full from the sale proceeds. The Company’s share of net cash proceeds from the sale, after debt repayment and closing costs, was $43.0 million. As the Company’s investment basis was $17.3 million, a gain of $25.7 million was recorded within the “Net gain on real estate venture transactions’ caption in the consolidated statements of operations. JBG Ventures JBG Ventures consists of 51 N 50 Patterson, Holdings, LLC Venture ("51 N Street") and 1250 First Street Office, LLC Venture ("1250 First Street"), with the Company owning a 70.0% equity interest and JBG/DC Manager, LLC ("JBG") owning a 30.0% equity interest in each of the two ventures. 51 N Street owns 0.9 acres of undeveloped land and 1250 First Street, owns 0.5 acres of undeveloped land. Based on the facts and circumstances at the formation of each of the two ventures with JBG, the Company determined that each venture is a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the variable interest model under the accounting standard for consolidation in order to determine whether to consolidate the JBG Ventures. JBG is the managing member of the ventures, and pursuant to the operating and related agreements, major decisions require the approval of both members. Based upon each member's shared power over the activities of each of the two ventures, which most significantly impact the economics of the ventures, neither venture is consolidated by the Company. Both ventures are accounted for under the equity method of accounting. 4040 Wilson Venture On July 31, 2013, the Company formed 4040 Wilson LLC Venture (“4040 Wilson”) a joint venture between the Company and Ashton Park Associates LLC (“Ashton Park”), an unaffiliated third party. Each of the Company and Ashton Park owns a 50% interest in 4040 Wilson. 4040 Wilson is developing a 427,500 square foot mixed-use building representing the final phase of the eight building, mixed-use, Liberty Center complex located in the Ballston submarket of Arlington, Virginia. The project is being constructed on a 1.3-acre land parcel contributed by Ashton Park to 4040 Wilson at an agreed upon value of $36.0 million. During the fourth quarter of 2017, 4040 Wilson achieved pre-leasing levels that enabled the venture to obtain a secured construction loan with a total borrowing capacity of $150.0 million for the remainder of the project costs. As of December 31, 2020, $141.9 million had been advanced under the construction loan and development of the building is in progress. Based upon the facts and circumstances at the formation of 4040 Wilson, the Company determined that 4040 Wilson is a VIE in accordance with the accounting standard for the consolidation of VIEs. As a result, the Company used the variable interest model under the accounting standard for consolidation in order to determine whether to consolidate 4040 Wilson. Based upon each member’s shared power over the activities of 4040 Wilson under the operating and related agreements, and the Company’s lack of control over the development and construction phases of the project, 4040 Wilson is accounted for under the equity method of accounting.

DEBT AND PREFERRED EQUITY SECUR

DEBT AND PREFERRED EQUITY SECURITIES	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
DEBT AND PREFERRED EQUITY SECURITIES	5. DEBT AND PREFERRED EQUITY INVESTMENTS As of December 31, 2020, the Company held one debt investment and one preferred equity investment in entities owning real estate assets. The Company accounts for these mandatorily redeemable investments as notes receivable, which are included within “Other assets” on the consolidated balance sheets. As of December 31, 2020, all debt and preferred equity investments were performing in accordance with their respective terms and remain on accrual status. Austin Preferred Equity Investment On December 31, 2020, the Company invested $50.0 million through a preferred equity interest in a single-purpose entity that owns two stabilized office buildings located in Austin, Texas. The preferred equity interest acquired by the Company accrues a 9.0% annual return, compounded and paid monthly. The investment is required to be redeemed no later than December 31, 2023 (subject to a one-year extension option). 1919 Venture Note Receivable During 2018, the Company and the other equity partner in 1919 Venture each provided a $44.4 million mortgage loan to 1919 Venture and, as a result, the Company recorded a related-party note receivable from 1919 Venture of $44.4 million. The loan bears interest at a fixed 4.0% per annum interest rate with a scheduled maturity on June 25, 2023. 1919 Venture used the proceeds from the loans to repay the venture’s then outstanding $88.8 million construction loan. See Note 4, ''Investment in Unconsolidated Real Estate Ventures” for further information regarding 1919 Venture.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
LEASES	6. LEASES Lessor Accounting The Company leases properties to tenants under operating leases with various expiration dates. Scheduled minimum lease payments on noncancellable leases at December 31, 2020 are as follows (in thousands): Year Minimum Rent 2021 $ 325,703 2022 310,208 2023 292,871 2024 268,062 2025 236,623 Thereafter 968,163 Lessee Accounting As of December 31, 2020, the Company is the lessee under six long-term ground leases classified as "operating leases" in the consolidated balance sheets. Certain of the Company’s ground leases contain extension options and the Company considered all relevant factors in determining if it was reasonably certain that it would exercise such extension options. The Company concluded that it was not reasonably certain that it would exercise the extension options and, therefore, has not included the extension period in the remaining lease terms. With the exception of certain ground leases that are subject to rent increases periodically based on the CPI index, all lease payments under the ground lease are fixed. The table below summarizes the Company’s operating lease cost (in thousands) recognized through “Property operating expenses” on the consolidated statements of operations (in thousands): Year Ended December 31, Lease Cost 2020 2019 Fixed lease cost $ 2,100 $ 2,100 Variable lease cost 45 54 Total $ 2,145 $ 2,154 Weighted-average remaining lease term (years) 55.9 56.6 Weighted-average discount rate 6.3 % 6.3 % Lease payments by the Company under the terms of all noncancellable ground leases of land are expensed on a straight-line basis regardless of when payments are due. The Company’s ground leases, excluding prepaid ground leases, have remaining lease terms ranging from 9 to 64 years. Lease payments on noncancellable leases at December 31, 2020 are as follows (in thousands): Year Minimum Rent 2021 $ 1,232 2022 1,248 2023 1,263 2024 1,305 2025 1,321 Thereafter 109,131 Total lease payments $ 115,500 Less: Imputed interest 92,742 Present value of operating lease liabilities $ 22,758 The Company obtained ground tenancy rights related to three 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 ground leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate
LEASES	6. LEASES Lessor Accounting The Company leases properties to tenants under operating leases with various expiration dates. Scheduled minimum lease payments on noncancellable leases at December 31, 2020 are as follows (in thousands): Year Minimum Rent 2021 $ 325,703 2022 310,208 2023 292,871 2024 268,062 2025 236,623 Thereafter 968,163 Lessee Accounting As of December 31, 2020, the Company is the lessee under six long-term ground leases classified as "operating leases" in the consolidated balance sheets. Certain of the Company’s ground leases contain extension options and the Company considered all relevant factors in determining if it was reasonably certain that it would exercise such extension options. The Company concluded that it was not reasonably certain that it would exercise the extension options and, therefore, has not included the extension period in the remaining lease terms. With the exception of certain ground leases that are subject to rent increases periodically based on the CPI index, all lease payments under the ground lease are fixed. The table below summarizes the Company’s operating lease cost (in thousands) recognized through “Property operating expenses” on the consolidated statements of operations (in thousands): Year Ended December 31, Lease Cost 2020 2019 Fixed lease cost $ 2,100 $ 2,100 Variable lease cost 45 54 Total $ 2,145 $ 2,154 Weighted-average remaining lease term (years) 55.9 56.6 Weighted-average discount rate 6.3 % 6.3 % Lease payments by the Company under the terms of all noncancellable ground leases of land are expensed on a straight-line basis regardless of when payments are due. The Company’s ground leases, excluding prepaid ground leases, have remaining lease terms ranging from 9 to 64 years. Lease payments on noncancellable leases at December 31, 2020 are as follows (in thousands): Year Minimum Rent 2021 $ 1,232 2022 1,248 2023 1,263 2024 1,305 2025 1,321 Thereafter 109,131 Total lease payments $ 115,500 Less: Imputed interest 92,742 Present value of operating lease liabilities $ 22,758 The Company obtained ground tenancy rights related to three 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 ground leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate

DEFERRED COSTS

DEFERRED COSTS	12 Months Ended
	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
DEFERRED COSTS	7. DEFERRED COSTS As of December 31, 2020 and 2019, the Company’s deferred costs were comprised of the following (in thousands): December 31, 2020 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 139,207 $ (55,656) $ 83,551 Financing costs - Revolving Credit Facility 6,299 (4,994) 1,305 Total $ 145,506 $ (60,650) $ 84,856 December 31, 2019 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 156,619 $ (63,257) $ 93,362 Financing costs - Revolving Credit Facility 6,299 (4,101) 2,198 Total $ 162,918 $ (67,358) $ 95,560

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	8. INTANGIBLE ASSETS As of December 31, 2020 and 2019, the Company’s intangible assets were comprised of the following (in thousands): December 31, 2020 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 91,552 $ (43,400) $ 48,152 Tenant relationship value 2,091 (1,938) 153 Above market leases acquired 530 (265) 265 Total intangible assets, net $ 94,173 $ (45,603) $ 48,570 Total Cost Accumulated Amortization Intangible Liabilities, net Intangible liabilities, net: Below market leases acquired $ 31,263 $ (12,815) $ 18,448 December 31, 2019 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 167,357 $ (84,123) $ 83,234 Tenant relationship value 5,268 (4,815) 453 Above market leases acquired 4,956 (3,792) 1,164 Total intangible assets, net $ 177,581 $ (92,730) $ 84,851 Total Cost Accumulated Amortization Intangible Liabilities, net Intangible liabilities, net: Below market leases acquired $ 44,757 $ (22,494) $ 22,263 For the years ended December 31, 2020, 2019, and 2018, the Company accelerated the amortization of intangible assets by approximately $0.3 million, $4.5 million, and $0.6 million, respectively, as a result of tenant move-outs prior to the end of the associated lease term. For the years ended December 31, 2020 and 2019 the Company accelerated the amortization of approximately $0.1 million and $2.2 million of intangible liabilities as a result of tenant move-outs. For the year ended December 31, 2018 the Company accelerated the amortization of a nominal amount of intangible liabilities as a result of tenant move-outs. As of December 31, 2020, the Company’s annual amortization for its intangible assets/liabilities, assuming no early lease terminations, are as follows (dollars in thousands): Assets Liabilities 2021 $ 16,190 $ 4,902 2022 10,354 2,723 2023 7,564 1,651 2024 5,214 1,425 2025 4,027 1,148 Thereafter 5,221 6,599 Total $ 48,570 $ 18,448

DEBT OBLIGATIONS

DEBT OBLIGATIONS	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
DEBT OBLIGATIONS	9. DEBT OBLIGATIONS The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Effective Maturity MORTGAGE DEBT: Two Logan Square (a) $ — $ 81,103 3.98% October 2020 Four Tower Bridge (b) — 9,291 4.50% February 2021 One Commerce Square (c) — 116,571 3.64% April 2023 Two Commerce Square (c) — 108,472 4.51% April 2023 Principal balance outstanding — 315,437 Plus: fair market value premium (discount), net — (1,383) Less: deferred financing costs — (242) Mortgage indebtedness $ — $ 313,812 UNSECURED DEBT $600 million Unsecured Credit Facility $ — $ — LIBOR + 1.10% July 2022 Seven 250,000 250,000 2.87% October 2022 $350.0M 3.95% Guaranteed Notes due 2023 350,000 350,000 3.87% February 2023 $350.0M 4.10% Guaranteed Notes due 2024 350,000 350,000 3.78% October 2024 $450.0M 3.95% Guaranteed Notes due 2027 450,000 450,000 4.03% November 2027 $350.0M 4.55% Guaranteed Notes due 2029 350,000 350,000 4.30% October 2029 Indenture IA (Preferred Trust I) 27,062 27,062 LIBOR + 1.25% March 2035 Indenture IB (Preferred Trust I) - Swapped to fixed 25,774 25,774 3.30% April 2035 Indenture II (Preferred Trust II) 25,774 25,774 LIBOR + 1.25% July 2035 Principal balance outstanding 1,828,610 1,828,610 Plus: original issue premium (discount), net 10,137 12,090 Less: deferred financing costs (8,152) (10,094) Total unsecured indebtedness $ 1,830,595 $ 1,830,606 Total Debt Obligations $ 1,830,595 $ 2,144,418 (a) On October 21, 2020, the Company acquired the $79.8 million remaining mortgage on this property from the lender. (b) On November 10, 2020, the Company repaid the remaining $9.1 million mortgage balance. (c) The properties encumbered by these mortgages were deconsolidated as a result of the Commerce Square Venture Transaction. See Note 3, ''Real Estate Investments," for further information. 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. On October 10, 2019, the Company completed underwriting offerings of an additional $100.0 million of its 4.10% Guaranteed Notes due 2024 (the "2024 Notes") and an additional $100.0 million of its 4.55% Guaranteed Notes due 2029 (the "2029 Notes"). The additional 2024 Notes were priced at 106.315% of their face amount and the additional 2029 Notes were priced at 110.058% of their face amount. The additional 2024 Notes and additional 2029 Notes have been reflected net of premiums of $5.3 million and $8.5 million, respectively, in the consolidated balance sheet as of December 31, 2019. On December 13, 2018, the Company amended and restated its $250.0 million seven-year term loan maturing October 8, 2022. In connection with the terms of the amendment, the credit spread on the term loan decreased from LIBOR plus 1.80% to LIBOR plus 1.25%, reducing the Company’s effective interest rate by 0.55%. Through a series of interest rate swaps, the $250.0 million outstanding balance of the term loan has a fixed interest rate of 2.87%. On July 17, 2018, the Company amended and restated its revolving credit agreement (as amended and restated, the “Unsecured Credit Facility”). The amendment and restatement, among other things: (i) maintained the total commitment of the revolving line of credit of $600.0 million; (ii) extended the maturity date from May 15, 2019 to July 15, 2022, with two six-month extensions at the Company’s election subject to specified conditions and subject to payment of an extension fee; (iii) reduced the interest rate margins applicable to Eurodollar loans; (iv) provided for an additional interest rate option based on a floating LIBOR rate; and (v) removed the covenant requiring the Company to maintain a minimum net worth. In connection with the amendments, the Company capitalized $2.7 million in financing costs, which will be amortized through the July 15, 2022 maturity date. At the Company's option, loans outstanding under the Unsecured Credit Facility will bear interest at a rate per annum equal to (1) LIBOR plus between 0.775% and 1.45%, based on the Company's credit rating, or (2) a base rate equal to the greatest of (a) the Administrative Agent's prime rate, (b) the Federal Funds rate plus 0.5% or (c) LIBOR for a one month period plus 1.00%, in each case, plus a margin ranging from 0.0% to 0.45% based on the Company's credit rating. The Unsecured Credit Facility also contains a competitive bid option that allows banks that are part of the lender consortium to bid to make loan advances to the Company at a reduced interest rate. In addition, the Company is also obligated to pay (1) in quarterly installments a facility fee on the total commitment at a rate per annum ranging from 0.125% to 0.30% based on the Company's credit rating and (2) an annual fee on the undrawn amount of each letter or credit equal to the LIBOR Margin. Based on the Company's current credit rating, the LIBOR margin is 1.10% and the facility fee is 0.25%. The terms of the Unsecured Credit Facility require that the Company maintain customary financial and other covenants, including: (i) a fixed charge coverage ratio greater than or equal to 1.5 to 1.00; (ii) a leverage ratio less than or equal to 0.60 to 1.00, subject to specified exceptions; (iii) a ratio of unsecured indebtedness to unencumbered asset value less than or equal to 0.60 to 1.00, subject to specified exceptions; (iv) a ratio of secured indebtedness to total asset value less than or equal to 0.40 to 1.00; and (v) a ratio of unencumbered cash flow to interest expense on unsecured debt greater than 1.75 to 1.00. In addition, the Unsecured Credit Facility restricts payments of dividends and distributions on shares in excess of 95% of the Company's funds from operations (FFO) except to the extent necessary to enable the Company to continue to qualify as a REIT for Federal income tax purposes. The Company had no borrowings under the Unsecured Credit Facility as of December 31, 2020 and 2019. During the twelve months ended December 31, 2020, the weighted-average interest rate on Unsecured Credit Facility borrowings was 1.48% resulting in $0.5 million of interest expense. During the twelve months ended December 31, 2019, the weighted-average interest rate on Unsecured Credit Facility borrowings was 3.52% resulting in $4.4 million of interest expense. The Company was in compliance with all financial covenants as of December 31, 2020 and 2019. Management continuously monitors the Company’s compliance with and anticipated compliance with the covenants. Certain of the covenants restrict the Company’s ability to obtain alternative sources of capital. While the Company currently believes it will remain in compliance with its covenants, in the event that the economy deteriorates in the future, the Company may not be able to remain in compliance with such covenants, in which case a default would result absent a lender waiver. As of December 31, 2020, the Company’s aggregate scheduled principal payments of debt obligations are as follows (in thousands): 2021 $ — 2022 250,000 2023 350,000 2024 350,000 2025 — Thereafter 878,610 Total principal payments 1,828,610 Net unamortized premiums/(discounts) 10,137 Net deferred financing costs (8,152) Outstanding indebtedness $ 1,830,595

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	10. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company determined the fair values disclosed below using available market information and discounted cash flow analyses as of December 31, 2020 and 2019, respectively. The discount rate used in calculating fair value is the sum of the current risk free rate and the risk premium on the date of measurement of the instruments or obligations. Considerable judgment is necessary to interpret market data and to develop the related estimates of fair value. Accordingly, the estimates presented are not necessarily indicative of the amounts that the Company could realize upon disposition. The use of different estimation methodologies may have a material effect on the estimated fair value amounts shown. The Company believes that the carrying amounts reflected in the consolidated balance sheets at December 31, 2020 and 2019 approximate the fair values for cash and cash equivalents, accounts receivable, other assets, accounts payable and accrued expenses because they are short-term in duration. The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands): December 31, 2020 December 31, 2019 Carrying Amount (a) Fair Value Carrying Amount (a) Fair Value Unsecured notes payable $ 1,502,901 $ 1,607,310 $ 1,503,435 $ 1,591,830 Variable rate debt $ 327,694 $ 308,838 $ 327,171 $ 309,947 Mortgage notes payable $ — $ — $ 313,812 $ 317,031 Notes receivable $ 94,430 $ 97,372 $ 44,430 $ 43,322 (a) The carrying amounts presented in the table above are net of deferred financing costs of $7.2 million and $8.7 million for unsecured notes payable, $0.9 million and $1.4 million for variable rate debt and $0.0 million and $0.2 million for mortgage notes payable as of December 31, 2020 and December 31, 2019, respectively. On June 26, 2018, the Company provided a $44.4 million mortgage loan to 1919 Venture, an unconsolidated real estate venture in which the Company holds a 50% ownership interest, and recorded a note receivable of $44.4 million. For additional information regarding the transaction, see Note 4, ''Investment in Unconsolidated Real Estate Ventures.” The Company used quoted market prices as of December 31, 2020 and December 31, 2019 to value the unsecured notes payable and, as such, categorized them as Level 2. The inputs utilized to determine the fair value of the Company’s mortgage notes payable and variable rate debt are categorized as Level 3. The fair value of the variable rate debt was determined using a discounted cash flow model that considered borrowing rates available to the Company for loans with similar terms and characteristics. The fair value of the mortgage notes payable was determined using a discounted cash flow model that considered the contractual interest and principal payments discounted at a blended market rate for loans with similar terms, maturities and loan-to-value. These inputs have been categorized as Level 3 because the Company considers the rates used in the valuation techniques to be unobservable. The inputs utilized to determine fair value of the Company's notes receivable are unobservable and, as such, were categorized as Level 3. Fair value was determined using a discounted cash flow model that considered the contractual interest and principal payments discounted at a blended interest rate of the notes receivable. For the Company’s Level 3 financial instruments for which fair value is disclosed, an increase in the discount rate used to determine fair value would result in a decrease to the fair value. Conversely, a decrease in the discount rate would result in an increase to the fair value. Disclosure about the fair value of financial instruments is based upon pertinent information available to management as of December 31, 2020 and December 31, 2019. Although management is not aware of any factors that would significantly affect the fair value amounts, such amounts were not comprehensively revalued for purposes of these financial statements since December 31, 2020. Current estimates of fair value may differ from the amounts presented herein.

DERIVATIVE FINANCIAL INSTRUMENT

DERIVATIVE FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE FINANCIAL INSTRUMENTS	11. DERIVATIVE FINANCIAL INSTRUMENTS Use of Derivative Financial Instruments The Company’s use of derivative instruments is limited to the utilization of interest rate agreements or other instruments to manage interest rate risk exposures and not for speculative purposes. The principal objective of such arrangements is to minimize the risks and/or costs associated with the Company’s operating and financial structure, as well as to hedge specific transactions. The counterparties to these arrangements are major financial institutions with which the Company and its affiliates may also have other financial relationships. The Company is potentially exposed to credit loss in the event of non-performance by these counterparties. However, because of the high credit ratings of the counterparties, the Company does not anticipate that any of the counterparties will fail to meet these obligations as they come due. The Company does not hedge credit or property value market risks through derivative financial instruments. The Company formally assesses, both at the inception of a hedge and on an on-going basis, whether each derivative is highly-effective in offsetting changes in cash flows of the hedged item. If management determines that a derivative is not highly-effective as a hedge or if a derivative ceases to be a highly-effective hedge, the Company will discontinue hedge accounting prospectively for either the entire hedge or the portion of the hedge that is determined to be ineffective. The related ineffectiveness would be charged to the consolidated statement of operations. The valuation of these instruments is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves and implied volatilities. The fair values of interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments (or receipts) are based on an expectation of future interest rates (forward curves) derived from observable market interest rate curves. To comply with the provisions of the accounting standard for fair value measurements and disclosures, the Company incorporates credit valuation adjustments to appropriately reflect both its own nonperformance risk and the respective counterparty’s nonperformance risk in the fair value measurements. In adjusting the fair value of its derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts, and guarantees. The following table summarizes the terms and fair values of the Company’s derivative financial instruments as of December 31, 2020 and December 31, 2019. The notional amounts provide an indication of the extent of the Company’s involvement in these instruments at that time but do not represent exposure to credit, interest rate or market risks (amounts presented in thousands). Hedge Product Hedge Type Designation Notional Amount Strike Trade Date Maturity Date Fair value 12/31/2020 12/31/2019 12/31/2020 12/31/2019 Liabilities Swap Interest Rate Cash Flow (a) $ 250,000 $ 250,000 2.868 % October 8, 2015 October 8, 2022 $ (6,627) $ (562) Swap Interest Rate Cash Flow (a) 25,774 25,774 3.300 % December 22, 2011 January 30, 2021 (120) (94) $ 275,774 $ 275,774 (a) Hedging unsecured variable rate debt. The Company measures its derivative instruments at fair value and records them in the “Other assets” and (“Other liabilities”) captions on the Company’s consolidated balance sheets. Although the Company has determined that the majority of the inputs used to value its derivatives fall within Level 2 of the fair value hierarchy, the credit valuation adjustments associated with its derivatives utilize Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default by itself and its counterparties. The Company has assessed the significance of the impact of the credit valuation adjustments on the overall valuation of its derivative positions and has determined that the credit valuation adjustments are not significant to the overall valuation of its derivatives. As a result, the Company has determined that the inputs utilized to determine the fair value of derivative instruments are classified in Level 2 of the fair value hierarchy. Disclosure about the fair value of derivative instruments is based upon pertinent information available to management as of December 31, 2020 and December 31, 2019. Although management is not aware of any factors that would significantly affect the fair value amounts, such amounts have not been comprehensively revalued for purposes of these financial statements since December 31, 2020. Current estimates of fair value may differ from the amounts presented herein. Concentration of Credit Risk Concentrations of credit risk arise for the Company when multiple tenants of the Company are engaged in similar business activities, or are located in the same geographic region, or have similar economic features that impact in a similar manner

LIMITED PARTNERS' NONCONTROLLIN

LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY	12 Months Ended
	Dec. 31, 2020
Noncontrolling Interest [Abstract]
LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY	12. LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY Noncontrolling 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 by the Operating Partnership. Operating Partnership The aggregate book value of the noncontrolling interests associated with the redeemable common limited partnership interests that were consolidated in the accompanying consolidated balance sheet of the Parent Company as of December 31, 2020 and December 31, 2019, was $10.5 million and $9.3 million, respectively. Under the applicable accounting guidance, the redemption value of limited partnership units are carried at fair value. The Parent Company believes that the aggregate settlement value of these interests (based on the number of units outstanding and the closing price of the common shares on the balance sheet date) was approximately $11.7 million and $15.5 million, respectively, as of December 31, 2020 and December 31, 2019.

BENEFICIARIES' EQUITY OF THE PA

BENEFICIARIES' EQUITY OF THE PARENT COMPANY	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
BENEFICIARIES' EQUITY OF THE PARENT COMPANY	13. BENEFICIARIES' EQUITY OF THE PARENT COMPANY Earnings per Share (EPS) The following table details the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year Ended December 31, 2020 2019 2018 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 307,326 $ 307,326 $ 34,529 $ 34,529 $ 135,472 $ 135,472 Net income attributable to noncontrolling interests (1,799) (1,799) (262) (262) (954) (954) Nonforfeitable dividends allocated to unvested restricted shareholders (410) (410) (396) (396) (369) (369) Net income attributable to common shareholders $ 305,117 $ 305,117 $ 33,871 $ 33,871 $ 134,149 $ 134,149 Denominator Weighted-average shares outstanding 171,926,079 171,926,079 176,132,941 176,132,941 178,519,748 178,519,748 Contingent securities/Share based compensation — 390,997 — 553,872 — 1,121,744 Weighted-average shares outstanding 171,926,079 172,317,076 176,132,941 176,686,813 178,519,748 179,641,492 Earnings per Common Share: Net income attributable to common shareholders $ 1.77 $ 1.77 $ 0.19 $ 0.19 $ 0.75 $ 0.75 The contingent securities/share based compensation impact is calculated using the treasury stock method and relates to employee awards settled in shares of the Parent Company. The effect of these securities is anti-dilutive for periods that the Parent Company incurs a net loss from continuing operations available to common shareholders and therefore is excluded from the dilutive earnings per share calculation in such periods. Redeemable common limited partnership units, totaling 981,634 as of December 31, 2020 and 2019 and 982,871 as of December 31, 2018, 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 years ended December 31, 2020, 2019 and 2018, earnings representing nonforfeitable dividends 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 December 8, 2020, the Parent Company declared a distribution of $0.19 per common share, totaling $32.7 million, which was paid on January 20, 2021 to shareholders of record as of January 6, 2021. Of the 20,000,000 preferred shares authorized, none were outstanding as of December 31, 2020 or December 31, 2019. Common Share Repurchases The Parent Company maintains a common share repurchase program under which the Board of Trustees has authorized the Parent Company to repurchase common shares. On January 3, 2019, the Board of Trustees replenished this program by authorizing the Parent Company to repurchase up to $150 million common shares under the program from and after January 3, 2019. During the year ended December 31, 2020 the Company repurchased and retired 6,248,483 common shares at an average price of $9.60 per share, totaling $60.0 million. During the year ended December 31, 2019, the Company repurchased and retired 1,337,169 common shares at an average price of $12.92 per share, totaling $17.3 million. During the year ended December 31, 2018, the Company repurchased and retired 1,729,278 common shares at an average price of $12.64 per share, totaling $21.9 million. The Company expects to fund any additional share repurchases with a combination of available cash balances and availability under its unsecured revolving credit facility. The timing and amounts of any repurchases will depend on a variety of factors, including market conditions, regulatory requirements, share prices, capital availability and other factors as determined by the Company’s management team. The repurchase program does not require the purchase of any minimum number of shares and may be suspended or discontinued at any time without notice. In connection with the Parent Company’s common share repurchase program, one common unit of the Operating Partnership is retired for each common share repurchased. During the year ended December 31, 2020 the Company repurchased and retired 6,248,483 common units at an average price of $9.60 per unit, totaling $60.0 million. During the year ended December 31, 2019, the Company repurchased and retired 1,337,169 common units at an average price of $12.92 per unit, totaling $17.3 million. During the year ended December 31, 2018, the Company repurchased and retired 1,729,278 units at an average price of $12.64 per unit totaling $21.9 million. During the year ended December 31, 2017 there were no repurchases under the program. The Company expects to fund any additional unit repurchases with a combination of available cash balances and availability under its unsecured revolving credit facility. The timing and amounts of any purchases will depend on a variety of factors, including market conditions, regulatory requirements, unit prices, capital availability and other factors as determined by the Company’s management team. The repurchase program does not require the purchase of any minimum number of units and may be suspended or discontinued at any time without notice. The common shares repurchased were retired and, as a result, were accounted for in accordance with Maryland law, which does not contemplate treasury stock. The repurchases were recorded as a reduction of common shares (at $0.01 par value per unit) and a decrease to General Partnership Capital. Continuous Offering Program On January 10, 2017, the Parent Company entered into a continuous offering program (the “Offering Program”), that permitted the Parent Company to sell up to an aggregate of 16,000,000 common shares in at-the-market offerings. There was no activity under the Offering Program during 2020 and 2019. During 2018, the Parent Company issued 23,311 common shares under the Offering Program at a weighted average price per share of $18.04, receiving net cash proceeds of $0.4 million. At December 31, 2020, no common shares remained available for issuance under the Offering Program, which terminated on January 10, 2020.

PARTNER'S EQUITY OF THE PARENT

PARTNER'S EQUITY OF THE PARENT COMPANY	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
PARTNERS' EQUITY OF THE PARENT COMPANY	14. PARTNERS' EQUITY OF THE PARENT COMPANY Earnings per Common Partnership Unit The following table details the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year Ended December 31, 2020 2019 2018 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 307,326 $ 307,326 $ 34,529 $ 34,529 $ 135,472 $ 135,472 Net income attributable to noncontrolling interests (20) (20) (69) (69) (55) (55) Nonforfeitable dividends allocated to unvested restricted unitholders (410) (410) (396) (396) (369) (369) Net income attributable to common unitholders $ 306,896 $ 306,896 $ 34,064 $ 34,064 $ 135,048 $ 135,048 Denominator Weighted-average units outstanding 172,907,713 172,907,713 177,114,932 177,114,932 179,959,370 179,959,370 Contingent securities/Share based compensation — 390,997 — 553,872 — 1,121,744 Total weighted-average units outstanding 172,907,713 173,298,710 177,114,932 177,668,804 179,959,370 181,081,114 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 1.77 $ 1.77 $ 0.19 $ 0.19 $ 0.75 $ 0.75 Unvested restricted units are considered participating securities which require the use of the two-class method for the computation of basic and diluted earnings per unit. For the years ended December 31, 2020, 2019 and 2018, earnings representing nonforfeitable dividends were allocated to the unvested restricted units issued to the Parent Company’s executives and other employees under the Parent Company’s shareholder-approved long-term incentive plan. Common Partnership Units and Preferred Mirror Units The Operating Partnership issues partnership units to the Parent Company in exchange for the contribution of the net proceeds of any equity security issuance by the Parent Company. The number and terms of such partnership units correspond to the number and terms of the related equity securities issued by the Parent Company. In addition, the Operating Partnership may also issue separate classes of partnership units. Historically, the Operating Partnership has had the following types of partnership units outstanding: (i) Preferred Partnership Units which have been issued to parties other than the Parent Company; (ii) Preferred Mirror Partnership Units which have been issued to the Parent Company; and (iii) Common Partnership Units which include both interests held by the Parent Company and those held by other limited partners. Preferred Mirror Partnership Units In exchange for the proceeds received in corresponding offerings by the Parent Company of preferred shares of beneficial interest, the Operating Partnership has issued to the Parent Company a corresponding amount of Preferred Mirror Partnership Units with terms consistent with that of the preferred securities issued by the Parent Company. No preferred units were outstanding as of December 31, 2020 or December 31, 2019. Common Partnership Units (Redeemable and General) The Operating Partnership has two classes of Common Partnership Units outstanding as of December 31, 2020: (i) Class A Limited Partnership Interest which are held by both the Parent Company and outside third parties and (ii) General Partnership Interests which are held solely by the Parent Company (collectively, the Class A Limited Partnership Interest, and General Partnership Interests are referred to as “Common Partnership Units”). The holders of the Common Partnership Units are entitled to share in cash distributions from, and in profits and losses of, the Operating Partnership, in proportion to their respective percentage interests, subject to preferential distributions on the preferred mirror units and the preferred units. The Common Partnership Units held by the Parent Company (comprised of both General Partnership Units and Class A Limited Partnership Units) are presented as partner’s equity in the consolidated financial statements. Class A Limited Partnership Interest held by parties other than the Parent Company are redeemable at the option of the holder for a like number of common shares of the Parent Company, or cash, or a combination thereof, at the election of the Parent Company. Because the form of settlement of these redemption rights are not within the control of the Operating Partnership, these Common Partnership Units have been excluded from partner’s equity and are presented as redeemable limited partnership units measured at the potential cash redemption value as of the end of the periods presented based on the closing market price of the Parent Company’s common shares at December 31, 2020, 2019 and 2018, which was $11.91, $15.75 and $12.87, respectively. Class A Units of 981,634 as of December 31, 2020 and 2019 and 982,871 as of December 31, 2018, respectively, were outstanding and owned by outside limited partners of the Operating Partnership. On December 8, 2020, the Operating Partnership declared a distribution of $0.19 per common unit, totaling $32.7 million, which was paid on January 20, 2021 to unitholders of record as of January 6, 2021. Common Unit Repurchases In connection with the Parent Company’s common share repurchase program, one common unit of the Operating Partnership is retired for each common share repurchased. On January 3, 2019, the Board of Trustees replenished this program by authorizing the Parent Company to repurchase of up to $150.0 million common shares under the program from and after January 3, 2019. During the year ended December 31, 2020 the Company repurchased and retired 6,248,483 common units at an average price of $9.60 per unit, totaling $60.0 million. During the year ended December 31, 2019, the Company Repurchased 1,337,169 common units at an average price of $12.92 per unit, totaling $17.3 million. During the year ended December 31, 2018, the Company repurchased and retired 1,729,278 common units at an average price of $12.64 per unit, totaling $21.9 million. The Company expects to fund any additional unit repurchases with a combination of available cash balances and availability under its unsecured revolving credit facility. The timing and amounts of any purchases will depend on a variety of factors, including market conditions, regulatory requirements, unit prices, capital availability and other factors as determined by the Company’s management team. The repurchase program does not require the purchase of any minimum number of units and may be suspended or discontinued at any time without notice. The common units repurchased were retired and, as a result, were accounted for in accordance with Maryland law, which does not contemplate treasury stock. The repurchases were recorded as a reduction of common units (at $0.01 par value per unit) and a decrease to General Partnership Capital. Continuous Offering Program On January 10, 2017, the Parent Company entered into a continuous offering program (the “Offering Program”), which permitted it to sell up to an aggregate of 16,000,000 common units in at-the-market offerings. In connection with the commencement of the Offering Program, $0.2 million of upfront costs were recorded to General Partner Capital. There was no activity under the Offering Program during 2020 and 2019. During 2018, the Parent Company issued 23,311 common units under the Offering Program at a weighted average price per unit of $18.04, receiving net cash proceeds of $0.4 million. As of December 31, 2020, no common shares remained available for issuance under the Offering Program, which terminated on January 10, 2020.

SHARE BASED COMPENSATION ,401(K

SHARE BASED COMPENSATION ,401(K) PLAN AND DEFERRED COMPENSATION	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
SHARE BASED COMPENSATION, 401(k) PLAN AND DEFERRED COMPENSATION	15. SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION Stock Options On December 31, 2020, options exercisable for 300,046 common shares were outstanding under the Parent Company’s shareholder approved equity incentive plan (referred to as the “Equity Incentive Plan”). During the years ended December 31, 2020, 2019 and 2018, the Company did not recognize any compensation expense related to unvested options. During the years ended December 31, 2020, 2019 and 2018, the Company did not capitalize any compensation expense related to stock options as part of the Company’s review of employee salaries eligible for capitalization. Options outstanding as of December 31, 2020 and changes during the year-ended December 31, 2020 were as follows: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at January 1, 2020 334,561 $ 11.88 1.0 Exercised (34,515) $ 11.62 $ 10.1 Outstanding at December 31, 2020 300,046 $ 11.91 0.1 $ 81.1 Vested/Exercisable at December 31, 2020 300,046 $ 11.91 0.1 $ 81.1 401(k) Plan The Company sponsors a 401(k) defined contribution plan for its employees. Each employee may contribute up to 100% of annual compensation, subject to specific limitations under the Internal Revenue Code. At its discretion, the Company can make matching contributions equal to a percentage of the employee’s elective contribution and profit sharing contributions. The Company funds its 401(k) contributions annually and plan participants must be employed as of December 31 in order to receive employer contributions, except for employees eligible for qualifying retirement, as defined under the Internal Revenue Code. The Company contributions were $0.5 million, $0.4 million, and $0.5 million in 2020, 2019, and 2018, respectively. Restricted Share Rights Awards As of December 31, 2020, 488,735 restricted share rights ("Restricted Share Rights") were outstanding under the Equity Incentive Plan. These Restricted Share Rights vest over one The following table summarizes the Company’s Restricted Share Rights activity during the year-ended December 31, 2020: Shares Weighted Average Grant Date Fair Value Non-vested at January 1, 2020 479,144 $ 15.90 Granted 295,049 $ 13.10 Vested (283,431) $ 14.20 Forfeited (2,027) $ 15.63 Non-vested at December 31, 2020 488,735 $ 15.19 On March 5, 2020, the Compensation Committee of the Parent Company’s Board of Trustees awarded to officers of the Company an aggregate of 183,758 Restricted Share Rights, which generally vest over three years from the grant date. Each Restricted Share Right entitles the holder to one common share upon settlement. The Parent Company pays dividend equivalents on the Restricted Share Rights prior to the settlement date. Vesting and/or settlement would accelerate if the recipient of the award were to die, become disabled or, in the case of certain of such Restricted Share Rights, retire in a qualifying retirement prior to the vesting or settlement date. Qualifying retirement generally means the recipient’s voluntary termination of employment after reaching at least age 57 and accumulating at least 15 years of service with the Company. In addition, vesting would also accelerate if the Parent Company were to undergo a change of control and, on or before the first anniversary of the change of control, the recipient’s employment were to cease due to a termination without cause or resignation with good reason. The Restricted Share Rights granted in 2020 and 2019 to certain senior executives include an “outperformance feature” whereby additional shares may be earned, up to 200% of the shares subject to the basic award, based on the Company’s achievement of targets for same-store net operating cash income growth and investment/development activity provided certain operating and balance sheet metrics are also achieved during the three-year period ending December 31, 2022 and December 31, 2021 for the 2019 and 2020 awards, respectively. Half of any additional shares earned will vest based on continued service through each of January 1, 2023 and January 1, 2024 for the 2020 award and January 1, 2022 and January 1, 2023 for the 2019 award, provided that this additional service requirement will be waived in the event of a death, disability or qualifying retirement. In addition to the basic award, up to 316,306 shares and 233,890 shares may be awarded under the outperformance feature for the 2020 award and 2019 award, respectively. As of December 31, 2020, the Company has not recognized any compensation expense related to the outperformance feature for the 2020 awards and has recognized $0.2 million related to the outperformance feature for the 2019 award. The Company will continue to evaluate progress towards achievement of the performance metrics on a quarterly basis and recognize compensation expense for these awards should it be determined that achievement of these metrics is probable. In addition, on March 5, 2020, the Compensation Committee awarded non-officer employees an aggregate of 40,920 Restricted Share Rights that vest in three equal installments on April 15, 2020, 2021, and 2022. Vesting of these awards is subject to acceleration upon death, disability or termination without cause within one year following a change of control. On May 20, 2020, the Compensation Committee awarded the Trustees an aggregate of 70,371 fully vested common shares. In accordance with the accounting standard for share-based compensation, the Company amortizes share-based compensation costs through the qualifying retirement dates for those executives and Trustees who meet the conditions for qualifying retirement during the scheduled vesting period and whose award agreements provide for vesting upon a qualifying retirement. Restricted Performance Share Units Plan The Compensation Committee of the Parent Company’s Board of Trustees has granted performance share-based awards (referred to as Restricted Performance Share Units, or RPSUs) to officers of the Parent Company. The RPSUs are settled in common shares, with the number of common shares issuable in settlement determined based on the Company’s total shareholder return over specified measurement periods compared to total shareholder returns of comparative groups over the measurement periods. The table below presents certain information as to unvested RPSU awards. RPSU Grant Date 2/28/2018 2/21/2019 3/5/2020 Total (Amounts below in shares, unless otherwise noted) Non-vested at January 1, 2020 190,296 206,069 — 396,365 Units Granted — — 319,600 319,600 Non-vested at December 31, 2020 190,296 206,069 319,600 715,965 Measurement Period Commencement Date 1/1/2018 1/1/2019 1/1/2020 Measurement Period End Date 12/31/2020 12/31/2021 12/31/2022 Units Granted 209,193 213,728 319,600 Fair Value of Units on Grant Date (in thousands) $ 4,276 $ 4,627 $ 5,389 The Company values each RPSU on its grant date using a Monte Carlo simulation. The fair values of each award are being amortized over the three year performance period. During the performance period, dividend equivalents are credited as additional RPSU's, subject to the same terms and conditions as the original RPSU's. The performance period will be abbreviated and the delivery of earned shares will be accelerated in the event of 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 end of the otherwise applicable three year performance period; provided that, in the case of qualifying retirement for the March 5, 2020 grant, the number of shares deliverable will be pro-rated based on the portion of the performance period actually worked before retirement. In accordance with the accounting standard for share-based compensation, the Company amortizes stock-based compensation costs for the February 2019 and 2018 grants through the qualifying retirement date for those executives who meet the conditions for qualifying retirement during the scheduled vesting period. For the year ended December 31, 2020, the Company recognized amortization of the 2020, 2019 and 2018 RPSU awards of $3.0 million, of which $0.4 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the year ended December 31, 2019, amortization for the 2019, 2018 and 2017 RPSU awards was $4.2 million, of which $0.6 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. For the year ended December 31, 2018, amortization for the 2018, 2017, and 2016 RPSU awards was $3.9 million, of which $1.1 million was capitalized consistent with the Company’s policies for capitalizing eligible portions of employee compensation. The remaining compensation expense to be recognized with respect to the non-vested RPSU's at December 31, 2020 was approximately $4.5 million and is expected to be recognized over a weighted average remaining vesting period o f 1.5 years. The Company issued 121,897 common shares on February 1, 2020 in settlement of RPSUs that had been awarded on March 1, 2017 (with a three-year measurement period ended December 31, 2019). Holders of these RPSUs also received a cash dividend of $0.19 per share for these common shares on January 22, 2020. Employee Share Purchase Plan The Parent Company’s shareholders approved the 2007 Non-Qualified Employee Share Purchase Plan (the “ESPP”), which is intended to provide eligible employees with a convenient means to purchase common shares of the Parent Company through payroll deductions and voluntary cash purchases at an amount equal to 85% of the average closing price per share for a specified period. Under the plan document, the maximum participant contribution for the 2020 plan year is limited to the lesser of 20% of compensation or $50,000. The ESPP allows the Parent Company to make open market purchases, which reflects all purchases made under the plan to date. In addition, the number of shares separately reserved for issuance under the ESPP is 1.25 million . E mployees made purchases under the ESPP of $0.4 million during the year ended December 31, 2020, $0.5 million during the year ended December 31, 2019 and $0.5 million during the year ended December 31, 2018. The Company recognized $0.1 million of compensation expense related to the ESPP during each of the years ended December 31, 2020, 2019, and 2018. Compensation expense represents the 15% discount on the purchase price. The Board of Trustees of the Parent Company may terminate the ESPP at its sole discretion at any time. Deferred Compensation In January 2005, the Parent Company adopted a Deferred Compensation Plan (the “Plan”) that allows trustees and certain key employees to defer compensation voluntarily. Compensation expense is recorded for the deferred compensation and a related liability is recognized. Participants may elect designated benchmark investment options for the notional investment of their deferred compensation. The deferred compensation obligation is adjusted for deemed income or loss related to the investments selected. At the time the participants defer compensation, the Company records a liability, which is included in the Company’s consolidated balance sheets. The liability is adjusted for changes in the market value of the participant-selected investments at the end of each accounting period, and the impact of adjusting the liability is recorded as an increase or decrease to compensation cost. The Company has purchased mutual funds which can be utilized as a funding source for the Company’s obligations under the Plan. Participants in the Plan have no interest in any assets set aside by the Company to meet its obligations under the Plan. For each of the years ended December 31, 2020, December 31, 2019 and December 31, 2018, the Company recorded a nominal amount of deferred compensation costs, net of investments in the company-owned policies and mutual funds. Participants in the Plan may elect to have all, or a portion of their deferred compensation invested in the Company’s common shares. The Company holds these shares in a rabbi trust, which is subject to the claims of the Company’s creditors in the event of the Company’s bankruptcy or insolvency. The Plan does not permit diversification of a participant’s deferral allocated to the Company common shares and deferrals allocated to Company common shares can only be settled with a fixed number of shares. In accordance with the accounting standard for deferred compensation arrangements where amounts earned are held in a rabbi trust and invested, the deferred compensation obligation associated with the Company’s common shares is classified as a component of shareholder’s equity and the related shares are treated as shares to be issued and are included in total shares outstanding. At December 31, 2020 and 2019, 1.2 million and 1.1 million of such shares were included in total shares outstanding, respectively. Subsequent changes in the fair value of the common shares are not reflected in operations or shareholders’ equity of the Company.

DISTRIBUTIONS

DISTRIBUTIONS	12 Months Ended
	Dec. 31, 2020
Distributions [Abstract]
DISTRIBUTIONS	16. DISTRIBUTIONS The following table provides the tax characteristics of the 2020, 2019 and 2018 distributions paid: Years ended December 31, 2020 2019 2018 (in thousands, except per share amounts) Common Share Distributions: Ordinary income $ 0.41 $ 0.62 $ 0.55 Capital gain 0.35 — — Non-taxable distributions — 0.14 0.17 Distributions per share $ 0.76 $ 0.76 $ 0.72 Percentage classified as ordinary income 53.90 % 81.00 % 76.20 % Percentage classified as capital gain 46.10 % — % — % Percentage classified as non-taxable distribution — % 19.00 % 23.80 %

INCOME TAXES AND TAX CREDIT TRA

INCOME TAXES AND TAX CREDIT TRANSACTIONS	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES AND TAX CREDIT TRANSACTIONS	17. INCOME TAXES AND TAX CREDIT TRANSACTIONS Income Tax Provision/Benefit The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases, and for net operating loss, capital loss and tax credit carryforwards. The deferred tax assets and liabilities are measured using the enacted income tax rates in effect for the year in which those temporary differences are expected to be realized or settled. The effect on the deferred tax assets and liabilities from a change in tax rates is recognized in earnings in the period when the new rate is enacted. However, deferred tax assets are recognized only to the extent that it is more likely than not that they will be realized based on consideration of all available evidence, including the future reversals of existing taxable temporary differences, future projected taxable income and tax planning strategies. Valuation allowances are provided if, based upon the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. As of December 31, 2020 there were no deferred tax assets included within “Other assets” in the consolidated balance sheets. As of December 31, 2019, there were nominal deferred tax assets included within “Other assets” in the consolidated balance sheets. The Company had no accruals for tax uncertainties as of December 31, 2020 and December 31, 2019. For the year ended December 31, 2020, there was no deferred income tax expense and $0.2 million of current income tax benefit. For the year ended December 31, 2019, there was $0.1 million of deferred income tax expense and $0.1 million of current income tax benefit. For the year ended December 31, 2018, there was $0.3 million of deferred income tax expense and $0.1 million of current income tax expense. These amounts are included in “Income tax (provision) benefit” in the consolidated statements of operations.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	12 Months Ended
	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	18. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) The following table details the components of accumulated other comprehensive income (loss) of the Parent Company and the Operating Partnership as of and for the three years ended December 31, 2020 (in thousands): Parent Company Cash Flow Hedges Balance at January 1, 2018 $ 2,399 Change in fair market value during year 1,478 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (39) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 5,029 Change in fair market value during year (8,210) Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests 41 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 770 Balance at December 31, 2019 $ (2,370) Change in fair market value during year (5,972) Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests 29 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 752 Balance at December 31, 2020 $ (7,561) Operating Partnership Cash Flow Hedges Balance at January 1, 2018 $ 2,056 Change in fair market value during year 1,478 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 4,725 Change in fair market value during year (8,210) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 770 Balance at December 31, 2019 $ (2,715) Change in fair market value during year (5,972) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 752 Balance at December 31, 2020 $ (7,935) Over time, the unrealized gains and losses held in Accumulated Other Comprehensive Income (“AOCI”) will be reclassified to interest expense when the related hedged items are recognized in earnings. The current balance held in AOCI is expected to be reclassified to interest expense for realized losses on forecasted debt transactions over the related term of the debt obligation, as applicable. The Company expects to reclassify $0.8 million from AOCI into interest expense within the next twelve months.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	19. SEGMENT INFORMATION During the year ended December 31, 2020, the Company owned and managed its portfolio within five segments: (1) Philadelphia Central Business District (Philadelphia CBD), (2) Pennsylvania Suburbs, (3) Austin, Texas (4) Metropolitan Washington, D.C., and (5) Other. The Philadelphia CBD segment includes properties located in the City of Philadelphia, Pennsylvania. The Pennsylvania Suburbs segment includes properties in Chester, Delaware, and Montgomery counties in the Philadelphia suburbs. The Austin, Texas segment includes properties in the City of Austin, Texas. The Metropolitan Washington, D.C. segment includes properties in the District of Columbia, Northern Virginia and Southern Maryland. The Other segment includes properties located in Camden County, New Jersey and properties in New Castle County, Delaware. In addition to the five segments, the corporate group is responsible for cash and investment management, development of certain real estate properties during the construction period, and certain other general support functions. Land held for development and construction in progress is transferred to operating properties by region upon completion of the associated construction or project. The following tables provide selected asset information as of December 31, 2020 and 2019 and results of operations of the Company’s reportable segments for the years ended December 31, 2020, 2019 and 2018 (in thousands): Real estate investments, at cost: December 31, 2020 December 31, 2019 Philadelphia CBD $ 1,433,927 $ 1,726,299 Pennsylvania Suburbs 871,530 1,003,890 Austin, Texas 728,741 721,255 Metropolitan Washington, D.C. 352,794 468,035 Other 87,117 86,980 Operating Properties $ 3,474,109 $ 4,006,459 Corporate Right of use asset - operating leases, net $ 20,977 $ 21,656 Construction-in-progress $ 210,311 $ 180,718 Land held for development $ 117,984 $ 96,124 Prepaid leasehold interests in land held for development, net $ 39,185 $ 39,592 . Net operating income: Year Ended December 31, 2020 2019 2018 Total revenue Operating expenses (a) Net operating income (loss) Total revenue Operating expenses (a) Net operating income (loss) Total revenue Operating expenses (a) Net operating income (loss) Philadelphia CBD $ 232,028 $ (82,505) $ 149,523 $ 263,769 $ (100,219) $ 163,550 $ 256,717 $ (99,449) $ 157,268 Pennsylvania Suburbs 141,613 (46,281) 95,332 141,084 (47,418) 93,666 138,279 (49,433) 88,846 Austin, Texas 102,982 (39,759) 63,223 104,157 (38,285) 65,872 38,665 (16,739) 21,926 Metropolitan Washington, D.C. 40,223 (20,791) 19,432 51,498 (23,455) 28,043 90,308 (34,072) 56,236 Other 13,469 (9,815) 3,654 14,558 (9,328) 5,230 16,757 (11,888) 4,869 Corporate 4,537 (6,305) (1,768) 5,351 (7,141) (1,790) 3,619 (6,518) (2,899) Operating properties $ 534,852 $ (205,456) $ 329,396 $ 580,417 $ (225,846) $ 354,571 $ 544,345 $ (218,099) $ 326,246 (a) Includes property operating expense, real estate taxes and third party management expense. Unconsolidated real estate ventures: Investment in real estate ventures, at equity Equity in income (loss) of real estate venture As of Years ended December 31, December 31, 2020 December 31, 2019 2020 2019 2018 Philadelphia CBD $ 268,562 $ 17,524 $ (9,090) $ 328 $ (105) Metropolitan Washington, D.C. 99,769 102,840 (3,019) (4,234) (15,065) Mid-Atlantic Office JV 32,996 — 96 — — MAP Venture (11,516) (70) (6,571) (6,102) (2,155) Other — — — 86 407 Austin, Texas — — — — 1,687 Total $ 389,811 $ 120,294 $ (18,584) $ (9,922) $ (15,231) Net operating income (“NOI”) is a non-GAAP financial measure, which we define as total revenue less property operating expenses, real estate taxes, and third party management expenses. Property operating expenses that are included in determining NOI consist of costs that are necessary and allocable to our operating properties such as utilities, property-level salaries, repairs and maintenance, property insurance, management fees, and bad debt expense. General and administrative expenses that are not reflected in NOI primarily consist of corporate-level salaries, amortization of share awards and professional fees that are incurred as part of corporate office management. NOI presented by the Company may not be comparable to NOI reported by other companies that define NOI differently. NOI is the measure that is used by the Company to evaluate the operating performance of its real estate assets by segment. The Company believes NOI provides useful information to investors regarding the financial condition and results of operations because it reflects only those income and expense items that are incurred at the property level. While NOI is a relevant and widely used measure of operating performance of real estate investment trusts, it does not represent cash flow from operations or net income as defined by GAAP and should not be considered as an alternative to those measures in evaluating our liquidity or operating performance. NOI does not reflect interest expenses, real estate impairment losses, depreciation and amortization costs, capital expenditures and leasing costs. The Company believes that net income (loss), as defined by GAAP, is the most appropriate earnings measure. The following is a reconciliation of consolidated net income (loss), as defined by GAAP, to consolidated NOI, (in thousands): Year Ended December 31, 2020 2019 2018 Net income $ 307,326 $ 34,529 $ 135,472 Plus: Interest expense 73,911 81,512 78,199 Interest expense - amortization of deferred financing costs 2,904 2,768 2,498 Depreciation and amortization 188,283 210,005 176,000 General and administrative expenses 30,288 32,156 27,802 Equity in loss of Real Estate Ventures 18,584 9,922 15,231 Provision for impairment — — 71,707 Loss on early extinguishment of debt — — 105 Less: Interest income 1,939 2,318 4,703 Income tax (provision) benefit 224 (12) (423) Net gain on disposition of real estate 289,461 356 2,932 Net gain on sale of undepreciated real estate 201 2,020 3,040 Net gain on real estate venture transactions 75 11,639 142,233 Gain on promoted interest in unconsolidated real estate venture — — 28,283 Consolidated net operating income $ 329,396 $ 354,571 $ 326,246

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	20. COMMITMENTS AND CONTINGENCIES Legal Proceedings The Company is involved from time to time in litigation on various matters, including disputes with tenants, disputes with vendors, employee disputes and disputes arising out of agreements to purchase or sell properties or joint ventures or disputes relating to state and local taxes. Given the nature of the Company’s business activities, these lawsuits are considered routine to the conduct of its business. The result of any particular lawsuit cannot be predicted, because of the very nature of litigation, the litigation process and its adversarial nature, and the jury system. The Company will establish reserves for specific legal proceedings when it determines that the likelihood of an unfavorable outcome is probable and when the amount of loss is reasonably estimable. The Company does not expect that the liabilities, if any, that may ultimately result from 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. Fair Value of Contingent Consideration On April 2, 2015, the Company purchased 618 Market Street in Philadelphia, Pennsylvania. The allocated purchase price included contingent consideration of $2.0 million payable to the seller upon commencement of development. The liability was recorded at a fair value of $1.6 million and has fully accreted through interest expense to $2.0 million as of December 31, 2020. The fair value of this contingent consideration was determined using a probability weighted discounted cash flow model based on the period until development was originally expected to commence. The significant inputs to the discounted cash flow model were the discount rate and weighted probability scenarios. As the inputs were unobservable, the Company determined the inputs used to value this liability fall within Level 3 for fair value reporting. Debt Guarantees As of December 31, 2020, the Real Estate Ventures had aggregate indebtedness of $963.2 million. These loans are generally mortgage or construction loans, most of which are non-recourse to the Company, except for customary recourse carve-outs. As of December 31, 2020, the $150.0 million construction loan obtained by 4040 Wilson, for which the Company has guaranteed payment up to $41.3 million, is recourse to the Company. In addition, during construction undertaken by real estate ventures, including 4040 Wilson, the Company has provided and expects to continue to provide cost overrun and completion guarantees, with rights of contribution among partners or members in the real estate ventures, as well as customary environmental indemnities and guarantees of customary exceptions to nonrecourse provisions in loan agreements. Other Commitments or Contingencies In connection with the Schuylkill Yards Project, the Company entered into a neighborhood engagement program and, as of December 31, 2020, had $7.7 million of future fixed contractual obligations. The Company is also committed to make additional contributions under the program. As of December 31, 2020, the Company estimates that, as of December 31, 2020, these additional contributions, which are not fixed under the terms of agreement, will be $2.6 million. In connection with the formation of the Commerce Square Venture, the Company has committed to investing an additional $20.0 million of preferred equity in the properties on a pari passu basis with its joint venture partner. As part of the Company’s September 2004 acquisition of a portfolio of properties from The Rubenstein Company (which the Company refers to as the “TRC acquisition”), the Company acquired its interest in Two Logan Square, a 708,844 square foot office building in Philadelphia, Pennsylvania primarily through its ownership of a second and third mortgage secured by this property. This property is consolidated, as the borrower is a variable interest entity and the Company, through its ownership of the second and third mortgages, is the primary beneficiary. On October 21, 2020, the Company also acquired the $79.8 million first mortgage on the property from the third-party mortgage lender pursuant to an agreement with certain of the former owners. Under the agreement, the Company has agreed to not take title to Two Logan until the earlier of June 2026 or the occurrence of certain events related to the ownership interests of certain former owners. If the Company were to sell the restricted property before the expiration of the restricted period in a non-exempt transaction, the Company may be required to make significant payments to certain of the former owners of Two Logan Square on account of tax liabilities attributed to them. Additionally, the Company will be required to pay these certain former owners an amount estimated at approximately $0.9 million to redeem their residual interest in the fee owner of this property. The $0.9 million payment is included within "Other liabilities" on the consolidated balance sheets. Similarly, as part of the 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to not sell these two properties in certain taxable transactions prior to October 20, 2021 without the holder’s consent. The Commerce Square Venture Transaction did not violate such covenant. As part of the Company’s acquisition of properties from time to time in tax-deferred transactions, the Company has agreed to provide certain of the prior owners of the acquired properties the right to guarantee Company indebtedness. If the Company were to seek to repay the indebtedness guaranteed by the prior owner before the expiration of the applicable agreement, the Company would be required to provide the prior owner an opportunity to guaranty qualifying replacement debt. These debt maintenance agreements may limit the Company’s ability to refinance indebtedness on terms favorable to the Company. As part of its 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to maintain qualifying mortgage debt through October 20, 2021, in the amounts of not less than $125.0 million on One Commerce Square and $100.0 million on Two Commerce Square. Similarly, the Company agreed with other contributors of assets that obligate it to maintain debt available for them to guaranty. The Company invests in its properties and regularly incurs capital expenditures in the ordinary course of business to maintain the properties. The Company believes that such expenditures enhance its competitiveness. The Company also enters into construction, utility and service contracts in the ordinary course of business which may extend beyond one year. These contracts typically provide for cancellation with insignificant or no cancellation penalties.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	21. SUBSEQUENT EVENTS On February 2, 2021, the Company formed a joint venture with an unaffiliated third party to develop a 570,000 square foot mixed-use building at property under a long-term ground lease of 3025 JFK Boulevard, Philadelphia, Pennsylvania, also known as "Schuylkill Yards West." The estimated project cost is approximately $287 million, and the joint venture partner has agreed, subject to customary funding conditions, to fund up to approximately $58 million of the project costs in exchange for a 45% preferred equity interest in the venture. We have agreed to provide a completion guaranty in connection with the development of the project.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule II Valuation and Qualifying Accounts	Schedule II Valuation and Qualifying Accounts (in thousands) Description Balance at Beginning of Year Additions Deductions (1) Balance at End of Year Allowance for doubtful accounts: December 31, 2020 $ 7,975 $ — $ 2,889 $ 5,086 December 31, 2019 $ 12,919 $ — $ 4,944 $ 7,975 December 31, 2018 $ 17,112 $ 1,775 $ 5,968 $ 12,919

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real Estate and Accumulated Depreciation	BRANDYWINE REALTY TRUST AND BRANDYWINE OPERATING PARTNERSHIP, L.P. Schedule III Real Estate and Accumulated Depreciation — December 31, 2020 (in thousands) Initial Cost Gross Amount Which Carried Property Name City State Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (a) Accumulated Depreciation at December 31, 2020 (b) Year of Construction Year Acquired Depreciable Life PENNSYLVANIA SUBURBS Six Tower Bridge (181 Washington Street) Conshohocken PA $ 6,927 $ 14,722 $ 2,166 $ 6,237 $ 17,578 $ 23,815 $ 4,228 1999 2013 (c) 426 West Lancaster Avenue Devon PA 1,689 6,756 8,833 1,686 15,592 17,278 512 1990 1998 (c) 52 Swedesford Square East Whiteland Twp. PA 4,241 16,579 (20,820) — — — — 1988 1998 (c) 640 Freedom Business Center (d) King Of Prussia PA 1,015 20,098 4,838 387 25,564 25,951 15,229 1991 1998 (c) 620 Freedom Business Center (d) King Of Prussia PA 666 13,118 1,888 252 15,420 15,672 9,416 1986 1998 (c) 1000 First Avenue King Of Prussia PA — 13,708 3,235 — 16,943 16,943 11,450 1980 1998 (c) 1060 First Avenue King Of Prussia PA — 13,665 4,279 — 17,944 17,944 11,741 1987 1998 (c) 630 Freedom Business Center Drive (d) King Of Prussia PA 666 13,251 3,497 255 17,159 17,414 10,139 1989 1998 (c) 1020 First Avenue King Of Prussia PA — 10,744 4,306 — 15,050 15,050 9,726 1984 1998 (c) 1040 First Avenue King Of Prussia PA — 14,142 5,218 — 19,360 19,360 12,870 1985 1998 (c) 610 Freedom Business Center Drive (d) King Of Prussia PA 485 9,602 2,554 185 12,456 12,641 7,514 1985 1998 (c) 650 Park Avenue King Of Prussia PA 1,916 4,378 (4,378) 1,916 — 1,916 — 1968 1998 (c) 600 Park Avenue King Of Prussia PA 1,012 4,048 385 1,012 4,433 5,445 2,768 1964 1998 (c) 933 First Avenue King Of Prussia PA 3,127 20,794 (1,125) 3,127 19,669 22,796 3,085 2017 N/A (c) 500 North Gulph Road King Of Prussia PA 1,303 5,201 21,471 1,303 26,672 27,975 2,363 1979 1996 (c) 401 Plymouth Road Plymouth Meeting PA 6,199 16,131 15,658 6,199 31,789 37,988 15,816 2001 2000 (c) Metroplex (4000 Chemical Road) Plymouth Meeting PA 4,373 24,546 4,627 4,373 29,173 33,546 8,071 2007 2001 (c) 610 West Germantown Pike Plymouth Meeting PA 3,651 14,514 3,578 3,651 18,092 21,743 8,855 1987 2002 (c) 600 West Germantown Pike Plymouth Meeting PA 3,652 15,288 2,463 3,652 17,751 21,403 8,450 1986 2002 (c) 630 West Germantown Pike Plymouth Meeting PA 3,558 14,743 2,189 3,558 16,932 20,490 8,115 1988 2002 (c) 620 West Germantown Pike Plymouth Meeting PA 3,572 14,435 1,866 3,572 16,301 19,873 7,411 1990 2002 (c) 660 West Germantown Pike Plymouth Meeting PA 3,694 5,487 19,682 5,405 23,458 28,863 6,822 1987 2012 (c) 351 Plymouth Road Plymouth Meeting PA 1,043 555 — 1,043 555 1,598 218 N/A 2000 (c) 150 Radnor Chester Road Radnor PA 11,925 36,986 21,658 11,897 58,672 70,569 20,187 1983 2004 (c) One Radnor Corporate Center Radnor PA 7,323 28,613 19,813 7,323 48,426 55,749 30,728 1998 2004 (c) 201 King of Prussia Road Radnor PA 8,956 29,811 4,307 8,949 34,125 43,074 20,508 2001 2004 (c) 555 Lancaster Avenue Radnor PA 8,014 16,508 19,871 8,609 35,784 44,393 20,245 1973 2004 (c) Four Radnor Corporate Center Radnor PA 5,406 21,390 12,633 5,705 33,724 39,429 17,020 1995 2004 (c) Five Radnor Corporate Center Radnor PA 6,506 25,525 8,906 6,578 34,359 40,937 13,689 1998 2004 (c) Three Radnor Corporate Center Radnor PA 4,773 17,961 2,173 4,791 20,116 24,907 10,527 1998 2004 (c) Two Radnor Corporate Center Radnor PA 3,937 15,484 2,879 3,942 18,358 22,300 10,463 1998 2004 (c) 130 Radnor Chester Road Radnor PA 2,573 8,338 (134) 2,567 8,210 10,777 3,764 1983 2004 (c) 170 Radnor Chester Road Radnor PA 2,514 8,147 1,728 2,509 9,880 12,389 4,784 1983 2004 (c) 200 Radnor Chester Road Radnor PA 3,366 — 3,621 3,366 3,621 6,987 857 2014 2005 (c) 101 West Elm Street W. Conshohocken PA 6,251 25,209 2,940 6,251 28,149 34,400 10,949 1999 2005 (c) 1 West Elm Street W. Conshohocken PA 3,557 14,249 984 3,557 15,233 18,790 5,955 1999 2005 (c) Four Tower Bridge (200 Barr Harbor Drive) W. Conshohocken PA 6,000 14,734 390 6,000 15,124 21,124 1,213 1998 2018 (c) Initial Cost Gross Amount Which Carried December 31, 2020 Property Name City State Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (a) Accumulated Depreciation at December 31, 2020 (b) Year of Construction Year Acquired Depreciable Life PHILADELPHIA CBD Cira Centre (2929 Arch Street) Philadelphia PA — 208,570 (16,549) 12,586 179,435 192,021 68,536 2005 N/A (c) Three Logan Square (1717 Arch Street) Philadelphia PA — 98,188 83,981 25,195 156,974 182,169 46,611 1990 2010 (c) One Logan Square (130 North 18th Street) Philadelphia PA 14,496 107,736 29,992 14,473 137,751 152,224 67,932 1998 2004 (c) Two Logan Square (100 North 18th Street) Philadelphia PA 16,066 100,255 27,936 16,066 128,191 144,257 53,177 1988 2004 (c) Cira Centre South Garage (129 South 30th Street) (d) Philadelphia PA — 76,008 26,961 6,816 96,153 102,969 22,377 2010 N/A (c) 1900 Market Street Philadelphia PA 7,768 17,263 63,616 7,768 80,879 88,647 20,545 1981 2012 (c) 3020 Market Street Philadelphia PA — 21,417 7,827 — 29,244 29,244 11,501 1959 2011 (c) 618-634 Market Street Philadelphia PA 13,365 5,791 2,810 13,365 8,601 21,966 6,522 1966 2015 (c) FMC Tower at Cira Centre South (2929 Walnut Street) Philadelphia PA — 400,294 18,005 — 418,299 418,299 63,196 2016 N/A (c) 2100 Market Street Philadelphia PA 18,827 — 6,433 18,854 6,406 25,260 1,517 N/A 2015 (c) 1505-11 Race Street Philadelphia PA 3,662 6,061 8 3,670 6,061 9,731 25 1922 2020 (c) The Bulletin Building (3025 Market Street) (e) Philadelphia PA — 24,377 42,669 — 67,046 67,046 4,405 1953 2017 (c) 3001-3003 JFK Boulevard (f) Philadelphia PA — — 111 — 111 111 17 N/A 2018 N/A 3025 JFK Boulevard (f) Philadelphia PA — — — — — — — N/A 2018 N/A METROPOLITAN WASHINGTON, D.C. 6600 Rockledge Drive Bethesda MD — 37,421 10,036 — 47,457 47,457 16,270 1981 2006 (c) 2340 Dulles Corner Boulevard Herndon VA 16,345 65,379 524 16,129 66,119 82,248 23,858 1987 2006 (c) 1676 International Drive McLean VA 18,437 97,538 17,656 18,785 114,846 133,631 27,969 1999 2006 (c) 8260 Greensboro Drive McLean VA 7,952 33,964 5,313 8,102 39,127 47,229 12,664 1980 2006 (c) 8521 Leesburg Pike Vienna VA 4,316 30,885 7,007 4,397 37,811 42,208 12,898 1984 2006 (c) AUSTIN, TX 11501 Burnet Road - Building 1 Austin TX 3,755 22,702 12 3,755 22,714 26,469 3,788 1991 2015 (c) 11501 Burnet Road - Building 2 Austin TX 2,732 16,305 1,479 2,732 17,784 20,516 3,471 1991 2015 (c) 11501 Burnet Road - Building 3 Austin TX 3,688 22,348 10 3,688 22,358 26,046 3,729 1991 2015 (c) 11501 Burnet Road - Building 4 Austin TX 2,614 15,740 8 2,614 15,748 18,362 2,628 1991 2015 (c) 11501 Burnet Road - Building 5 Austin TX 3,689 22,354 13 3,689 22,367 26,056 3,733 1991 2015 (c) 11501 Burnet Road - Building 6 Austin TX 2,676 15,972 14,133 2,676 30,105 32,781 5,446 1991 2015 (c) 11501 Burnet Road - Building 8 Austin TX 1,400 7,422 1,523 1,400 8,945 10,345 1,536 1991 2015 (c) 11501 Burnet Road - Parking Garage Austin TX — 19,826 6 — 19,832 19,832 4,378 1991 2015 (c) Four Points Centre 3 (11120 Four Points Drive) Austin TX 1,140 — 40,330 1,141 40,329 41,470 3,279 2019 2013 (c) One Barton Skyway (1501 South MoPac Expressway) Austin TX 10,496 47,670 3,448 10,495 51,119 61,614 2,826 1999 2018 (c) Two Barton Skyway (1601 South MoPac Expressway) Austin TX 10,849 53,868 2,820 10,848 56,689 67,537 3,532 2000 2018 (c) Three Barton Skyway (1221 South MoPac Expressway) Austin TX 10,374 47,624 304 10,373 47,929 58,302 2,603 2001 2018 (c) Four Barton Skyway (1301 South MoPac Expressway) Austin TX 13,301 57,041 2,904 13,300 59,946 73,246 3,162 2001 2018 (c) Initial Cost Gross Amount Which Carried December 31, 2020 Property Name City State Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (a) Accumulated Depreciation at December 31, 2020 (b) Year of Construction Year Acquired Depreciable Life Four Points Centre (11305 Four Points Drive) Austin TX 7,800 43,581 3,923 7,800 47,504 55,304 3,024 2008 2018 (c) River Place - Building 1 (6500 River Place Boulevard) Austin TX 2,004 17,680 537 2,004 18,217 20,221 1,072 2000 2018 (c) River Place - Building 2 (6500 River Place Boulevard) Austin TX 3,137 29,254 618 3,137 29,872 33,009 1,634 2000 2018 (c) River Place - Building 3 (6500 River Place Boulevard) Austin TX 3,064 26,705 279 3,064 26,984 30,048 1,429 2000 2018 (c) River Place - Building 4 (6500 River Place Boulevard Austin TX 2,273 18,617 1,047 2,273 19,664 21,937 1,345 2000 2018 (c) River Place - Building 5 (6500 River Place Boulevard) Austin TX 1,752 14,315 97 1,752 14,412 16,164 768 2001 2018 (c) River Place - Building 6 (6500 River Place Boulevard) Austin TX 1,598 12,945 22 1,598 12,967 14,565 690 2001 2018 (c) River Place - Building 7 (6500 River Place Boulevard) Austin TX 1,801 16,486 1,094 1,801 17,580 19,381 1,210 2002 2018 (c) Quarry Lake II (4516 Seton Center Parkway) Austin TX 3,970 30,546 1,024 3,867 31,673 35,540 1,772 1998 2018 (c) OTHER 10 Foster Avenue Gibbsboro NJ 244 971 164 244 1,135 1,379 659 1983 1997 (c) 7 Foster Avenue Gibbsboro NJ 231 921 31 231 952 1,183 575 1983 1997 (c) 2 Foster Avenue Gibbsboro NJ 185 730 11 185 741 926 741 1974 1997 (c) 4 Foster Avenue Gibbsboro NJ 183 726 6 183 732 915 732 1974 1997 (c) 1 Foster Avenue Gibbsboro NJ 93 364 8 93 372 465 372 1972 1997 (c) 5 U.S. Avenue Gibbsboro NJ 21 81 2 21 83 104 83 1987 1997 (c) 5 Foster Avenue Gibbsboro NJ 9 32 3 9 35 44 35 1968 1997 (c) Main Street - Plaza 1000 Voorhees NJ 2,732 10,942 284 2,732 11,226 13,958 11,017 1988 1997 (c) Main Street - Piazza Voorhees NJ 696 2,802 3,631 704 6,425 7,129 3,837 1990 1997 (c) Main Street - Promenade Voorhees NJ 532 2,052 326 532 2,378 2,910 1,432 1988 1997 (c) 920 North King Street Wilmington DE 6,141 21,140 8,059 6,141 29,199 35,340 14,492 1989 2004 (c) 300 Delaware Avenue Wilmington DE 6,369 13,739 2,657 6,369 16,396 22,765 9,823 1989 2004 (c) Total: $ 366,673 $ 2,494,108 $ 613,328 $ 407,514 $ 3,066,595 $ 3,474,109 $ 896,561 The following table reconciles the real estate investments from January 1, 2018 to December 31, 2020 (in thousands): 2020 2019 2018 Balance at beginning of year $ 4,006,459 $ 3,951,719 $ 3,830,824 Additions: Acquisitions 9,722 — 509,654 Capital expenditures and assets placed into service 113,221 145,378 129,274 Less: Dispositions/impairments/placed into redevelopment (619,086) (50,792) (469,517) Retirements (36,207) (39,846) (48,516) Balance at end of year $ 3,474,109 $ 4,006,459 $ 3,951,719 Per consolidated balance sheet $ 3,474,109 $ 4,006,459 $ 3,951,719 The aggregate cost for federal income tax purposes is $2.9 billion as of December 31, 2020. (b) Reconciliation of Accumulated Depreciation: The following table reconciles the accumulated depreciation on real estate investments from January 1, 2018 to December 31, 2020 (in thousands): 2020 2019 2018 Balance at beginning of year $ 973,318 $ 885,407 $ 913,297 Additions: Depreciation expense 138,822 144,131 137,213 Less: Dispositions/impairments/placed into redevelopment (182,526) (16,783) (117,589) Retirements (33,053) (39,437) (47,514) Balance at end of year $ 896,561 $ 973,318 $ 885,407 Per consolidated balance sheet $ 896,561 $ 973,318 $ 885,407 (c) Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 55 years. (d) Land value represents unamortized prepaid ground lease. (e) Reflects original construction date. Significant improvements were made to The Bulletin Building in 2012.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The Company consolidates variable interest entities (“VIEs”) in which it is considered to be the primary beneficiary. VIEs are entities in which the equity investors do not have sufficient equity at risk to finance their endeavors without additional financial support or that the holders of the equity investment at risk do not have a controlling financial interest. The primary beneficiary is defined by the entity having both of the following characteristics: (i) the power to direct those matters that most significantly impact the activities of the VIE and (ii) the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. For entities that the Company has the obligations to fund losses, its maximum exposure to loss is not limited to the carrying amount of its investments. The Company continuously assesses its determination of the primary beneficiary for each entity and assesses reconsideration events that may cause a change in the original determinations. As of December 31, 2020 and 2019, the Company included in its consolidated balance sheets consolidated VIEs having total assets of $49.2 million and $392.0 million, respectively, and total liabilities of $21.6 million and $255.6 million, respectively. When an entity is not deemed to be a VIE, the Company consolidates entities for which it has significant decision making control over the entity’s operations. The Company’s judgment with respect to its level of influence or control of an entity involves consideration of various factors including the form of the Company’s ownership interest, its representation in the entity’s governance, the size of its investment (including loans), estimates of future cash flows, its ability to participate in policy making decisions and the rights of the other investors to participate in the decision making process and to replace the Company as manager and/or liquidate the venture, if applicable. The Company’s assessment of its influence or control over an entity affects the presentation of these investments in the Company’s consolidated financial statements. In addition to evaluating control rights, the Company consolidates entities in which the outside partner has no substantive kick-out rights to remove the Company as managing member. The portion of the consolidated entities that are not owned by the Company is presented as noncontrolling interest as of and during the periods consolidated. All intercompany transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America ("US GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates.
Operating Properties	Operating Properties Operating properties are carried at historical cost less accumulated depreciation and impairment losses. The value of operating properties reflects their purchase price or development cost. Acquisition costs related to business combinations are expensed as incurred, whereas the costs related to asset acquisitions are capitalized as incurred. Costs incurred for the renovation and betterment of an operating property are capitalized to the Company’s investment in that property. Ordinary repairs and maintenance are expensed as incurred.
Purchase Price Allocation	Purchase Price Allocation For acquisitions of real estate or in-substance real estate that are accounted for as business combinations, we recognize the assets acquired (including the intangible value of acquired above- or below-market leases, acquired in-place leases and tenant relationship values), liabilities assumed, noncontrolling interests, and previously existing ownership interests at fair value as of the acquisition date. Any excess (deficit) of the consideration transferred relative to the fair value of the net assets acquired is accounted for as goodwill (bargain purchase gain). Acquisition costs related to business combinations are expensed as incurred. Acquisitions of real estate and in-substance real estate that do not meet the definition of a business are accounted for as asset acquisitions. The Company generally expects that acquisitions of real estate or in-substance real estate will not meet the definition of business and therefore are accounted for as asset acquisitions, unless specifically noted otherwise. The accounting model for asset acquisitions is similar to the accounting model for business combinations except that the acquisition consideration (including acquisition costs) is allocated to the individual assets acquired and liabilities assumed on a relative fair value basis. As a result, asset acquisitions do not result in recognition of goodwill or a bargain purchase gain. Additionally, because the accounting model for asset acquisitions is a cost accumulation model, preexisting interests in the acquired assets, if any, are not remeasured to fair value but continue to be accounted for at their historical cost. Direct acquisition costs are capitalized if an asset acquisition is probable. If we determine that an asset acquisition is no longer probable, no new costs are capitalized and all capitalized costs that are not recoverable are written off. The purchase price is allocated to the acquired assets and assumed liabilities, including land and buildings, as if vacant based on highest and best use for the acquired assets. The Company assesses and considers fair value of the operating properties based on estimated cash flow projections that utilize discount and/or capitalization rates that it deems appropriate, as well as available market information. Estimates of future cash flows are based on a number of factors including the historical operating results, known and anticipated trends, and market and economic conditions. The Company allocates the purchase price of properties considered to be business combinations and asset acquisitions to net tangible and identified intangible assets acquired based on fair values. Above-market and below-market in-place lease values for acquired properties are recorded based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) the Company’s estimate of the fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining noncancellable term of the lease (including the below market fixed renewal periods that are considered probable, if applicable). Capitalized above-market lease values are amortized as a reduction of rental income over the remaining noncancellable terms of the respective leases. Capitalized below-market lease values are amortized as an increase to rental income over the remaining noncancellable terms of the respective leases, including any below market fixed-rate renewal option periods that are considered probable. Other intangible assets also include in-place leases based on the Company’s evaluation of the specific characteristics of each tenant’s lease and the Company’s overall relationship with the respective tenant. The Company estimates the cost to execute leases with terms similar to the remaining lease terms of the in-place leases, including leasing commissions, legal and other related expenses. This intangible asset is amortized to expense over the remaining term of the respective leases and any fixed-rate bargain renewal periods. Factors considered by the Company in this analysis include an estimate of the carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. In estimating carrying costs, the Company includes real estate taxes, insurance, and other operating expenses, and estimates of lost rents at market rates during the expected lease-up periods, which primarily range from four In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) are recorded to revenue.
Depreciation and Amortization	Depreciation and Amortization The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements (5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset (1 to 16 years) or (ii) the lease term).
Construction-in-Progress	Construction-in-ProgressProject costs directly associated with the development and construction of a real estate project are capitalized as construction-in-progress. Construction-in-progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes, and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. Interest expense is capitalized using the Company’s weighted average interest rate. Internal direct costs are capitalized to projects in which qualifying expenditures are being incurred.
Ground Leases	Ground Leases The Company is the lessee under long-term ground leases classified as operating leases. The Company makes significant assumptions and judgments when determining the discount rate for the lease to calculate the present value of the lease payments. As the rate implicit in the lease is not readily determinable, the Company estimates the incremental borrowing rate (“IBR”) that it would need to pay to borrow, on a collateralized basis, an amount equal to the lease payments in a similar economic environment, over a similar lease term. The Company utilizes a market-based approach to estimate the IBR for each individual lease. The base IBR is estimated utilizing observable mortgage and corporate bond rates, which are then adjusted to account for considerations related to the Company’s credit rating and the lease term to select an incremental borrowing rate for each lease. The right of use assets and lease liabilities are presented as “Right of use asset - operating leases, net” and “Lease liability - operating leases”, respectively, on the consolidated balance sheet as of December 31, 2020. The lease liabilities and right of use assets are amortized on a straight-line basis over the lease term with the corresponding expense classified in “Property operating expenses” on the consolidated statements of operations. The most recent CPI adjustment is used to determine the present value of the lease payments for an indexed lease and ultimately the right of use asset and corresponding lease liability. Rent payments for amounts in excess of this estimated growth rate will be expensed on a cash basis as incurred and are considered variable lease costs.
Impairment of Long-Lived Assets	Impairment of Real Estate Investments The Company reviews its real estate investments for impairment following the end of each quarter for each of its real estate investments where events or changes in circumstances indicate that the carrying amounts may not be recoverable. The Company updates leasing and other assumptions regularly, paying particular attention to real estate investments where there is an event or change in circumstances that indicates an impairment in value. Additionally, the Company considers strategic decisions regarding the future development plans for real estate investment under development and other market factors. For real estate investments to be held and used, the Company analyzes recoverability based on the estimated undiscounted future cash flows expected to be generated from the operations and eventual disposition of the assets over, in most cases, a 10-year hold period. If there is significant possibility that the Company will dispose of assets earlier, it analyzes the recoverability using a probability weighted analysis of the undiscounted future cash flows expected to be generated from the operations and eventual disposition of each asset using various probable hold periods. If the recoverability analysis indicates that the carrying value of the tested real estate investment is not recoverable, the real estate investment is written down to its fair value and an impairment is recognized in the amount of the excess of the carrying amount of the asset over its fair value. If and when the Company’s plans change, it revises its recoverability analysis to use cash flows expected from operations and eventual disposition of each asset using hold periods that are consistent with its revised plans. Estimated future cash flows used in such analysis are based on the Company’s plans for the real estate investment and its views of market economic conditions. The estimates consider assumptions, including but not limited to market rental rates, capitalization rates, and recent sales data for comparable real estate investments. Future cash flows are discounted when determining fair value of an asset. Most of these assumptions are influenced by our direct experience with the real estate investments and their markets as well as market data obtained from real estate leasing and brokerage firms.
Assets Held for Sale	Assets Held for Sale The Company generally reclassifies assets to held for sale when the transaction has been approved by its Board of Trustees, or by officers vested with authority to approve the transaction, and there are no known significant contingencies relating to the sale of the real estate investment within one year of the consideration date and the consummation of the transaction is otherwise considered probable. When a real estate investment is designated as held for sale, the Company stops depreciating the real estate investment and estimates the real estate investment’s fair value, net of selling costs. If the determination is made that the estimated fair value, net of selling costs, is less than the net carrying value of the real estate investment, an impairment is recognized, reducing the net carrying value of the real estate investment to estimated fair value less selling costs. For periods in which a real estate investment is classified as held for sale, the Company classifies the assets and liabilities, as applicable, of the real estate investment as held for sale on the consolidated balance sheet for such periods.
Impairment of Land Held for Development	Impairment of Land Held for Development When demand for build-to-suit properties declines and the ability to sell land held for development deteriorates, or other market factors indicate possible impairment in the recoverability of land held for development, it is reviewed for impairment by comparing its fair value to its carrying value. If the estimated sales value is less than the carrying value, the carrying value is written down to its estimated fair value. Estimated fair value is generally determined using a market valuation approach, comparing the subject property to recent comparable market transactions in a similar location; or using estimated cash flows.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are highly-liquid investments with original maturities of three months or less. The Company maintains cash equivalents in money market accounts with financial institutions in excess of insured limits, but believes this risk is mitigated by only investing in or through major financial institutions. The Company does not invest its available cash balances in money market funds. As such, available cash balances are appropriately reflected as cash and cash equivalents on the consolidated balance sheets.
Restricted Cash	Restricted Cash Restricted cash consists of cash held as collateral to provide credit enhancement for the Company’s mortgage debt, cash for property taxes, capital expenditures and tenant improvements. Restricted cash also includes cash held by qualified intermediaries for possible investments in like-kind exchanges in accordance with Section 1031 of the Internal Revenue Code in connection with sales of the Company’s properties. Restricted cash is included in “Other assets” in the consolidated balance sheets.
Accounts Receivable And Accrued Rent Receivable	Accounts Receivable and Accrued Rent Receivable Generally, leases with tenants are accounted for as operating leases. Minimum lease payments under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payment terms are recorded as “Accrued rent receivable, net” on the consolidated balance sheets. Included in current tenant receivables are tenant reimbursements which are comprised of amounts recoverable from tenants for common area maintenance expenses and certain other recoverable expenses that are recognized as revenue in the period in which the related expenses are incurred.
Investments in Unconsolidated Real Estate Ventures	Investments in Unconsolidated Real Estate Ventures Under the equity method, investments in real estate ventures are recorded initially at cost and subsequently adjusted for equity in earnings, contributions, distributions, and impairments. For real estate ventures that are constructing assets to commence planned principal operations, the Company capitalizes interest expense to the extent that it is recoverable using the Company’s weighted average interest rate of consolidated debt and its investment balance as a basis. Planned principal operations commence when a property is available to lease and at that point in time, the Company ceases capitalizing interest to its investment basis. At least quarterly, management assesses whether there are any other than temporary impairment indicators of the Company’s investments in real estate ventures. An investment is other than temporarily impaired only if the fair value of the investment in a real estate venture, as estimated by management, is less than the carrying value and the decline is other than temporary. To the extent that an other than temporary impairment has occurred, an impairment charge is recorded in the amount of the excess of the carrying amount of the investment over the estimated fair value. Management is required to make significant judgments about the estimated fair value of its investments to determine if an impairment exists. Fair value is generally determined through income valuation approaches, including discounted cash flows and direct capitalization models.
Deferred Costs	Deferred Costs Certain costs incurred in connection with property leasing are capitalized as deferred leasing costs. Deferred leasing costs consist primarily of third-party and internal leasing commissions that are amortized using the straight-line method over the life of the respective lease which generally ranges from 1 to 16 years. Management re-evaluates the remaining useful lives of leasing costs in conjunction with changes in the respective lease term.
Notes Receivable	Notes Receivable The Company accounts for notes receivable on its balance sheet at amortized cost, net of allowance for loan losses. Interest income is recognized over the term of the notes receivable and is calculated based on the contractual terms of each note agreement. At inception and on a quarterly basis, the Company evaluates notes receivable for the current estimate of expected credit losses over the contractual term using a probability-of-default method and reports in net income (as a credit loss expense) the amount necessary to adjust the allowance for credit losses to reflect management's current estimate. Management considers performance and/or value of the underlying collateral property as well as the financial and operating capability of the borrower/sponsor in its evaluation.
Deferred Financing Costs	Deferred Financing CostsCosts incurred in connection with debt financing are capitalized as a direct deduction from the carrying value of the debt, except for costs capitalized related to the Company’s revolving credit facility, which are capitalized within the “Deferred costs, net” caption on the accompanying consolidated balance sheets. Deferred financing costs are charged to interest expense over the terms of the related debt agreements. Deferred financing costs consist primarily of loan fees which are amortized over the related loan term on a basis that approximates the effective interest method. Deferred financing costs are accelerated, when debt is extinguished, as part of the “Interest expense-amortization of deferred financing costs” caption within the Company’s consolidated statements of operations. Original issue discounts are recognized as part of the gain or loss on extinguishment of debt, as appropriate.
Revenue Recognition	Revenue Recognition Rental Revenue The Company generates revenue under leases with tenants occupying the Properties. Generally, leases with tenants are accounted for as operating leases. As of December 31, 2020 and 2019, the Company does not have any leases classified as direct-financing or sales-type leases. The operating leases have various expiration dates. Fixed lease payments under tenant leases are recognized on a straight-line basis over the term of the related lease. The cumulative difference between lease revenue recognized under the straight-line method and contractual lease payments are recorded as “Accrued rent receivable” on the consolidated balance sheets. Variable lease payments are recognized as lease revenue in the period in which changes occur in facts and circumstances on which the variable lease payments are based. Topic 842 requires a binary approach to evaluating leases for collectability. Lessors are required to determine if it is probable that substantially all of the lease payments will be collected from the tenant over the lease term. Should the lessor determine that it is not probable that substantially all of the lease payments will be collected, the standard requires that the lessor write off any accrued rent receivable and begin recognizing lease payments on a cash basis. The Company’s lease revenue is impacted by the Company’s determination of whether improvements to the property, whether made by the Company or by the tenant, are landlord assets. The determination of whether an improvement is a landlord asset requires judgment. In making this judgment, the Company’s primary consideration is whether an improvement would be utilizable by another tenant upon the then-existing tenant vacating the improved space. If the Company has funded an improvement that it determines not to be landlord assets, then it treats the cost of the improvement as a lease incentive. If the tenant has funded an improvement that the Company determines to be landlord assets, then the Company treats the costs of the improvement as deferred revenue and amortizes these costs into revenue over the lease term. For certain leases, the Company also makes significant assumptions and judgments in determining the lease term, including assumptions when the lease provides the tenant with an early termination option or purchase option. The lease term impacts the period over which the Company determines and records lease payments and also impacts the period over which it amortizes lease-related costs. The Company considers all relevant factors that create an economic incentive for the lessee and uses judgment to determine if those factors, considered together, signify that the lessee is reasonably certain to exercise the option. For leases where a tenant executes a lease termination, termination fees are recognized over the modified term of the lease as rental income. Additionally, any deferred rents receivable are accelerated over the modified lease term. The Company’s leases also typically provide for tenant reimbursement of a portion of common area maintenance expenses and other operating expenses to the extent that a tenant’s pro rata share of expenses exceeds a base year level set in the lease or to the extent that the tenant has a lease on a triple net basis. As the timing and pattern of revenue recognition is the same, rents and tenant reimbursements are treated as a combined lease component and included in the "Rents" caption within the Company's consolidated statements of operations. Fixed lease payments include contractual rents under lease agreements with tenants recognized on a straight-line basis over the lease term, including amortization of lease incentives and above or below market rent intangibles, and parking income that is fixed under a long-term contract. Variable lease payments include reimbursements billed to tenants, termination fees, bad debt expense, and parking income that is not fixed under a long-term contract. Point of Sale Revenue Point of sale revenue consists of parking, restaurant, and flexible stay revenue from the Company’s hotel operations. Point of sale service obligations are performed daily, and the customer obtains control of those services simultaneously as they are performed. Accordingly, revenue is recorded on an accrual basis as it is earned, coinciding with the services that are provided to the Company’s customers. Parking and flexible stay revenue is recognized within rents and restaurant income is recognized within other income on the consolidated statements of operations. Third party management fees, labor reimbursement, and leasing The Company performs property management services for third-party property owners of real estate that consist of: (i) providing leasing services, (ii) property inspections, (iii) repairs and maintenance monitoring, and (iv) financial and accounting oversight. For these services, the Company earns management fees monthly, which are based on a fixed percentage of each managed property’s financial results, and is reimbursed for the labor costs incurred by its property management employees as services are rendered to the property owners. The Company determined that control over the services is passed to its customers simultaneously as performance occurs. Accordingly, management fee revenue is earned as the services are provided to the Company’s customers. Lease commissions are earned when the Company, as a broker for the third party property owner, executes a lease agreement with a tenant. Based on the terms of the Company’s lease commission contracts, the Company's performance obligation to the customer has been completed upon execution of each lease agreement. The Company’s lease commissions are earned based on a fixed percentage of rental income generated for each executed lease agreement and there is no variable income component. Development fee revenue is earned through two different sources: (i) the Company performs development services for third parties as an agent and earns fixed development fees based on a percentage of construction costs incurred over the construction period, and (ii) the Company acts as a general contractor on behalf of one of its managed real estate ventures. The Company acts as the principal construction company for the real estate ventures and records gross revenue as it provides construction services based on the quantifiable construction outputs. In applying the cost based output method of revenue recognition, the Company uses the actual costs incurred relative to the total estimated costs to determine its progress towards contract completion and to calculate the corresponding gross revenue
Income Taxes	Income Taxes Parent Company The Parent Company has elected to be treated as a REIT under Sections 856 through 860 of the Internal Revenue Code of 1986, as amended (the “Code”). In order to continue to qualify as a REIT, the Parent Company is required to, among other things, distribute at least 90% of its annual REIT taxable income to its shareholders and meet certain tests regarding the nature of its income and assets. As a REIT, the Parent Company is not subject to federal and state (in states that follow federal rules) income taxes with respect to the portion of its income that meets certain criteria and is distributed annually to its shareholders. Accordingly, a nominal provision for federal and state (as applicable) income taxes is included in the accompanying consolidated financial statements with respect to the operations of the Parent Company. The Parent Company intends to continue to operate in a manner that allows it to meet the requirements for taxation as a REIT. If the Parent Company fails to qualify as a REIT in any taxable year, it will be subject to federal and state (as applicable) income taxes and may not be able to qualify as a REIT for the four subsequent tax years. The Parent Company is subject to certain local income taxes. Provision for federal income taxes is recorded in the income tax provision line item and state and local income taxes have been included in operating expenses in the Parent Company’s consolidated statements of operations. The tax basis of the Parent Company’s assets was $2.9 billion and $3.2 billion for the years ended December 31, 2020 and December 31, 2019, respectively. The Parent Company is subject to a 4% federal excise tax if sufficient taxable income is not distributed within prescribed time limits. The excise tax equals 4% of the annual amount, if any, by which the sum of (a) 85% of the Parent Company’s ordinary income and (b) 95% of the Parent Company’s net capital gain exceeds cash distributions and certain taxes paid by the Parent Company. No excise tax was incurred in 2020, 2019 or 2018. The Parent Company has elected to treat several of its subsidiaries as taxable REIT subsidiaries (each a “TRS”). A TRS is subject to federal, state and local income tax. In general, a TRS may perform non-customary services for tenants, hold assets that the Parent Company, as a REIT, cannot hold directly and generally may engage in any real estate or non-real estate related business. The Company’s taxable REIT subsidiaries did not have material tax provisions or deferred income tax items as of December 31, 2020 and December 31, 2019. Operating Partnership In general, the Operating Partnership is not subject to federal and state income taxes, and accordingly, no provision for income taxes has been made in the accompanying consolidated financial statements. The partners of the Operating Partnership are required to include their respective share of the Operating Partnership’s profits or losses in their respective tax returns. The Operating Partnership’s tax returns and the amount of allocable partnership profits and losses are subject to examination by federal and state taxing authorities. For any year beginning on or after January 1, 2017, the Operating Partnership can be assessed with federal income tax in the course of an audit by the IRS. Under the new partnership audit rules included in the Bipartisan Budget Act of 2015, the Operating Partnership has the option to make a push-out election and allocate the partnership adjustments to all the former partners for the tax year under audit. The tax basis of the Operating Partnership’s assets was $2.9 billion and $3.2 billion for the years ended December 31, 2020 and December 31, 2019, respectively. The Operating Partnership may elect to treat a subsidiary REIT under Sections 856 through 860 of the Code, if applicable. Each subsidiary REIT would be required to meet the requirements for treatment as a REIT under Sections 856 through 860 of the Code. If a subsidiary REIT fails to qualify as a REIT in any taxable year, that subsidiary REIT would be subject to federal and state income taxes and would not be able to qualify as a REIT for the four subsequent taxable years. Also, each subsidiary REIT would be subject to certain local income taxes. The Operating Partnership has elected to treat several of its subsidiaries as TRSs, which are subject to federal, state and local income tax.
Earnings Per Share	Earnings Per Share Basic earnings per share (“EPS”) is computed by dividing net income available to common shareholders, as adjusted for unallocated earnings, if any, of certain securities, by the weighted average number of common shares outstanding during the year. Diluted EPS reflects the potential dilution that could occur from common shares issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options, and conversion of the noncontrolling interests in the Operating Partnership. Anti-dilutive shares are excluded from the calculation. Earnings Per Unit Basic earnings per unit is computed by dividing net income available to common unitholders, as adjusted for unallocated earnings, if any, of certain securities issued by the Operating Partnership, by the weighted average number of common unit equivalents outstanding during the year. Diluted earnings per unit reflects the potential dilution that could occur from units issuable in connection with awards under share-based compensation plans, including upon the exercise of stock options. Anti-dilutive units are excluded from the calculation.
Share-Based Compensation Plans	Share-Based Compensation PlansThe Parent Company maintains a shareholder-approved equity-incentive plan known as the Amended and Restated 1997 Long-Term Incentive Plan (the “1997 Plan”). The 1997 Plan is administered by the Compensation Committee of the Parent Company’s Board of Trustees. Under the 1997 Plan, the Compensation Committee is authorized to award equity and equity-based awards, including incentive stock options, non-qualified stock options, restricted share rights and performance-based share units.
Comprehensive Income	Comprehensive Income Comprehensive income is recorded in accordance with the provisions of the accounting standard for comprehensive income. The accounting standard establishes standards for reporting comprehensive income and its components in the financial statements. Comprehensive income includes the effective portions of changes in the fair value of derivatives.
Accounting for Derivative Instruments and Hedging Activities	Accounting for Derivative Instruments and Hedging Activities The Company accounts for its derivative instruments and hedging activities in accordance with the accounting standard for derivative and hedging activities. The accounting standard requires the Company to measure every derivative instrument (including certain derivative instruments embedded in other contracts) at fair value and record them on the balance sheet as either an asset or liability. See disclosures below related to the accounting standard for fair value measurements and disclosures. For derivatives designated as cash flow hedges, the effective portions of changes in the fair value of the derivative are reported in other comprehensive income while the ineffective portions are recognized in earnings. The Company actively manages its ratio of fixed-to-floating rate debt. To manage its fixed and floating rate debt in a cost-effective manner, the Company, from time to time, enters into interest rate swap agreements as cash flow hedges, under which it agrees to exchange various combinations of fixed and/or variable interest rates based on agreed upon notional amounts.
Fair Value Measurements	Fair Value Measurements The Company estimates the fair value of its derivatives in accordance with the accounting standard for fair value measurements and disclosures. The accounting standard defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. It also establishes a fair value hierarchy which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value. Financial assets and liabilities recorded on the consolidated balance sheets are categorized based on the inputs to the valuation techniques as follows: • Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access; • Level 2 inputs are inputs, other than quoted prices included in Level 1, which are observable for the asset or liability, either directly or indirectly. Level 2 inputs may include quoted prices for similar assets and liabilities in active markets, as well as inputs that are observable for the asset or liability (other than quoted prices), such as interest rates, foreign exchange rates, and yield curves that are observable at commonly quoted intervals; and • Level 3 inputs are unobservable inputs for the asset or liability, which is typically based on an entity’s own assumptions, as there is little if any, related market activity or information. In instances where the determination of the fair value measurement is based on inputs from different levels of the fair value hierarchy, the level in the fair value hierarchy within which the entire fair value measurement falls is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the asset or liability.
Risks And Uncertainties - COVID-19	Risks and Uncertainties - COVID-19 Currently, one of the most significant risks and uncertainties the Company faces is the potential adverse effect of the ongoing global COVID-19 pandemic, which has significantly slowed global economic activity, caused significant volatility in financial markets, and resulted in unprecedented job losses, causing many to fear an imminent global recession. The responses of many countries, including the U.S., have included mandatory quarantines, restrictions on business activities, including construction activities, restrictions on group gatherings, restrictions on travel and mandatory closures. These actions are creating disruption in the global economy and supply chains and adversely impacting many industries, including owners and developers of real estate. Moreover, there is significant uncertainty around the breadth and duration of business disruptions related to the COVID-19 pandemic, as well as its impact on the U.S. economy and consumer confidence. Demand for space at the Company's properties is dependent on a variety of macroeconomic factors, such as employment levels, interest rates, changes in stock market valuations, rent levels and availability of competing space. The extent to which the COVID-19 pandemic impacts the Company's results will depend on future developments, many of which are highly uncertain and cannot be predicted, including new information which may emerge concerning the severity of COVID-19, future action plans, and vaccination efforts. The COVID-19 pandemic has caused continued negative economic impacts, market volatility, and business disruption, which could negatively impact the Company's tenants’ ability to pay rent, the Company's ability to lease vacant space, and the Company's ability to complete development and redevelopment projects. These consequences, in turn, could materially impact the Company's results of operations.
Accounting Standards Updates	Recent Accounting Pronouncements In May 2020, the SEC adopted amendments to requirements for companies relating to significant acquisitions and dispositions of businesses as well as amendments to the significance tests in the ‘significant subsidiary’ definition. Additionally, significant modifications were made to the requirements related to the presentation of pro forma financial information. The amendments are effective on January 1, 2021, with voluntary compliance permitted in advance of the effective date. The Company has elected to early adopt the amendments as of September 30, 2020. On April 10, 2020, the FASB issued a Staff Q&A to respond to some frequently asked questions about accounting for lease concessions related to the effects of the COVID-19 pandemic. Consequently, for concessions related to the effects of the COVID-19 pandemic, an entity will not have to analyze each contract to determine whether enforceable rights and obligations for concessions exist in the contract and can elect to apply or not apply the lease modification guidance to those contracts. Entities may make the elections for any lessor-provided concession related to the effects of the COVID-19 pandemic (e.g., deferrals of lease payments, cash payments made to the lessee, reduced future lease payments) as long as the concession does not result in a substantial increase in the rights of the lessor or the obligations of the lessee. The Company has elected to account for lease concessions as though the enforceable rights and obligations for the concessions existed in the original lease. To date, the impact of lease concessions granted has not had a material effect on the Company's financial statements. The Company continues to evaluate the impact of lease concessions and the appropriate accounting for those concessions. In March 2020, the FASB issued ASU 2020-04 Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments provide practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance is optional and is effective between March 12, 2020 and December 31, 2022. The guidance may be elected over time as reference rate reform activities occur. The Company continues to evaluate the impact of the guidance and may apply elections as applicable as additional changes in the market occur. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments Credit Losses (Topic 326), which changes how entities measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The guidance replaces the current incurred loss model with an expected loss approach, resulting in more timely recognition of such losses. In November 2018, the FASB released ASU 2018-19, Codification Improvements to Topic 326, Financial Instrument - Credit Losses, which clarifies that receivables arising from operating leases are not within the scope of Subtopic 326-20. The guidance was effective for the Company as of January 1, 2020. The Company adopted ASU 2016-13 effective January 1, 2020 and it did not have a material impact on the consolidated financial statements.

ORGANIZATION OF THE PARENT CO_2

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Core Portfolio of Operating Properties and Excludes Development and Redevelopment Properties Under Construction	The Company’s core portfolio of operating properties (the “Core Properties”) excludes development properties, redevelopment properties, and properties held for sale. The Properties were comprised of the following as of December 31, 2020: Number of Properties Rentable Square Feet Office properties 73 12,470,257 Mixed-use properties 5 942,334 Core Properties 78 13,412,591 Development property 1 205,803 Redevelopment properties 3 234,070 The Properties 82 13,852,464

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Disaggregation of Revenue	The following is a summary of revenue earned by the Company’s reportable segments (see Note 19, ''Segment Information,” for further information) during the year ended December 31, 2020 (in thousands): Philadelphia CBD Pennsylvania Suburbs Austin, Texas Metropolitan Washington, D.C. Other Corporate (a) Total Fixed rent $ 166,286 $ 128,044 $ 63,366 $ 29,830 $ 8,064 $ (2,412) $ 393,178 Variable rent 51,410 12,951 35,123 3,544 2,401 (1,343) 104,086 Total lease revenue 217,696 140,995 98,489 33,374 10,465 (3,755) 497,264 Amortization of deferred market rents 1,146 (12) 3,531 — 203 — 4,868 Daily parking & hotel flexible stay 10,777 179 49 135 232 — 11,372 Total rents 229,619 141,162 102,069 33,509 10,900 (3,755) 513,504 Third party management fees, labor reimbursement and leasing 927 39 689 6,541 2,560 7,824 18,580 Other income 1,482 412 224 173 9 468 2,768 Total revenue $ 232,028 $ 141,613 $ 102,982 $ 40,223 $ 13,469 $ 4,537 $ 534,852 The following is a summary of revenue earned by the Company’s reportable segments (see Note 19, ''Segment Information,” for further information) during the year ended December 31, 2019 (in thousands): Philadelphia CBD Pennsylvania Suburbs Austin, Texas Metropolitan Washington, D.C. Other Corporate (a) Total Fixed rent $ 178,481 $ 125,969 $ 62,232 $ 39,420 $ 7,834 $ (2,412) $ 411,524 Variable rent 58,580 14,282 34,748 4,029 3,080 (495) 114,224 Total lease revenue 237,061 140,251 96,980 43,449 10,914 (2,907) 525,748 Amortization of deferred market rents 3,745 (12) 4,638 — 486 — 8,857 Daily parking & hotel flexible stay 18,665 174 165 824 232 — 20,060 Total rents 259,471 140,413 101,783 44,273 11,632 (2,907) 554,665 Third party management fees, labor reimbursement and leasing 876 43 1,956 6,922 2,915 6,914 19,626 Other income 3,422 628 418 303 11 1,344 6,126 Total revenue $ 263,769 $ 141,084 $ 104,157 $ 51,498 $ 14,558 $ 5,351 $ 580,417 (a) Corporate includes intercompany eliminations necessary to reconcile to consolidated Company totals.

REAL ESTATE INVESTMENTS (Tables

REAL ESTATE INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Real Estate [Abstract]
Gross Carrying Value of Operating Properties	As of December 31, 2020 and 2019, the gross carrying value of the operating properties was as follows (in thousands): December 31, 2020 December 31, 2019 Land $ 407,514 $ 489,702 Building and improvements 2,665,232 3,049,395 Tenant improvements 401,363 467,362 Total $ 3,474,109 $ 4,006,459
Capitalized Construction Costs	The following table shows the amount of compensation costs (including bonuses and benefits) capitalized for the years presented (in thousands): December 31, 2020 2019 2018 Development $ 4,802 $ 3,047 $ 3,185 Redevelopment 543 775 968 Tenant Improvements 3,021 3,609 2,811 Total $ 8,366 $ 7,431 $ 6,964
Schedule of Acquisitions	The following table summarizes the property acquisitions during the year ended December 31, 2020 (dollars in thousands): Property/Portfolio Name Acquisition Date Location Property Type Rentable Square Feet/Acres Purchase Price (a) 145 King of Prussia Road February 27, 2020 Radnor, PA Land 7.75 acres $ 11,250 1505-11 Race Street November 5, 2020 Philadelphia, PA Office 119,763 $ 9,700 250 King of Prussia Road (b) November 30, 2020 Radnor, PA Office 169,843 $ 20,250 (a) Exclusive of transaction costs and price adjustments. See purchase price allocation table below for a breakout of the net purchase price for wholly owned properties. (b) This property was placed into redevelopment and is therefore included within Construction-in-progress on the consolidated balance sheets.
Schedule of Asset Acquisition	The acquisition values have been allocated as follows (in thousands): 1505-11 Race Street Building, land and improvements $ 9,723 Intangible assets acquired 2,422 Below market lease liabilities assumed (2,193) Total unencumbered acquisition value 9,952 Amortization period of intangible assets 1.5 years Amortization period of below market liabilities assumed 1.5 years
Schedule of Purchase Price Allocation	The acquisition values have been allocated as follows (in thousands): Quarry Lake II Austin Venture Portfolio Four Tower Bridge Acquisition Date 12/19/2018 12/11/2018 1/5/2018 Building, land and improvements $ 35,120 $ 457,390 $ 20,734 Intangible assets acquired 5,809 76,925 3,144 Below market lease liabilities assumed (1,524) (13,769) (182) Deferred gain (a) — 14,594 — Total unencumbered acquisition value $ 39,405 $ 535,140 $ 23,696 Mortgage debt assumed - at fair value (b) — — (9,940) Total encumbered acquisition value $ 39,405 $ 535,140 $ 13,756 Total unencumbered acquisition value 39,405 535,140 23,696 Mortgage debt assumed - at fair value (b) — — (9,940) Mortgage debt repaid at settlement (c) — (115,461) — Investment in unconsolidated real estate ventures — (14,594) (3,502) Gain on promoted interest in unconsolidated real estate venture — (28,283) — Gain on real estate venture transactions — (103,847) (11,633) Purchase price reduction for note receivable (d) — (130,742) — Net working capital assumed (368) (24,865) 1,379 Total cash payment at settlement $ 39,037 $ 117,348 $ — Weighted average amortization period of intangible assets 0 5.5 years 4.1 years Weighted average amortization period of below market liabilities assumed 3.0 years 4.6 years 4.8 years (a) Represents a deferred gain recognized at settlement, which resulted in a reduction of the acquisition value. (b) The outstanding principal balance on mortgage debt for Four Tower Bridge, assumed on January 5, 2018, was $9.7 million. (c) On December 11, 2018, the Company assumed $115.5 million of mortgage debt which was repaid in full at settlement. (d) Represents a note receivable due from the DRA Austin Venture that represents a purchase price reduction.
Schedule of Pro Forma Information	The unaudited pro forma information below summarizes the Company’s combined results of operations for the years ended December 31, 2018 and December 31, 2017, respectively, as though the acquisition of the Austin Venture Portfolio was completed on January 1, 2017. The supplemental pro forma operating data is not necessarily indicative of what the actual results of operations would have been assuming the transaction had been completed as set forth above, nor do they purport to represent the Company’s results of operations for future periods (in thousands). December 31, 2018 2017 Pro forma revenue $ 602,713 $ 582,244 Pro forma net income 134,142 115,475 Pro forma net income available to common shareholders 134,142 115,475
Summary of Gain on Sale for Each Land Parcel	The following table summarizes the property dispositions during the years ended December 31, 2020, 2019 and 2018 (dollars in thousands): Property/Portfolio Name Disposition Date Location Property Type Rentable Square Feet/Acres Sales Price Gain/(Loss) on Sale (a) Mid-Atlantic Office Portfolio (b) (g) December 21, 2020 Various Office 1,128,645 $ 192,943 $ 15,164 One and Two Commerce Square (c) July 21, 2020 Philadelphia, PA Office 1,896,142 $ 115,000 $ 271,905 Keith Valley June 15, 2020 Horsham, PA Land 14.0 Acres $ 4,000 $ 201 52 East Swedesford Road March 19, 2020 Malvern, PA Office 131,077 $ 18,000 $ 2,336 1900 Gallows Rd September 11, 2019 Vienna, VA Office 210,632 $ 36,400 $ (367) 9 Presidential Boulevard March 15, 2019 Bala Cynwyd, PA Land 2.7 Acres $ 5,325 $ 751 Subaru National Training Center (d) December 21, 2018 Camden, NJ Mixed-use 83,000 $ 45,300 $ 2,570 Rockpoint Portfolio (e) December 20, 2018 Herndon, VA Office 1,293,197 $ 312,000 $ 397 20 East Clementon Road June 21, 2018 Gibbsboro, NJ Office 38,260 $ 2,000 $ (35) Garza Ranch - Office (f) March 16, 2018 Austin, TX Land 6.6 acres $ 14,571 $ 1,515 Westpark Land January 10, 2018 Durham, NC Land 13.1 acres $ 485 $ 22 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) The Company sold a 60% equity interest in a portfolio of twelve suburban office properties containing an aggregate of 1.1 million square feet ("Mid-Atlantic Office Portfolio"), nine of which are located in the Pennsylvania suburbs and three of which are located in Maryland, to an unrelated third party for a gross sales price of $192.9 million. The transaction resulted in deconsolidation of the properties and formation of PA/MD NNN Office JV, LLC ("Mid-Atlantic Office JV"). The Company recorded its investment at fair value and recognized a gain of $15.2 million in "Net gain on disposition of real estate" on the Consolidated Statements of Operations. See Note 4, ''Investment in Unconsolidated Real Estate Ventures," for further information. (c) The Company sold a 30% preferred equity interest in two office buildings located in Philadelphia, Pennsylvania, to an unrelated third party for $115.0 million (the "Commerce Square Venture Transaction"), which resulted in deconsolidation of the properties and formation of Brandywine Commerce I LP and Brandywine Commerce II LP (collectively, the "Commerce Square Venture"). The transaction valued the properties at $600.0 million. The Company recorded its investment at fair value and recognized a gain of $271.9 million in "Net gain on disposition of real estate" on the Consolidated Statements of Operations. See Note 4, ''Investment in Unconsolidated Real Estate Ventures," for further information. (d) During the third quarter of 2018, the tenant, Subaru, exercised its purchase option for the Subaru National Training Center Development. The lease with Subaru was classified as a direct finance lease within "Other assets" on the consolidated balance sheets. In connection with the lease, the Company recognized $1.6 million in interest income during the twelve months ended December 31, 2018, in accordance with accounting guidance for direct finance leases under ASC 840. (e) For information related to this transaction, see the “Herndon Innovation Center Metro Portfolio Venture, LLC” section in Note 4, “Investment in Unconsolidated Real Estate Ventures.” (f) The Company had continuing involvement in this property through a completion guaranty, which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcel. The Company recorded the cash received at settlement as “Deferred income, gains and rent” on the consolidated balance sheet. The Company subsequently recognized the land sale and the $3.0 million gain on sale during the twelve months ended December 31, 2018 upon substantial completion of the infrastructure improvements and transfer of control to the buyer. six

INVESTMENT IN UNCONSOLIDATED _2

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES (Tables)	12 Months Ended
	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Summary of Unconsolidated Real Estate Ventures	The Company’s investment in the Real Estate Ventures as of December 31, 2020 and 2019, and the Company’s share of the Real Estate Ventures’ income (loss) for the years ended December 31, 2020 and 2019 was as follows (in thousands): Ownership Percentage Carrying Amount Company's Share of Real Estate Venture Income (Loss) Real Estate Venture Debt at 100%, gross 2020 2019 2020 2019 2020 2019 Office Properties Commerce Square Venture 70% (a) $ 253,128 $ — $ (9,150) $ — $ 219,168 $ — Mid-Atlantic Office Venture 40% (a) 32,996 — 96 — 120,831 — Brandywine - AI Venture LLC 50% 10,302 10,116 185 (2,800) — — Herndon Innovation Center Metro Portfolio Venture, LLC 15% 16,019 16,446 (358) (498) 207,302 207,302 MAP Venture 50% (11,516) (70) (6,570) (6,102) 185,000 185,000 PJP VII 25% (b) — — — 190 — — PJP II 30% (b) — — — 81 — — PJP VI 25% (b) — — — (185) — — Other 1919 Venture 50% 15,434 17,524 59 328 88,860 88,860 Development Properties 4040 Wilson Venture (c) 50% 34,454 37,002 (2,162) (368) 141,857 114,845 JBG - 51 N Street (c) 70% 21,237 21,531 (457) (313) — — JBG - 1250 First Street Office (c) 70% 17,757 17,745 (227) (255) — — $ 389,811 $ 120,294 $ (18,584) $ (9,922) $ 963,018 $ 596,007 (a) Ownership percentage represents the Company’s combined interest including preferred and common equity holdings. See "Commerce Square Venture" and "Mid-Atlantic Office JV" sections below for more information. (b) On October 29, 2019, the Company sold its interest in PJP II, PJP VI and PJP VII. See "PJP Ventures" section below for more information on the disposal. (c) This entity is a VIE. The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2020 and December 31, 2019 (in thousands): December 31, 2020 December 31, 2019 Net property $ 1,520,804 $ 834,367 Other assets 488,805 342,002 Other liabilities 333,049 290,071 Debt, net 956,688 585,068 Equity (a) 719,872 301,230 (a) This amount does not include 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. The following is a summary of results of operations of the Real Estate Ventures in which the Company had interests during the twelve-month periods ended December 31, 2020, 2019 and 2018 (in thousands): Year Ended December 31, 2020 2019 2018 Revenue $ 150,276 $ 132,358 $ 165,326 Operating expenses (85,812) (71,784) (82,035) Interest expense, net (22,661) (21,908) (29,774) Depreciation and amortization (70,805) (53,331) (53,826) Provision for impairment — (5,664) (20,832) Loss on extinguishment of debt — (1,231) (1,385) Net loss $ (29,002) $ (21,560) $ (22,526) Ownership interest % Various Various Various Company's share of net loss $ (18,540) $ (9,865) $ (11,924) Other-than-temporary impairment — — (4,076) Basis adjustments and other (44) (57) 769 Equity in loss of Real Estate Ventures $ (18,584) $ (9,922) $ (15,231)
Schedule of Maturities of Long-term Debt	As of December 31, 2020, the aggregate principal payments of the Real Estate Ventures recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2021 $ 148,693 2022 8,543 2023 477,649 2024 328,133 2025 — Thereafter — Total principal payments 963,018 Net deferred financing costs (8,224) Net original issue premium 1,894 Outstanding indebtedness $ 956,688 As of December 31, 2020, the Company’s aggregate scheduled principal payments of debt obligations are as follows (in thousands): 2021 $ — 2022 250,000 2023 350,000 2024 350,000 2025 — Thereafter 878,610 Total principal payments 1,828,610 Net unamortized premiums/(discounts) 10,137 Net deferred financing costs (8,152) Outstanding indebtedness $ 1,830,595

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Operating Lease Scheduled Minimum Lease Payments	The Company leases properties to tenants under operating leases with various expiration dates. Scheduled minimum lease payments on noncancellable leases at December 31, 2020 are as follows (in thousands): Year Minimum Rent 2021 $ 325,703 2022 310,208 2023 292,871 2024 268,062 2025 236,623 Thereafter 968,163
Lease Costs	The table below summarizes the Company’s operating lease cost (in thousands) recognized through “Property operating expenses” on the consolidated statements of operations (in thousands): Year Ended December 31, Lease Cost 2020 2019 Fixed lease cost $ 2,100 $ 2,100 Variable lease cost 45 54 Total $ 2,145 $ 2,154 Weighted-average remaining lease term (years) 55.9 56.6 Weighted-average discount rate 6.3 % 6.3 %
Operating Lease Liability Maturities	Lease payments on noncancellable leases at December 31, 2020 are as follows (in thousands): Year Minimum Rent 2021 $ 1,232 2022 1,248 2023 1,263 2024 1,305 2025 1,321 Thereafter 109,131 Total lease payments $ 115,500 Less: Imputed interest 92,742 Present value of operating lease liabilities $ 22,758

DEFERRED COSTS (Tables)

DEFERRED COSTS (Tables)	12 Months Ended
	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure	As of December 31, 2020 and 2019, the Company’s deferred costs were comprised of the following (in thousands): December 31, 2020 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 139,207 $ (55,656) $ 83,551 Financing costs - Revolving Credit Facility 6,299 (4,994) 1,305 Total $ 145,506 $ (60,650) $ 84,856 December 31, 2019 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 156,619 $ (63,257) $ 93,362 Financing costs - Revolving Credit Facility 6,299 (4,101) 2,198 Total $ 162,918 $ (67,358) $ 95,560

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets and Liabilities	As of December 31, 2020 and 2019, the Company’s intangible assets were comprised of the following (in thousands): December 31, 2020 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 91,552 $ (43,400) $ 48,152 Tenant relationship value 2,091 (1,938) 153 Above market leases acquired 530 (265) 265 Total intangible assets, net $ 94,173 $ (45,603) $ 48,570 Total Cost Accumulated Amortization Intangible Liabilities, net Intangible liabilities, net: Below market leases acquired $ 31,263 $ (12,815) $ 18,448 December 31, 2019 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 167,357 $ (84,123) $ 83,234 Tenant relationship value 5,268 (4,815) 453 Above market leases acquired 4,956 (3,792) 1,164 Total intangible assets, net $ 177,581 $ (92,730) $ 84,851 Total Cost Accumulated Amortization Intangible Liabilities, net Intangible liabilities, net: Below market leases acquired $ 44,757 $ (22,494) $ 22,263
Summary of Amortization for Intangible Assets and Liabilities	As of December 31, 2020, the Company’s annual amortization for its intangible assets/liabilities, assuming no early lease terminations, are as follows (dollars in thousands): Assets Liabilities 2021 $ 16,190 $ 4,902 2022 10,354 2,723 2023 7,564 1,651 2024 5,214 1,425 2025 4,027 1,148 Thereafter 5,221 6,599 Total $ 48,570 $ 18,448

DEBT OBLIGATIONS (Tables)

DEBT OBLIGATIONS (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Consolidated debt obligations	The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2020 and 2019 (in thousands): December 31, 2020 December 31, 2019 Effective Maturity MORTGAGE DEBT: Two Logan Square (a) $ — $ 81,103 3.98% October 2020 Four Tower Bridge (b) — 9,291 4.50% February 2021 One Commerce Square (c) — 116,571 3.64% April 2023 Two Commerce Square (c) — 108,472 4.51% April 2023 Principal balance outstanding — 315,437 Plus: fair market value premium (discount), net — (1,383) Less: deferred financing costs — (242) Mortgage indebtedness $ — $ 313,812 UNSECURED DEBT $600 million Unsecured Credit Facility $ — $ — LIBOR + 1.10% July 2022 Seven 250,000 250,000 2.87% October 2022 $350.0M 3.95% Guaranteed Notes due 2023 350,000 350,000 3.87% February 2023 $350.0M 4.10% Guaranteed Notes due 2024 350,000 350,000 3.78% October 2024 $450.0M 3.95% Guaranteed Notes due 2027 450,000 450,000 4.03% November 2027 $350.0M 4.55% Guaranteed Notes due 2029 350,000 350,000 4.30% October 2029 Indenture IA (Preferred Trust I) 27,062 27,062 LIBOR + 1.25% March 2035 Indenture IB (Preferred Trust I) - Swapped to fixed 25,774 25,774 3.30% April 2035 Indenture II (Preferred Trust II) 25,774 25,774 LIBOR + 1.25% July 2035 Principal balance outstanding 1,828,610 1,828,610 Plus: original issue premium (discount), net 10,137 12,090 Less: deferred financing costs (8,152) (10,094) Total unsecured indebtedness $ 1,830,595 $ 1,830,606 Total Debt Obligations $ 1,830,595 $ 2,144,418 (a) On October 21, 2020, the Company acquired the $79.8 million remaining mortgage on this property from the lender. (b) On November 10, 2020, the Company repaid the remaining $9.1 million mortgage balance. (c) The properties encumbered by these mortgages were deconsolidated as a result of the Commerce Square Venture Transaction. See Note 3, ''Real Estate Investments," for further information.
Schedule of Maturities of Long-term Debt	As of December 31, 2020, the aggregate principal payments of the Real Estate Ventures recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2021 $ 148,693 2022 8,543 2023 477,649 2024 328,133 2025 — Thereafter — Total principal payments 963,018 Net deferred financing costs (8,224) Net original issue premium 1,894 Outstanding indebtedness $ 956,688 As of December 31, 2020, the Company’s aggregate scheduled principal payments of debt obligations are as follows (in thousands): 2021 $ — 2022 250,000 2023 350,000 2024 350,000 2025 — Thereafter 878,610 Total principal payments 1,828,610 Net unamortized premiums/(discounts) 10,137 Net deferred financing costs (8,152) Outstanding indebtedness $ 1,830,595

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments With Fair Values Different From Their Carrying Amount	The following are financial instruments for which the Company’s estimates of fair value differ from the carrying amounts (in thousands): December 31, 2020 December 31, 2019 Carrying Amount (a) Fair Value Carrying Amount (a) Fair Value Unsecured notes payable $ 1,502,901 $ 1,607,310 $ 1,503,435 $ 1,591,830 Variable rate debt $ 327,694 $ 308,838 $ 327,171 $ 309,947 Mortgage notes payable $ — $ — $ 313,812 $ 317,031 Notes receivable $ 94,430 $ 97,372 $ 44,430 $ 43,322 (a) The carrying amounts presented in the table above are net of deferred financing costs of $7.2 million and $8.7 million for unsecured notes payable, $0.9 million and $1.4 million for variable rate debt and $0.0 million and $0.2 million for mortgage notes payable as of December 31, 2020 and December 31, 2019, respectively.

DERIVATIVE FINANCIAL INSTRUME_2

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following table summarizes the terms and fair values of the Company’s derivative financial instruments as of December 31, 2020 and December 31, 2019. The notional amounts provide an indication of the extent of the Company’s involvement in these instruments at that time but do not represent exposure to credit, interest rate or market risks (amounts presented in thousands). Hedge Product Hedge Type Designation Notional Amount Strike Trade Date Maturity Date Fair value 12/31/2020 12/31/2019 12/31/2020 12/31/2019 Liabilities Swap Interest Rate Cash Flow (a) $ 250,000 $ 250,000 2.868 % October 8, 2015 October 8, 2022 $ (6,627) $ (562) Swap Interest Rate Cash Flow (a) 25,774 25,774 3.300 % December 22, 2011 January 30, 2021 (120) (94) $ 275,774 $ 275,774 (a) Hedging unsecured variable rate debt.

BENEFICIARIES' EQUITY OF THE _2

BENEFICIARIES' EQUITY OF THE PARENT COMPANY (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Earnings Per Share (EPS), Basic and Diluted	The following table details the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year Ended December 31, 2020 2019 2018 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 307,326 $ 307,326 $ 34,529 $ 34,529 $ 135,472 $ 135,472 Net income attributable to noncontrolling interests (1,799) (1,799) (262) (262) (954) (954) Nonforfeitable dividends allocated to unvested restricted shareholders (410) (410) (396) (396) (369) (369) Net income attributable to common shareholders $ 305,117 $ 305,117 $ 33,871 $ 33,871 $ 134,149 $ 134,149 Denominator Weighted-average shares outstanding 171,926,079 171,926,079 176,132,941 176,132,941 178,519,748 178,519,748 Contingent securities/Share based compensation — 390,997 — 553,872 — 1,121,744 Weighted-average shares outstanding 171,926,079 172,317,076 176,132,941 176,686,813 178,519,748 179,641,492 Earnings per Common Share: Net income attributable to common shareholders $ 1.77 $ 1.77 $ 0.19 $ 0.19 $ 0.75 $ 0.75 The following table details the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year Ended December 31, 2020 2019 2018 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 307,326 $ 307,326 $ 34,529 $ 34,529 $ 135,472 $ 135,472 Net income attributable to noncontrolling interests (20) (20) (69) (69) (55) (55) Nonforfeitable dividends allocated to unvested restricted unitholders (410) (410) (396) (396) (369) (369) Net income attributable to common unitholders $ 306,896 $ 306,896 $ 34,064 $ 34,064 $ 135,048 $ 135,048 Denominator Weighted-average units outstanding 172,907,713 172,907,713 177,114,932 177,114,932 179,959,370 179,959,370 Contingent securities/Share based compensation — 390,997 — 553,872 — 1,121,744 Total weighted-average units outstanding 172,907,713 173,298,710 177,114,932 177,668,804 179,959,370 181,081,114 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 1.77 $ 1.77 $ 0.19 $ 0.19 $ 0.75 $ 0.75

PARTNER'S EQUITY OF THE PAREN_2

PARTNER'S EQUITY OF THE PARENT COMPANY (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Earnings Per Share (EPS), Basic and Diluted	The following table details the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year Ended December 31, 2020 2019 2018 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 307,326 $ 307,326 $ 34,529 $ 34,529 $ 135,472 $ 135,472 Net income attributable to noncontrolling interests (1,799) (1,799) (262) (262) (954) (954) Nonforfeitable dividends allocated to unvested restricted shareholders (410) (410) (396) (396) (369) (369) Net income attributable to common shareholders $ 305,117 $ 305,117 $ 33,871 $ 33,871 $ 134,149 $ 134,149 Denominator Weighted-average shares outstanding 171,926,079 171,926,079 176,132,941 176,132,941 178,519,748 178,519,748 Contingent securities/Share based compensation — 390,997 — 553,872 — 1,121,744 Weighted-average shares outstanding 171,926,079 172,317,076 176,132,941 176,686,813 178,519,748 179,641,492 Earnings per Common Share: Net income attributable to common shareholders $ 1.77 $ 1.77 $ 0.19 $ 0.19 $ 0.75 $ 0.75 The following table details the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year Ended December 31, 2020 2019 2018 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 307,326 $ 307,326 $ 34,529 $ 34,529 $ 135,472 $ 135,472 Net income attributable to noncontrolling interests (20) (20) (69) (69) (55) (55) Nonforfeitable dividends allocated to unvested restricted unitholders (410) (410) (396) (396) (369) (369) Net income attributable to common unitholders $ 306,896 $ 306,896 $ 34,064 $ 34,064 $ 135,048 $ 135,048 Denominator Weighted-average units outstanding 172,907,713 172,907,713 177,114,932 177,114,932 179,959,370 179,959,370 Contingent securities/Share based compensation — 390,997 — 553,872 — 1,121,744 Total weighted-average units outstanding 172,907,713 173,298,710 177,114,932 177,668,804 179,959,370 181,081,114 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 1.77 $ 1.77 $ 0.19 $ 0.19 $ 0.75 $ 0.75

SHARE BASED COMPENSATION, 401(K

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Option Activity	Options outstanding as of December 31, 2020 and changes during the year-ended December 31, 2020 were as follows: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at January 1, 2020 334,561 $ 11.88 1.0 Exercised (34,515) $ 11.62 $ 10.1 Outstanding at December 31, 2020 300,046 $ 11.91 0.1 $ 81.1 Vested/Exercisable at December 31, 2020 300,046 $ 11.91 0.1 $ 81.1
Company's Restricted Share Activity	The following table summarizes the Company’s Restricted Share Rights activity during the year-ended December 31, 2020: Shares Weighted Average Grant Date Fair Value Non-vested at January 1, 2020 479,144 $ 15.90 Granted 295,049 $ 13.10 Vested (283,431) $ 14.20 Forfeited (2,027) $ 15.63 Non-vested at December 31, 2020 488,735 $ 15.19
Schedule of Restricted Performance Share Units Plan	The table below presents certain information as to unvested RPSU awards. RPSU Grant Date 2/28/2018 2/21/2019 3/5/2020 Total (Amounts below in shares, unless otherwise noted) Non-vested at January 1, 2020 190,296 206,069 — 396,365 Units Granted — — 319,600 319,600 Non-vested at December 31, 2020 190,296 206,069 319,600 715,965 Measurement Period Commencement Date 1/1/2018 1/1/2019 1/1/2020 Measurement Period End Date 12/31/2020 12/31/2021 12/31/2022 Units Granted 209,193 213,728 319,600 Fair Value of Units on Grant Date (in thousands) $ 4,276 $ 4,627 $ 5,389

DISTRIBUTIONS (Tables)

DISTRIBUTIONS (Tables)	12 Months Ended
	Dec. 31, 2020
Distributions [Abstract]
Schedule of Dividends Payable	The following table provides the tax characteristics of the 2020, 2019 and 2018 distributions paid: Years ended December 31, 2020 2019 2018 (in thousands, except per share amounts) Common Share Distributions: Ordinary income $ 0.41 $ 0.62 $ 0.55 Capital gain 0.35 — — Non-taxable distributions — 0.14 0.17 Distributions per share $ 0.76 $ 0.76 $ 0.72 Percentage classified as ordinary income 53.90 % 81.00 % 76.20 % Percentage classified as capital gain 46.10 % — % — % Percentage classified as non-taxable distribution — % 19.00 % 23.80 %

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table details the components of accumulated other comprehensive income (loss) of the Parent Company and the Operating Partnership as of and for the three years ended December 31, 2020 (in thousands): Parent Company Cash Flow Hedges Balance at January 1, 2018 $ 2,399 Change in fair market value during year 1,478 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (39) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 5,029 Change in fair market value during year (8,210) Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests 41 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 770 Balance at December 31, 2019 $ (2,370) Change in fair market value during year (5,972) Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests 29 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 752 Balance at December 31, 2020 $ (7,561) Operating Partnership Cash Flow Hedges Balance at January 1, 2018 $ 2,056 Change in fair market value during year 1,478 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,191 Balance at December 31, 2018 $ 4,725 Change in fair market value during year (8,210) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 770 Balance at December 31, 2019 $ (2,715) Change in fair market value during year (5,972) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 752 Balance at December 31, 2020 $ (7,935)

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Real Estate Investments, Net Operating Income and Unconsolidated Real Estate Ventures of Reportable Segments	The following tables provide selected asset information as of December 31, 2020 and 2019 and results of operations of the Company’s reportable segments for the years ended December 31, 2020, 2019 and 2018 (in thousands): Real estate investments, at cost: December 31, 2020 December 31, 2019 Philadelphia CBD $ 1,433,927 $ 1,726,299 Pennsylvania Suburbs 871,530 1,003,890 Austin, Texas 728,741 721,255 Metropolitan Washington, D.C. 352,794 468,035 Other 87,117 86,980 Operating Properties $ 3,474,109 $ 4,006,459 Corporate Right of use asset - operating leases, net $ 20,977 $ 21,656 Construction-in-progress $ 210,311 $ 180,718 Land held for development $ 117,984 $ 96,124 Prepaid leasehold interests in land held for development, net $ 39,185 $ 39,592 . Net operating income: Year Ended December 31, 2020 2019 2018 Total revenue Operating expenses (a) Net operating income (loss) Total revenue Operating expenses (a) Net operating income (loss) Total revenue Operating expenses (a) Net operating income (loss) Philadelphia CBD $ 232,028 $ (82,505) $ 149,523 $ 263,769 $ (100,219) $ 163,550 $ 256,717 $ (99,449) $ 157,268 Pennsylvania Suburbs 141,613 (46,281) 95,332 141,084 (47,418) 93,666 138,279 (49,433) 88,846 Austin, Texas 102,982 (39,759) 63,223 104,157 (38,285) 65,872 38,665 (16,739) 21,926 Metropolitan Washington, D.C. 40,223 (20,791) 19,432 51,498 (23,455) 28,043 90,308 (34,072) 56,236 Other 13,469 (9,815) 3,654 14,558 (9,328) 5,230 16,757 (11,888) 4,869 Corporate 4,537 (6,305) (1,768) 5,351 (7,141) (1,790) 3,619 (6,518) (2,899) Operating properties $ 534,852 $ (205,456) $ 329,396 $ 580,417 $ (225,846) $ 354,571 $ 544,345 $ (218,099) $ 326,246 (a) Includes property operating expense, real estate taxes and third party management expense. Unconsolidated real estate ventures: Investment in real estate ventures, at equity Equity in income (loss) of real estate venture As of Years ended December 31, December 31, 2020 December 31, 2019 2020 2019 2018 Philadelphia CBD $ 268,562 $ 17,524 $ (9,090) $ 328 $ (105) Metropolitan Washington, D.C. 99,769 102,840 (3,019) (4,234) (15,065) Mid-Atlantic Office JV 32,996 — 96 — — MAP Venture (11,516) (70) (6,571) (6,102) (2,155) Other — — — 86 407 Austin, Texas — — — — 1,687 Total $ 389,811 $ 120,294 $ (18,584) $ (9,922) $ (15,231)
Reconciliation of Consolidated Net Income (Loss) to Consolidated NOI	The following is a reconciliation of consolidated net income (loss), as defined by GAAP, to consolidated NOI, (in thousands): Year Ended December 31, 2020 2019 2018 Net income $ 307,326 $ 34,529 $ 135,472 Plus: Interest expense 73,911 81,512 78,199 Interest expense - amortization of deferred financing costs 2,904 2,768 2,498 Depreciation and amortization 188,283 210,005 176,000 General and administrative expenses 30,288 32,156 27,802 Equity in loss of Real Estate Ventures 18,584 9,922 15,231 Provision for impairment — — 71,707 Loss on early extinguishment of debt — — 105 Less: Interest income 1,939 2,318 4,703 Income tax (provision) benefit 224 (12) (423) Net gain on disposition of real estate 289,461 356 2,932 Net gain on sale of undepreciated real estate 201 2,020 3,040 Net gain on real estate venture transactions 75 11,639 142,233 Gain on promoted interest in unconsolidated real estate venture — — 28,283 Consolidated net operating income $ 329,396 $ 354,571 $ 326,246

ORGANIZATION OF THE PARENT CO_3

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Narrative (Details)	12 Months Ended
	Dec. 31, 2020ft²apropertymanagementCompanyparcel
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	82
Area of real estate property	13,852,464
Number of management companies | managementCompany	7
Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	13,900,000
Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of undeveloped parcels of land | a	228.5
Area of undeveloped land held for sale | a	35.2
Area of additional undeveloped parcels of land with option to purchase | a	55.5
Total potential development capacity	14,200,000
Parent Company | Land Parcel One
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Land Parcel Two
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Parent Company | Held for Sale Properties Included in Continuing Operations
Organization of The Parent Company and The Operating Partnership [Line Items]
Total potential development capacity	200,000
Wholly-owned Management Company Subsidiaries
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	24,700,000
Wholly-owned Management Company Subsidiaries | Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	13,900,000
Wholly-owned Management Company Subsidiaries | Partially Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	10,800,000
Leashold Interest Land
Organization of The Parent Company and The Operating Partnership [Line Items]
Lease agreement term	99 years
Leashold Interest Land | Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | parcel	2
Undeveloped parcels of land held | a	1.8
Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	99.40%
BRSCO | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BMH | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BPI | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BBL | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BPM | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BBS | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
BGCS | BRANDYWINE OPERATING PARTNERSHIP, L.P. | Brandywine Operating Partnership LP
Organization of The Parent Company and The Operating Partnership [Line Items]
Ownership in the operating partnership	100.00%
Unconsolidated Real Estate Ventures | Unconsolidated Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	9

ORGANIZATION OF THE PARENT CO_4

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Summary of Properties (Details)	Dec. 31, 2020ft²property
Real Estate Properties [Line Items]
Number of Properties | property	82
Area of real estate property | ft²	13,852,464
Office properties
Real Estate Properties [Line Items]
Number of Properties | property	73
Area of real estate property | ft²	12,470,257
Mixed-use properties
Real Estate Properties [Line Items]
Number of Properties | property	5
Area of real estate property | ft²	942,334
Core Properties
Real Estate Properties [Line Items]
Number of Properties | property	78
Area of real estate property | ft²	13,412,591
Development property
Real Estate Properties [Line Items]
Number of Properties | property	1
Area of real estate property | ft²	205,803
Redevelopment properties
Real Estate Properties [Line Items]
Number of Properties | property	3
Area of real estate property | ft²	234,070

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Principles of Consolidation (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets	$ 3,900,106	$ 4,075,969
Liabilities	2,095,458	2,387,666
Variable Interest Entity
Variable Interest Entity [Line Items]
Assets	49,200	392,000
Liabilities	$ 21,600	$ 255,600

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Purchase Price Allocation and Depreciation and Amortization (Details)	12 Months Ended
	Dec. 31, 2020
Minimum
Construction in Progress [Line Items]
Expected lease-up periods	4 months
Minimum | Buildings and Improvements
Construction in Progress [Line Items]
Buildings and improvements useful life	5 years
Minimum | Tenant Improvements
Construction in Progress [Line Items]
Buildings and improvements useful life	1 year
Maximum
Construction in Progress [Line Items]
Expected lease-up periods	12 months
Maximum | Buildings and Improvements
Construction in Progress [Line Items]
Buildings and improvements useful life	55 years
Maximum | Tenant Improvements
Construction in Progress [Line Items]
Buildings and improvements useful life	16 years

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impairment of Real Estate Assets (Details)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Disposition of assets, holding period	10 years

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deferred Costs (Details)	Dec. 31, 2020
Minimum
Lessor, Lease, Description [Line Items]
Deferred cost, amortization period	1 year
Maximum
Lessor, Lease, Description [Line Items]
Deferred cost, amortization period	16 years

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 534,852	$ 580,417	$ 544,345
Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	393,178	411,524
Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	104,086	114,224
Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	497,264	525,748
Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	4,868	8,857
Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	11,372	20,060
Rents
Disaggregation of Revenue [Line Items]
Total revenue	513,504	554,665	515,044
Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	18,580	19,626	22,557
Other
Disaggregation of Revenue [Line Items]
Total revenue	2,768	6,126	$ 6,744
Philadelphia CBD
Disaggregation of Revenue [Line Items]
Total revenue	232,028	263,769
Philadelphia CBD | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	166,286	178,481
Philadelphia CBD | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	51,410	58,580
Philadelphia CBD | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	217,696	237,061
Philadelphia CBD | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	1,146	3,745
Philadelphia CBD | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	10,777	18,665
Philadelphia CBD | Rents
Disaggregation of Revenue [Line Items]
Total revenue	229,619	259,471
Philadelphia CBD | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	927	876
Philadelphia CBD | Other
Disaggregation of Revenue [Line Items]
Total revenue	1,482	3,422
Pennsylvania Suburbs
Disaggregation of Revenue [Line Items]
Total revenue	141,613	141,084
Pennsylvania Suburbs | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	128,044	125,969
Pennsylvania Suburbs | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	12,951	14,282
Pennsylvania Suburbs | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	140,995	140,251
Pennsylvania Suburbs | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	(12)	(12)
Pennsylvania Suburbs | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	179	174
Pennsylvania Suburbs | Rents
Disaggregation of Revenue [Line Items]
Total revenue	141,162	140,413
Pennsylvania Suburbs | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	39	43
Pennsylvania Suburbs | Other
Disaggregation of Revenue [Line Items]
Total revenue	412	628
Austin, Texas
Disaggregation of Revenue [Line Items]
Total revenue	102,982	104,157
Austin, Texas | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	63,366	62,232
Austin, Texas | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	35,123	34,748
Austin, Texas | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	98,489	96,980
Austin, Texas | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	3,531	4,638
Austin, Texas | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	49	165
Austin, Texas | Rents
Disaggregation of Revenue [Line Items]
Total revenue	102,069	101,783
Austin, Texas | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	689	1,956
Austin, Texas | Other
Disaggregation of Revenue [Line Items]
Total revenue	224	418
Metropolitan DC
Disaggregation of Revenue [Line Items]
Total revenue	40,223	51,498
Metropolitan DC | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	29,830	39,420
Metropolitan DC | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	3,544	4,029
Metropolitan DC | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	33,374	43,449
Metropolitan DC | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Metropolitan DC | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	135	824
Metropolitan DC | Rents
Disaggregation of Revenue [Line Items]
Total revenue	33,509	44,273
Metropolitan DC | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	6,541	6,922
Metropolitan DC | Other
Disaggregation of Revenue [Line Items]
Total revenue	173	303
Other
Disaggregation of Revenue [Line Items]
Total revenue	13,469	14,558
Other | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	8,064	7,834
Other | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	2,401	3,080
Other | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	10,465	10,914
Other | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	203	486
Other | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	232	232
Other | Rents
Disaggregation of Revenue [Line Items]
Total revenue	10,900	11,632
Other | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	2,560	2,915
Other | Other
Disaggregation of Revenue [Line Items]
Total revenue	9	11
Corporate
Disaggregation of Revenue [Line Items]
Total revenue	4,537	5,351
Corporate | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue	(2,412)	(2,412)
Corporate | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue	(1,343)	(495)
Corporate | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue	(3,755)	(2,907)
Corporate | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Corporate | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Corporate | Rents
Disaggregation of Revenue [Line Items]
Total revenue	(3,755)	(2,907)
Corporate | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue	7,824	6,914
Corporate | Other
Disaggregation of Revenue [Line Items]
Total revenue	$ 468	$ 1,344

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Income Taxes (Details) - USD ($) $ in Billions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Tax basis of assets, cost for income tax purposes	$ 2.9	$ 3.2
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Income Tax Contingency [Line Items]
Tax basis of assets, cost for income tax purposes	$ 2.9	$ 3.2

REAL ESTATE INVESTMENTS - Gross

REAL ESTATE INVESTMENTS - Gross Carrying Value of Operating Properties (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Real Estate [Abstract]
Land	$ 407,514	$ 489,702
Building and improvements	2,665,232	3,049,395
Tenant improvements	401,363	467,362
Total	$ 3,474,109	$ 4,006,459

REAL ESTATE INVESTMENTS - Capit

REAL ESTATE INVESTMENTS - Capitalized Construction Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 8,366	$ 7,431	$ 6,964
Capitalized interest	4,600	3,200	3,600
Development
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	4,802	3,047	3,185
Redevelopment
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	543	775	968
Tenant Improvements
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 3,021	$ 3,609	$ 2,811

REAL ESTATE INVESTMENTS - Summa

REAL ESTATE INVESTMENTS - Summary of Acquired Properties (Details) $ in Thousands	Nov. 30, 2020USD ($)ft²	Nov. 05, 2020USD ($)ft²	Feb. 27, 2020USD ($)a	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Purchase Price (a)				$ 41,950	$ 0	$ 196,625
Land | 145 King of Prussia Road
Business Acquisition [Line Items]
Acres | a			7.75
Office Properties | 145 King of Prussia Road
Business Acquisition [Line Items]
Purchase Price (a)			$ 11,250
Office Properties | 1505-11 Race Street
Business Acquisition [Line Items]
Rentable square feet | ft²		119,763
Purchase Price (a)		$ 9,700
Office Properties | 250 King of Prussia Road (b)
Business Acquisition [Line Items]
Rentable square feet | ft²	169,843
Purchase Price (a)	$ 20,250

REAL ESTATE INVESTMENTS - Acqui

REAL ESTATE INVESTMENTS - Acquisitions Narrative (Details) $ in Thousands	Dec. 19, 2018USD ($)ft²	Dec. 11, 2018USD ($)ft²property	Jun. 29, 2018USD ($)ft²	Mar. 22, 2018USD ($)ft²	Jan. 05, 2018USD ($)ft²	Dec. 31, 2020USD ($)ft²property	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 21, 2020	Nov. 05, 2020USD ($)
Business Acquisition [Line Items]
Number of properties | property						82
Area of real estate property | ft²						13,852,464
Net gain on real estate venture transactions						$ 75	$ 11,639	$ 142,233
Gain on promoted interest in unconsolidated real estate venture						0	0	28,283
Prepaid leasehold interests in land held for development, net						39,185	39,592
Sale of ownership interest percentage									60.00%
Revenue						534,852	580,417	544,345
Net income (loss)						$ 305,527	$ 34,267	134,518
Seven Tower Bridge
Business Acquisition [Line Items]
Sale of ownership interest percentage					20.00%
1505-11 Race Street
Business Acquisition [Line Items]
Transaction costs capitalized										$ 300
Quarry Lake II
Business Acquisition [Line Items]
Rentable square feet | ft²	120,559
Gross purchase value of office property	$ 39,500
Mortgage debt assumed repaid at settlement	0
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Working Capital Assumed	368
Aggregate cash payment	$ 39,037
Revenue								100
Net income (loss)								100
DRA Austin Venture
Business Acquisition [Line Items]
Gross purchase value of office property		$ 535,100
Ownership percentage		50.00%
Number of properties | property		12
Area of real estate property | ft²		1,570,123
Net gain on real estate venture transactions		$ 103,800
Gain on promoted interest in unconsolidated real estate venture		28,300
Investment in real estate venture		14,600
Mortgage debt assumed repaid at settlement		115,461
Credit settlement for notes receivable provided to venture		130,700
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Working Capital Assumed		24,865
Aggregate cash payment		$ 117,348
Percentage of ownership interests		50.00%
Revenue								3,400
Net income (loss)								1,300
3025 JFK Boulevard
Business Acquisition [Line Items]
Lease agreement term			99 years
Acres | ft²			1
Prepaid leasehold interests in land held for development, net			$ 15,000
Capitalized transaction costs			300
Leasehold valuation credit			5,600
3001-3003 and 3025 JFK Boulevard
Business Acquisition [Line Items]
Leasehold valuation credit applied to development			$ 2,400
Minimum floor area ratio required for realization of credit (sq. feet) | ft²			1,200,000
Remaining leasehold valuation credit			$ 3,200
Reimbursable leasehold valuation credit			$ 3,200
3001-3003 JFK Boulevard
Business Acquisition [Line Items]
Lease agreement term				99 years
Acres | ft²				1
Prepaid leasehold interests in land held for development, net				$ 24,600
Capitalized transaction costs				$ 300
Four Tower Bridge
Business Acquisition [Line Items]
Ownership percentage					35.00%
Area of real estate property | ft²					86,021
Mortgage debt assumed repaid at settlement					$ 0
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Working Capital Assumed					(1,379)
Aggregate cash payment					$ 0
Percentage of ownership interest after non-monetary exchange transaction					100.00%
Real estate property debt					$ 9,700
Fair value of unencumbered acquisition related costs, to tangible and intangible assets and liabilities					$ 23,600
Revenue								2,800
Net income (loss)								$ 300

REAL ESTATE INVESTMENTS - Asset

REAL ESTATE INVESTMENTS - Asset Acquisition (Details) - 1505-11 Race Street $ in Thousands	Nov. 05, 2020USD ($)
Schedule of Investments [Line Items]
Building, land and improvements	$ 9,723
Intangible assets acquired	2,422
Below market lease liabilities assumed	(2,193)
Total unencumbered acquisition value	$ 9,952
Below Market Lease
Schedule of Investments [Line Items]
Weighted average amortization period	1 year 6 months
Intangible Assets Acquired
Schedule of Investments [Line Items]
Weighted average amortization period	1 year 6 months

REAL ESTATE INVESTMENTS - Purch

REAL ESTATE INVESTMENTS - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 19, 2018	Dec. 11, 2018	Jan. 05, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Mortgage notes payable, net				$ 0	$ 313,812
Repayments of Secured Debt				$ 94,993	$ 7,595	$ 122,180
Quarry Lake II
Business Acquisition [Line Items]
Building, land and improvements	$ 35,120
Intangible assets acquired	5,809
Below market lease liabilities assumed	(1,524)
Deferred gain	0
Total unencumbered acquisition value	39,405
Mortgage debt assumed - at fair value	0
Total encumbered acquisition value	39,405
Mortgage debt repaid at settlement	0
Investment in unconsolidated real estate ventures	0
Gain on promoted interest in unconsolidated real estate venture	0
Gain on real estate venture transactions	0
Purchase price reduction for note receivable	0
Net working capital assumed	(368)
Total cash payment at settlement	$ 39,037
DRA Austin Venture
Business Acquisition [Line Items]
Building, land and improvements		$ 457,390
Intangible assets acquired		76,925
Below market lease liabilities assumed		(13,769)
Deferred gain		14,594
Total unencumbered acquisition value		535,140
Mortgage debt assumed - at fair value		0
Total encumbered acquisition value		535,140
Mortgage debt repaid at settlement		(115,461)
Investment in unconsolidated real estate ventures		(14,594)
Gain on promoted interest in unconsolidated real estate venture		(28,283)
Gain on real estate venture transactions		(103,847)
Purchase price reduction for note receivable		(130,742)
Net working capital assumed		(24,865)
Total cash payment at settlement		$ 117,348
Four Tower Bridge
Business Acquisition [Line Items]
Building, land and improvements			$ 20,734
Intangible assets acquired			3,144
Below market lease liabilities assumed			(182)
Deferred gain			0
Total unencumbered acquisition value			23,696
Mortgage debt assumed - at fair value			(9,940)
Total encumbered acquisition value			13,756
Mortgage debt repaid at settlement			0
Investment in unconsolidated real estate ventures			(3,502)
Gain on promoted interest in unconsolidated real estate venture			0
Gain on real estate venture transactions			(11,633)
Purchase price reduction for note receivable			0
Net working capital assumed			1,379
Total cash payment at settlement			$ 0
Intangible Assets Acquired | Quarry Lake II
Business Acquisition [Line Items]
Weighted average amortization period	0 years
Intangible Assets Acquired | DRA Austin Venture
Business Acquisition [Line Items]
Weighted average amortization period		5 years 6 months
Intangible Assets Acquired | Four Tower Bridge
Business Acquisition [Line Items]
Weighted average amortization period			4 years 1 month 6 days
Below Market Lease | Quarry Lake II
Business Acquisition [Line Items]
Weighted average amortization period	3 years
Below Market Lease | DRA Austin Venture
Business Acquisition [Line Items]
Weighted average amortization period		4 years 7 months 6 days
Below Market Lease | Four Tower Bridge
Business Acquisition [Line Items]
Weighted average amortization period			4 years 9 months 18 days
Mortgage Debt Assumed - at Fair Value
Business Acquisition [Line Items]
Repayments of Secured Debt		$ 115,500
Mortgage Debt Assumed - at Fair Value | Four Tower Bridge
Business Acquisition [Line Items]
Mortgage notes payable, net			$ 9,700

REAL ESTATE INVESTMENTS - Pro F

REAL ESTATE INVESTMENTS - Pro Forma (Details) - DRA Austin Venture - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro forma revenue	$ 602,713	$ 582,244
Pro forma net income	134,142	115,475
Pro forma net income available to common shareholders	$ 134,142	$ 115,475

REAL ESTATE INVESTMENTS - Sum_2

REAL ESTATE INVESTMENTS - Summary of Office Properties Sold (Details) $ in Thousands

Dec. 21, 2020USD ($)ft²property

Jul. 21, 2020USD ($)ft²property

Jun. 15, 2020USD ($)a

Mar. 19, 2020USD ($)ft²

Sep. 11, 2019USD ($)ft²

Mar. 15, 2019USD ($)a

Dec. 21, 2018USD ($)ft²

Dec. 20, 2018USD ($)ft²

Jun. 21, 2018USD ($)ft²

Mar. 16, 2018USD ($)a

Jan. 10, 2018USD ($)a

Sep. 30, 2020USD ($)

Sep. 30, 2018USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Gain (loss) on sale

$ 289,461

$ 356

$ 2,932

Sale of ownership interest percentage

60.00%

Mid-Atlantic Office Portfolio

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Variable consideration

$ 4,100

Mid-Atlantic Office Portfolio | Minimum

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Variable consideration holdback term

6 months

Mid-Atlantic Office Portfolio | Maximum

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Variable consideration holdback term

9 months

Commerce Square

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Sales price

$ 115,000

Sale of ownership interest percentage

30.00%

Value of assets disposed of

$ 600,000

Deconsolidation gain

$ 271,900

Subaru National Training Center

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Direct finance lease, interest income

$ 1,600

Office Properties | Mid-Atlantic Office JV

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

1,128,645

Sales price

$ 192,900

Office Properties | Mid-Atlantic Office Portfolio

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

1,128,645

Sales price

$ 192,943

Gain (loss) on sale

$ 15,164

Number of properties sold | property

12

Office Properties | Mid-Atlantic Office Portfolio | Pennsylvania

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Number of properties sold | property

9

Office Properties | Mid-Atlantic Office Portfolio | Maryland

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Number of properties sold | property

3

Office Properties | Commerce Square

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

1,896,142

Sales price

$ 115,000

Gain (loss) on sale

$ 271,905

Number of properties sold | property

2

Office Properties | 52 Swedesford Square

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

131,077

Sales price

$ 18,000

Gain (loss) on sale

$ 2,336

Office Properties | 1900 Gallows Rd

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

210,632

Sales price

$ 36,400

Gain (loss) on sale

$ (367)

Office Properties | Rockpoint Portfolio

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

1,293,197

Sales price

$ 312,000

Gain (loss) on sale

$ 397

Office Properties | 20 East Clementon Road

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

38,260

Sales price

$ 2,000

Gain (loss) on sale

$ (35)

Land

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Gain (loss) on sale

$ 1,000

Land | Keith Valley

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Acres | a

14

Sales price

$ 4,000

Gain (loss) on sale

$ 201

Land | 9 Presidential Boulevard

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Acres | a

2.7

Sales price

$ 5,325

Gain (loss) on sale

$ 751

Land | Garza Ranch Office

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Acres | a

6.6

Sales price

$ 14,571

Gain (loss) on sale

$ 1,515

Land | Westpark Land

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Acres | a

13.1

Sales price

$ 485

Gain (loss) on sale

$ 22

Land | Garza Ranch - Multi-family

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Gain (loss) on sale

$ 3,000

Mixed-use properties | Subaru National Training Center

Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]

Rentable square feet | ft²

83,000

Sales price

$ 45,300

Gain (loss) on sale

$ 2,570

REAL ESTATE INVESTMENTS - Dispo

REAL ESTATE INVESTMENTS - Dispositions Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate	$ 289,461	$ 356	$ 2,932
Prior Period Disposals
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate		700
Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate		$ 1,000

REAL ESTATE INVESTMENTS - Held

REAL ESTATE INVESTMENTS - Held for Use Impairment and Sale (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020USD ($)aproperty	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)ft²property
Impairment of properties held for use	$ 0	$ 0
Number of properties | property	82
Building and improvements	$ 2,665,232,000	3,049,395,000
Assets held for sale, net	$ 7,349,000	$ 7,349,000
Other
Impairment of properties held for use			$ 14,800,000
Number of properties | property			1
Carrying value of real estate prior to impairment			$ 52,800,000
Building and improvements			$ 38,000,000
Impairment hold period			10 years
Other | Land Held For Development | Assets Held-for-sale
Number of properties | property	2
Assets held for sale, net	$ 7,300,000
Acres | a	35.2
Residual Capitalization Rates | Other
Measurement input for impairment on assets held for sale			0.075
Discount Rates | Other
Measurement input for impairment on assets held for sale			0.095
Metropolitan Washington, D.C. - Office | Assets Held-for-sale
Number of properties | property			8
Impairment hold period			10 years
Rentable square feet | ft²			1,293,197
Provision for impairment on assets held for sale			$ 56,900,000
Metropolitan Washington, D.C. - Office | Residual Capitalization Rates | Assets Held-for-sale
Measurement input for impairment on assets held for sale			0.0747
Metropolitan Washington, D.C. - Office | Discount Rates | Assets Held-for-sale
Measurement input for impairment on assets held for sale			0.0860

INVESTMENT IN UNCONSOLIDATED _3

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details) $ in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2020USD ($)aft²investmentapartmentproperty	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Number of properties | property	82
Investment in Real Estate Ventures, equity method	$ 389,811	$ 120,294
Accounts receivable	13,536	16,363
Real Estate Venture
Schedule of Equity Method Investments [Line Items]
Accounts receivable	1,200	800
Real Estate Venture | Management Fees
Schedule of Equity Method Investments [Line Items]
Service and other revenue	4,700	4,300	$ 6,300
Real Estate Venture | Leasing Commission Income
Schedule of Equity Method Investments [Line Items]
Service and other revenue	1,100	$ 1,700	$ 2,500
Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	389,800
Unconsolidated Real Estate Ventures | Other Liabilities
Schedule of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	$ (11,500)
Unconsolidated Real Estate Ventures | Minimum
Schedule of Equity Method Investments [Line Items]
Ownership percentage	15.00%
Unconsolidated Real Estate Ventures | Maximum
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%
Unconsolidated Real Estate Ventures | Office Properties
Schedule of Equity Method Investments [Line Items]
Number of properties | investment	5
Rentable square feet | ft²	8.4
Unconsolidated Real Estate Ventures | Unconsolidated Properties
Schedule of Equity Method Investments [Line Items]
Number of properties | property	9
Number of real estate properties with negative investment balances | property	1
Unconsolidated Real Estate Ventures | Land Held For Development
Schedule of Equity Method Investments [Line Items]
Number of properties | investment	2
Acres | a	1.4
Unconsolidated Real Estate Ventures | Land Under Active Development
Schedule of Equity Method Investments [Line Items]
Number of properties | investment	1
Acres | a	1.3
Unconsolidated Real Estate Ventures | Residential Tower
Schedule of Equity Method Investments [Line Items]
Number of properties | investment	1
Number of property units | apartment	321

INVESTMENT IN UNCONSOLIDATED _4

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Investment in Real Estate Ventures and Share of Real Estate Ventures' Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 21, 2020	Aug. 01, 2018	Jun. 26, 2018	May 29, 2015	Jul. 31, 2013
Schedule of Equity Method Investments [Line Items]
Carrying Amount	$ 389,811	$ 120,294
Company's Share of Real Estate Venture Income (Loss)	(18,584)	(9,922)	$ (15,231)
Real Estate Venture Debt at 100%, gross	$ 963,018	596,007
Commerce Square Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%
Carrying Amount	$ 253,128	0
Company's Share of Real Estate Venture Income (Loss)	(9,150)	0
Real Estate Venture Debt at 100%, gross	$ 219,168	0
Mid-Atlantic Office JV
Schedule of Equity Method Investments [Line Items]
Ownership percentage	40.00%			40.00%
Carrying Amount	$ 32,996	0
Company's Share of Real Estate Venture Income (Loss)	96	0
Real Estate Venture Debt at 100%, gross	$ 120,831	0
Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Carrying Amount	$ 10,302	10,116
Company's Share of Real Estate Venture Income (Loss)	185	(2,800)
Real Estate Venture Debt at 100%, gross	$ 0	0
Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	15.00%
Carrying Amount	$ 16,019	16,446
Company's Share of Real Estate Venture Income (Loss)	(358)	(498)
Real Estate Venture Debt at 100%, gross	$ 207,302	207,302
MAP Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Carrying Amount	$ (11,516)	(70)
Company's Share of Real Estate Venture Income (Loss)	(6,570)	(6,102)
Real Estate Venture Debt at 100%, gross	$ 185,000	185,000			$ 180,800
PJP VII
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Carrying Amount	$ 0	0
Company's Share of Real Estate Venture Income (Loss)	0	190
Real Estate Venture Debt at 100%, gross	$ 0	0
PJP Two
Schedule of Equity Method Investments [Line Items]
Ownership percentage	30.00%
Carrying Amount	$ 0	0
Company's Share of Real Estate Venture Income (Loss)	0	81
Real Estate Venture Debt at 100%, gross	$ 0	0
PJP VI
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Carrying Amount	$ 0	0
Company's Share of Real Estate Venture Income (Loss)	0	(185)
Real Estate Venture Debt at 100%, gross	$ 0	0
1919 Ventures
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%					50.00%
Carrying Amount	$ 15,434	17,524
Company's Share of Real Estate Venture Income (Loss)	59	328
Real Estate Venture Debt at 100%, gross	$ 88,860	88,860
4040 Wilson Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%							50.00%
Carrying Amount	$ 34,454	37,002
Company's Share of Real Estate Venture Income (Loss)	(2,162)	(368)
Real Estate Venture Debt at 100%, gross	$ 141,857	114,845
JBG 51 N 50 Patterson
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%						70.00%
Carrying Amount	$ 21,237	21,531
Company's Share of Real Estate Venture Income (Loss)	(457)	(313)
Real Estate Venture Debt at 100%, gross	$ 0	0
JBG 1250 First Street Office
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%						70.00%
Carrying Amount	$ 17,757	17,745
Company's Share of Real Estate Venture Income (Loss)	(227)	(255)
Real Estate Venture Debt at 100%, gross	$ 0	$ 0

INVESTMENT IN UNCONSOLIDATED _5

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Summary of Financial Position of Real Estate Ventures (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Real Estate Investment Property, Net	$ 2,966,005	$ 3,371,231
Other assets	176,747	115,678
Other liabilities	47,573	15,985
Outstanding indebtedness	1,830,595	2,144,418
Equity	1,804,648	1,688,303	$ 1,811,028	$ 1,826,870
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Real Estate Investment Property, Net	1,520,804	834,367
Other assets	488,805	342,002
Other liabilities	333,049	290,071
Outstanding indebtedness	956,688	585,068
Equity	$ 719,872	$ 301,230

INVESTMENT IN UNCONSOLIDATED _6

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Summary of Results of Operations of Real Estate Ventures with Interests (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Total revenue	$ 534,852	$ 580,417	$ 544,345
Operating expenses	(424,027)	(468,007)	(493,608)
Interest expense, net	(73,911)	(81,512)	(78,199)
Depreciation and amortization	(188,283)	(210,005)	(176,000)
Provision for impairment	0	0	(71,707)
Loss on early extinguishment of debt	0	0	(105)
Net income	307,326	34,529	135,472
Equity in loss of Real Estate Ventures	(18,584)	(9,922)	(15,231)
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Total revenue	150,276	132,358	165,326
Operating expenses	(85,812)	(71,784)	(82,035)
Interest expense, net	(22,661)	(21,908)	(29,774)
Depreciation and amortization	(70,805)	(53,331)	(53,826)
Provision for impairment	0	(5,664)	(20,832)
Loss on early extinguishment of debt	0	(1,231)	(1,385)
Net income	(29,002)	(21,560)	(22,526)
Company's share of net loss	(18,540)	(9,865)	(11,924)
Other-than-temporary impairment	0	0	(4,076)
Basis adjustments and other	(44)	(57)	769
Equity in loss of Real Estate Ventures	$ (18,584)	$ (9,922)	$ (15,231)

INVESTMENT IN UNCONSOLIDATED _7

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Aggregate Principal Payments of Recourse and Non-recourse Debt Payable to Third-parties (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Total Debt Obligations	$ 1,830,595	$ 2,144,418
Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
2021	148,693
2022	8,543
2023	477,649
2024	328,133
2025	0
Thereafter	0
Real estate property debt	963,018
Net deferred financing costs	(8,224)
Net unamortized premiums/(discounts)	1,894
Total Debt Obligations	$ 956,688

INVESTMENT IN UNCONSOLIDATED _8

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Mid-Atlantic Office JV (Details) $ in Millions	Dec. 21, 2020USD ($)ft²property	Dec. 31, 2020property
Schedule of Equity Method Investments [Line Items]
Number of Properties | property		82
Mid-Atlantic Office JV
Schedule of Equity Method Investments [Line Items]
Ownership percentage	40.00%	40.00%
Ownership percentage of total common equity	20.00%
Joint venture, funding from debt | $	$ 147.4
Proceeds from issuance of secured debt | $	$ 120.8
Mid-Atlantic Office JV | Mid-Atlantic Office JV Loan | Maximum
Schedule of Equity Method Investments [Line Items]
Debt instrument, interest rate, stated percentage	5.60%
Mid-Atlantic Office JV | LIBOR | Mid-Atlantic Office JV Loan
Schedule of Equity Method Investments [Line Items]
Variable interest rate	3.15%
Mid-Atlantic Office JV | Preferred Equity Securities
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Investment in real estate venture | $	$ 20
Mid-Atlantic Office JV | Common Equity Securities
Schedule of Equity Method Investments [Line Items]
Ownership percentage	15.00%
Mid-Atlantic Office JV | Office Properties
Schedule of Equity Method Investments [Line Items]
Number of Properties | property	12
Rentable square feet | ft²	1,128,645
Sales price | $	$ 192.9
Mid-Atlantic Office JV | Office Properties | Philadelphia CBD
Schedule of Equity Method Investments [Line Items]
Number of Properties | property	9
Mid-Atlantic Office JV | Office Properties | Metropolitan DC
Schedule of Equity Method Investments [Line Items]
Number of Properties | property	3

INVESTMENT IN UNCONSOLIDATED _9

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Commerce Square Venture (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 21, 2020	Jul. 21, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage		60.00%
Outstanding indebtedness	$ 1,830,595			$ 2,144,418
Secured Debt
Schedule of Equity Method Investments [Line Items]
Outstanding indebtedness	$ 0			$ 313,812
Philadelphia Office | Secured Debt
Schedule of Equity Method Investments [Line Items]
Outstanding indebtedness			$ 222,100
Commerce Square
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage			30.00%
Commerce Square
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%
Commerce Square | Preferred Equity Securities
Schedule of Equity Method Investments [Line Items]
Ownership percentage	32.00%
Commerce Square | Common Equity Securities
Schedule of Equity Method Investments [Line Items]
Ownership percentage	38.00%

INVESTMENT IN UNCONSOLIDATED_10

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - PJP Ventures (Details) $ in Thousands	Oct. 29, 2019USD ($)ft²property	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²		13,852,464
Proceeds from the sale of properties		$ 278,114	$ 41,795	$ 324,090
Net gain on real estate venture transactions		$ 75	$ 11,639	$ 142,233
Charlottesville VA | PJP II, PJP VII, And PJP VII
Schedule of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property	3
Area of real estate property | ft²	204,347
Sales price	$ 51,000
Proceeds from the sale of properties	9,100
Net gain on real estate venture transactions	$ 8,000
Minimum | Charlottesville VA | PJP II, PJP VII, And PJP VII
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Maximum | Charlottesville VA | PJP II, PJP VII, And PJP VII
Schedule of Equity Method Investments [Line Items]
Ownership percentage	30.00%

INVESTMENT IN UNCONSOLIDATED_11

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Hernadon Innovation Center Metro Portfolio Venture, LLC (Details)	Apr. 12, 2019USD ($)	Apr. 11, 2019USD ($)	Mar. 29, 2019USD ($)property	Dec. 20, 2018USD ($)ft²property	Sep. 30, 2018USD ($)	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²						13,852,464
Proceeds from the sale of properties						$ 278,114,000	$ 41,795,000	$ 324,090,000
Net gain on disposition of real estate						$ 289,461,000	$ 356,000	$ 2,932,000
Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage						15.00%
Metropolitan Washington, D.C. - Office | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Number of properties contributed to a joint venture | property				8
Area of real estate property | ft²				1,293,197
Sales price				$ 312,000,000
Ownership percentage				15.00%
Cash proceeds received from sale of properties				$ 265,200,000
Closing costs				2,200,000
Working capital contribution				600,000
Proceeds from the sale of properties				262,400,000
Capital credit				$ 47,700,000
Provision for impairment on assets held for sale					$ 56,900,000
Net gain on disposition of real estate					$ 400,000
Rockpoint | Metropolitan Washington, D.C. - Office | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage				85.00%
Secured Debt | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Debt instrument, face amount			$ 134,100,000
Number of properties used to secure debt | property			4
Proceeds from issuance of debt		$ 94,200,000	$ 113,100,000
Distributions From Loan One | Secured Debt | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Proceeds from issuance of debt	$ 16,700,000
Variable interest rate						1.95%
Distributions From Loan Two | Secured Debt | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Debt instrument, face amount		$ 115,300,000
Proceeds from issuance of debt	$ 13,800,000
Variable interest rate						1.80%
Minimum | Distributions From Loan One | Secured Debt | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Effective interest rate						5.45%
Maximum | Distributions From Loan One | Secured Debt | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Effective interest rate						6.45%
Maximum | Distributions From Loan Two | Secured Debt | Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Debt instrument, interest rate, stated percentage						6.30%

INVESTMENT IN UNCONSOLIDATED_12

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Austin Venture (Details) $ in Millions	Dec. 11, 2018USD ($)ft²property	Dec. 31, 2020ft²property	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Oct. 16, 2013USD ($)ft²property
Schedule of Equity Method Investments [Line Items]
Number of properties | property		82
Area of real estate property | ft²		13,852,464
Brandywine Realty Trust
Schedule of Equity Method Investments [Line Items]
Ownership percentage		50.00%
Equity method investment, additional distribution rights		10.00%
Brandywine Realty Trust | Austin Joint Venture
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²					1,398,826
Number of properties contributed to a joint venture | property					7
Aggregate gross sales price of a joint venture | $					$ 330
Equity method investment, agreement to pay future capital expenditures | $			$ 4.4	$ 0.8	$ 5.2
DRA Advisors LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage		50.00%
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Number of properties | property	12
Area of real estate property | ft²	1,570,123
Ownership percentage	50.00%
Aggregate purchase price | $	$ 535.1

INVESTMENT IN UNCONSOLIDATED_13

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Brandywine - AI Venture (Details)	12 Months Ended
	Dec. 31, 2020USD ($)property	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)ft²property
Schedule of Equity Method Investments [Line Items]
Impairment of properties held for use	$ 0	$ 0
Outstanding indebtedness	1,830,595,000	2,144,418,000
Net gain on real estate venture transactions	75,000	11,639,000	$ 142,233,000
Proceeds from real estate venture sales	$ 0	9,730,000	60,346,000
Fairview Properties
Schedule of Equity Method Investments [Line Items]
Other-than-temporary impairment			$ 4,100,000
Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Number of office properties owned | property	1		2
Impairment of properties held for use		$ 5,600,000	$ 20,800,000
Impairment hold period			10 years
Falls Church, Virginia | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Rentable square feet | ft²		180,659
Outstanding indebtedness		$ 26,000,000
Net gain on real estate venture transactions		2,200,000
Station Square | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Rentable square feet | ft²			510,202
Net gain on real estate venture transactions			$ 1,500,000
Number of properties sold | property			3
Gross sales price			$ 107,000,000
Encumbrances			66,500,000
Debt prepayment penalty			700,000
Gross proceeds from sale			34,800,000
Proceeds from real estate venture sales			$ 17,400,000
Residual Capitalization Rates | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input			0.080
Minimum | Discount Rates | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input			0.090
Maximum | Discount Rates | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input			0.095
Brandywine Realty Trust | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Impairment of properties held for use		$ 2,800,000	$ 10,400,000

INVESTMENT IN UNCONSOLIDATED_14

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - MAP Venture (Details) $ in Thousands	Aug. 01, 2018USD ($)	Dec. 31, 2020USD ($)ft²property	Dec. 31, 2019USD ($)	Jan. 01, 2019USD ($)
Schedule of Equity Method Investments [Line Items]
Real estate ventures aggregate indebtedness to third parties		$ 963,018	$ 596,007
MAP Venture
Schedule of Equity Method Investments [Line Items]
Ground lease annual payments		$ 11,900
Ground lease annual rent expense increase percentage through November 2025		2.50%
Ground lease annual rent expense increase after November 2025		2.50%
Real estate ventures aggregate indebtedness to third parties	$ 180,800	$ 185,000	185,000
MAP Venture | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Number of office properties owned | property		58
Rentable square feet | ft²		3,924,783
MAP Venture | Cumulative Effect, Period of Adoption, Adjustment
Schedule of Equity Method Investments [Line Items]
Retained earnings			$ 4,600	$ 9,200
Secured Debt | MAP Venture
Schedule of Equity Method Investments [Line Items]
Debt instrument, face amount	$ 185,000
Variable interest rate	2.45%

INVESTMENT IN UNCONSOLIDATED_15

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - 1919 Ventures (Details) - 1919 Ventures	12 Months Ended
	Dec. 31, 2020ft²storycarapartment
Schedule of Equity Method Investments [Line Items]
Number of floors of a building | story	29
Square foot of contemporary glass tower development	455,000
Number of luxury apartments | apartment	321
Square feet of commercial space	24,000
Number of car structured parking facility | car	215

INVESTMENT IN UNCONSOLIDATED_16

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Four Tower Bridge Acquisition (Details) $ in Thousands	Jan. 05, 2018USD ($)ft²	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 21, 2020
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage					60.00%
Area of real estate property | ft²		13,852,464
Net gain on real estate venture transactions		$ 75	$ 11,639	$ 142,233
Four Tower Bridge
Schedule of Equity Method Investments [Line Items]
Ownership percentage	35.00%
Area of real estate property | ft²	86,021
Real estate property debt	$ 9,700
Net gain on real estate venture transactions	$ 11,600
Seven Tower Bridge
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage	20.00%

INVESTMENT IN UNCONSOLIDATED_17

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - evo at Cira Centre South Venture (Details) $ in Thousands	Jan. 10, 2018USD ($)housing_unit	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 21, 2020
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage					60.00%
Proceeds from real estate venture sales		$ 0	$ 9,730	$ 60,346
Net gain on real estate venture transactions		$ 75	$ 11,639	$ 142,233
Evo At Cira Disposition
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage	50.00%
Number of property units sold | housing_unit	345
Sales price	$ 197,500
Development costs contemplated debt financing	110,900
Proceeds from real estate venture sales	43,000
Cost of equity method investment	17,300
Net gain on real estate venture transactions	$ 25,700

INVESTMENT IN UNCONSOLIDATED_18

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - JGB Ventures (Details)	Dec. 31, 2020property	May 29, 2015a
Schedule of Equity Method Investments [Line Items]
Number of properties | property	82
JBG 51 N 50 Patterson
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%	70.00%
Area owned by real estate venture of undeveloped parcels of land | a		0.9
JBG 1250 First Street Office
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%	70.00%
Area owned by real estate venture of undeveloped parcels of land | a		0.5
JBG Ventures
Schedule of Equity Method Investments [Line Items]
Number of properties | property	2
JBG Ventures | JBG 51 N 50 Patterson
Schedule of Equity Method Investments [Line Items]
Ownership percentage		30.00%
JBG Ventures | JBG 1250 First Street Office
Schedule of Equity Method Investments [Line Items]
Ownership percentage		30.00%

INVESTMENT IN UNCONSOLIDATED_19

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - 4040 Wilson Venture (Details) $ in Thousands	Jul. 31, 2013USD ($)aft²property	Dec. 31, 2020USD ($)ft²property	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²		13,852,464
Number of properties | property		82
Cash paid to acquire real estate ventures		$ 0	$ 2,181	$ 0
Advanced under the construction loan		$ 719	$ 253	$ 908
4040 Wilson Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%
Area owned by real estate venture of undeveloped parcels of land | a	1.3
Secured construction loan with total borrowing capacity					$ 150,000
Advanced under the construction loan		$ 141,900
Mixed Use Property | 4040 Wilson Venture
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²	427,500
Number of properties | property	8
Brandywine Realty Trust
Schedule of Equity Method Investments [Line Items]
Ownership percentage		50.00%
Brandywine Realty Trust | 4040 Wilson Venture
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire real estate ventures	$ 36,000

DEBT AND PREFERRED EQUITY SEC_2

DEBT AND PREFERRED EQUITY SECURITIES (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)investmentproperty	Dec. 31, 2018USD ($)
Summary of Investment Holdings [Line Items]
Number of Properties | property	82
1919 Ventures
Summary of Investment Holdings [Line Items]
Repayment of construction loan		$ 88.8
Austin Preferred Equity Investment
Summary of Investment Holdings [Line Items]
Investments	$ 50
Number of Properties | property	2
Annual preferred return on invested capital	9.00%
Mandatory redemption term	1 year
1919 Ventures
Summary of Investment Holdings [Line Items]
Debt, net		44.4
Note receivable		$ 44.4
Notes Receivable, Interest Rate		4.00%
Notes Receivable
Summary of Investment Holdings [Line Items]
Number Of Investments | investment	1
Preferred Equity Investment
Summary of Investment Holdings [Line Items]
Number Of Investments | investment	1

LEASES - Lessor Accounting Matu

LEASES - Lessor Accounting Maturities (Details) $ in Thousands	Dec. 31, 2020USD ($)
Year
2021	$ 325,703
2022	310,208
2023	292,871
2024	268,062
2025	236,623
Thereafter	$ 968,163

LEASES - Narrative (Details)

LEASES - Narrative (Details)	12 Months Ended
	Dec. 31, 2020leaseproperty
Lessee, Lease, Description [Line Items]
Number of ground leases considered operating lease | lease	6
Number of properties subject to ground leases | property	3
Minimum
Lessee, Lease, Description [Line Items]
Lease terms	9 years
Maximum
Lessee, Lease, Description [Line Items]
Lease terms	64 years

LEASES - Lease Cost (Details)

LEASES - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Fixed lease cost	$ 2,100	$ 2,100
Variable lease cost	45	54
Total	$ 2,145	$ 2,154
Weighted-average remaining lease term (years)	55 years 10 months 24 days	56 years 7 months 6 days
Weighted-average discount rate	6.30%	6.30%

LEASES - Lessee Accounting Matu

LEASES - Lessee Accounting Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2021	$ 1,232
2022	1,248
2023	1,263
2024	1,305
2025	1,321
Thereafter	109,131
Total lease payments	115,500
Less: Imputed interest	92,742
Present value of operating lease liabilities	$ 22,758	$ 22,554

DEFERRED COSTS - Deferred Costs

DEFERRED COSTS - Deferred Costs (Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs [Line Items]
Leasing costs, Total Cost	$ 139,207	$ 156,619
Total Cost	145,506	162,918
Leasing costs, Accumulated Amortization	(55,656)	(63,257)
Total, Accumulated Amortization	(60,650)	(67,358)
Leasing costs, Deferred Costs, net	83,551	93,362
Deferred Costs	84,856	95,560
Revolving Credit Facility
Deferred Costs [Line Items]
Financing costs, Total Cost	6,299	6,299
Financing costs, Accumulated Amortization	(4,994)	(4,101)
Financing costs, Deferred Costs, net	$ 1,305	$ 2,198

DEFERRED COSTS - Narrative (Det

DEFERRED COSTS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs (Textual) [Abstract]
Capitalized internal direct leasing costs	$ 1.6	$ 1.7	$ 3.9

INTANGIBLE ASSETS - Intangible

INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Intangible assets, net:
Intangible assets, total cost	$ 94,173	$ 177,581
Intangible assets, accumulated amortization	(45,603)	(92,730)
Intangible assets, net	48,570	84,851
Intangible liabilities, net:
Acquired lease intangibles, gross	31,263	44,757
Acquired lease intangibles, accumulated amortization	(12,815)	(22,494)
Acquired lease intangibles, net	18,448	22,263
In-place lease value
Intangible assets, net:
Intangible assets, total cost	91,552	167,357
Intangible assets, accumulated amortization	(43,400)	(84,123)
Intangible assets, net	48,152	83,234
Tenant relationship value
Intangible assets, net:
Intangible assets, total cost	2,091	5,268
Intangible assets, accumulated amortization	(1,938)	(4,815)
Intangible assets, net	153	453
Above market leases acquired
Intangible assets, net:
Intangible assets, total cost	530	4,956
Intangible assets, accumulated amortization	(265)	(3,792)
Intangible assets, net	$ 265	$ 1,164

INTANGIBLE ASSETS - Narrative (

INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Tenant Move Outs Prior To End Of Lease Term
Finite-Lived Intangible Assets [Line Items]
Intangible assets written off through accelerated amortization	$ 0.3	$ 4.5	$ 0.6
Tenant Move-Outs
Finite-Lived Intangible Assets [Line Items]
Intangible assets written off through accelerated amortization	$ 0.1	$ 2.2	$ 0

INTANGIBLE ASSETS - Annual Amor

INTANGIBLE ASSETS - Annual Amortization of Intangible Assets, Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
2021	$ 16,190
2022	10,354
2023	7,564
2024	5,214
2025	4,027
Thereafter	5,221
Intangible assets, net	48,570	$ 84,851
Liabilities
2021	4,902
2022	2,723
2023	1,651
2024	1,425
2025	1,148
Thereafter	6,599
Acquired lease intangibles, net	$ 18,448	$ 22,263

DEBT OBLIGATIONS - Consolidated

DEBT OBLIGATIONS - Consolidated Debt Obligations Outstanding (Details) - USD ($) $ in Thousands	Nov. 10, 2020	Oct. 21, 2020	Dec. 13, 2018	Dec. 12, 2018	Dec. 31, 2020	Dec. 31, 2019
Consolidated debt obligations
Total Debt Obligations					$ 1,830,595	$ 2,144,418
Four Tower Bridge
Consolidated debt obligations
Repayments of long-term debt	$ 9,100
Secured Debt
Consolidated debt obligations
Long-term debt, gross					0	315,437
Plus: premiums/(discounts), net					0	(1,383)
Net deferred financing costs					0	(242)
Total Debt Obligations					0	313,812
Secured Debt | Two Logan Square
Consolidated debt obligations
Long-term debt, gross					$ 0	81,103
Effective interest rate					3.98%
Repayments of long-term debt		$ 79,800
Secured Debt | Four Tower Bridge
Consolidated debt obligations
Long-term debt, gross					$ 0	9,291
Effective interest rate					4.50%
Secured Debt | One Commerce Square
Consolidated debt obligations
Long-term debt, gross					$ 0	116,571
Effective interest rate					3.64%
Secured Debt | Two Commerce Square
Consolidated debt obligations
Long-term debt, gross					$ 0	108,472
Effective interest rate					4.51%
Unsecured Debt
Consolidated debt obligations
Long-term debt, gross					$ 1,828,610	1,828,610
Plus: premiums/(discounts), net					10,137	12,090
Net deferred financing costs					(8,152)	(10,094)
Total Debt Obligations					1,830,595	1,830,606
Unsecured Debt | $600 million Unsecured Credit Facility
Consolidated debt obligations
Debt instrument, face amount					600,000
Long-term debt, gross					$ 0	0
Unsecured Debt | Seven-Year Term Loan - Swapped to fixed
Consolidated debt obligations
Debt instrument, term			7 years		7 years
Debt instrument, interest rate, stated percentage			2.87%
Long-term debt, gross			$ 250,000		$ 250,000	250,000
Effective interest rate					2.87%
Unsecured Debt | $350.0M 3.95% Guaranteed Notes due 2023
Consolidated debt obligations
Debt instrument, face amount					$ 350,000
Debt instrument, interest rate, stated percentage					3.95%
Long-term debt, gross					$ 350,000	350,000
Effective interest rate					3.87%
Unsecured Debt | $350.0M 4.10% Guaranteed Notes due 2024
Consolidated debt obligations
Debt instrument, face amount					$ 350,000
Debt instrument, interest rate, stated percentage					4.10%
Long-term debt, gross					$ 350,000	350,000
Effective interest rate					3.78%
Unsecured Debt | $450.0M 3.95% Guaranteed Notes due 2027
Consolidated debt obligations
Debt instrument, face amount					$ 450,000
Debt instrument, interest rate, stated percentage					3.95%
Long-term debt, gross					$ 450,000	450,000
Effective interest rate					4.03%
Unsecured Debt | $350.0M 4.55% Guaranteed Notes due 2029
Consolidated debt obligations
Debt instrument, face amount					$ 350,000
Debt instrument, interest rate, stated percentage					4.55%
Long-term debt, gross					$ 350,000	350,000
Effective interest rate					4.30%
Unsecured Debt | Indenture IA (Preferred Trust I)
Consolidated debt obligations
Long-term debt, gross					$ 27,062	27,062
Unsecured Debt | Indenture IB (Preferred Trust I) - Swapped to fixed
Consolidated debt obligations
Long-term debt, gross					$ 25,774	25,774
Effective interest rate					3.30%
Unsecured Debt | Indenture II (Preferred Trust II)
Consolidated debt obligations
Long-term debt, gross					$ 25,774	$ 25,774
LIBOR | Unsecured Debt | $600 million Unsecured Credit Facility
Consolidated debt obligations
Variable interest rate					1.10%
LIBOR | Unsecured Debt | Seven-Year Term Loan - Swapped to fixed
Consolidated debt obligations
Variable interest rate			1.25%	1.80%
LIBOR | Unsecured Debt | Indenture IA (Preferred Trust I)
Consolidated debt obligations
Variable interest rate					1.25%
LIBOR | Unsecured Debt | Indenture II (Preferred Trust II)
Consolidated debt obligations
Variable interest rate					1.25%

DEBT OBLIGATIONS - Narrative (D

DEBT OBLIGATIONS - Narrative (Details)	Dec. 13, 2018USD ($)	Dec. 12, 2018	Jul. 17, 2018USD ($)extension	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Oct. 10, 2019USD ($)
Guaranteed Notes Due 2029
Debt Instrument [Line Items]
Debt instrument, face amount						$ 100,000,000
Debt instrument, interest rate, stated percentage						4.55%
Debt instrument, premium, percentage of face amount						110.058%
Net original issue premium					$ 8,500,000
Guaranteed Notes Due 2024
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage						4.10%
Debt instrument, premium, percentage of face amount						106.315%
Net original issue premium					$ 5,300,000
Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit				$ 0
Long-term debt, weighted average interest rate				1.48%	3.52%
Interest expense borrowings				$ 500,000	$ 4,400,000
Revolving Credit Facility | 2018 Credit Facility
Debt Instrument [Line Items]
Debt instrument, number of extensions | extension			2
Debt instrument, extension term duration			6 months
Debt financing costs			$ 2,700,000
Minimum credit Spread on a LIBOR rate loan				0.00%
Maximum credit spread on a LIBOR rate Loan				0.45%
Commitment fee percentage				0.25%
Minimum fixed charge coverage ratio				1.5
Maximum leverage ratio				0.60
Maximum unsecured indebtedness to unencumbered asset value ratio				0.60
Maximum secured indebtedness to total asset value ratio				0.40
Minimum unencumbered cash flow to interest expense on unsecured debt ratio				1.75
Maximum percent of payments of dividends and distributions				95.00%
Revolving Credit Facility | 2018 Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage				0.125%
Revolving Credit Facility | 2018 Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage				0.30%
Revolving Credit Facility | 2018 Credit Facility | LIBOR
Debt Instrument [Line Items]
Variable interest rate				1.10%
Basis spread on variable rate				1.00%
Revolving Credit Facility | 2018 Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Variable interest rate				0.775%
Revolving Credit Facility | 2018 Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Variable interest rate				1.45%
Revolving Credit Facility | 2018 Credit Facility | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate				0.50%
Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross				$ 1,828,610,000	1,828,610,000
Unsecured Debt | Seven-Year Term Loan - Swapped to fixed
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage	2.87%
Long-term debt, gross	$ 250,000,000			$ 250,000,000	250,000,000
Debt instrument, term	7 years			7 years
Decrease in interest rate	(0.55%)
Unsecured Debt | Seven-Year Term Loan - Swapped to fixed | LIBOR
Debt Instrument [Line Items]
Variable interest rate	1.25%	1.80%
Unsecured Debt | $600 million Unsecured Credit Facility
Debt Instrument [Line Items]
Debt instrument, face amount				$ 600,000,000
Long-term debt, gross				$ 0	$ 0
Maximum borrowing capacity			$ 600,000,000
Unsecured Debt | $600 million Unsecured Credit Facility | LIBOR
Debt Instrument [Line Items]
Variable interest rate				1.10%

DEBT OBLIGATIONS - Aggregate Sc

DEBT OBLIGATIONS - Aggregate Scheduled Principal Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total Debt Obligations	$ 1,830,595	$ 2,144,418
Unsecured Debt
Debt Instrument [Line Items]
2021	0
2022	250,000
2023	350,000
2024	350,000
2025	0
Thereafter	878,610
Total principal payments	1,828,610	1,828,610
Net unamortized premiums/(discounts)	10,137	12,090
Net deferred financing costs	(8,152)	(10,094)
Total Debt Obligations	$ 1,830,595	$ 1,830,606

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Estimates of Fair Value Differ from Carrying Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage notes payable, net	$ 0	$ 313,812
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable	94,430	44,430
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable, fair value	97,372	43,322
Unsecured notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs, net	8,152	10,094
Unsecured notes payable | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured notes payable	1,502,901	1,503,435
Deferred financing costs, net	7,200	8,700
Unsecured notes payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	1,607,310	1,591,830
Variable rate debt | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Variable rate debt	327,694	327,171
Deferred financing costs, net	900	1,400
Variable rate debt | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	308,838	309,947
Mortgage notes payable | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage notes payable, net	0	313,812
Deferred financing costs, net	0	200
Mortgage notes payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	$ 0	$ 317,031

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS - Narrative (Details) - 1919 Ventures - USD ($) $ in Millions	Dec. 31, 2020	Jun. 26, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loan		$ 44.4
Ownership percentage	50.00%	50.00%
Other Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loan		$ 44.4

DERIVATIVE FINANCIAL INSTRUME_3

DERIVATIVE FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, notional amount	$ 275,774	$ 275,774
2.868% Interest Rate Swap Maturing October 8, 2022 | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	$ 250,000	250,000
Derivative, fixed interest rate	2.868%
Derivative liability, fair value, gross liability	$ (6,627)	(562)
3.300% Interest Rate Swap Maturing January 30, 2021 | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	$ 25,774	25,774
Derivative, fixed interest rate	3.30%
Derivative liability, fair value, gross liability	$ (120)	$ (94)

LIMITED PARTNERS' NONCONTROLL_2

LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Noncontrolling Interest [Abstract]
Aggregate amount related to non-controlling interests classified within equity	$ 10.5	$ 9.3
Settlement value of non controlling interest in operating partnership	$ 11.7	$ 15.5

BENEFICIARIES' EQUITY OF THE _3

BENEFICIARIES' EQUITY OF THE PARENT COMPANY - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator
Net income	$ 307,326	$ 34,529	$ 135,472
Net income attributable to noncontrolling interests, Basic	(1,799)	(262)	(954)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(410)	(396)	(369)
Net income attributable to Common Shareholders/ Unitholders of Brandywine Realty Trust	305,117	33,871	134,149
Net income attributable to noncontrolling interests, Diluted	(1,799)	(262)	(954)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(410)	(396)	(369)
Net income attributable to common shareholders, Diluted	$ 305,117	$ 33,871	$ 134,149
Denominator
Basic weighted average shares outstanding (in shares)	171,926,079	176,132,941	178,519,748
Contingent securities/Share based compensation (in shares)	390,997	553,872	1,121,744
Diluted weighted average shares outstanding (in shares)	172,317,076	176,686,813	179,641,492
Earnings per Common Share:
Net income attributable to common shareholders, Basic (USD per share)	$ 1.77	$ 0.19	$ 0.75
Net income attributable to common shareholders, Diluted (USD per share)	$ 1.77	$ 0.19	$ 0.75

BENEFICIARIES' EQUITY OF THE _4

BENEFICIARIES' EQUITY OF THE PARENT COMPANY - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 08, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 03, 2019	Jan. 10, 2017
Class of Stock [Line Items]
Dividends, common stock	$ 32,700
Preferred shares authorized (in shares)		20,000,000	20,000,000
Preferred shares outstanding (in shares)		0	0
Repurchased and retired (in shares)		6,248,483	1,337,169	1,729,278	0
Share price (in usd per share)		$ 9.60	$ 12.92	$ 12.64
Repurchased and retired, value		$ 59,999	$ 17,281	$ 21,858
Common stock, par or stated value per share (usd per share)		$ 0.01	$ 0.01
Common stock, shares authorized (in shares)		400,000,000	400,000,000
Cash proceeds, net of issuance costs		$ 0	$ 0	$ 416
Common shares remain available for issuance (in shares)		0
Offering Program
Class of Stock [Line Items]
Common stock, shares authorized (in shares)							16,000,000
Common shares issued under offering program (in shares)		0	0	23,311
Weighted average price per share (usd per share)				$ 18.04
Cash proceeds, net of issuance costs				$ 400
Maximum
Class of Stock [Line Items]
Authorized amount						$ 150,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Repurchase program, number of common units retired for each common share repurchased (in units)		1
Cash proceeds, net of issuance costs		$ 0	$ 0	$ 416
Dividend Declared
Class of Stock [Line Items]
Dividends payable, amount per share (in usd per share)	$ 0.19
Redeemable Common Limited Partnership Units
Class of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share (in units)		981,634	981,634	982,871

PARTNER'S EQUITY OF THE PAREN_3

PARTNER'S EQUITY OF THE PARENT COMPANY - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator
Net income	$ 307,326	$ 34,529	$ 135,472
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(410)	(396)	(369)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	$ (410)	$ (396)	$ (369)
Denominator
Basic weighted average shares outstanding (in shares)	171,926,079	176,132,941	178,519,748
Contingent securities/Share based compensation (in shares)	390,997	553,872	1,121,744
Diluted weighted average shares outstanding (in shares)	172,317,076	176,686,813	179,641,492
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 1.77	$ 0.19	$ 0.75
Net income attributable to common shareholders, Diluted (USD per share)	$ 1.77	$ 0.19	$ 0.75
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 307,326	$ 34,529	$ 135,472
Net income attributable to noncontrolling interests	(20)	(69)	(55)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(410)	(396)	(369)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(410)	(396)	(369)
Net income attributable to common unitholders, Basic	306,896	34,064	135,048
Net income attributable to common unitholders, Diluted	$ 306,896	$ 34,064	$ 135,048
Denominator
Basic weighted average shares outstanding (in shares)	172,907,713	177,114,932	179,959,370
Contingent securities/Share based compensation (in shares)	390,997	553,872	1,121,744
Diluted weighted average shares outstanding (in shares)	173,298,710	177,668,804	181,081,114
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 1.77	$ 0.19	$ 0.75
Net income attributable to common shareholders, Diluted (USD per share)	$ 1.77	$ 0.19	$ 0.75

PARTNER'S EQUITY OF THE PAREN_4

PARTNER'S EQUITY OF THE PARENT COMPANY - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 08, 2020	Jan. 10, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 03, 2019
Earnings Per Common Partnership Unit [Line Items]
Dividends, common stock	$ 32,700
Repurchased and retired (in shares)			6,248,483	1,337,169	1,729,278	0
Share price (in usd per share)			$ 9.60	$ 12.92	$ 12.64
Repurchased and retired, value			$ 59,999	$ 17,281	$ 21,858
Common stock, par or stated value per share (usd per share)			$ 0.01	$ 0.01
Common stock, shares authorized (in shares)			400,000,000	400,000,000
Cash proceeds, net of issuance costs			$ 0	$ 0	$ 416
Common shares remain available for issuance (in shares)			0
Offering Program
Earnings Per Common Partnership Unit [Line Items]
Common stock, shares authorized (in shares)		16,000,000
Upfront costs		$ 200
Common shares issued under offering program (in shares)			0	0	23,311
Weighted average price per share (usd per share)					$ 18.04
Cash proceeds, net of issuance costs					$ 400
Maximum
Earnings Per Common Partnership Unit [Line Items]
Authorized amount							$ 150,000
Dividend Declared
Earnings Per Common Partnership Unit [Line Items]
Dividends payable, amount per share (in usd per share)	$ 0.19
Class A Units
Earnings Per Common Partnership Unit [Line Items]
Redeemable limited partnership unit price (in usd per unit)			$ 11.91	$ 15.75	$ 12.87
Limited partners' capital account, units outstanding (in units)			981,634	981,634	982,871
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings Per Common Partnership Unit [Line Items]
Preferred units, outstanding (in units)			0	0
Repurchase program, number of mirror unit of operating partnership retired for each common share repurchased			1
Cash proceeds, net of issuance costs			$ 0	$ 0	$ 416

SHARE BASED COMPENSATION, 401_2

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Narrative (Details)	Mar. 05, 2020installmentshares	Feb. 21, 2019	Feb. 01, 2019shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)	May 20, 2020shares	Jan. 22, 2019$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation arrangement by share-based payment award, options, outstanding, number | shares				300,046	334,561
Defined contribution plan, maximum annual contribution per employee, percent				100.00%
Defined contribution plan, employer discretionary contribution amount | $				$ 500,000	$ 400,000	$ 500,000
Threshold age for qualifying retirement				57
Number of vesting installments | installment	3
Number of shares to be issued under deferred compensation plan included in total shares outstanding | shares				1,200,000	1,100,000
Restricted Share Rights Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted share rights outstanding (in shares) | shares				488,735	479,144
Unrecognized compensation expenses | $				$ 1,800,000
Weighted average period over which options will be recognized				9 months 18 days
Share-based compensation expense | $				$ 4,300,000	$ 3,900,000	3,600,000
Share-based compensation expense, capitalized | $				$ 400,000	300,000	600,000
Granted (in shares) | shares	183,758			295,049
Number of restricted share right will get settled for common share | shares	1
Accumulated service period for voluntary termination	15 years
Restricted Share Rights Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				1 year
Restricted Share Rights Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years			3 years
Restricted Performance Share Units Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Unrecognized compensation expenses | $				$ 4,500,000
Weighted average period over which options will be recognized				1 year 6 months
Share-based compensation expense | $				$ 3,000,000	4,200,000	3,900,000
Share-based compensation expense, capitalized | $				$ 400,000	$ 600,000	1,100,000
Common shares issued for share based compensation | shares			121,897
Dividends payable, amount per share (in usd per share) | $ / shares								$ 0.19
Restricted Performance Share Units Plan | Executive Officers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted share rights outstanding (in shares) | shares				715,965	396,365
Granted (in shares) | shares				319,600
Performance earning potential		200.00%
Outperformance feature measurement term		3 years		3 years
Restricted Performance Share Units Plan | Executive Officers | 2020 Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $				$ 0
Awards issuable under outperformance feature (in shares) | shares				316,306
Restricted Performance Share Units Plan | Executive Officers | 2019 Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $				$ 200,000
Awards issuable under outperformance feature (in shares) | shares				233,890
Restricted Performance Share Units Plan | Non-Officer Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted share rights outstanding (in shares) | shares	40,920						70,371
Employee Share Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense | $				$ 100,000	$ 100,000	100,000
Share-based compensation, percentage of closing price				85.00%
Maximum participant contribution, percentage of compensation				20.00%
Maximum participant contribution, dollar amount | $				$ 50,000
Aggregate share-based awards awarded to executives | shares				1,250,000
Stock issued during period, value, employee stock purchase plan | $				$ 400,000	$ 500,000	$ 500,000
Share-based compensation arrangement by share-based payment award, discount from market price, purchase				15.00%

SHARE BASED COMPENSATION, 401_3

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Shares
Outstanding at beginning of year (in shares)	334,561
Exercised (in shares)	(34,515)
Outstanding at end of year, shares (in shares)	300,046	334,561
Vested/Exercisable at end of year (in shares)	300,046
Weighted Average Exercise Price
Outstanding at beginning of year, Weighted Average Exercise Price (in dollars per shares)	$ 11.88
Exercised, Weighted Average Exercise Price (in dollars per shares)	11.62
Outstanding at end of year, Weighted Average Exercise price (in dollars per shares)	11.91	$ 11.88
Vested/Exercisable at end of period, Weighted Average Exercise Price (in dollars per shares)	$ 11.91
Weighted Average Remaining Contractual Term (in years)	1 month 6 days	1 year
Vested/Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	1 month 6 days
Outstanding, Aggregate Intrinsic Value	$ 81,100
Exercised, Aggregated Intrinsic Value	10,100
Vested/Exercisable at end of year, Aggregate Intrinsic Value	$ 81,100

SHARE BASED COMPENSATION, 401_4

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Restricted Share Activity (Details) - Restricted Share Rights Awards - $ / shares	Mar. 05, 2020	Dec. 31, 2020
Shares
Beginning balance (in shares)		479,144
Granted (in shares)	183,758	295,049
Vested (in shares)		(283,431)
Forfeited (in shares)		(2,027)
Ending balance (in shares)		488,735
Weighted Average Grant Date Fair Value
Non-vested at beginning of year, Weighted Average Grant Date Fair Value (in dollars per shares)		$ 15.90
Granted, Weighted Average Grant Date Fair Value (in dollars per shares)		13.10
Vested, Weighted Average Grant Date Fair Value (in dollars per shares)		14.20
Forfeited, Weighted Average Grant Date Fair Value (in dollars per shares)		15.63
Non-vested at end of year, Weighted Average Grant Date Fair Value (in dollars per shares)		$ 15.19

SHARE BASED COMPENSATION, 401_5

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Restricted Performance Share Units (Details) - Restricted Performance Share Units Plan - Executive Officers - USD ($) $ in Thousands	Feb. 21, 2020	Feb. 21, 2019	Feb. 28, 2018	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)				396,365
Granted (in shares)				319,600
Ending balance (in shares)				715,965
February 28, 2018 RSPU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)				190,296
Granted (in shares)				0
Ending balance (in shares)				190,296
Total number of shares authorized for issuance (in shares)			209,193
Fair Value of Units on Grant Date			$ 4,276
February 21, 2019 RSPU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)				206,069
Granted (in shares)				0
Ending balance (in shares)				206,069
Total number of shares authorized for issuance (in shares)		213,728
Fair Value of Units on Grant Date		$ 4,627
March 5, 2020 RSPU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)				0
Granted (in shares)				319,600
Ending balance (in shares)				319,600
Total number of shares authorized for issuance (in shares)	319,600
Fair Value of Units on Grant Date	$ 5,389

DISTRIBUTIONS (Details)

DISTRIBUTIONS (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Distributions [Abstract]
Common share distributions payments of ordinary dividends (in usd per share)	$ 0.41	$ 0.62	$ 0.55
Common share distributions capital gain (in usd per share)	0.35	0	0
Common share distributions non-taxable distributions (in usd per share)	0	0.14	0.17
Common stock dividends per share paid (in usd per share)	$ 0.76	$ 0.76	$ 0.72
Percentage of distributions classified as ordinary income	53.90%	81.00%	76.20%
Percentage of distributions classified as capital gain	46.10%	0.00%	0.00%
Percentage of distributions classified as non-taxable distributions	0.00%	19.00%	23.80%

INCOME TAXES AND TAX CREDIT T_2

INCOME TAXES AND TAX CREDIT TRANSACTIONS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Accruals for tax uncertainties	$ 0	$ 0
Deferred income tax expense (benefit)	0	100,000	$ 300,000
Current income tax expense (benefit)	$ (200,000)	$ (100,000)	$ 100,000

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Beneficiaries' Equity, beginning balance		$ 1,688,303	$ 1,811,028	$ 1,826,870
Unrealized gain (loss) on derivative financial instruments		(5,972)	(8,210)	1,478
Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests		29	41	(39)
Amortization of interest rate contracts reclassified from comprehensive income to interest expense	[1]	752	770	1,191
Beneficiaries' Equity, ending balance		1,804,648	1,688,303	1,811,028
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Partners' Equity, beginning balance		1,672,915	1,798,508	1,799,955
Unrealized gain (loss) on derivative financial instruments		(5,972)	(8,210)	1,478
Amortization of interest rate contracts reclassified from comprehensive income to interest expense	[1]	752	770	1,191
Partners' Equity, ending balance		1,793,082	1,672,915	1,798,508
Accumulated Other Comprehensive Income (Loss)
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Beneficiaries' Equity, beginning balance		(2,370)	5,029	2,399
Beneficiaries' Equity, ending balance		(7,561)	(2,370)	5,029
Accumulated Other Comprehensive Income (Loss) | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Partners' Equity, beginning balance		(2,715)	4,725	2,056
Partners' Equity, ending balance		$ (7,935)	$ (2,715)	$ 4,725
[1]	Amounts reclassified from comprehensive income to interest expense within the Consolidated Statements of Operations.

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Narrative (Details) $ in Millions	Dec. 31, 2020USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Gains (losses) expected to be reclassified from AOCI into interest expense within the next twelve months	$ 0.8

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details)	12 Months Ended
	Dec. 31, 2020segment
Segment Reporting [Abstract]
Number of reportable segments	5

SEGMENT INFORMATION - Real Esta

SEGMENT INFORMATION - Real Estate Investments, at Cost of Company's Reportable Segments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Operating properties	$ 3,474,109	$ 4,006,459	$ 3,951,719
Right of use asset - operating leases, net	20,977	21,656
Construction-in-progress	210,311	180,718
Land held for development	117,984	96,124
Prepaid leasehold interests in land held for development, net	39,185	39,592
Philadelphia CBD
Segment Reporting Information [Line Items]
Operating properties	1,433,927	1,726,299
Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Operating properties	871,530	1,003,890
Austin, Texas
Segment Reporting Information [Line Items]
Operating properties	728,741	721,255
Metropolitan DC
Segment Reporting Information [Line Items]
Operating properties	352,794	468,035
Other
Segment Reporting Information [Line Items]
Operating properties	$ 87,117	$ 86,980

SEGMENT INFORMATION - Net Opera

SEGMENT INFORMATION - Net Operating Income of Company's Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 534,852	$ 580,417	$ 544,345
Operating expenses	(205,456)	(225,846)	(218,099)
Net operating income (loss)	329,396	354,571	326,246
Philadelphia CBD
Segment Reporting Information [Line Items]
Total revenue	232,028	263,769
Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Total revenue	141,613	141,084
Austin, Texas
Segment Reporting Information [Line Items]
Total revenue	102,982	104,157
Metropolitan DC
Segment Reporting Information [Line Items]
Total revenue	40,223	51,498
Operating Segments | Philadelphia CBD
Segment Reporting Information [Line Items]
Total revenue	232,028	263,769	256,717
Operating expenses	(82,505)	(100,219)	(99,449)
Net operating income (loss)	149,523	163,550	157,268
Operating Segments | Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Total revenue	141,613	141,084	138,279
Operating expenses	(46,281)	(47,418)	(49,433)
Net operating income (loss)	95,332	93,666	88,846
Operating Segments | Austin, Texas
Segment Reporting Information [Line Items]
Total revenue	102,982	104,157	38,665
Operating expenses	(39,759)	(38,285)	(16,739)
Net operating income (loss)	63,223	65,872	21,926
Operating Segments | Metropolitan DC
Segment Reporting Information [Line Items]
Total revenue	40,223	51,498	90,308
Operating expenses	(20,791)	(23,455)	(34,072)
Net operating income (loss)	19,432	28,043	56,236
Operating Segments | Other
Segment Reporting Information [Line Items]
Total revenue	13,469	14,558	16,757
Operating expenses	(9,815)	(9,328)	(11,888)
Net operating income (loss)	3,654	5,230	4,869
Corporate
Segment Reporting Information [Line Items]
Total revenue	4,537	5,351	3,619
Operating expenses	(6,305)	(7,141)	(6,518)
Net operating income (loss)	$ (1,768)	$ (1,790)	$ (2,899)

SEGMENT INFORMATION - Unconsoli

SEGMENT INFORMATION - Unconsolidated Real Estate Ventures of Company's Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	$ 389,811	$ 120,294
Equity in loss of Real Estate Ventures	(18,584)	(9,922)	$ (15,231)
Philadelphia CBD
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	268,562	17,524
Equity in loss of Real Estate Ventures	(9,090)	328	(105)
Metropolitan DC
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	99,769	102,840
Equity in loss of Real Estate Ventures	(3,019)	(4,234)	(15,065)
Mid-Atlantic Office JV
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	32,996	0
Equity in loss of Real Estate Ventures	96	0	0
MAP Venture
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	(11,516)	(70)
Equity in loss of Real Estate Ventures	(6,571)	(6,102)	(2,155)
Other
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	0	0
Equity in loss of Real Estate Ventures	0	86	407
Austin, Texas
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	0	0
Equity in loss of Real Estate Ventures	$ 0	$ 0	$ 1,687

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation of Consolidated Net Income (Loss) to Consolidated NOI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Net income	$ 307,326	$ 34,529	$ 135,472
Plus:
Interest expense	73,911	81,512	78,199
Interest expense - amortization of deferred financing costs	2,904	2,768	2,498
Depreciation and amortization	188,283	210,005	176,000
General and administrative expenses	30,288	32,156	27,802
Equity in loss of Real Estate Ventures	18,584	9,922	15,231
Provision for impairment	0	0	71,707
Loss on early extinguishment of debt	0	0	105
Less:
Interest income	1,939	2,318	4,703
Income tax (provision) benefit	224	(12)	(423)
Net gain on disposition of real estate	289,461	356	2,932
Net gain on sale of undepreciated real estate	201	2,020	3,040
Net gain on real estate venture transactions	75	11,639	142,233
Gain on promoted interest in unconsolidated real estate venture	0	0	28,283
Consolidated net operating income	$ 329,396	$ 354,571	$ 326,246

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	Oct. 21, 2020USD ($)	Apr. 02, 2015USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2004ft²
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness to third parties			$ 963,018	$ 596,007
Commerce Square | Preferred Equity Investment Obligation
Property Subject to or Available for Operating Lease [Line Items]
Required spending in capital improvements to property			$ 20,000
Prentiss Properties Trust | Commerce Square
Property Subject to or Available for Operating Lease [Line Items]
Non-controlling interest, ownership percentage by non-controlling Owners			1.00%
618 Market Street
Property Subject to or Available for Operating Lease [Line Items]
Contingent consideration, liability		$ 2,000
Fair value of contingent consideration		1,600
Interest expense		$ 2,000
Drexel Square
Property Subject to or Available for Operating Lease [Line Items]
Required spending in capital improvements to property			$ 7,700
Estimated potential additional contribution obligation			2,600
One Commerce Square
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation			125,000
Two Commerce Square
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation			100,000
Unconsolidated Real Estate Ventures
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness to third parties			963,200
4040 Wilson Venture
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness to third parties			141,857	$ 114,845
Secured construction loan with total borrowing capacity					$ 150,000
4040 Wilson Venture | 4040 Wilson Venture
Property Subject to or Available for Operating Lease [Line Items]
Secured construction loan with total borrowing capacity			150,000
Guarantees, maximum exposure amount			41,300
Two Logan Square
Property Subject to or Available for Operating Lease [Line Items]
Rentable square feet | ft²						708,844
Settlement liabilities			$ 900
Two Logan Square | Secured Debt
Property Subject to or Available for Operating Lease [Line Items]
Repayments of long-term debt	$ 79,800

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent Event - Schuylkill Yards West ft² in Thousands, $ in Millions	Feb. 02, 2021USD ($)ft²
Subsequent Event [Line Items]
Area of building to be constructed | ft²	570
Estimated project cost	$ 287
Funding committed by other party	$ 58
Ownership interest held by partner	45.00%

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 7,975	$ 12,919	$ 17,112
Additions	0	0	1,775
Deductions	2,889	4,944	5,968
Balance at End of Year	$ 5,086	$ 7,975	$ 12,919

Schedule III - Real Estate an_2

Schedule III - Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Initial Cost
Land	$ 366,673
Buildings and Improvements	2,494,108
Net Improvements (Retirements) Since Acquisition	613,328
Gross Amount Which Carried
Land	407,514
Buildings and Improvements	3,066,595
Total	3,474,109	$ 4,006,459	$ 3,951,719	$ 3,830,824
Accumulated Depreciation at December 31, 2019	896,561	973,318	$ 885,407	$ 913,297
Pennsylvania Suburbs | Six Tower Bridge (181 Washington Street)
Initial Cost
Land		6,927
Buildings and Improvements		14,722
Net Improvements (Retirements) Since Acquisition		2,166
Gross Amount Which Carried
Land		6,237
Buildings and Improvements		17,578
Total		23,815
Accumulated Depreciation at December 31, 2019		4,228
Pennsylvania Suburbs | 426 West Lancaster Avenue
Initial Cost
Land		1,689
Buildings and Improvements		6,756
Net Improvements (Retirements) Since Acquisition		8,833
Gross Amount Which Carried
Land		1,686
Buildings and Improvements		15,592
Total		17,278
Accumulated Depreciation at December 31, 2019		512
Pennsylvania Suburbs | 52 Swedesford Square
Initial Cost
Land		4,241
Buildings and Improvements		16,579
Net Improvements (Retirements) Since Acquisition		(20,820)
Gross Amount Which Carried
Land		0
Buildings and Improvements		0
Total		0
Accumulated Depreciation at December 31, 2019		0
Pennsylvania Suburbs | 640 Freedom Business Center
Initial Cost
Land		1,015
Buildings and Improvements		20,098
Net Improvements (Retirements) Since Acquisition		4,838
Gross Amount Which Carried
Land		387
Buildings and Improvements		25,564
Total		25,951
Accumulated Depreciation at December 31, 2019		15,229
Pennsylvania Suburbs | 620 Freedom Business Center
Initial Cost
Land		666
Buildings and Improvements		13,118
Net Improvements (Retirements) Since Acquisition		1,888
Gross Amount Which Carried
Land		252
Buildings and Improvements		15,420
Total		15,672
Accumulated Depreciation at December 31, 2019		9,416
Pennsylvania Suburbs | 1000 First Avenue
Initial Cost
Land		0
Buildings and Improvements		13,708
Net Improvements (Retirements) Since Acquisition		3,235
Gross Amount Which Carried
Land		0
Buildings and Improvements		16,943
Total		16,943
Accumulated Depreciation at December 31, 2019		11,450
Pennsylvania Suburbs | 1060 First Avenue
Initial Cost
Land		0
Buildings and Improvements		13,665
Net Improvements (Retirements) Since Acquisition		4,279
Gross Amount Which Carried
Land		0
Buildings and Improvements		17,944
Total		17,944
Accumulated Depreciation at December 31, 2019		11,741
Pennsylvania Suburbs | 630 Freedom Business Center Drive
Initial Cost
Land		666
Buildings and Improvements		13,251
Net Improvements (Retirements) Since Acquisition		3,497
Gross Amount Which Carried
Land		255
Buildings and Improvements		17,159
Total		17,414
Accumulated Depreciation at December 31, 2019		10,139
Pennsylvania Suburbs | 1020 First Avenue
Initial Cost
Land		0
Buildings and Improvements		10,744
Net Improvements (Retirements) Since Acquisition		4,306
Gross Amount Which Carried
Land		0
Buildings and Improvements		15,050
Total		15,050
Accumulated Depreciation at December 31, 2019		9,726
Pennsylvania Suburbs | 1040 First Avenue
Initial Cost
Land		0
Buildings and Improvements		14,142
Net Improvements (Retirements) Since Acquisition		5,218
Gross Amount Which Carried
Land		0
Buildings and Improvements		19,360
Total		19,360
Accumulated Depreciation at December 31, 2019		12,870
Pennsylvania Suburbs | 610 Freedom Business Center Drive
Initial Cost
Land		485
Buildings and Improvements		9,602
Net Improvements (Retirements) Since Acquisition		2,554
Gross Amount Which Carried
Land		185
Buildings and Improvements		12,456
Total		12,641
Accumulated Depreciation at December 31, 2019		7,514
Pennsylvania Suburbs | 650 Park Avenue
Initial Cost
Land		1,916
Buildings and Improvements		4,378
Net Improvements (Retirements) Since Acquisition		(4,378)
Gross Amount Which Carried
Land		1,916
Buildings and Improvements		0
Total		1,916
Accumulated Depreciation at December 31, 2019		0
Pennsylvania Suburbs | 600 Park Avenue
Initial Cost
Land		1,012
Buildings and Improvements		4,048
Net Improvements (Retirements) Since Acquisition		385
Gross Amount Which Carried
Land		1,012
Buildings and Improvements		4,433
Total		5,445
Accumulated Depreciation at December 31, 2019		2,768
Pennsylvania Suburbs | 933 First Avenue
Initial Cost
Land		3,127
Buildings and Improvements		20,794
Net Improvements (Retirements) Since Acquisition		(1,125)
Gross Amount Which Carried
Land		3,127
Buildings and Improvements		19,669
Total		22,796
Accumulated Depreciation at December 31, 2019		3,085
Pennsylvania Suburbs | 500 North Gulph Road
Initial Cost
Land		1,303
Buildings and Improvements		5,201
Net Improvements (Retirements) Since Acquisition		21,471
Gross Amount Which Carried
Land		1,303
Buildings and Improvements		26,672
Total		27,975
Accumulated Depreciation at December 31, 2019		2,363
Pennsylvania Suburbs | 401 Plymouth Road
Initial Cost
Land		6,199
Buildings and Improvements		16,131
Net Improvements (Retirements) Since Acquisition		15,658
Gross Amount Which Carried
Land		6,199
Buildings and Improvements		31,789
Total		37,988
Accumulated Depreciation at December 31, 2019		15,816
Pennsylvania Suburbs | Metroplex (4000 Chemical Road)
Initial Cost
Land		4,373
Buildings and Improvements		24,546
Net Improvements (Retirements) Since Acquisition		4,627
Gross Amount Which Carried
Land		4,373
Buildings and Improvements		29,173
Total		33,546
Accumulated Depreciation at December 31, 2019		8,071
Pennsylvania Suburbs | 610 West Germantown Pike
Initial Cost
Land		3,651
Buildings and Improvements		14,514
Net Improvements (Retirements) Since Acquisition		3,578
Gross Amount Which Carried
Land		3,651
Buildings and Improvements		18,092
Total		21,743
Accumulated Depreciation at December 31, 2019		8,855
Pennsylvania Suburbs | 600 West Germantown Pike
Initial Cost
Land		3,652
Buildings and Improvements		15,288
Net Improvements (Retirements) Since Acquisition		2,463
Gross Amount Which Carried
Land		3,652
Buildings and Improvements		17,751
Total		21,403
Accumulated Depreciation at December 31, 2019		8,450
Pennsylvania Suburbs | 630 West Germantown Pike
Initial Cost
Land		3,558
Buildings and Improvements		14,743
Net Improvements (Retirements) Since Acquisition		2,189
Gross Amount Which Carried
Land		3,558
Buildings and Improvements		16,932
Total		20,490
Accumulated Depreciation at December 31, 2019		8,115
Pennsylvania Suburbs | 620 West Germantown Pike
Initial Cost
Land		3,572
Buildings and Improvements		14,435
Net Improvements (Retirements) Since Acquisition		1,866
Gross Amount Which Carried
Land		3,572
Buildings and Improvements		16,301
Total		19,873
Accumulated Depreciation at December 31, 2019		7,411
Pennsylvania Suburbs | 660 West Germantown Pike
Initial Cost
Land		3,694
Buildings and Improvements		5,487
Net Improvements (Retirements) Since Acquisition		19,682
Gross Amount Which Carried
Land		5,405
Buildings and Improvements		23,458
Total		28,863
Accumulated Depreciation at December 31, 2019		6,822
Pennsylvania Suburbs | 351 Plymouth Road
Initial Cost
Land		1,043
Buildings and Improvements		555
Net Improvements (Retirements) Since Acquisition		0
Gross Amount Which Carried
Land		1,043
Buildings and Improvements		555
Total		1,598
Accumulated Depreciation at December 31, 2019		218
Pennsylvania Suburbs | 150 Radnor Chester Road
Initial Cost
Land		11,925
Buildings and Improvements		36,986
Net Improvements (Retirements) Since Acquisition		21,658
Gross Amount Which Carried
Land		11,897
Buildings and Improvements		58,672
Total		70,569
Accumulated Depreciation at December 31, 2019		20,187
Pennsylvania Suburbs | One Radnor Corporate Center
Initial Cost
Land		7,323
Buildings and Improvements		28,613
Net Improvements (Retirements) Since Acquisition		19,813
Gross Amount Which Carried
Land		7,323
Buildings and Improvements		48,426
Total		55,749
Accumulated Depreciation at December 31, 2019		30,728
Pennsylvania Suburbs | 201 King of Prussia Road
Initial Cost
Land		8,956
Buildings and Improvements		29,811
Net Improvements (Retirements) Since Acquisition		4,307
Gross Amount Which Carried
Land		8,949
Buildings and Improvements		34,125
Total		43,074
Accumulated Depreciation at December 31, 2019		20,508
Pennsylvania Suburbs | 555 Lancaster Avenue
Initial Cost
Land		8,014
Buildings and Improvements		16,508
Net Improvements (Retirements) Since Acquisition		19,871
Gross Amount Which Carried
Land		8,609
Buildings and Improvements		35,784
Total		44,393
Accumulated Depreciation at December 31, 2019		20,245
Pennsylvania Suburbs | Four Radnor Corporate Center
Initial Cost
Land		5,406
Buildings and Improvements		21,390
Net Improvements (Retirements) Since Acquisition		12,633
Gross Amount Which Carried
Land		5,705
Buildings and Improvements		33,724
Total		39,429
Accumulated Depreciation at December 31, 2019		17,020
Pennsylvania Suburbs | Five Radnor Corporate Center
Initial Cost
Land		6,506
Buildings and Improvements		25,525
Net Improvements (Retirements) Since Acquisition		8,906
Gross Amount Which Carried
Land		6,578
Buildings and Improvements		34,359
Total		40,937
Accumulated Depreciation at December 31, 2019		13,689
Pennsylvania Suburbs | Three Radnor Corporate Center
Initial Cost
Land		4,773
Buildings and Improvements		17,961
Net Improvements (Retirements) Since Acquisition		2,173
Gross Amount Which Carried
Land		4,791
Buildings and Improvements		20,116
Total		24,907
Accumulated Depreciation at December 31, 2019		10,527
Pennsylvania Suburbs | Two Radnor Corporate Center
Initial Cost
Land		3,937
Buildings and Improvements		15,484
Net Improvements (Retirements) Since Acquisition		2,879
Gross Amount Which Carried
Land		3,942
Buildings and Improvements		18,358
Total		22,300
Accumulated Depreciation at December 31, 2019		10,463
Pennsylvania Suburbs | 130 Radnor Chester Road
Initial Cost
Land		2,573
Buildings and Improvements		8,338
Net Improvements (Retirements) Since Acquisition		(134)
Gross Amount Which Carried
Land		2,567
Buildings and Improvements		8,210
Total		10,777
Accumulated Depreciation at December 31, 2019		3,764
Pennsylvania Suburbs | 170 Radnor Chester Road
Initial Cost
Land		2,514
Buildings and Improvements		8,147
Net Improvements (Retirements) Since Acquisition		1,728
Gross Amount Which Carried
Land		2,509
Buildings and Improvements		9,880
Total		12,389
Accumulated Depreciation at December 31, 2019		4,784
Pennsylvania Suburbs | 200 N. Radnor Chester Rd.
Initial Cost
Land		3,366
Buildings and Improvements		0
Net Improvements (Retirements) Since Acquisition		3,621
Gross Amount Which Carried
Land		3,366
Buildings and Improvements		3,621
Total		6,987
Accumulated Depreciation at December 31, 2019		857
Pennsylvania Suburbs | 101 West Elm Street
Initial Cost
Land		6,251
Buildings and Improvements		25,209
Net Improvements (Retirements) Since Acquisition		2,940
Gross Amount Which Carried
Land		6,251
Buildings and Improvements		28,149
Total		34,400
Accumulated Depreciation at December 31, 2019		10,949
Pennsylvania Suburbs | 1 West Elm Street
Initial Cost
Land		3,557
Buildings and Improvements		14,249
Net Improvements (Retirements) Since Acquisition		984
Gross Amount Which Carried
Land		3,557
Buildings and Improvements		15,233
Total		18,790
Accumulated Depreciation at December 31, 2019		5,955
Pennsylvania Suburbs | Four Tower Bridge (200 Barr Harbor Drive)
Initial Cost
Land		6,000
Buildings and Improvements		14,734
Net Improvements (Retirements) Since Acquisition		390
Gross Amount Which Carried
Land		6,000
Buildings and Improvements		15,124
Total		21,124
Accumulated Depreciation at December 31, 2019		$ 1,213
Philadelphia CBD | Cira Centre (2929 Arch Street)
Initial Cost
Land	0
Buildings and Improvements	208,570
Net Improvements (Retirements) Since Acquisition	(16,549)
Gross Amount Which Carried
Land	12,586
Buildings and Improvements	179,435
Total	192,021
Accumulated Depreciation at December 31, 2019	68,536
Philadelphia CBD | Three Logan Square (1717 Arch Street)
Initial Cost
Land	0
Buildings and Improvements	98,188
Net Improvements (Retirements) Since Acquisition	83,981
Gross Amount Which Carried
Land	25,195
Buildings and Improvements	156,974
Total	182,169
Accumulated Depreciation at December 31, 2019	46,611
Philadelphia CBD | One Logan Square (130 North 18th Street)
Initial Cost
Land	14,496
Buildings and Improvements	107,736
Net Improvements (Retirements) Since Acquisition	29,992
Gross Amount Which Carried
Land	14,473
Buildings and Improvements	137,751
Total	152,224
Accumulated Depreciation at December 31, 2019	67,932
Philadelphia CBD | Two Logan Square (100 North 18th Street)
Initial Cost
Land	16,066
Buildings and Improvements	100,255
Net Improvements (Retirements) Since Acquisition	27,936
Gross Amount Which Carried
Land	16,066
Buildings and Improvements	128,191
Total	144,257
Accumulated Depreciation at December 31, 2019	53,177
Philadelphia CBD | Cira Centre South Garage (129 South 30th Street)
Initial Cost
Land	0
Buildings and Improvements	76,008
Net Improvements (Retirements) Since Acquisition	26,961
Gross Amount Which Carried
Land	6,816
Buildings and Improvements	96,153
Total	102,969
Accumulated Depreciation at December 31, 2019	22,377
Philadelphia CBD | 1900 Market Street
Initial Cost
Land	7,768
Buildings and Improvements	17,263
Net Improvements (Retirements) Since Acquisition	63,616
Gross Amount Which Carried
Land	7,768
Buildings and Improvements	80,879
Total	88,647
Accumulated Depreciation at December 31, 2019	20,545
Philadelphia CBD | 3020 Market Street
Initial Cost
Land	0
Buildings and Improvements	21,417
Net Improvements (Retirements) Since Acquisition	7,827
Gross Amount Which Carried
Land	0
Buildings and Improvements	29,244
Total	29,244
Accumulated Depreciation at December 31, 2019	11,501
Philadelphia CBD | 618-634 Market Street
Initial Cost
Land	13,365
Buildings and Improvements	5,791
Net Improvements (Retirements) Since Acquisition	2,810
Gross Amount Which Carried
Land	13,365
Buildings and Improvements	8,601
Total	21,966
Accumulated Depreciation at December 31, 2019	6,522
Philadelphia CBD | FMC Tower at Cira Centre South (2929 Walnut Street)
Initial Cost
Land	0
Buildings and Improvements	400,294
Net Improvements (Retirements) Since Acquisition	18,005
Gross Amount Which Carried
Land	0
Buildings and Improvements	418,299
Total	418,299
Accumulated Depreciation at December 31, 2019	63,196
Philadelphia CBD | 2100 Market Street
Initial Cost
Land	18,827
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	6,433
Gross Amount Which Carried
Land	18,854
Buildings and Improvements	6,406
Total	25,260
Accumulated Depreciation at December 31, 2019	1,517
Philadelphia CBD | 1505-11 Race Street
Initial Cost
Land	3,662
Buildings and Improvements	6,061
Net Improvements (Retirements) Since Acquisition	8
Gross Amount Which Carried
Land	3,670
Buildings and Improvements	6,061
Total	9,731
Accumulated Depreciation at December 31, 2019	25
Philadelphia CBD | The Bulletin Building (3025 Market Street)
Initial Cost
Land	0
Buildings and Improvements	24,377
Net Improvements (Retirements) Since Acquisition	42,669
Gross Amount Which Carried
Land	0
Buildings and Improvements	67,046
Total	67,046
Accumulated Depreciation at December 31, 2019	4,405
Philadelphia CBD | 3001-3003 JFK Boulevard
Initial Cost
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	111
Gross Amount Which Carried
Land	0
Buildings and Improvements	111
Total	111
Accumulated Depreciation at December 31, 2019	17
Philadelphia CBD | 3025 JFK Boulevard
Initial Cost
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	0
Gross Amount Which Carried
Land	0
Buildings and Improvements	0
Total	0
Accumulated Depreciation at December 31, 2019	0
Metropolitan DC | 6600 Rockledge Drive
Initial Cost
Land	0
Buildings and Improvements	37,421
Net Improvements (Retirements) Since Acquisition	10,036
Gross Amount Which Carried
Land	0
Buildings and Improvements	47,457
Total	47,457
Accumulated Depreciation at December 31, 2019	16,270
Metropolitan DC | 2340 Dulles Corner Boulevard
Initial Cost
Land	16,345
Buildings and Improvements	65,379
Net Improvements (Retirements) Since Acquisition	524
Gross Amount Which Carried
Land	16,129
Buildings and Improvements	66,119
Total	82,248
Accumulated Depreciation at December 31, 2019	23,858
Metropolitan DC | 1676 International Drive
Initial Cost
Land	18,437
Buildings and Improvements	97,538
Net Improvements (Retirements) Since Acquisition	17,656
Gross Amount Which Carried
Land	18,785
Buildings and Improvements	114,846
Total	133,631
Accumulated Depreciation at December 31, 2019	27,969
Metropolitan DC | 8260 Greensboro Drive
Initial Cost
Land	7,952
Buildings and Improvements	33,964
Net Improvements (Retirements) Since Acquisition	5,313
Gross Amount Which Carried
Land	8,102
Buildings and Improvements	39,127
Total	47,229
Accumulated Depreciation at December 31, 2019	12,664
Metropolitan DC | 8521 Leesburg Pike
Initial Cost
Land	4,316
Buildings and Improvements	30,885
Net Improvements (Retirements) Since Acquisition	7,007
Gross Amount Which Carried
Land	4,397
Buildings and Improvements	37,811
Total	42,208
Accumulated Depreciation at December 31, 2019	12,898
Austin, Texas | 11501 Burnet Road - Building 1
Initial Cost
Land	3,755
Buildings and Improvements	22,702
Net Improvements (Retirements) Since Acquisition	12
Gross Amount Which Carried
Land	3,755
Buildings and Improvements	22,714
Total	26,469
Accumulated Depreciation at December 31, 2019	3,788
Austin, Texas | 11501 Burnet Road - Building 2
Initial Cost
Land	2,732
Buildings and Improvements	16,305
Net Improvements (Retirements) Since Acquisition	1,479
Gross Amount Which Carried
Land	2,732
Buildings and Improvements	17,784
Total	20,516
Accumulated Depreciation at December 31, 2019	3,471
Austin, Texas | 11501 Burnet Road - Building 3
Initial Cost
Land	3,688
Buildings and Improvements	22,348
Net Improvements (Retirements) Since Acquisition	10
Gross Amount Which Carried
Land	3,688
Buildings and Improvements	22,358
Total	26,046
Accumulated Depreciation at December 31, 2019	3,729
Austin, Texas | 11501 Burnet Road - Building 4
Initial Cost
Land	2,614
Buildings and Improvements	15,740
Net Improvements (Retirements) Since Acquisition	8
Gross Amount Which Carried
Land	2,614
Buildings and Improvements	15,748
Total	18,362
Accumulated Depreciation at December 31, 2019	2,628
Austin, Texas | 11501 Burnet Road - Building 5
Initial Cost
Land	3,689
Buildings and Improvements	22,354
Net Improvements (Retirements) Since Acquisition	13
Gross Amount Which Carried
Land	3,689
Buildings and Improvements	22,367
Total	26,056
Accumulated Depreciation at December 31, 2019	3,733
Austin, Texas | 11501 Burnet Road - Building 6
Initial Cost
Land	2,676
Buildings and Improvements	15,972
Net Improvements (Retirements) Since Acquisition	14,133
Gross Amount Which Carried
Land	2,676
Buildings and Improvements	30,105
Total	32,781
Accumulated Depreciation at December 31, 2019	5,446
Austin, Texas | 11501 Burnet Road - Building 8
Initial Cost
Land	1,400
Buildings and Improvements	7,422
Net Improvements (Retirements) Since Acquisition	1,523
Gross Amount Which Carried
Land	1,400
Buildings and Improvements	8,945
Total	10,345
Accumulated Depreciation at December 31, 2019	1,536
Austin, Texas | 11501 Burnet Road - Parking Garage
Initial Cost
Land	0
Buildings and Improvements	19,826
Net Improvements (Retirements) Since Acquisition	6
Gross Amount Which Carried
Land	0
Buildings and Improvements	19,832
Total	19,832
Accumulated Depreciation at December 31, 2019	4,378
Austin, Texas | Four Points Centre 3, 11120 Four Points Drive
Initial Cost
Land	1,140
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	40,330
Gross Amount Which Carried
Land	1,141
Buildings and Improvements	40,329
Total	41,470
Accumulated Depreciation at December 31, 2019	3,279
Austin, Texas | One Barton Skyway (1501 South MoPac Expressway)
Initial Cost
Land	10,496
Buildings and Improvements	47,670
Net Improvements (Retirements) Since Acquisition	3,448
Gross Amount Which Carried
Land	10,495
Buildings and Improvements	51,119
Total	61,614
Accumulated Depreciation at December 31, 2019	2,826
Austin, Texas | Two Barton Skyway (1601 South MoPac Expressway)
Initial Cost
Land	10,849
Buildings and Improvements	53,868
Net Improvements (Retirements) Since Acquisition	2,820
Gross Amount Which Carried
Land	10,848
Buildings and Improvements	56,689
Total	67,537
Accumulated Depreciation at December 31, 2019	3,532
Austin, Texas | Three Barton Skyway (1221 South MoPac Expressway)
Initial Cost
Land	10,374
Buildings and Improvements	47,624
Net Improvements (Retirements) Since Acquisition	304
Gross Amount Which Carried
Land	10,373
Buildings and Improvements	47,929
Total	58,302
Accumulated Depreciation at December 31, 2019	2,603
Austin, Texas | Four Barton Skyway (1301 South MoPac Expressway)
Initial Cost
Land	13,301
Buildings and Improvements	57,041
Net Improvements (Retirements) Since Acquisition	2,904
Gross Amount Which Carried
Land	13,300
Buildings and Improvements	59,946
Total	73,246
Accumulated Depreciation at December 31, 2019	3,162
Austin, Texas | Four Points Centre (11305 Four Points Drive)
Initial Cost
Land	7,800
Buildings and Improvements	43,581
Net Improvements (Retirements) Since Acquisition	3,923
Gross Amount Which Carried
Land	7,800
Buildings and Improvements	47,504
Total	55,304
Accumulated Depreciation at December 31, 2019	3,024
Austin, Texas | River Place - Building 1 (6500 River Place Boulevard)
Initial Cost
Land	2,004
Buildings and Improvements	17,680
Net Improvements (Retirements) Since Acquisition	537
Gross Amount Which Carried
Land	2,004
Buildings and Improvements	18,217
Total	20,221
Accumulated Depreciation at December 31, 2019	1,072
Austin, Texas | River Place - Building 2 (6500 River Place Boulevard)
Initial Cost
Land	3,137
Buildings and Improvements	29,254
Net Improvements (Retirements) Since Acquisition	618
Gross Amount Which Carried
Land	3,137
Buildings and Improvements	29,872
Total	33,009
Accumulated Depreciation at December 31, 2019	1,634
Austin, Texas | River Place - Building 3 (6500 River Place Boulevard)
Initial Cost
Land	3,064
Buildings and Improvements	26,705
Net Improvements (Retirements) Since Acquisition	279
Gross Amount Which Carried
Land	3,064
Buildings and Improvements	26,984
Total	30,048
Accumulated Depreciation at December 31, 2019	1,429
Austin, Texas | River Place - Building 4 (6500 River Place Boulevard
Initial Cost
Land	2,273
Buildings and Improvements	18,617
Net Improvements (Retirements) Since Acquisition	1,047
Gross Amount Which Carried
Land	2,273
Buildings and Improvements	19,664
Total	21,937
Accumulated Depreciation at December 31, 2019	1,345
Austin, Texas | River Place - Building 5 (6500 River Place Boulevard)
Initial Cost
Land	1,752
Buildings and Improvements	14,315
Net Improvements (Retirements) Since Acquisition	97
Gross Amount Which Carried
Land	1,752
Buildings and Improvements	14,412
Total	16,164
Accumulated Depreciation at December 31, 2019	768
Austin, Texas | River Place - Building 6 (6500 River Place Boulevard)
Initial Cost
Land	1,598
Buildings and Improvements	12,945
Net Improvements (Retirements) Since Acquisition	22
Gross Amount Which Carried
Land	1,598
Buildings and Improvements	12,967
Total	14,565
Accumulated Depreciation at December 31, 2019	690
Austin, Texas | River Place - Building 7 (6500 River Place Boulevard)
Initial Cost
Land	1,801
Buildings and Improvements	16,486
Net Improvements (Retirements) Since Acquisition	1,094
Gross Amount Which Carried
Land	1,801
Buildings and Improvements	17,580
Total	19,381
Accumulated Depreciation at December 31, 2019	1,210
Austin, Texas | Quarry Lake II (4516 Seton Center Parkway)
Initial Cost
Land	3,970
Buildings and Improvements	30,546
Net Improvements (Retirements) Since Acquisition	1,024
Gross Amount Which Carried
Land	3,867
Buildings and Improvements	31,673
Total	35,540
Accumulated Depreciation at December 31, 2019	1,772
Other | 10 Foster Avenue
Initial Cost
Land	244
Buildings and Improvements	971
Net Improvements (Retirements) Since Acquisition	164
Gross Amount Which Carried
Land	244
Buildings and Improvements	1,135
Total	1,379
Accumulated Depreciation at December 31, 2019	659
Other | 7 Foster Avenue
Initial Cost
Land	231
Buildings and Improvements	921
Net Improvements (Retirements) Since Acquisition	31
Gross Amount Which Carried
Land	231
Buildings and Improvements	952
Total	1,183
Accumulated Depreciation at December 31, 2019	575
Other | 2 Foster Avenue
Initial Cost
Land	185
Buildings and Improvements	730
Net Improvements (Retirements) Since Acquisition	11
Gross Amount Which Carried
Land	185
Buildings and Improvements	741
Total	926
Accumulated Depreciation at December 31, 2019	741
Other | 4 Foster Avenue
Initial Cost
Land	183
Buildings and Improvements	726
Net Improvements (Retirements) Since Acquisition	6
Gross Amount Which Carried
Land	183
Buildings and Improvements	732
Total	915
Accumulated Depreciation at December 31, 2019	732
Other | 1 Foster Avenue
Initial Cost
Land	93
Buildings and Improvements	364
Net Improvements (Retirements) Since Acquisition	8
Gross Amount Which Carried
Land	93
Buildings and Improvements	372
Total	465
Accumulated Depreciation at December 31, 2019	372
Other | 5 U.S. Avenue
Initial Cost
Land	21
Buildings and Improvements	81
Net Improvements (Retirements) Since Acquisition	2
Gross Amount Which Carried
Land	21
Buildings and Improvements	83
Total	104
Accumulated Depreciation at December 31, 2019	83
Other | 5 Foster Avenue
Initial Cost
Land	9
Buildings and Improvements	32
Net Improvements (Retirements) Since Acquisition	3
Gross Amount Which Carried
Land	9
Buildings and Improvements	35
Total	44
Accumulated Depreciation at December 31, 2019	35
Other | Main Street-Plaza 1000
Initial Cost
Land	2,732
Buildings and Improvements	10,942
Net Improvements (Retirements) Since Acquisition	284
Gross Amount Which Carried
Land	2,732
Buildings and Improvements	11,226
Total	13,958
Accumulated Depreciation at December 31, 2019	11,017
Other | Main Street-Piazza
Initial Cost
Land	696
Buildings and Improvements	2,802
Net Improvements (Retirements) Since Acquisition	3,631
Gross Amount Which Carried
Land	704
Buildings and Improvements	6,425
Total	7,129
Accumulated Depreciation at December 31, 2019	3,837
Other | Main Street-Promenade
Initial Cost
Land	532
Buildings and Improvements	2,052
Net Improvements (Retirements) Since Acquisition	326
Gross Amount Which Carried
Land	532
Buildings and Improvements	2,378
Total	2,910
Accumulated Depreciation at December 31, 2019	1,432
Other | 920 North King Street
Initial Cost
Land	6,141
Buildings and Improvements	21,140
Net Improvements (Retirements) Since Acquisition	8,059
Gross Amount Which Carried
Land	6,141
Buildings and Improvements	29,199
Total	35,340
Accumulated Depreciation at December 31, 2019	14,492
Other | 300 Delaware Avenue
Initial Cost
Land	6,369
Buildings and Improvements	13,739
Net Improvements (Retirements) Since Acquisition	2,657
Gross Amount Which Carried
Land	6,369
Buildings and Improvements	16,396
Total	22,765
Accumulated Depreciation at December 31, 2019	$ 9,823

Schedule III - Real Estate an_3

Schedule III - Real Estate and Accumulated Depreciation (Reconciliations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year	$ 4,006,459	$ 3,951,719	$ 3,830,824
Additions:
Acquisitions	9,722	0	509,654
Capital expenditures and assets placed into service	113,221	145,378	129,274
Less:
Dispositions/impairments/placed into redevelopment	(619,086)	(50,792)	(469,517)
Retirements	(36,207)	(39,846)	(48,516)
Balance at the end of the year	3,474,109	4,006,459	3,951,719
Operating properties	3,474,109	4,006,459	3,951,719
Tax basis of assets, cost for income tax purposes	2,900,000	3,200,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	973,318	885,407	913,297
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense	138,822	144,131	137,213
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions/impairments/placed into redevelopment	(182,526)	(16,783)	(117,589)
Retirements	(33,053)	(39,437)	(47,514)
Balance at the end of the year	896,561	973,318	885,407
Per consolidated balance sheet	$ 896,561	$ 973,318	$ 885,407
Leashold Interest Land
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Lease agreement term	99 years
Maximum
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Useful life	55 years