Brandywine Operating Partnership 10-K 2 Mar 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity Registrant Name	Brandywine Realty Trust
Entity Central Index Key	0000790816
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
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
Entity Shell Company	false
Entity Public Float			$ 2,466,793,544
Entity Common Stock, Shares Outstanding		176,602,359
Documents Incorporated by Reference	Portions of the proxy statement for the 2020 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
Entity Shell Company	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Real estate investments:
Operating properties	$ 4,006,459	$ 3,951,719
Accumulated depreciation	(973,318)	(885,407)
Right of use asset - operating leases, net	21,656	0
Operating real estate investments, net	3,054,797	3,066,312
Construction-in-progress	180,718	150,263
Land held for development	96,124	86,401
Prepaid leasehold interests in land held for development, net	39,592	39,999
Total real estate investments, net	3,371,231	3,342,975
Assets held for sale, net	7,349	11,599
Cash and cash equivalents	90,499	22,842
Accounts receivable, net of allowance of $284 and $1,653 as of December 31, 2019 and December 31, 2018, respectively	16,363	16,394
Accrued rent receivable, net of allowance of $7,691 and $11,266 as of December 31, 2019 and December 31, 2018, respectively	174,144	165,243
Investment in Real Estate Ventures, equity method	120,294	169,100
Deferred costs, net	95,560	91,075
Intangible assets, net	84,851	131,348
Other assets	115,678	126,400
Total assets	4,075,969	4,076,976
LIABILITIES AND EQUITY
Mortgage notes payable, net	313,812	320,869
Unsecured credit facility	0	92,500
Unsecured term loan, net	248,561	248,042
Unsecured senior notes, net	1,582,045	1,366,635
Accounts payable and accrued expenses	113,347	125,696
Distributions payable	33,815	33,632
Deferred income, gains and rent	35,284	28,293
Intangible liabilities, net	22,263	31,783
Lease Liability - operating leases	22,554	0
Other liabilities	15,985	18,498
Total liabilities	2,387,666	2,265,948
Commitments and contingencies (See Note 19)
Equity:
Common Shares of Brandywine Realty Trust's beneficial interest, $0.01 par value; shares authorized 400,000,000; 176,480,095 and 176,873,324 issued and outstanding as of December 31, 2019 and December 31, 2018, respectively	1,766	1,770
Additional paid-in-capital	3,192,158	3,200,312
Deferred compensation payable in common shares	16,216	14,021
Common shares in grantor trust, 1,105,542 and 977,120 issued and outstanding as of December 31, 2019 and December 31, 2018, respectively	(16,216)	(14,021)
Cumulative earnings	804,556	775,625
Accumulated other comprehensive income	(2,370)	5,029
Total Brandywine Operating Partnership, L.P.'s equity		1,796,316
Cumulative distributions	(2,318,233)	(2,183,909)
Total Brandywine Realty Trust's equity	1,677,877	1,798,827
Noncontrolling interests	10,426	12,201
Total beneficiaries' equity	1,688,303	1,811,028
Total partners' equity		1,798,508
Total liabilities and partners' equity	4,075,969	4,076,976
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Real estate investments:
Operating properties	4,006,459	3,951,719
Accumulated depreciation	(973,318)	(885,407)
Right of use asset - operating leases, net	21,656	0
Operating real estate investments, net	3,054,797	3,066,312
Construction-in-progress	180,718	150,263
Land held for development	96,124	86,401
Prepaid leasehold interests in land held for development, net	39,592	39,999
Total real estate investments, net	3,371,231	3,342,975
Assets held for sale, net	7,349	11,599
Cash and cash equivalents	90,499	22,842
Accounts receivable, net of allowance of $284 and $1,653 as of December 31, 2019 and December 31, 2018, respectively	16,363	16,394
Accrued rent receivable, net of allowance of $7,691 and $11,266 as of December 31, 2019 and December 31, 2018, respectively	174,144	165,243
Investment in Real Estate Ventures, equity method	120,294	169,100
Deferred costs, net	95,560	91,075
Intangible assets, net	84,851	131,348
Other assets	115,678	126,400
Total assets	4,075,969	4,076,976
LIABILITIES AND EQUITY
Mortgage notes payable, net	313,812	320,869
Unsecured credit facility	0	92,500
Unsecured term loan, net	248,561	248,042
Unsecured senior notes, net	1,582,045	1,366,635
Accounts payable and accrued expenses	113,347	125,696
Distributions payable	33,815	33,632
Deferred income, gains and rent	35,284	28,293
Intangible liabilities, net	22,263	31,783
Lease Liability - operating leases	22,554	0
Other liabilities	15,985	18,498
Total liabilities	2,387,666	2,265,948
Commitments and contingencies (See Note 19)
Redeemable limited partnership units at redemption value; 981,634 and 982,871 issued and outstanding as of December 31, 2019 and December 31, 2018, respectively	15,388	12,520
Equity:
General Partnership Capital; 176,480,095 and 176,873,324 units issued and outstanding as of December 31, 2019 and December 31, 2018, respectively	1,674,539	1,791,591
Accumulated other comprehensive income	(2,715)	4,725
Total Brandywine Operating Partnership, L.P.'s equity	1,671,824	1,796,316
Noncontrolling interest - consolidated real estate ventures	1,091	2,192
Total partners' equity	1,672,915	1,798,508
Total liabilities and partners' equity	$ 4,075,969	$ 4,076,976

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable, allowance	$ 284	$ 1,653
Accrued rent receivable, allowance	$ 7,691	$ 11,266
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)	176,480,095	176,873,324
Common Stock, Shares, Outstanding (in shares)	176,480,095	176,873,324
Common Shares in Grantor Trust, Issued and Outstanding (in shares)	1,105,542	977,120
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Accounts receivable, allowance	$ 284	$ 1,653
Accrued rent receivable, allowance	$ 7,691	$ 11,266
Temporary Equity, Shares Issued	981,634	982,871
Redeemable Limited Partnership Units Issued and Outstanding (in units)	981,634	982,871
General Partners' Capital Account, Units Issued (in units)	176,480,095	176,873,324
General Partners' Capital Account, Units Issued and Outstanding (in units)	176,480,095	176,873,324

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue
Total revenue	$ 580,417	$ 544,345	$ 520,493
Operating expenses:
Property operating expenses	154,361	154,848	150,911
Real estate taxes	62,237	51,341	45,204
Third party management expenses	9,248	11,910	9,960
Depreciation and amortization	210,005	176,000	180,323
General and administrative expenses	32,156	27,802	28,538
Provision for impairment	0	71,707	3,057
Total operating expenses	468,007	493,608	417,993
Gain on sale of real estate
Net gain on disposition of real estate	356	2,932	32,017
Net gain on sale of undepreciated real estate	2,020	3,040	953
Total gain on sale of real estate	2,376	5,972	32,970
Operating income	114,786	56,709	135,470
Other income (expense):
Interest income	2,318	4,703	1,113
Interest expense	(81,512)	(78,199)	(81,886)
Interest expense - amortization of deferred financing costs	(2,768)	(2,498)	(2,435)
Equity in loss of Real Estate Ventures	(9,922)	(15,231)	(8,306)
Net gain on real estate venture transactions	11,639	142,233	80,526
Gain on promoted interest in unconsolidated real estate venture	0	28,283	0
Loss on early extinguishment of debt	0	(105)	(3,933)
Net income before income taxes	34,541	135,895	120,549
Income tax (provision) benefit	(12)	(423)	628
Net income	34,529	135,472	121,177
Net income attributable to noncontrolling interests	(262)	(954)	(1,004)
Net income attributable to Brandywine Realty Trust	34,267	134,518	120,173
Distribution to preferred shareholders	0	0	(2,032)
Preferred share redemption charge	0	0	(3,181)
Nonforfeitable dividends allocated to unvested restricted shareholders	(396)	(369)	(327)
Net income attributable to Common Shareholders/ Unitholders of Brandywine Realty Trust	$ 33,871	$ 134,149	$ 114,633
Basic income per Common Share (in dollars per share)	$ 0.19	$ 0.75	$ 0.65
Diluted income per Common Share (in dollars per share)	$ 0.19	$ 0.75	$ 0.65
Basic weighted average shares outstanding (in shares)	176,132,941	178,519,748	175,484,350
Diluted weighted average shares outstanding (in shares)	176,686,813	179,641,492	176,808,166
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Total revenue	$ 580,417	$ 544,345	$ 520,493
Operating expenses:
Property operating expenses	154,361	154,848	150,911
Real estate taxes	62,237	51,341	45,204
Third party management expenses	9,248	11,910	9,960
Depreciation and amortization	210,005	176,000	180,323
General and administrative expenses	32,156	27,802	28,538
Provision for impairment	0	71,707	3,057
Total operating expenses	468,007	493,608	417,993
Gain on sale of real estate
Net gain on disposition of real estate	356	2,932	32,017
Net gain on sale of undepreciated real estate	2,020	3,040	953
Total gain on sale of real estate	2,376	5,972	32,970
Operating income	114,786	56,709	135,470
Other income (expense):
Interest income	2,318	4,703	1,113
Interest expense	(81,512)	(78,199)	(81,886)
Interest expense - amortization of deferred financing costs	(2,768)	(2,498)	(2,435)
Equity in loss of Real Estate Ventures	(9,922)	(15,231)	(8,306)
Net gain on real estate venture transactions	11,639	142,233	80,526
Gain on promoted interest in unconsolidated real estate venture	0	28,283	0
Loss on early extinguishment of debt	0	(105)	(3,933)
Net income before income taxes	34,541	135,895	120,549
Income tax (provision) benefit	(12)	(423)	628
Net income	34,529	135,472	121,177
Net income attributable to noncontrolling interests - consolidated real estate ventures	(69)	(55)	(29)
Distribution to preferred shareholders	0	0	(2,032)
Preferred share redemption charge	0	0	(3,181)
Nonforfeitable dividends allocated to unvested restricted shareholders	(396)	(369)	(327)
Net income attributable to Common Shareholders/ Unitholders of Brandywine Realty Trust	34,064	135,048	115,608
Net income attributable to Brandywine Operating Partnership	34,460	135,417	121,148
Distribution to preferred unitholders	0	0	(2,032)
Preferred unit redemption charge	0	0	(3,181)
Nonforfeitable dividends allocated to unvested restricted unitholders	$ (396)	$ (369)	$ (327)
Basic income per Common Share (in dollars per share)	$ 0.19	$ 0.75	$ 0.65
Diluted income per Common Share (in dollars per share)	$ 0.19	$ 0.75	$ 0.65
Basic weighted average shares outstanding (in shares)	177,114,932	179,959,370	176,964,149
Diluted weighted average shares outstanding (in shares)	177,668,804	181,081,114	178,287,965
Rents
Revenue
Rents	$ 554,665	$ 515,044	$ 487,323
Total revenue	554,665
Rents | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Rents	554,665	515,044	487,323
Third party management fees, labor reimbursement and leasing
Revenue
Service and other revenue	19,626	22,557	28,345
Third party management fees, labor reimbursement and leasing | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Service and other revenue	19,626	22,557	28,345
Other
Revenue
Service and other revenue	6,126	6,744	4,825
Other | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Revenue
Service and other revenue	$ 6,126	$ 6,744	$ 4,825

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income		$ 34,529	$ 135,472	$ 121,177
Comprehensive income (loss):
Unrealized gain (loss) on derivative financial instruments		(8,210)	1,478	2,948
Amortization of interest rate contracts	[1]	770	1,191	1,230
Total comprehensive income (loss)		(7,440)	2,669	4,178
Comprehensive income		27,089	138,141	125,355
Comprehensive income attributable to noncontrolling interest		(221)	(993)	(1,036)
Comprehensive income attributable to Brandywine Realty Trust/Brandywine Operating Partnership		26,868	137,148	124,319
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Net income		34,529	135,472	121,177
Comprehensive income (loss):
Unrealized gain (loss) on derivative financial instruments		(8,210)	1,478	2,948
Amortization of interest rate contracts	[1]	770	1,191	1,230
Total comprehensive income (loss)		(7,440)	2,669	4,178
Comprehensive income		27,089	138,141	125,355
Comprehensive income attributable to noncontrolling interest		(69)	(55)	(29)
Comprehensive income attributable to Brandywine Realty Trust/Brandywine Operating Partnership		$ 27,020	$ 138,086	$ 125,326
[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	Preferred Stock	Common Stock	Deferred Compensation Payable in Common Shares	Additional Paid-in Capital	Common Shares in Grantor Trust	Cumulative Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Distributions	Noncontrolling Interests
Beneficiaries' Equity, Beginning Balance at Dec. 31, 2016	$ 1,864,388	$ 40	$ 1,752	$ 13,684	$ 3,258,386	$ (13,684)	$ 520,914	$ (1,745)	$ (1,931,892)	$ 16,933
Beginning Balance (in shares) at Dec. 31, 2016		4,000,000	175,140,760	899,457
Net income	121,177						120,173			1,004
Other comprehensive income	4,178							4,144		34
Issuance of Common Shares of Beneficial Interest	51,225		$ 29		51,196
Issuance of Common Shares of Beneficial Interest (in shares)			2,858,991
Redemption of Preferred Shares	(96,850)	$ (40)			(96,810)
Redemption of Preferred Shares (in shares)		(4,000,000)
Issuance of partnership interest in consolidated real estate venture	85									85
Distributions from consolidated real estate venture	(48)									(48)
Equity issuance costs	(499)				(499)
Bonus share issuance	110				110
Bonus share issuance (in shares)			6,752
Share Choice Plan Issuance (in shares)			(1,423)
Preferred Share distributions	(2,032)								(2,032)
Preferred Share redemption charges	$ (3,181)								(3,181)
Repurchase and retirement of Common Shares of Beneficial Interest (in shares)	0
Share-based compensation activity	$ 6,698		$ 3		6,689		6
Share-based compensation activity (in shares)			333,127	39,870
Share Issuance from/(to) Deferred Compensation Plan	(768)			$ (1,239)	(768)	1,239
Share Issuance from/(to) Deferred Compensation Plan (in shares)			(52,971)	(44,591)
Reallocation of Noncontrolling Interest					(227)					227
Distributions declared	(117,613)								(116,636)	(977)
Beneficiaries' Equity, Ending Balance at Dec. 31, 2017	1,826,870	$ 0	$ 1,784	$ 12,445	3,218,077	(12,445)	641,093	2,399	(2,053,741)	17,258
Ending Balance (in shares) at Dec. 31, 2017		0	178,285,236	894,736
Net income	135,472						134,518			954
Other comprehensive income	2,669							2,630		39
Issuance of Common Shares of Beneficial Interest	416				416
Issuance of Common Shares of Beneficial Interest (in shares)			23,311
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)
Preferred Share distributions	0
Repurchase and retirement of Common Shares of Beneficial Interest	$ (21,858)		$ (17)		(21,841)
Repurchase and retirement of Common Shares of Beneficial Interest (in shares)	(1,729,278)		(1,729,278)
Redemption of LP Units	$ (7,043)									(7,043)
Share-based compensation activity	5,845		$ 2		5,829		14
Share-based compensation activity (in shares)			196,151
Share Issuance from/(to) Deferred Compensation Plan	(111)		$ 1	$ 1,576	(112)	(1,576)
Share Issuance from/(to) Deferred Compensation Plan (in shares)			99,189	82,384
Reallocation of Noncontrolling Interest	0				(2,057)					2,057
Distributions declared	(131,154)								(130,168)	(986)
Beneficiaries' Equity, Ending Balance at Dec. 31, 2018	1,811,028	$ 0	$ 1,770	$ 14,021	3,200,312	(14,021)	775,625	5,029	(2,183,909)	12,201
Ending Balance (in shares) at Dec. 31, 2018		0	176,873,324	977,120
Net income	34,529						34,267			262
Other comprehensive income	(7,440)							(7,399)		(41)
Issuance of partnership interest in consolidated real estate venture	27									27
Preferred Share distributions	0
Repurchase and retirement of Common Shares of Beneficial Interest	$ (17,281)		$ (13)		(17,268)
Repurchase and retirement of Common Shares of Beneficial Interest (in shares)	(1,337,169)		(1,337,169)
Purchase of partnership interest in consolidated real estate venture	$ (2,180)				(983)					(1,197)
Redemption of LP Units					16					(16)
Redemption of LP Units (in shares)			1,245
Share-based compensation activity	10,027		$ 9		10,018
Share-based compensation activity (in shares)			845,210	41,342
Share Issuance from/(to) Deferred Compensation Plan				$ 2,195		(2,195)
Share Issuance from/(to) Deferred Compensation Plan (in shares)			97,485	87,080
Reallocation of Noncontrolling Interest					63					(63)
Distributions declared	(135,071)								(134,324)	(747)
Beneficiaries' Equity, Ending Balance at Dec. 31, 2019	$ 1,688,303	$ 0	$ 1,766	$ 16,216	$ 3,192,158	$ (16,216)	$ 804,556	$ (2,370)	$ (2,318,233)	$ 10,426
Ending Balance (in shares) at Dec. 31, 2019		0	176,480,095	1,105,542

Consolidated Statements of Be_2

Consolidated Statements of Beneficiaries' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Distributions declared per Common Share (in dollars per share)	$ 0.76	$ 0.73	$ 0.66

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.Series E-Linked Preferred Mirror Units	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
Partners' Equity, Beginning Balance at Dec. 31, 2016				$ 1,840,593	$ 96,850	$ (2,122)	$ 2,150	$ 1,743,715
Beginning Balance (in shares) at Dec. 31, 2016					4,000,000			175,140,760
Net income	$ 121,177		$ 1,004	121,177			29	$ 121,148
Other comprehensive income	4,178	$ 4,144	34	4,178		4,178
Redemption of Preferred Mirror Units				(96,850)	$ (96,850)
Redemption of Preferred Mirror Units (in shares)					(4,000,000)
Deferred compensation obligation	(768)			(768)				$ (768)
Deferred compensation obligation (in shares)								52,971
Issuance of LP Units				50,726				$ 50,726
Issuance of LP Units (in shares)								2,858,991
Issuance of partnership interest in consolidated real estate venture	85		85	85			85
Distributions from consolidated real estate venture	(48)		(48)	(48)			(48)
Share Choice Plan Issuance (in shares)								(1,423)
Bonus share issuance	110			110				$ 110
Bonus share issuance (in shares)								6,752
Share-based compensation activity	6,698			6,697				$ 6,697
Share-based compensation activity (in shares)								333,127
Adjustment of redeemable partnership units to liquidation value at period end				(4,096)			(1)	$ (4,095)
Preferred Share distributions	(2,032)			(2,032)				(2,032)
Preferred share redemption charge	(3,181)			(3,181)				(3,181)
Distributions declared to general partnership unitholders				(116,636)				(116,636)
Partners' Equity, Ending Balance at Dec. 31, 2017				1,799,955	$ 0	2,056	2,215	$ 1,795,684
Ending Balance (in shares) at Dec. 31, 2017					0			178,285,236
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	(111)			(111)				$ (111)
Deferred compensation obligation (in shares)								(99,189)
Issuance of LP Units				416				$ 416
Issuance of LP Units (in shares)								23,311
Repurchase and retirement of LP units				(21,858)				$ (21,858)
Repurchase and retirement of LP units (in shares)								(1,729,278)
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	5,845			5,848				$ 5,848
Share-based compensation activity (in shares)								196,151
Redemption value of limited partnership units				6,363				$ 6,363
Preferred Share distributions	0			0
Preferred share redemption charge	0			0
Distributions declared to general partnership unitholders				(130,168)				(130,168)
Partners' Equity, Ending Balance at Dec. 31, 2018	1,798,508			1,798,508	$ 0	4,725	2,192	$ 1,791,591
Ending Balance (in shares) at Dec. 31, 2018					0			176,873,324
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
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				(17,297)				$ (17,297)
Repurchase and retirement of LP units (in shares)								(1,337,169)
Issuance of partnership interest in consolidated real estate venture	27		27	27			27
Share-based compensation activity	10,027			10,027				$ 10,027
Share-based compensation activity (in shares)								845,210
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)
Preferred Share distributions	0			0
Preferred share redemption charge	$ 0			0
Distributions declared to general partnership unitholders				(134,324)				(134,324)
Partners' Equity, Ending Balance at Dec. 31, 2019				$ 1,672,915	$ 0	$ (2,715)	$ 1,091	$ 1,674,539
Ending Balance (in shares) at Dec. 31, 2019					0			176,480,095

Consolidated Statements of Pa_2

Consolidated Statements of Partners' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
BRANDYWINE OPERATING PARTNERSHIP, L.P. | General Partner Capital
Distributions to general partnership unitholders (USD per share)	$ 0.76	$ 0.73	$ 0.66

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Cash flows from operating activities:
Net income	$ 34,529	$ 135,472	$ 121,177
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	210,005	176,000	180,323
Amortization of deferred financing costs	2,768	2,498	2,435
Amortization of debt discount/(premium), net	189	702	1,569
Amortization of stock compensation costs	6,876	5,716	4,883
Straight-line rent income	(11,369)	(12,283)	(27,115)
Amortization of acquired above (below) market leases, net	(8,857)	(3,344)	(3,071)
Ground rent expense	1,470	431	164
Provision for doubtful accounts	(1,345)	1,775	2,207
Net gain on real estate venture transactions	(11,639)	(142,233)	(80,526)
Gain on promoted interest in unconsolidated real estate venture	0	(28,283)	0
Net gain on sale of interests in real estate	(2,376)	(5,972)	(32,970)
Loss on early extinguishment of debt	0	105	3,933
Provision for impairment	0	71,707	3,057
Other than temporary impairment	0	4,076	4,844
Income from Real Estate Ventures, net of distributions	10,242	12,871	3,462
Income tax provision (benefit)	12	423	(628)
Income tax provision (benefit)
Accounts receivable	(248)	3,524	(6,266)
Other assets	9,368	(14,334)	1,752
Accounts payable and accrued expenses	(5,599)	12,579	4,004
Deferred income, gains and rent	9,319	3,017	(1,482)
Other liabilities	(9,115)	2,902	829
Net cash provided by operating activities	234,230	227,349	182,581
Cash flows from investing activities:
Acquisition of properties	0	(196,625)	(72,523)
Acquisition of partners interest in consolidated real estate venture	(2,181)	0	0
Proceeds from the sale of properties	41,795	324,090	171,860
Proceeds from real estate venture sales	9,730	60,346	145,416
Issuance of mortgage note receivable	0	(175,172)	0
Proceeds from repayment of mortgage notes receivable	3,341	192	151
Proceeds from repayment of a capital lease	0	181	0
Capital expenditures for tenant improvements	(67,258)	(65,264)	(60,586)
Capital expenditures for redevelopments	(53,846)	(48,231)	(34,679)
Capital expenditures for developments	(77,192)	(99,104)	(66,915)
Advances for the purchase of tenant assets, net of repayments	(1,035)	410	18
Investment in unconsolidated Real Estate Ventures	(253)	(908)	(6,638)
Deposits for real estate	(4,181)	(8,234)	573
Escrowed cash	0	5,694	0
Capital distributions from Real Estate Ventures	35,906	6,526	20,781
Leasing costs paid	(15,485)	(18,407)	(17,657)
Net cash provided by (used in) investing activities	(130,659)	(214,506)	79,801
Cash flows from financing activities:
Repayments of mortgage notes payable	(7,595)	(122,180)	(4,931)
Proceeds from credit facility borrowings	348,500	455,500	341,000
Repayments of credit facility borrowings	(441,000)	(363,000)	(341,000)
Proceeds from unsecured notes	216,373	0	550,131
Repayments of unsecured notes	0	0	(628,590)
Debt financing costs paid	(1,965)	(3,430)	(4,727)
Redemption of preferred shares	0	0	(100,000)
Proceeds from the exercise of stock options	3,771	0	1,229
Proceeds from the issuance of common shares	0	416	51,225
Shares used for employee taxes upon vesting of share awards	(1,554)	(1,494)	(674)
Partner contributions to consolidated real estate venture	27	16	85
Partner distributions from consolidated real estate venture	0	(94)	(48)
Repurchase and retirement of common shares	(17,282)	(21,841)	0
Redemption of limited partnership units	0	(7,043)	0
Distributions paid to shareholders	(134,140)	(128,859)	(116,311)
Distributions to noncontrolling interest	(747)	(1,065)	(947)
Net cash used in financing activities	(35,612)	(193,074)	(253,558)
Increase/(Decrease) in cash and cash equivalents and restricted cash	67,959	(180,231)	8,824
Cash and cash equivalents, beginning of period	22,842	202,179	193,919
Restricted cash, beginning of period	369	1,263	699
Cash and cash equivalents and restricted cash at beginning of year	23,211	203,442	194,618
Cash and cash equivalents, end of period	90,499	22,842	202,179
Restricted cash, end of period	671	369	1,263
Cash and cash equivalents and restricted cash at end of period	91,170	23,211	203,442
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the years ended December 31, 2019, 2018 and 2017 of $2,246, $3,586, and $3,527, respectively	66,508	76,858	83,139
Cash paid for income taxes	1,385	405	225
Supplemental disclosure of non-cash activity:
Dividends and distributions declared but not paid	33,815	33,632	32,456
Change in construction-in-progress related to non-cash disposition of land	0	27,231	0
Change in deferred income, gains and rent to the non-cash disposition of land	0	(29,780)	0
Change in investment in real estate ventures as a result of dispositions	1,806	14,169	(64,792)
Change in Notes receivable as a result of a noncash acquisition of an operating property	0	130,742	0
Change in real estate ventures as a result of other than temporary impairment	0	(4,076)	(4,844)
Change in operating real estate related to a non-cash acquisition of an operating property	0	(20,653)	0
Change in intangible assets, net related to non-cash acquisition of an operating property	0	(3,144)	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	0	182	0
Change in investments in joint venture related to non-cash acquisition of property	0	(16,832)	0
Change in mortgage notes payable related to acquisition of an operating property	0	9,940	0
Change in capital expenditures financed through accounts payable at period end	(10,618)	8,784	(6,593)
Change in capital expenditures financed through retention payable at period end	(946)	(2,912)	(159)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Cash flows from operating activities:
Net income	34,529	135,472	121,177
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	210,005	176,000	180,323
Amortization of deferred financing costs	2,768	2,498	2,435
Amortization of debt discount/(premium), net	189	702	1,569
Amortization of stock compensation costs	6,876	5,716	4,883
Straight-line rent income	(11,369)	(12,283)	(27,115)
Amortization of acquired above (below) market leases, net	(8,857)	(3,344)	(3,071)
Ground rent expense	1,470	431	164
Provision for doubtful accounts	(1,345)	1,775	2,207
Net gain on real estate venture transactions	(11,639)	(142,233)	(80,526)
Gain on promoted interest in unconsolidated real estate venture	0	(28,283)	0
Net gain on sale of interests in real estate	(2,376)	(5,972)	(32,970)
Loss on early extinguishment of debt	0	105	3,933
Provision for impairment	0	71,707	3,057
Other than temporary impairment	0	4,076	4,844
Income from Real Estate Ventures, net of distributions	10,242	12,871	3,462
Income tax provision (benefit)	12	423	(628)
Income tax provision (benefit)
Accounts receivable	(248)	3,524	(6,266)
Other assets	9,368	(14,334)	1,752
Accounts payable and accrued expenses	(5,599)	12,579	4,004
Deferred income, gains and rent	9,319	3,017	(1,482)
Other liabilities	(9,115)	2,902	829
Net cash provided by operating activities	234,230	227,349	182,581
Cash flows from investing activities:
Acquisition of properties	0	(196,625)	(72,523)
Acquisition of partners interest in consolidated real estate venture	(2,181)	0	0
Proceeds from the sale of properties	41,795	324,090	171,860
Proceeds from real estate venture sales	9,730	60,346	145,416
Issuance of mortgage note receivable	0	(175,172)	0
Proceeds from repayment of mortgage notes receivable	3,341	192	151
Proceeds from repayment of a capital lease	0	181	0
Capital expenditures for tenant improvements	(67,258)	(65,264)	(60,586)
Capital expenditures for redevelopments	(53,846)	(48,231)	(34,679)
Capital expenditures for developments	(77,192)	(99,104)	(66,915)
Advances for the purchase of tenant assets, net of repayments	(1,035)	410	18
Investment in unconsolidated Real Estate Ventures	(253)	(908)	(6,638)
Deposits for real estate	(4,181)	(8,234)	573
Escrowed cash	0	5,694	0
Capital distributions from Real Estate Ventures	35,906	6,526	20,781
Leasing costs paid	(15,485)	(18,407)	(17,657)
Net cash provided by (used in) investing activities	(130,659)	(214,506)	79,801
Cash flows from financing activities:
Repayments of mortgage notes payable	(7,595)	(122,180)	(4,931)
Proceeds from credit facility borrowings	348,500	455,500	341,000
Repayments of credit facility borrowings	(441,000)	(363,000)	(341,000)
Proceeds from unsecured notes	216,373	0	550,131
Repayments of unsecured notes	0	0	(628,590)
Debt financing costs paid	(1,965)	(3,430)	(4,727)
Redemption of preferred shares	0	0	(100,000)
Proceeds from the exercise of stock options	3,771	0	1,229
Proceeds from the issuance of common shares	0	416	51,225
Shares used for employee taxes upon vesting of share awards	(1,554)	(1,494)	(674)
Partner contributions to consolidated real estate venture	27	16	85
Partner distributions from consolidated real estate venture	0	(94)	(48)
Repurchase and retirement of common shares	(17,282)	(21,841)	0
Redemption of limited partnership units	0	(7,043)	0
Distributions paid to shareholders	(134,887)	(129,924)	(117,258)
Net cash used in financing activities	(35,612)	(193,074)	(253,558)
Increase/(Decrease) in cash and cash equivalents and restricted cash	67,959	(180,231)	8,824
Cash and cash equivalents, beginning of period	22,842	202,179	193,919
Restricted cash, beginning of period	369	1,263	699
Cash and cash equivalents and restricted cash at beginning of year	23,211	203,442	194,618
Cash and cash equivalents, end of period	90,499	22,842	202,179
Restricted cash, end of period	671	369	1,263
Cash and cash equivalents and restricted cash at end of period	91,170	23,211	203,442
Supplemental disclosure:
Cash paid for interest, net of capitalized interest during the years ended December 31, 2019, 2018 and 2017 of $2,246, $3,586, and $3,527, respectively	66,508	76,858	83,139
Cash paid for income taxes	1,385	405	225
Supplemental disclosure of non-cash activity:
Dividends and distributions declared but not paid	33,815	33,632	32,456
Change in construction-in-progress related to non-cash disposition of land	0	27,231	0
Change in deferred income, gains and rent to the non-cash disposition of land	0	(29,780)	0
Change in investment in real estate ventures as a result of dispositions	1,806	14,169	(64,792)
Change in Notes receivable as a result of a noncash acquisition of an operating property	0	130,742	0
Change in real estate ventures as a result of other than temporary impairment	0	(4,076)	(4,844)
Change in intangible assets, net related to non-cash acquisition of an operating property	0	(3,144)	0
Change in acquired lease intangibles, net related to non-cash acquisition of an operating property	0	182	0
Change in investments in joint venture related to non-cash acquisition of property	0	(16,832)	0
Change in mortgage notes payable related to acquisition of an operating property	0	9,940	0
Change in capital expenditures financed through accounts payable at period end	(10,618)	8,784	(6,593)
Change in capital expenditures financed through retention payable at period end	(946)	(2,912)	(159)
Change in operating real estate related to a non-cash acquisition of an operating property	$ 0	$ (20,653)	$ 0

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Capitalized interest	$ 2,246	$ 3,586	$ 3,527
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Capitalized interest	$ 2,246	$ 3,586	$ 3,527

ORGANIZATION OF THE PARENT COMP

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP	12 Months Ended
	Dec. 31, 2019
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, 2019 , 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, 2019 , the Company owned 95 properties that contained an aggregate of approximately 16.7 million net rentable square feet (collectively, the “Properties”). The Company’s core portfolio of operating properties, as of December 31, 2019 , excludes one development property and four redevelopment properties under construction or committed for construction (collectively, the “Core Properties”). The Properties were comprised of the following as of December 31, 2019 : Number of Properties Rentable Square Feet Office properties 86 15,450,417 Mixed-use properties 4 659,625 Core Properties 90 16,110,042 Development property 1 204,108 Redevelopment properties 4 397,237 The Properties 95 16,711,387 In addition to the Properties, as of December 31, 2019 , the Company owned land held for development comprised of 234.7 acres of undeveloped land, 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, 2019 , the total potential development that these land parcels 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 the 35.2 acres held for sale. As of December 31, 2019 , the Company also owned economic interests in seven 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 six 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”) and Brandywine Brokerage Services, LLC (“BBS”). BRSCO, BMI and BPI are each a taxable REIT subsidiary. BBS, BBL, and BPM are tax disregarded entities wholly owned by the taxable REIT subsidiary entities. As of December 31, 2019 , the Operating Partnership owned, directly and indirectly, 100% of each of BRSCO, BMI, BPI, BBL, BPM and BBS. As of December 31, 2019 , the Management Company subsidiaries were managing properties containing an aggregate of approximately 24.3 million net rentable square feet, of which approximately 16.7 million net rentable square feet related to Properties owned by the Company and approximately 7.6 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, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Revision of Previously Issued Financial Statements The Company’s comparative 2017 and 2018 results have been adjusted to correct for the effects of errors discovered during the second quarter of 2019 relating to the purchase price allocation and depreciable lives for two acquisitions made in a prior period. The Company has evaluated the impact of the errors to the previously issued financial statements and concluded that the errors were immaterial to the previously issued financial statements; however, to correct the cumulative effect of the errors in 2019 would significantly impact the 2019 financial statements. Accordingly, the previously issued financial statements have been corrected. The corrections to the balance sheets include a reduction in cumulative earnings and operating properties and an increase to accumulated depreciation. The corrections to the prior period income statements result in an increase in depreciation and amortization and property operating expenses in each period, and an increase in net gain on disposition of real estate for the for the twelve months ended December 31, 2017. In addition, the impact of an immaterial out of period depreciation adjustment, which was previously disclosed in the Company’s Quarterly Report on Form 10-Q for the three months ended March 31, 2019, has been reflected in the correct period. The following tables and paragraphs present line items of the previously issued financial statements that have been corrected as a result of the revision: Balance sheet impacts (in thousands) : December 31, 2018 Balance Sheet: As previously reported Adjustments As adjusted Assets (Parent Company and Operating Partnership) Operating properties 3,953,319 (1,600 ) 3,951,719 Accumulated depreciation (865,462 ) (19,945 ) (885,407 ) Operating real estate investments, net 3,087,857 (21,545 ) 3,066,312 Total assets 4,098,521 (21,545 ) 4,076,976 Equity (Parent Company) Additional Paid-in Capital 3,200,850 (538 ) 3,200,312 Cumulative Earnings 796,513 (20,888 ) 775,625 Total Brandywine Realty Trust's equity 1,820,253 (21,426 ) 1,798,827 Noncontrolling interests 12,320 (119 ) 12,201 Total beneficiaries' equity 1,832,573 (21,545 ) 1,811,028 Total liabilities and beneficiaries' equity 4,098,521 (21,545 ) 4,076,976 Equity (Operating Partnership) General Partnership Capital 1,813,136 (21,545 ) 1,791,591 Total Brandywine Operating Partnership, L.P.'s equity 1,817,861 (21,545 ) 1,796,316 Total partners' equity 1,820,053 (21,545 ) 1,798,508 Total liabilities and partners' equity 4,098,521 (21,545 ) 4,076,976 Statement of Beneficiaries’ / Partners’ Equity impacts (in thousands): Twelve months ended December 31, 2018 Brandywine Realty Trust As previously reported Adjustments As adjusted Statement of Beneficiaries' Equity: Additional paid-in capital, beginning of period 3,218,564 (487 ) 3,218,077 Cumulative earnings, beginning of period 660,174 (19,081 ) 641,093 Noncontrolling interest, beginning of period 17,420 (162 ) 17,258 Additional paid-in capital, December 31, 2018 3,200,850 (538 ) 3,200,312 Cumulative earnings, December 31, 2018 796,513 (20,888 ) 775,625 Noncontrolling interests, December 31, 2018 12,320 (119 ) 12,201 Brandywine Operating Partnership Statement of Partners' Equity: Partner Capital, beginning of period 1,815,411 (19,727 ) 1,795,684 Partner Capital, December 31, 2018 1,813,136 (21,545 ) 1,791,591 Twelve months ended December 31, 2017 Brandywine Realty Trust As previously reported Adjustments As adjusted Statement of Beneficiaries' Equity: Additional paid-in capital, beginning of period 3,258,870 (484 ) 3,258,386 Cumulative earnings, beginning of period 539,319 (18,405 ) 520,914 Noncontrolling interest, beginning of period 17,093 (160 ) 16,933 Additional paid-in capital, December 31, 2017 3,218,564 (487 ) 3,218,077 Cumulative earnings, December 31, 2017 660,174 (19,081 ) 641,093 Noncontrolling interests, December 31, 2017 17,420 (162 ) 17,258 Brandywine Operating Partnership Statement of Partners' Equity: Partner Capital, beginning of period 1,762,764 (19,049 ) 1,743,715 Partner Capital, December 31, 2017 1,815,411 (19,727 ) 1,795,684 Statement of Operations impacts: Net income for the twelve months ended December 31, 2018 and 2017 has been reduced by $1.8 million and $0.7 million respectively, with a $0.01 decrease to basic and diluted income per common share and per common partnership unit for the twelve months ended December 31, 2018. There was a $0.01 decrease to basic income per common share and per common partnership unit for the twelve months ended December 31, 2017. There was no change to the previously reported diluted income per common share or per common partnership unit for the twelve months ended December 31, 2017. There were no impacts to cash flows from operating activities in any period. 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, 2019 and 2018 , the Company included in its consolidated balance sheets consolidated VIEs having total assets of $392.0 million and $414.3 million , respectively, and total liabilities of $255.6 million and $254.1 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 to twelve months. The Company also considers information obtained about each property as a result of its pre-acquisition due diligence, marketing, and leasing activities in estimating the fair value of the tangible and intangible assets acquired. The Company also uses the information obtained as a result of its pre-acquisition due diligence as part of its consideration of the accounting standard governing asset retirement obligations and when necessary, will record a conditional asset retirement obligation as part of its purchase price. The Company also evaluates tenant relationships on a tenant-specific basis. On most of the Company’s acquisitions, this intangible has not been material and, as a result, no value has been assigned. In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) are recorded to revenue. Depreciation and Amortization The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements ( 5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset ( 1 to 16 years) or (ii) the lease term). Construction-in-Progress Project costs directly associated with the development and construction of a real estate project are capitalized as construction-in-progress. Construction-in-progress also includes costs related to ongoing tenant improvement projects. In addition, interest, real estate taxes, and other expenses that are directly associated with the Company’s development activities are capitalized until the property is placed in service. 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” and “Lease liability - operating leases”, respectively, on the consolidated balance sheet as of December 31, 2019. 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 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. 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, 2019 and 2018, 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 ov

REAL ESTATE INVESTMENTS

REAL ESTATE INVESTMENTS	12 Months Ended
	Dec. 31, 2019
Real Estate [Abstract]
REAL ESTATE INVESTMENTS	3. REAL ESTATE INVESTMENTS As of December 31, 2019 and 2018 , the gross carrying value of the operating properties was as follows (in thousands): December 31, 2019 December 31, 2018 Land $ 489,702 $ 487,301 Building and improvements 3,049,395 3,048,889 Tenant improvements 467,362 415,529 Total $ 4,006,459 $ 3,951,719 Construction-in-Progress Internal direct construction costs totaling $7.4 million in 2019 , $7.0 million in 2018 , and $6.1 million in 2017 and interest totaling $3.2 million in 2019 , $3.6 million in 2018 , and $3.1 million in 2017 were capitalized related to the development of certain properties and land holdings. During the years ended December 31, 2019 , 2018 and 2017 , 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, 2019 2018 2017 Development $ 3,047 $ 3,185 $ 4,390 Redevelopment 775 968 319 Tenant Improvements 3,609 2,811 1,354 Total $ 7,431 $ 6,964 $ 6,063 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 2017 Acquisitions On October 13, 2017, the Company acquired, through a 99 -year prepaid ground lease, the leasehold interest in an office property containing 282,709 rentable square feet located at 3025 Market Street in Philadelphia, Pennsylvania, known as The Bulletin Building, for a gross purchase price of $35.0 million . The purchase price and acquisition-related costs have been allocated as follows (in thousands): October 13, 2017 Building and improvements $ 30,583 Construction-in-progress 672 Intangible assets acquired (a) 10,575 Below market lease liabilities assumed (b) (4,055 ) $ 37,775 (a) Weighted average amortization period of 7.9 years . (b) Weighted average amortization period of 7.0 years . The Bulletin Building contributed approximately $1.2 million of revenue and approximately $0.4 million of net loss in the Company’s consolidated statements of operations, for the period from October 13, 2017 through December 31, 2017. On July 28, 2017, the Company acquired an office building containing 58,587 rentable square feet located at 3000 Market Street, in Philadelphia, Pennsylvania, for $32.7 million . The purchase price and acquisition-related costs have been allocated as follows (in thousands): July 28, 2017 Building, land and improvements $ 32,004 Intangible assets acquired (a) 2,562 Below market lease liabilities assumed (b) (1,818 ) $ 32,748 (a) Weighted average amortization period of 5.9 years . (b) Weighted average amortization period of 6.0 years . 3000 Market Street contributed approximately $0.8 million of revenue and a $0.5 million of net loss in the Company’s consolidated statements of operations, for the period from July 28, 2017 through December 31, 2018. Dispositions The following table summarizes the properties sold during the years ended December 31, 2019, 2018 and 2017 (dollars in thousands): Property/Portfolio Name Disposition Date Location Property Type Rentable Square Feet/ Acres Sales Price Gain/(Loss) on Sale (a) 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 (b) December 21, 2018 Camden, NJ Mixed-use 83,000 45,300 2,570 Rockpoint Portfolio (c) 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 (d) 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 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) November 22, 2017 Newtown Square, PA Office 252,802 42,000 19,642 630 Allendale Road October 31, 2017 King of Prussia, PA Office 150,000 17,500 3,605 50 E. Swedesford Square September 13, 2017 Malvern, PA Land 12.0 acres 7,200 882 Bishop's Gate July 18, 2017 Mount Laurel, NJ Land 49.5 acres 6,000 71 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) (e) June 27, 2017 Marlton, NJ Office 134,794 9,700 (325 ) 7000 Midlantic Drive June 12, 2017 Mount Laurel, NJ Retail 10,784 8,200 1,413 Garza Ranch - Multi-family (d) April 28, 2017 Austin, TX Land 8.4 acres 11,800 1,311 200, 210 & 220 Lake Drive East (Woodland Falls) March 30, 2017 Cherry Hill, NJ Office 215,465 19,000 (249 ) Philadelphia Marine Center (Marine Piers) (f) March 15, 2017 Philadelphia, PA Mixed-use 181,900 21,400 6,498 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) (g) March 13, 2017 Beltsville, MD Office 313,810 9,000 — Gateway Land - Site C February 15, 2017 Richmond, VA Land 4.8 acres 1,100 — 1200 & 1220 Concord Avenue (Concord Airport Plaza) February 2, 2017 Concord, CA Office 350,256 33,100 551 Garza Ranch - Hotel (d) January 30, 2017 Austin, TX Land 1.7 acres 3,500 192 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) 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. (c) 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.” (d) The Company had continuing involvement in these properties through a completion guaranty, which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. 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 sales 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. (e) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million . The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25% , respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy. The loss on sale in the table above represents additional closing costs. (f) On the closing date, the buyer paid $12.0 million in cash and the Company received cash proceeds of $11.2 million , after closing costs and prorations. The $9.4 million balance of the purchase price was due on (a) January 31, 2020 , in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it was appropriate to recognize the sale of the sublease interest in the Marine Piers and to defer the remaining $9.4 million balance due under the purchase and sale agreement until collectability can be determined. During the first quarter of 2019, the tenant at the Marine Piers exercised its option to extend the term of its sublease. As a result, the $9.4 million balance of the purchase price is due on January 15, 2024, and the Company will recognize the additional gain on sale when the gain is realized or realizable. (g) During the twelve months ended 2017, there was a price reduction of $1.7 million under the agreement of sale and additional impairment of $1.7 million was recognized. 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. We 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, 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, 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 December 31, 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, 2018, the Company determined that the sale of three parcels of land (two within the Other segment and one with Pennsylvania Suburbs segment) totaling 37.9 acres was probable and classified these properties as held for sale. As such, $11.6 million was classified as “Assets held for sale, net” on the consolidated balance sheets. As of December 31, 2019 and 2018, 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, 2019
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES	4. INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES As of December 31, 2019 , the Company held ownership interests in seven unconsolidated real estate ventures for an aggregate investment balance of $120.3 million . 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, 2019 , three of the real estate ventures owned properties that contained an aggregate of approximately 5.4 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 its Real Estate Ventures of $4.3 million , $6.3 million and $6.4 million for the years ended December 31, 2019 , 2018 and 2017 , respectively. The Company earned leasing commission income from the Real Estate Ventures of $1.7 million , $2.5 million and $4.5 million for the years ended December 31, 2019 , 2018 and 2017 , respectively. The Company has outstanding accounts receivable balances from its Real Estate Ventures of $0.8 million for both the years ended December 31, 2019 and 2018 . 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 does not record operating losses of a real estate venture in excess of its investment balance unless the Company is liable for the obligations of the real estate venture or is otherwise committed to provide financial support to the real estate venture. The Company’s investment in Real Estate Ventures as of December 31, 2019 and 2018 , and the Company’s share of the Real Estate Ventures’ income (loss) for the years ended December 31, 2019 and 2018 was as follows (in thousands): Ownership Percentage (a) Carrying Amount Company's Share of Real Estate Venture Income (Loss) Real Estate Venture Debt at 100%, gross 2019 2018 2019 2018 2019 2018 Office Properties Brandywine - AI Venture LLC 50% $ 10,116 $ 11,731 $ (2,800 ) $ (14,559 ) $ — $ 26,111 Herndon Innovation Center Metro Portfolio Venture, LLC 15% 16,446 47,834 (498 ) 83 207,302 — MAP Venture 50% (70 ) 11,173 (6,102 ) (2,155 ) 185,000 185,000 PJP VII 25% (b) — 1,100 190 157 — 3,777 PJP II 30% (b) — 663 81 179 — 2,214 PJP VI 25% (b) — 125 (185 ) 71 — 7,069 Austin Venture 50% (c) — — — 1,687 — — Other 1919 Venture 50% 17,524 19,897 328 253 88,860 88,860 evo at Cira Centre South Venture 50% — — — (358 ) — — Development Properties 4040 Wilson Venture (d) 50% 37,002 37,371 (368 ) (192 ) 114,845 57,288 JBG - 51 N Street (d) 70% 21,531 21,368 (313 ) (137 ) — — JBG - 1250 First Street Office (d) 70% 17,745 17,838 (255 ) (260 ) — — $ 120,294 $ 169,100 $ (9,922 ) $ (15,231 ) $ 596,007 $ 370,319 (a) Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable. (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) The Company’s purchased its partner’s entire 50% interest in this venture on December 11, 2018. Refer to the "Austin Venture" section below for more information. (d) This entity is a VIE. The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2019 and December 31, 2018 (in thousands): December 31, 2019 MAP Venture Brandywine-AI Venture LLC Other Total Net property 192,582 24,651 617,134 $ 834,367 Other assets (a) 256,453 3,000 82,549 342,002 Other liabilities (a) 266,200 824 23,047 290,071 Debt, net (b) 181,525 — 403,543 585,068 Equity (c) 1,310 26,827 273,093 301,230 December 31, 2018 MAP Venture Brandywine-AI Venture LLC Other Total Net property 198,043 47,043 590,897 835,983 Other assets (a) 65,465 11,206 82,828 159,499 Other liabilities (a) 59,348 2,002 24,331 85,681 Debt, net (b) 180,555 26,020 159,132 365,707 Equity (c) 23,605 30,227 490,262 544,094 (a) The increase is primarily due to the recording of lease related assets and liabilities of $197.1 million and $206.4 million , respectively, for MAP Venture in connection with the adoption of Topic 842. (b) The increase is primarily due to third-party debt financing received by Herndon Innovation Center Venture during 2019. See “Herndon Innovation Center Metro Portfolio Venture” section below for further information. (c) 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, 2019 , 2018 and 2017 (in thousands): Year Ended December 31, 2019 MAP Venture Brandywine-AI Venture LLC Other Total Revenue $ 70,366 $ 6,022 $ 55,970 $ 132,358 Operating expenses (47,362 ) (2,912 ) (21,510 ) (71,784 ) Provision for impairment — (5,664 ) — (5,664 ) Interest expense, net (9,752 ) (698 ) (11,458 ) (21,908 ) Depreciation and amortization (25,413 ) (2,514 ) (25,404 ) (53,331 ) Loss on extinguishment of debt — — (1,231 ) (1,231 ) Net loss $ (12,161 ) $ (5,766 ) $ (3,633 ) $ (21,560 ) Ownership interest % 50 % 50 % Various Various Company's share of net loss $ (6,081 ) $ (2,883 ) $ (901 ) $ (9,865 ) Basis adjustments and other (21 ) 83 (119 ) (57 ) Equity in loss of Real Estate Ventures $ (6,102 ) $ (2,800 ) $ (1,020 ) $ (9,922 ) Year Ended December 31, 2018 MAP Venture Austin Venture Brandywine-AI Venture LLC evo at Cira Centre South Other Total Revenue $ 68,622 $ 53,476 $ 23,515 $ 163 $ 19,550 $ 165,326 Operating expenses (41,056 ) (22,994 ) (10,483 ) (256 ) (7,246 ) (82,035 ) Interest expense, net (12,690 ) (9,083 ) (3,478 ) (123 ) (4,400 ) (29,774 ) Depreciation and amortization (18,891 ) (19,226 ) (8,991 ) (409 ) (6,309 ) (53,826 ) Provision for impairment — — (20,832 ) — — (20,832 ) Loss on extinguishment of debt (334 ) (356 ) (695 ) — — (1,385 ) Net income (loss) $ (4,349 ) $ 1,817 $ (20,964 ) $ (625 ) $ 1,595 $ (22,526 ) Ownership interest % 50 % 50 % 50 % 50 % Various Various Company's share of net income (loss) $ (2,175 ) $ 909 $ (10,482 ) $ (313 ) $ 137 $ (11,924 ) Other than temporary impairment — — (4,076 ) — — (4,076 ) Basis adjustments and other 20 778 (1 ) (45 ) 17 769 Equity in income (loss) of Real Estate Ventures $ (2,155 ) $ 1,687 $ (14,559 ) $ (358 ) $ 154 $ (15,231 ) Year Ended December 31, 2017 MAP Venture Austin Venture Brandywine-AI Venture LLC evo at Cira Centre South Other Total Revenue $ 68,573 $ 85,500 $ 29,500 $ 12,285 $ 20,413 $ 216,271 Operating expenses (40,035 ) (35,997 ) (12,298 ) (3,075 ) (7,935 ) (99,340 ) Interest expense, net (13,677 ) (13,985 ) (4,707 ) (4,092 ) (3,752 ) (40,213 ) Depreciation and amortization (21,202 ) (34,026 ) (11,428 ) (4,512 ) (7,272 ) (78,440 ) Loss on extinguishment of debt — (2,613 ) (811 ) — — (3,424 ) Net income (loss) $ (6,341 ) $ (1,121 ) $ 256 $ 606 $ 1,454 $ (5,146 ) Ownership interest % 50 % 50 % 50 % 50 % Various Company's share of net income (loss) $ (3,171 ) $ (560 ) $ 128 $ 303 $ 1,436 $ (1,864 ) Other than temporary impairment — — (4,844 ) — — (4,844 ) Basis adjustments and other (272 ) (429 ) 251 146 (1,294 ) (1,598 ) Equity in income (loss) of Real Estate Ventures $ (3,443 ) $ (989 ) $ (4,465 ) $ 449 $ 142 $ (8,306 ) As of December 31, 2019 , the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2020 $ — 2021 114,845 2022 — 2023 273,860 2024 207,302 Thereafter — Total principal payments 596,007 Net deferred financing costs (10,939 ) Outstanding indebtedness $ 585,068 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 their sole operating office property, totaling 204,347 rentable square feet in Charlottesville, VA, 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 October 18, 2017, the Austin Venture sold eight office properties in Austin, Texas containing 1,164,496 square feet for a gross sales price of $333.3 million . Seven of the properties were encumbered by $151.0 million of mortgage debt. The Company’s share of cash proceeds, after payment of the of the mortgage debt, closing costs and prorations, was $86.4 million . The Company’s share of the Austin Venture’s gain on sale was $40.1 million . Additionally, the Company recorded a deferred gain on sale of $12.1 million , which was established on the Company’s consolidated balance sheets when certain assets were contributed to the Austin Venture at formation. In accordance with the relevant guidance for the sales of real estate, the contributed properties qualified as a partial sale and a portion of the gain was deferred and accreted. The Company met the criteria to recognize the unaccreted portion of the deferred gain on the partial sale as the sales process was complete upon the Austin Venture selling the properties to a third party. The summary of the transaction is as follows (in thousands); October 18, 2017 Gross sales price $ 333,250 Debt principal (150,968 ) Debt prepayment penalties (2,120 ) Closing costs and net prorations (7,420 ) Cash to Austin Venture $ 172,742 Company's ownership interest 50 % Cash to the Company $ 86,371 Cash to Austin Venture $ 172,742 Austin Venture basis of sold properties (92,559 ) Austin Venture gain on sale $ 80,183 Company's ownership interest 50 % Company's share of gain $ 40,092 Company's share of gain $ 40,092 Deferred gain from partial sale 12,072 Gain on real estate venture transactions $ 52,164 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, 2019 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% . During 2017, BDN - AI Venture sold 7101 Wisconsin Avenue, a property containing 230,904 rentable square feet located in Bethesda, Maryland, for a gross sales price of $105.7 million . At the time of sale, the property was encumbered by a mortgage of $37.4 million , which was repaid in full at closing, resulting in a debt prepayment penalty of $0.8 million . After mortgage payoff and closing costs, BDN - AI Venture received cash proceeds of $63.6 million , of which, the Company received $31.8 million and recognized a $13.8 million gain on the sale transaction. Additionally, in 2017, based on the Company’s evaluation of the fair value of its investment in the five remaining properties owned by BDN - AI Venture subsequent to the disposition of 7101 Wisconsin Avenue, the Company determined that a persistent weak demand office for space and intense competition for tenants had reduced the fair value of the investment below the carrying value. As a result, the Company recorded an other than temporary impairment of $4.8 million which was recognized in “Equity in Loss of Real Estate Ventures” in the consolidated statements of operations for the year ended December 31, 2017. The Company measured this impairment based on a discounted cash flow analysis, using a hold period of 10 years , a residual capitalization rate of 7.5% and discount rates ranging from 7.8% to 8.5% . 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% capped at a total maximum interest of 6.00% and maturing on August 1, 2023 . 1919 Ventures 1919 Ventures 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. During 2018, the Company and the other equity partner in 1919 ventures each provided a $44.4 million mortgage loan to 1919 Ventures and, as a result, the Company recorded a related-party note receivable from 1919 Ventures of $44.4 million which is reported within “Other assets” on the consolidated balance sheets. The loans bear interest at a fixed 4.0% per annum interest rate with a scheduled maturity on June 25, 2023 . 1919 Ventures used the loan to repay the venture’s then outstanding $88.8 million construction loan, comprised of $88.6 million in principal and $0.2 million of accrued interest. 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. The Parc at Plymouth Meeting Venture On January 31, 2017, the Company sold its 50% interest in TB-BDN Plymouth Apartments, L.P., a real estate venture with Toll Brothers, at a gross sales value of $100.5 million , of which the Company was allocated 50% for its interest. The venture developed and operated a 398 -unit multi-family complex in Plymouth Meeting, Pennsylvania encumbered by a $54.0 million construction loan. The construction loan was repaid commensurate with the sale of the Company’s 50% interest. As a result, the Company is no longer subject to a $3.2 million payment guarantee on the construction loan. The cash proceeds, after the payment of the Company’s share of the debt and closing costs, were $27.2 million . The carrying amount of the Company’s investment at the time of sale was $12.6 million , resulting in a $14.6 million gain on sale of an interest in the real estate venture which was recorded within “Net gain on real estate venture transactions" 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% interest and JBG/DC Manager, LLC ("JBG") owning a 30.0% 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, 2019 , $114.8 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.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
LEASES	5. LEASES Lessor Accounting The Company leases properties to tenants under operating leases with various expiration dates. Lease payments on noncancellable leases at December 31, 2019 are as follows (in thousands): Year Minimum Rent 2020 $ 389,956 2021 369,375 2022 338,435 2023 311,729 2024 280,631 Thereafter 1,234,006 Lease payments on noncancellable leases at December 31, 2018, which were determined under under ASC 840 and are therefore not adjusted for increases based on CPI, are as follows (in thousands): Year Minimum Rent 2019 392,058 2020 372,619 2021 349,160 2022 304,445 2023 277,388 Thereafter 1,265,810 Lessee Accounting As of December 31, 2019, the Company is the lessee under six long-term ground leases classified as operating leases. 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: Twelve Months Ended December 31, Lease Cost 2019 Fixed lease cost $ 2,100 Variable lease cost 54 Total $ 2,154 Weighted-average remaining lease term (years) 52.7 Weighted-average discount rate 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 65 years . Lease payments on noncancellable leases at December 31, 2019 are as follows (in thousands): Year Minimum Rent 2020 $ 1,217 2021 1,232 2022 1,248 2023 1,263 2024 1,305 Thereafter 110,452 Total lease payments $ 116,717 Less: Imputed interest 94,163 Present value of operating lease liabilities $ 22,554 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 leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate taxes. The above schedule of future minimum rental payments does not include any contingent rent amounts or any reimbursed expenses. Lease payments on noncancellable leases at December 31, 2018, which were determined under ASC 840 and are therefore not adjusted for increases based on CPI, are as follows (in thousands): Year Minimum Rent 2019 $ 1,222 2020 1,222 2021 1,222 2022 1,222 2023 1,222 Thereafter 55,689 Total $ 61,799
LEASES	5. LEASES Lessor Accounting The Company leases properties to tenants under operating leases with various expiration dates. Lease payments on noncancellable leases at December 31, 2019 are as follows (in thousands): Year Minimum Rent 2020 $ 389,956 2021 369,375 2022 338,435 2023 311,729 2024 280,631 Thereafter 1,234,006 Lease payments on noncancellable leases at December 31, 2018, which were determined under under ASC 840 and are therefore not adjusted for increases based on CPI, are as follows (in thousands): Year Minimum Rent 2019 392,058 2020 372,619 2021 349,160 2022 304,445 2023 277,388 Thereafter 1,265,810 Lessee Accounting As of December 31, 2019, the Company is the lessee under six long-term ground leases classified as operating leases. 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: Twelve Months Ended December 31, Lease Cost 2019 Fixed lease cost $ 2,100 Variable lease cost 54 Total $ 2,154 Weighted-average remaining lease term (years) 52.7 Weighted-average discount rate 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 65 years . Lease payments on noncancellable leases at December 31, 2019 are as follows (in thousands): Year Minimum Rent 2020 $ 1,217 2021 1,232 2022 1,248 2023 1,263 2024 1,305 Thereafter 110,452 Total lease payments $ 116,717 Less: Imputed interest 94,163 Present value of operating lease liabilities $ 22,554 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 leases also provide for payment by the Company of certain operating costs relating to the land, primarily real estate taxes. The above schedule of future minimum rental payments does not include any contingent rent amounts or any reimbursed expenses. Lease payments on noncancellable leases at December 31, 2018, which were determined under ASC 840 and are therefore not adjusted for increases based on CPI, are as follows (in thousands): Year Minimum Rent 2019 $ 1,222 2020 1,222 2021 1,222 2022 1,222 2023 1,222 Thereafter 55,689 Total $ 61,799

DEFERRED COSTS

DEFERRED COSTS	12 Months Ended
	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
DEFERRED COSTS	6. DEFERRED COSTS As of December 31, 2019 and 2018 , the Company’s deferred costs were comprised of the following (in thousands): 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 December 31, 2018 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 144,831 $ (56,846 ) $ 87,985 Financing costs - Revolving Credit Facility 6,298 (3,208 ) 3,090 Total $ 151,129 $ (60,054 ) $ 91,075 During the years ended December 31, 2019 , 2018 and 2017 , the Company capitalized internal direct leasing costs of $1.7 million , $3.9 million , and $4.6 million , respectively.

INTANGIBLE ASSETS

INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
INTANGIBLE ASSETS	7. INTANGIBLE ASSETS As of December 31, 2019 and 2018 , the Company’s intangible assets were comprised of the following (in thousands): 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 December 31, 2018 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 181,887 $ (53,376 ) $ 128,511 Tenant relationship value 9,564 (8,551 ) 1,013 Above market leases acquired 4,966 (3,142 ) 1,824 Total intangible assets, net $ 196,417 $ (65,069 ) $ 131,348 Total Cost Accumulated Amortization Intangible Liabilities, net Intangible liabilities, net: Below market leases acquired $ 49,655 $ (17,872 ) $ 31,783 For the years ended December 31, 2019 , 2018 , and 2017 , the Company accelerated the amortization of intangible assets by approximately $4.5 million , $0.7 million , and $0.6 million , respectively, as a result of tenant move-outs prior to the end of the associated lease term. For the year ended December 31, 2019 the Company accelerated the amortization of approximately $2.2 million of intangible liabilities as a result of tenant move-outs. For the years ended December 31, 2018 and 2017 the Company accelerated the amortization of a nominal amount of intangible liabilities as a result of tenant move-outs. As of December 31, 2019 , the Company’s annual amortization for its intangible assets/liabilities, assuming no early lease terminations, are as follows (dollars in thousands): Assets Liabilities 2020 $ 27,813 $ 5,270 2021 17,887 3,856 2022 12,067 2,263 2023 9,236 1,722 2024 6,317 1,434 Thereafter 11,531 7,718 Total $ 84,851 $ 22,263

DEBT OBLIGATIONS

DEBT OBLIGATIONS	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
DEBT OBLIGATIONS	8. DEBT OBLIGATIONS The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2019 and 2018 (in thousands): December 31, 2019 December 31, 2018 Effective Maturity Date MORTGAGE DEBT: Two Logan Square $ 81,103 $ 82,805 3.98% May 2020 Four Tower Bridge 9,291 9,526 4.50% (a) February 2021 One Commerce Square 116,571 120,183 3.64% April 2023 Two Commerce Square 108,472 110,518 4.51% April 2023 Principal balance outstanding 315,437 323,032 Plus: fair market value premium (discount), net (1,383 ) (1,759 ) Less: deferred financing costs (242 ) (404 ) Mortgage indebtedness $ 313,812 $ 320,869 UNSECURED DEBT $600 million Unsecured Credit Facility $ — $ 92,500 LIBOR + 1.10% July 2022 Seven-Year Term Loan - Swapped to fixed 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 350,000 250,000 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 350,000 250,000 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 1,721,110 Plus: original issue premium (discount), net 12,090 (4,096 ) Less: deferred financing costs (10,094 ) (9,837 ) Total unsecured indebtedness $ 1,830,606 $ 1,707,177 Total Debt Obligations $ 2,144,418 $ 2,028,046 (a) Assumed upon acquisition of the related property on January 5, 2018. The interest rate reflects the market rate at the time of acquisition. 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, 2019 . 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. As of December 31, 2018 , the Company had $92.5 million borrowings under the Credit Facility. During the twelve months ended December 31, 2018 , the weighted-average interest rate on Unsecured Credit Facility borrowings was 3.24% resulting in $1.0 million of interest expense. The Company was in compliance with all financial covenants as of December 31, 2019 and 2018 . 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, 2019 , the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands): 2020 $ 87,226 2021 15,143 2022 256,332 2023 556,736 2024 350,000 Thereafter 878,610 Total principal payments 2,144,047 Net unamortized premiums/(discounts) 10,707 Net deferred financing costs (10,336 ) Outstanding indebtedness $ 2,144,418

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	9. 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, 2019 and 2018 , 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, 2019 and 2018 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, 2019 December 31, 2018 Carrying Amount (a) Fair Value Carrying Amount (a) Fair Value Unsecured notes payable $ 1,503,435 $ 1,591,830 $ 1,288,024 $ 1,262,570 Variable rate debt $ 327,171 $ 309,947 $ 419,153 $ 402,924 Mortgage notes payable $ 313,812 $ 317,031 $ 320,869 $ 318,515 Notes receivable $ 44,430 $ 43,322 $ 47,771 $ 47,747 (a) The carrying amounts presented in the table above are net of deferred financing costs of $8.7 million and $7.9 million for unsecured notes payable, $1.4 million and $2.0 million for variable rate debt and $0.2 million and $0.4 million for mortgage notes payable as of December 31, 2019 and December 31, 2018 , respectively. On June 26, 2018, the Company provided a $44.4 million mortgage loan to Brandywine 1919 Ventures, 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 .” As of December 31, 2018, notes receivable also consisted of a $3.4 million note receivable that was provided to a third party to acquire a property. This note was repaid during the second quarter of 2019. The Company used quoted market prices as of December 31, 2019 and December 31, 2018 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, 2019 and December 31, 2018 . 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, 2019 . Current estimates of fair value may differ from the amounts presented herein.

DERIVATIVE FINANCIAL INSTRUMENT

DERIVATIVE FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE FINANCIAL INSTRUMENTS	10. 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, 2019 and December 31, 2018 . 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 12/31/2019 12/31/2018 12/31/2019 12/31/2018 Assets Swap Interest Rate Cash Flow (a) $ — $ 25,774 3.090 % January 6, 2012 October 30, 2019 $ — $ 183 Liabilities Swap Interest Rate Cash Flow (b) $ 250,000 $ 250,000 2.868 % October 8, 2015 October 8, 2022 $ (562 ) $ 7,008 Swap Interest Rate Cash Flow (b) $ 25,774 $ 25,774 3.300 % December 22, 2011 January 30, 2021 (94 ) 292 $ 275,774 $ 301,548 (a) On October 30, 2019, the interest rate hedge contract for this swap expired. (b) 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, 2019 and December 31, 2018 . 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, 2019 . 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 their ability to meet contractual obligations, including those to the Company. The Company regularly monitors its tenant base to assess potential concentrations of credit risk. Management believes the current credit risk portfolio is reasonably well diversified and does not contain an unusual concentration of credit risk. No tenant accounted for 10% or more of the Company’s rents during 2019 , 2018 and 2017 .

LIMITED PARTNERS' NONCONTROLLIN

LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY	12 Months Ended
	Dec. 31, 2019
Noncontrolling Interest [Abstract]
LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY	11. 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. 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, 2019 and December 31, 2018 , was $9.3 million and $10.1 million , respectively. Under the applicable accounting guidance, the redemption value of limited partnership units are carried at, on a limited partner basis, the greater of historical cost adjusted for the allocation of income and distributions or fair value. The Parent Company believes that the aggregate settlement value of these interests (based on the number of units outstanding and the closing price of the common shares on the balance sheet date) was approximately $15.5 million and $12.6 million , respectively, as of December 31, 2019 and December 31, 2018 .

BENEFICIARIES' EQUITY OF THE PA

BENEFICIARIES' EQUITY OF THE PARENT COMPANY	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
BENEFICIARIES' EQUITY OF THE PARENT COMPANY	12. BENEFICIARIES' EQUITY OF THE PARENT COMPANY Earnings per Share (EPS) The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year Ended December 31, 2019 2018 2017 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 34,529 $ 34,529 $ 135,472 $ 135,472 $ 121,177 $ 121,177 Net income attributable to noncontrolling interests (262 ) (262 ) (954 ) (954 ) (1,004 ) (1,004 ) Nonforfeitable dividends allocated to unvested restricted shareholders (396 ) (396 ) (369 ) (369 ) (327 ) (327 ) Distribution to preferred shareholders — — — — (2,032 ) (2,032 ) Preferred share redemption charge — — — — (3,181 ) (3,181 ) Net income attributable to common shareholders $ 33,871 $ 33,871 $ 134,149 $ 134,149 $ 114,633 $ 114,633 Denominator Weighted-average shares outstanding 176,132,941 176,132,941 178,519,748 178,519,748 175,484,350 175,484,350 Contingent securities/Share based compensation — 553,872 — 1,121,744 — 1,323,816 Weighted-average shares outstanding 176,132,941 176,686,813 178,519,748 179,641,492 175,484,350 176,808,166 Earnings per Common Share: Net income attributable to common shareholders $ 0.19 $ 0.19 $ 0.75 $ 0.75 $ 0.65 $ 0.65 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 , 982,871 , and 1,479,799 in 2019 , 2018 , and 2017 , 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, 2019 , 2018 and 2017 , 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 11, 2019, the Parent Company declared a distribution of $0.19 per common share, totaling $33.8 million , which was paid on January 22, 2020 to shareholders of record as of January 8, 2020 . Of the 20,000,000 preferred shares authorized, none were outstanding as of December 31, 2019 or December 31, 2018 . On April 11, 2017, the Parent Company redeemed all of its outstanding 4,000,000 Series E Preferred Shares at an aggregate redemption price of $25.51 per share, which includes $2.0 million of dividends accrued through the redemption date. The redemption was funded with existing cash balances on hand. Also, on April 11, 2017, the Parent Company recognized a $3.2 million charge related to the underwriting discount and related expenses incurred at issuance of the Series E Preferred Shares on April 11, 2012. This charge is included in the earnings per share calculations above, as well as within the Parent Company’s consolidated statements of operations as a reduction in net income to arrive at net income attributable to common shareholders under the caption “Preferred share redemption charge.” There were no comparable charges for the years ended December 31, 2019 or 2018. 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, 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. During the year ended December 31, 2017, there were no share repurchases under the program. 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, 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”), under which it may sell up to an aggregate of 16,000,000 common shares until January 10, 2020 in at-the-market offerings. There was no activity under the Offering Program during 2019. During 2018 and 2017, the Parent Company issued 23,311 and 2,858,991 common shares under the Offering Program at weighted average prices per share of $18.04 and $18.19 , receiving net cash proceeds of $0.4 million and $51.2 million , respectively. At December 31, 2019 , 13,117,698 common shares remain available for issuance under the Offering Program.

PARTNER'S EQUITY OF THE PARENT

PARTNER'S EQUITY OF THE PARENT COMPANY	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
PARTNERS' EQUITY OF THE OPERATING PARTNERSHIP	13. PARTNERS' EQUITY OF THE PARENT COMPANY Earnings per Common Partnership Unit The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year Ended December 31, 2019 2018 2017 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 34,529 $ 34,529 $ 135,472 $ 135,472 $ 121,177 $ 121,177 Net income attributable to noncontrolling interests (69 ) (69 ) (55 ) (55 ) (29 ) (29 ) Nonforfeitable dividends allocated to unvested restricted unitholders (396 ) (396 ) (369 ) (369 ) (327 ) (327 ) Preferred unit dividends — — — — (2,032 ) (2,032 ) Preferred unit redemption charge — — — — (3,181 ) (3,181 ) Net income attributable to common unitholders $ 34,064 $ 34,064 $ 135,048 $ 135,048 $ 115,608 $ 115,608 Denominator Weighted-average units outstanding 177,114,932 177,114,932 179,959,370 179,959,370 176,964,149 176,964,149 Contingent securities/Share based compensation — 553,872 — 1,121,744 — 1,323,816 Total weighted-average units outstanding 177,114,932 177,668,804 179,959,370 181,081,114 176,964,149 178,287,965 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 0.19 $ 0.19 $ 0.75 $ 0.75 $ 0.65 $ 0.65 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, 2019 , 2018 and 2017 , 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, 2019 or December 31, 2018 . Common Partnership Units (Redeemable and General) The Operating Partnership has two classes of Common Partnership Units outstanding as of December 31, 2019 : (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, 2019 , 2018 and 2017 , which was $15.75 , $12.87 and $18.19 , respectively. As of December 31, 2019 , 981,634 Class A Units were outstanding and owned by outside limited partners of the Operating Partnership. As of December 31, 2018 and 2017 , 982,871 and 1,479,799 Class A Units were outstanding and owned by outside limited partners of the Operating Partnership, respectively. On December 11, 2019, the Operating Partnership declared a distribution of $0.19 per common unit, totaling $33.8 million , which was paid on January 22, 2020 to unitholders of record as of January 8, 2020 . On April 11, 2017, the Operating Partnership redeemed all of its outstanding 4,000,000 Series E-Linked Preferred Mirror Units at an aggregate redemption price of $25.51 per unit, which includes $2.0 million of dividends accrued through the redemption date. The redemption of preferred units was funded with existing cash balances on hand. Also, on April 11, 2017, the Operating Partnership recognized a $3.2 million charge related to the underwriting discount and related expenses incurred at issuance of the Series E-Linked Preferred Mirror Units on April 11, 2012. This charge is included in the earnings per share calculations above, as well as within the Operating Partnership’s consolidated statements of operations as a reduction in net income to arrive at net income attributable to common partnership unitholders under the caption “Preferred unit redemption charge.” There were no comparable charges for the years ended December 31, 2019 or 2018. 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, 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. During the year ended December 31, 2017, there were no unit 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 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”), under which it may sell up to an aggregate of 16,000,000 common units until January 10, 2020 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 2019. During 2018 and 2017, the Parent Company issued 23,311 and 2,858,991 common units under the Offering Program at weighted average prices per unit of $18.04 and $18.19 , receiving net cash proceeds of $0.4 million and $51.2 million , respectively. As of December 31, 2019 , 13,117,698 common shares remain available for issuance under the Offering Program.

SHARE BASED COMPENSATION ,401(K

SHARE BASED COMPENSATION ,401(K) PLAN AND DEFERRED COMPENSATION	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
SHARE BASED COMPENSATION, 401(k) PLAN AND DEFERRED COMPENSATION	14. SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION Stock Options On December 31, 2019 , options exercisable for 334,561 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, 2019 , 2018 and 2017 , the Company did not recognize any compensation expense related to unvested options. During the years ended December 31, 2019 , 2018 and 2017 , 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, 2019 and changes during the year-ended December 31, 2019 were as follows: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at January 1, 2019 964,359 $ 9.13 1.3 Exercised (629,798 ) $ 7.67 $ 4,967.7 Outstanding at December 31, 2019 334,561 $ 11.88 1.0 $ 1,295.9 Vested/Exercisable at December 31, 2019 334,561 $ 11.88 1.0 $ 1,295.9 401(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 $0.4 million , $0.5 million , and $0.4 million in 2019 , 2018 , and 2017 , respectively. Restricted Share Rights Awards As of December 31, 2019 , 479,144 restricted share rights were outstanding under the Equity Incentive Plan. These Restricted Share Rights vest over two to three years from the initial grant dates . The remaining compensation expense to be recognized with respect to these awards at December 31, 2019 was $2.2 million and is expected to be recognized over a weighted average remaining vesting period of 1.05 years . For the years ended December 31, 2019 , 2018 , and 2017 , the amortization related to outstanding restricted shares was $3.9 million (of which $0.3 million was capitalized), $3.6 million (of which $0.6 million was capitalized), and $2.8 million (of which $0.4 million was capitalized), respectively. Compensation expense related to outstanding restricted shares is included in general and administrative expense. The following table summarizes the Company’s restricted share activity during the year-ended December 31, 2019 : Shares Weighted Average Grant Date Fair Value Aggregate Intrinsic Value (in thousands) Non-vested at January 1, 2019 466,439 $ 14.93 $ 70.7 Granted 278,442 $ 15.51 $ 65.6 Vested (248,607 ) $ 13.68 $ 538.3 Forfeited (17,130 ) $ 15.66 $ 1.6 Non-vested at December 31, 2019 479,144 $ 15.90 $ 44.7 On February 21, 2019, the Compensation Committee of the Parent Company’s Board of Trustees awarded to officers of the Company an aggregate of 196,667 Restricted Share Rights, which generally vest over two to 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 2019 to certain senior executives and that vest over three years 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 development activity provided certain operating and balance sheet metrics are also achieved during the three-year period ending December 31, 2021. Half of any additional shares earned will vest based on continued service through each of January 1, 2022 and January 1, 2023, 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 233,890 shares may be awarded under the outperformance feature. These shares have a $3.7 million intrinsic value using a $15.61 grant date fair value. As of December 31, 2019, the Company has not recognized any compensation expense for these awards as it has been determined that it is not probable that the performance metrics will be achieved. The Company will evaluate progression 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 February 21, 2019, the Compensation Committee awarded non-officer employees an aggregate of 37,472 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. 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 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 3/1/2017 2/28/2018 2/21/2019 Total (Amounts below in shares, unless otherwise noted) Non-vested at January 1, 2019 169,525 206,025 — 375,550 Units Granted — — 213,728 213,728 Units Vested (8,420 ) — — (8,420 ) Units Cancelled (1,935 ) (15,729 ) (7,659 ) (25,323 ) Non-vested at December 31, 2019 159,170 190,296 206,069 555,535 Measurement Period Commencement Date 1/1/2017 1/1/2018 1/1/2019 Measurement Period End Date 12/31/2019 12/31/2020 12/31/2021 Units Granted 174,854 209,193 213,728 Fair Value of Units on Grant Date (in thousands) $ 3,735 $ 4,276 $ 4,627 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. In accordance with the accounting standard for share-based compensation, the Company amortizes stock-based compensation costs through the qualifying retirement date for those executives who meet the conditions for qualifying retirement during the scheduled vesting period. For the year ended December 31, 2019 , the Company recognized amortization of the 2019 , 2018 and 2017 RPSU awards of $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. For the year ended December 31, 2017 , amortization for the 2017 , 2016 , and 2015 RPSU awards was $3.4 million , of which $0.8 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, 2019 was approximately $2.0 million and is expected to be recognized over a weighted average remaining vesting period of 1.7 years . The Company issued 147,111 common shares on February 1, 2019 in settlement of RPSUs that had been awarded on February 22, 2016 (with a three -year measurement period ended December 31, 2018). Holders of these RPSUs also received a cash dividend of $0.19 per share for these common shares on January 22, 2019. 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 2019 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 . Employees made purchases under the ESPP of $0.5 million in each of the years ended December 31, 2019 and 2018 and $0.4 million during the year ended December 31, 2017. The Company recognized $0.1 million of compensation expense related to the ESPP during each of the years ended December 31, 2019, 2018, and 2017. 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, 2019 , December 31, 2018 and December 31, 2017 , 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, 2019 and 2018, 1.1 million and 1.0 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, 2019
Distributions [Abstract]
DISTRIBUTIONS	15. DISTRIBUTIONS The following table provides the tax characteristics of the 2019 , 2018 and 2017 distributions paid: Years ended December 31, 2019 2018 2017 (in thousands, except per share amounts) Common Share Distributions: Ordinary income $ 0.62 $ 0.55 $ 0.38 Capital gain — — 0.26 Non-taxable distributions 0.14 0.17 — Distributions per share $ 0.76 $ 0.72 $ 0.64 Percentage classified as ordinary income 81.00 % 76.20 % 60.00 % Percentage classified as capital gain — % — % 40.00 % Percentage classified as non-taxable distribution 19.00 % 23.80 % — % Preferred Share Distributions: Total distributions paid $ — $ — $ 2,032 Percentage classified as ordinary income — % — % 60.00 % Percentage classified as capital gain — % — % 40.00 % Percentage classified as non-taxable distribution — % — % — %

INCOME TAXES AND TAX CREDIT TRA

INCOME TAXES AND TAX CREDIT TRANSACTIONS	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES AND TAX CREDIT TRANSACTIONS	16. 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, 2019 and 2018 , there were nominal deferred tax assets included within “Other assets” in the consolidated balance sheets. In projecting future taxable income, the analysis begins with historical results and incorporates assumptions about the amount of future state and federal pretax operating income adjusted for items that do not have tax consequences. The assumptions about future taxable income require significant judgment and are consistent with the plans and estimates the Company is using to manage the underlying businesses. The Company had no accruals for tax uncertainties as of December 31, 2019 and December 31, 2018 . For the year ended December 31, 2019 , there were $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 were $0.3 million of deferred income tax expense and $0.1 of current income tax expense. For the year ended December 31, 2017 , there were $0.6 million of deferred income tax benefit. 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, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	17. 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, 2019 (in thousands): Parent Company Cash Flow Hedges Balance at January 1, 2017 $ (1,745 ) Change in fair market value during year 2,948 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (34 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 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 ) Operating Partnership Cash Flow Hedges Balance at January 1, 2017 $ (2,122 ) Change in fair market value during year 2,948 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 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 ) 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.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	19. 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. Letters-of-Credit Under certain mortgages, the Company has funded required leasing and capital reserve accounts for the benefit of the mortgage lenders with letters-of-credit. There were no associated letters-of-credit for a mortgage lender on December 31, 2019 . Certain of the tenant rents at properties that secure these mortgage loans are deposited into the loan servicer’s depository accounts, which are used to fund debt service, operating expenses, capital expenditures and the escrow and reserve accounts, as necessary. Any excess cash is included in cash and cash equivalents. Environmental As an owner of real estate, the Company is subject to various environmental laws of federal, state, and local governments. The Company’s compliance with existing laws has not had a material adverse effect on its financial condition and results of operations, and the Company does not believe it will have a material adverse effect in the future. However, the Company cannot predict the impact of unforeseen environmental contingencies or new or changed laws or regulations on its current Properties or on properties that the Company may acquire. 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 will accrete through interest expense to $2.0 million over the expected period until development is commenced. The fair value of this contingent consideration was determined using a probability weighted discounted cash flow model. The significant inputs to the discounted cash flow model were the discount rate and weighted probability scenarios. As the inputs are unobservable, the Company determined the inputs used to value this liability fall within Level 3 for fair value reporting. As of December 31, 2019 , the liability had accreted to $1.97 million . As there were no significant changes to the inputs, the liability remains within Level 3 for fair value reporting. Debt Guarantees As of December 31, 2019 , the Company’s Real Estate Ventures had aggregate indebtedness of $596.0 million . These loans are generally mortgage or construction loans, most of which are non-recourse to the Company, except for customary carve-outs. As of December 31, 2019 , the $150.0 million construction loan obtained by the 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, 2019, had $8.5 million of future contractual obligations. The Company is also committed to make additional contributions under the program. As of December 31, 2019, the Company estimates that these additional contributions, which are not fixed under the terms of agreement, will be $2.8 million . The Company is under contract to acquire an office property containing approximately 170,000 rentable square feet located in Radnor, Pennsylvania for a purchase price of $20.3 million . The Company has paid $1 million towards the purchase price in the form of a non-refundable deposit and the transaction is expected to close during 2020. The Company was also under contract to acquire a 7.8 -acre land parcel located in Radnor, Pennsylvania for a purchase price of $11.3 million . The acquisition of the land parcel closed on February 27, 2020. As part of the Company’s September 2004 acquisition of a portfolio of properties from The Rubenstein Company (which the Company refers to as the “TRC acquisition”), the Company acquired its interest in Two Logan Square, a 708,844 square foot office building in Philadelphia, primarily through its ownership of a second and third mortgage secured by this property. This property is consolidated, as the borrower is a variable interest entity and the Company, through its ownership of the second and third mortgages, is the primary beneficiary. The Company currently does not expect to take title to Two Logan Square until, at the earliest, on or about August 2020. If the Company takes fee title to Two Logan Square upon foreclosure of its mortgage, the Company has agreed to pay an unaffiliated third party that holds a residual interest in the fee owner of this property an amount equal to $2.9 million . On the TRC acquisition date, the Company recorded a liability of $0.7 million and has been accreting the liability up to $2.9 million through January 2020. As of December 31, 2019 , the Company had a balance of $2.9 million for this liability in its consolidated balance sheets. As part of the Company’s 2006 merger with Prentiss Properties Trust (“Prentiss”), the 2004 TRC acquisition and several of our other transactions, the Company agreed not to sell certain of the properties it acquired in transactions that would trigger taxable income to the former owners. In the case of the TRC acquisition, the Company agreed not to sell acquired properties in non-exempt transactions for periods up to 15 years from the date of the TRC acquisition as follows at December 31, 2019 : One Logan Square, Two Logan Square and Radnor Corporate Center (January 2020). The Company subsequently agreed to extend the no-sale period applicable to Two Logan Square to on or about August 2020. If the Company were to sell a restricted property before the expiration of the restricted period in a non-exempt transaction, the Company may be required to make significant payments to the parties who sold the applicable property on account of tax liabilities attributed to them. Similarly, as part of the 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to not sell these two properties in certain taxable transactions prior to October 20, 2021 without the holder’s consent. As part of the Company’s acquisition of properties from time to time in tax-deferred transactions, the Company has agreed to provide certain of the prior owners of the acquired properties with the right to guarantee the Company’s indebtedness. If the Company were to seek to repay the indebtedness guaranteed by the prior owner before the expiration of the applicable agreement, the Company would be required to provide the prior owner an opportunity to guaranty qualifying replacement debt. These debt maintenance agreements may limit the Company’s ability to refinance indebtedness on terms favorable to the Company. As part of our 2013 acquisition of substantially all of the equity interests in the partnerships that own One and Two Commerce Square, the Company agreed, for the benefit of affiliates of the holder of the 1% residual ownership interest in these properties, to maintain qualifying mortgage debt through October 20, 2021, in the amounts of not less than $125.0 million on One Commerce Square and $100.0 million on Two Commerce Square. Similarly, the Company has agreements in place with other contributors of assets that obligate it to maintain debt available for them to guaranty. 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.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
SEGMENT INFORMATION	18. SEGMENT INFORMATION During the year ended December 31, 2019 , 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 and results of operations of the Company’s reportable segments as of and for the three years ended December 31, 2019 , 2018 and 2017 (in thousands): Real estate investments, at cost: December 31, 2019 December 31, 2018 December 31, 2017 Philadelphia CBD $ 1,726,299 $ 1,670,388 $ 1,643,296 Pennsylvania Suburbs 1,003,890 1,002,937 957,272 Austin, Texas (a) 721,255 667,698 163,653 Metropolitan Washington, D.C. (b) 468,035 524,190 978,257 Other 86,980 86,506 88,346 Operating Properties $ 4,006,459 $ 3,951,719 $ 3,830,824 Corporate Right of use asset - operating leases, net (c) $ 21,656 $ — $ — Construction-in-progress $ 180,718 $ 150,263 $ 121,188 Land held for development (d) $ 96,124 $ 86,401 $ 98,242 Prepaid leasehold interests in land held for development, net (e) $ 39,592 $ 39,999 $ — (a) Refer to Note 3, ''Real Estate Investments ,” for details related to the Company's acquisition of DRA Advisors' ownership interest in the Austin Venture in December 2018. (b) Refer to Note 4, ''Investment in Unconsolidated Real Estate Ventures .” for details of the Company's transaction with the Herndon Innovation Center Metro Portfolio Venture, LLC in December 2018. (c) Refer to Note 2, ''Summary of Significant Accounting Policies ,” for further information on the impact of adoption of Topic 842. (d) Does not include 35.2 acres, 37.9 acres, and 13.1 acres of land classified as held for sale as of December 31, 2019, 2018, and 2017, respectively. Refer to Note 3, ''Real Estate Investments ,” for further information. (e) Includes leasehold interests in prepaid 99 -year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania as of December 31, 2019 and December 31, 2018 . Refer to Note 3, ''Real Estate Investments ,” for further information. Year Ended December 31, 2019 2018 2017 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 Philadelphia CBD $ 263,769 $ (100,219 ) $ 163,550 $ 256,717 $ (99,449 ) $ 157,268 $ 226,673 $ (88,818 ) $ 137,855 Pennsylvania Suburbs 141,084 (47,418 ) 93,666 138,279 (49,433 ) 88,846 139,785 (47,845 ) 91,940 Austin, Texas 104,157 (38,285 ) 65,872 38,665 (16,739 ) 21,926 34,301 (15,456 ) 18,845 Metropolitan Washington, D.C. 51,498 (23,455 ) 28,043 90,308 (34,072 ) 56,236 92,024 (35,014 ) 57,010 Other 14,558 (9,328 ) 5,230 16,757 (11,888 ) 4,869 18,347 (11,749 ) 6,598 Corporate 5,351 (7,141 ) (1,790 ) 3,619 (6,518 ) (2,899 ) 9,363 (7,193 ) 2,170 Operating properties $ 580,417 $ (225,846 ) $ 354,571 $ 544,345 $ (218,099 ) $ 326,246 $ 520,493 $ (206,075 ) $ 314,418 (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, 2019 December 31, 2018 December 31, 2017 2019 2018 2017 Philadelphia CBD $ 17,524 $ 19,897 $ 39,939 $ 328 $ (105 ) $ 255 Pennsylvania Suburbs — — 3,503 — — 631 Metropolitan Washington, D.C. (a) 102,840 136,142 119,817 (4,234 ) (15,065 ) (5,044 ) MAP Venture (70 ) 11,173 15,450 (6,102 ) (2,155 ) (3,443 ) Other — 1,888 1,939 86 407 285 Austin, Texas (b) — — 13,973 — 1,687 (990 ) Total $ 120,294 $ 169,100 $ 194,621 $ (9,922 ) $ (15,231 ) $ (8,306 ) (a) Refer to Note 4, ''Investment in Unconsolidated Real Estate Ventures ," for details of the Company's transaction with the Herndon Innovation Center Metro Portfolio Venture, LLC in December 2018. (b) Refer to Note 3, ''Real Estate Investments ," for details related to the Company's acquisition of DRA Advisors' ownership interest in the Austin Venture in December 2018. Net operating income (“NOI”) is a non-GAAP financial measure defined 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. All companies may not calculate NOI in the same manner. NOI is the measure that is used by the Company to evaluate the operating performance of its real estate assets by segment. The Company 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, 2019 2018 2017 Net income $ 34,529 $ 135,472 $ 121,177 Plus: Interest expense 81,512 78,199 81,886 Interest expense - amortization of deferred financing costs 2,768 2,498 2,435 Depreciation and amortization 210,005 176,000 180,323 General and administrative expenses 32,156 27,802 28,538 Equity in loss of Real Estate Ventures 9,922 15,231 8,306 Provision for impairment — 71,707 3,057 Loss on early extinguishment of debt — 105 3,933 Less: Interest income 2,318 4,703 1,113 Income tax (provision) benefit (12 ) (423 ) 628 Net gain on disposition of real estate 356 2,932 32,017 Net gain on sale of undepreciated real estate 2,020 3,040 953 Net gain on real estate venture transactions 11,639 142,233 80,526 Gain on promoted interest in unconsolidated real estate venture — 28,283 — Consolidated net operating income $ 354,571 $ 326,246 $ 314,418

SUMMARY OF QUARTERLY RESULTS (U

SUMMARY OF QUARTERLY RESULTS (UNAUDITED)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
SUMMARY OF QUARTERLY RESULTS (UNAUDITED)	20. SUMMARY OF QUARTERLY RESULTS (UNAUDITED) The following is a summary of quarterly financial information as of and for the years ended December 31, 2019 and 2018 (in thousands, except per share data): Brandywine Realty Trust 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 2019 Total revenue $ 143,896 $ 144,151 $ 145,331 $ 147,039 Net income 4,583 6,252 6,820 16,874 (d) Net income allocated to Common Shares 4,404 6,112 6,679 16,676 Basic earnings per Common Share $ 0.03 $ 0.03 $ 0.04 $ 0.09 Diluted earnings per Common Share $ 0.03 $ 0.03 $ 0.04 $ 0.09 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,445 12,876 (43,522 ) (a) 121,673 (c) Net income (loss) allocated to Common Shares 43,956 12,661 (43,260 ) 120,792 Basic earnings (loss) per Common Share $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Share $ 0.24 $ 0.07 $ (0.24 ) $ 0.67 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) Driven by a $56.9 million impairment charge related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, ''Real Estate Investments ,” for further information. (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, ''Real Estate Investments ,” for further information on this transaction. (c) Increase primarily relates to gains of $103.8 million and $28.3 million , recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, ''Real Estate Investments ." (d) Increase primarily related to a gain of $8.0 million recorded in the "Net gains on real estate venture transactions" within the Company's consolidated statement of operations from the sale of three PJP Ventures properties. For further details, see Note 4, "Investment in Unconsolidated Joint Ventures." Brandywine Operating Partnership, L.P. 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 2019 Total revenue $ 143,896 $ 144,151 $ 145,331 $ 147,039 Net income 4,583 6,252 6,820 16,874 (d) Net income attributable to Common Partnership Unitholders 4,430 6,146 6,716 16,772 Basic earnings per Common Partnership Unit $ 0.03 $ 0.03 $ 0.04 $ 0.09 Diluted earnings per Common Partnership Unit $ 0.03 $ 0.03 $ 0.04 $ 0.09 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,445 12,876 (43,522 ) (a) 121,673 (c) Net income (loss) attributable to Common Partnership Unitholders 44,326 12,769 (43,622 ) 121,575 Basic earnings (loss) per Common Partnership Unit $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Partnership Unit $ 0.24 $ 0.07 $ (0.24 ) $ 0.67 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) Driven by a $56.9 million impairment charge related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, ''Real Estate Investments ,” for further information. (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, ''Real Estate Investments ,” for further information on this transaction. (c) Increase primarily relates to gains of $103.8 million and $28.3 million , recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, ''Real Estate Investments ." (d) Increase primarily related to a gain of $8.0 million recorded in the "Net gains on real estate venture transactions" within the Company's consolidated statement of operations from the sale of three PJP Ventures properties. For further details, see Note 4, "Investment in Unconsolidated Joint Ventures."

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Schedule of Valuation and Qualifying Accounts Disclosure	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, 2019 $ 12,919 $ — $ 4,944 $ 7,975 December 31, 2018 $ 17,112 $ 1,775 $ 5,968 $ 12,919 December 31, 2017 $ 16,116 $ 1,912 $ 916 $ 17,112 (1)

Schedule III - Real Estate and

Schedule III - Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Real Estate and Accumulated Depreciation Disclosure	BRANDYWINE REALTY TRUST AND BRANDYWINE OPERATING PARTNERSHIP, L.P. Schedule III Real Estate and Accumulated Depreciation — December 31, 2019 (in thousands) Initial Cost Gross Amount Which Carried Property Name City State Encumbrances (a) Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (b) Accumulated Depreciation at December 31, 2019 (c) Year of Construction Year Acquired Depreciable Life PENNSYLVANIA SUBURBS 400 Berwyn Park Berwyn PA $ — $ 2,657 $ 4,462 $ 12,841 $ 2,657 $ 17,303 $ 19,960 $ 7,583 1999 1999 (d) 300 Berwyn Park Berwyn PA — 2,206 13,422 4,145 2,206 17,567 19,773 10,516 1989 1997 (d) 1050 Westlakes Drive Berwyn PA — 2,611 10,445 2,210 2,611 12,655 15,266 6,238 1984 1999 (d) 1200 Swedesford Road Berwyn PA — 2,595 11,809 490 2,595 12,299 14,894 6,848 1994 2001 (d) 200 Berwyn Park Berwyn PA — 1,533 9,460 1,574 1,533 11,034 12,567 6,569 1987 1997 (d) 1180 Swedesford Road Berwyn PA — 2,086 8,342 2,865 2,086 11,207 13,293 5,802 1987 2001 (d) 100 Berwyn Park Berwyn PA — 1,180 7,290 1,419 1,180 8,709 9,889 5,252 1986 1997 (d) 1160 Swedesford Road Berwyn PA — 1,781 7,124 6,810 2,045 13,670 15,715 6,698 1986 2001 (d) 1100 Cassett Road Berwyn PA — 1,695 6,779 1,730 1,695 8,509 10,204 4,044 1997 2001 (d) Six Tower Bridge (181 Washington Street) Conshohocken PA — 6,927 14,722 2,511 6,237 17,923 24,160 3,803 1999 2013 (d) 52 Swedesford Square East Whiteland Twp. PA — 4,241 16,579 5,193 4,241 21,772 26,013 11,511 1988 1998 (d) 640 Freedom Business Center (g) King Of Prussia PA — 1,015 20,098 4,832 414 25,531 25,945 14,251 1991 1998 (d) 620 Freedom Business Center (g) King Of Prussia PA — 666 13,118 1,826 270 15,340 15,610 8,836 1986 1998 (d) 1000 First Avenue King Of Prussia PA — — 13,708 3,211 — 16,919 16,919 10,766 1980 1998 (d) 1060 First Avenue King Of Prussia PA — — 13,665 4,169 — 17,834 17,834 11,055 1987 1998 (d) 630 Freedom Business Center Drive (g) King Of Prussia PA — 666 13,251 3,259 273 16,903 17,176 9,861 1989 1998 (d) 1020 First Avenue King Of Prussia PA — — 10,744 3,931 — 14,675 14,675 9,089 1984 1998 (d) 1040 First Avenue King Of Prussia PA — — 14,142 5,080 — 19,222 19,222 12,076 1985 1998 (d) 610 Freedom Business Center Drive (g) King Of Prussia PA — 485 9,602 2,676 198 12,565 12,763 6,976 1985 1998 (d) 650 Park Avenue King Of Prussia PA — 1,916 4,378 (4,378 ) 1,916 — 1,916 — 1968 1998 (d) 600 Park Avenue King Of Prussia PA — 1,012 4,048 385 1,012 4,433 5,445 2,647 1964 1998 (d) 933 First Avenue King Of Prussia PA — 3,127 20,794 (1,125 ) 3,127 19,669 22,796 2,216 2017 N/A (d) 500 North Gulph Road King Of Prussia PA — 1,303 5,201 21,017 1,303 26,218 27,521 1,202 1979 1996 (d) 401 Plymouth Road Plymouth Meeting PA — 6,199 16,131 15,831 6,199 31,962 38,161 15,355 2001 2000 (d) Metroplex (4000 Chemical Road) Plymouth Meeting PA — 4,373 24,546 399 4,373 24,945 29,318 7,701 2007 2001 (d) 610 West Germantown Pike Plymouth Meeting PA — 3,651 14,514 3,285 3,651 17,799 21,450 8,669 1987 2002 (d) 600 West Germantown Pike Plymouth Meeting PA — 3,652 15,288 2,717 3,652 18,005 21,657 8,124 1986 2002 (d) 630 West Germantown Pike Plymouth Meeting PA — 3,558 14,743 2,714 3,558 17,457 21,015 7,906 1988 2002 (d) 620 West Germantown Pike Plymouth Meeting PA — 3,572 14,435 1,498 3,572 15,933 19,505 7,042 1990 2002 (d) 660 West Germantown Pike Plymouth Meeting PA — 3,694 5,487 20,715 5,405 24,491 29,896 6,850 1987 2012 (d) 351 Plymouth Road Plymouth Meeting PA — 1,043 555 — 1,043 555 1,598 205 N/A 2000 (d) 150 Radnor Chester Road Radnor PA — 11,925 36,986 10,142 11,897 47,156 59,053 22,504 1983 2004 (d) One Radnor Corporate Center Radnor PA — 7,323 28,613 22,885 7,323 51,498 58,821 30,974 1998 2004 (d) 201 King of Prussia Road Radnor PA — 8,956 29,811 2,871 8,949 32,689 41,638 19,061 2001 2004 (d) 555 Lancaster Avenue Radnor PA — 8,014 16,508 20,204 8,609 36,117 44,726 18,535 1973 2004 (d) Four Radnor Corporate Center Radnor PA — 5,406 21,390 12,770 5,705 33,861 39,566 15,781 1995 2004 (d) Five Radnor Corporate Center Radnor PA — 6,506 25,525 8,209 6,578 33,662 40,240 12,120 1998 2004 (d) Three Radnor Corporate Center Radnor PA — 4,773 17,961 1,273 4,791 19,216 24,007 9,598 1998 2004 (d) Two Radnor Corporate Center Radnor PA — 3,937 15,484 3,163 3,942 18,642 22,584 9,853 1998 2004 (d) 130 Radnor Chester Road Radnor PA — 2,573 8,338 3,188 2,567 11,532 14,099 6,716 1983 2004 (d) 170 Radnor Chester Road Radnor PA — 2,514 8,147 1,751 2,509 9,903 12,412 4,375 1983 2004 (d) 200 Radnor Chester Road Radnor PA — 3,366 — 3,653 3,366 3,653 7,019 772 2014 2005 (d) 101 West Elm Street W. Conshohocken PA — 6,251 25,209 3,853 6,251 29,062 35,313 10,721 1999 2005 (d) 1 West Elm Street W. Conshohocken PA — 3,557 14,249 3,376 3,557 17,625 21,182 6,823 1999 2005 (d) Four Tower Bridge (200 Barr Harbor Drive) W. Conshohocken PA 9,291 6,000 14,734 336 6,000 15,070 21,070 761 1998 2018 (d) Initial Cost Gross Amount Which Carried December 31, 2019 Property Name City State Encumbrances (a) Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (b) Accumulated Depreciation at December 31, 2019 (c) Year of Construction Year Acquired Depreciable Life PHILADELPHIA CBD Cira Centre (2929 Arch Street) Philadelphia PA — — 208,570 (17,837 ) 12,586 178,147 190,733 62,966 2005 N/A (d) Three Logan Square (1717 Arch Street) Philadelphia PA — — 98,188 75,116 25,195 148,109 173,304 40,161 1990 2010 (d) Two Commerce Square (2001 Market Street) Philadelphia PA 108,472 15,323 120,200 33,693 15,323 153,893 169,216 27,952 1992 2013 (d) One Logan Square (130 North 18th Street) Philadelphia PA — 14,496 107,736 30,019 14,473 137,778 152,251 62,425 1998 2004 (d) Two Logan Square (100 North 18th Street) Philadelphia PA 81,103 16,066 100,255 20,061 16,066 120,316 136,382 49,266 1988 2004 (d) One Commerce Square (2005 Market Street) Philadelphia PA 116,571 15,161 105,021 32,326 15,160 137,348 152,508 25,304 1987 2013 (d) Cira Centre South Garage (129 South 30th Street) Philadelphia PA — — 76,008 26,832 6,905 95,935 102,840 19,682 2010 N/A (d) 1900 Market Street Philadelphia PA — 7,768 17,263 63,292 7,768 80,555 88,323 15,492 1981 2012 (d) 3020 Market Street Philadelphia PA — — 21,417 8,272 — 29,689 29,689 10,492 1959 2011 (d) 618-634 Market Street Philadelphia PA — 13,365 5,791 2,176 13,365 7,967 21,332 5,975 1966 2015 (d) FMC Tower at Cira Centre South (2929 Walnut Street) Philadelphia PA — — 400,294 13,296 — 413,590 413,590 47,285 2016 N/A (d) 2100 Market Street Philadelphia PA — 18,827 — 6,433 18,854 6,406 25,260 1,027 N/A 2015 (d) 3000 Market Street (e) Philadelphia PA — 18,924 13,080 1,039 18,924 14,119 33,043 2,979 1937 2017 (d) The Bulletin Building (3025 Market Street) (e) Philadelphia PA — — 24,377 13,353 — 37,730 37,730 2,086 1953 2017 (d) 3001-3003 JFK Boulevard (f) Philadelphia PA — — — 111 — 111 111 10 N/A 2018 (d) 3025 JFK Boulevard (f) Philadelphia PA — — — — — — — — N/A 2018 N/A METROPOLITAN WASHINGTON, D.C. 6600 Rockledge Drive Bethesda MD — — 37,421 9,270 — 46,691 46,691 14,871 1981 2006 (d) 2340 Dulles Corner Boulevard Herndon VA — 16,345 65,379 524 16,129 66,119 82,248 22,150 1987 2006 (d) 1676 International Drive Mclean VA — 18,437 97,538 (962 ) 18,785 96,228 115,013 25,451 1999 2006 (d) 8260 Greensboro Drive Mclean VA — 7,952 33,964 4,955 8,102 38,769 46,871 11,152 1980 2006 (d) 2273 Research Boulevard Rockville MD — 5,167 31,110 5,799 5,237 36,839 42,076 11,928 1999 2006 (d) 2275 Research Boulevard Rockville MD — 5,059 29,668 7,588 5,154 37,161 42,315 13,308 1990 2006 (d) 2277 Research Boulevard Rockville MD — 4,649 26,952 18,853 4,733 45,721 50,454 17,093 1986 2006 (d) 8521 Leesburg Pike Vienna VA — 4,316 30,885 7,145 4,397 37,949 42,346 11,925 1984 2006 (d) AUSTIN, TX 11501 Burnet Road - Building 1 Austin TX — 3,755 22,702 115 3,755 22,817 26,572 3,193 1991 2015 (d) 11501 Burnet Road - Building 2 Austin TX — 2,732 16,305 1,551 2,732 17,856 20,588 2,920 1991 2015 (d) 11501 Burnet Road - Building 3 Austin TX — 3,688 22,348 94 3,688 22,442 26,130 3,161 1991 2015 (d) 11501 Burnet Road - Building 4 Austin TX — 2,614 15,740 75 2,614 15,815 18,429 2,242 1991 2015 (d) 11501 Burnet Road - Building 5 Austin TX — 3,689 22,354 118 3,689 22,472 26,161 3,207 1991 2015 (d) 11501 Burnet Road - Building 6 Austin TX — 2,676 15,972 13,973 2,676 29,945 32,621 3,408 1991 2015 (d) 11501 Burnet Road - Building 8 Austin TX — 1,400 7,422 1,547 1,400 8,969 10,369 1,172 1991 2015 (d) 11501 Burnet Road - Parking Garage Austin TX — — 19,826 63 — 19,889 19,889 3,628 1991 2015 (d) Four Points Centre 3 (11120 Four Points Drive) Austin TX — 1,140 — 40,564 1,140 40,564 41,704 1,511 2019 2013 (d) One Barton Skyway (1501 South MoPac Expressway) Austin TX — 10,496 47,670 113 10,495 47,784 58,279 1,378 1999 2018 (d) Two Barton Skyway (1601 South MoPac Expressway) Austin TX — 10,849 53,868 2,828 10,848 56,697 67,545 1,810 2000 2018 (d) Three Barton Skyway (1221 South MoPac Expressway) Austin TX — 10,374 47,624 184 10,373 47,809 58,182 1,343 2001 2018 (d) Four Barton Skyway (1301 South MoPac Expressway) Austin TX — 13,301 57,041 (40 ) 13,300 57,002 70,302 1,583 2001 2018 (d) Initial Cost Gross Amount Which Carried December 31, 2019 Property Name City State Encumbrances (a) Land Building & Improvements Net Improvements (Retirements) Since Acquisition Land Building & Improvements Total (b) Accumulated Depreciation at December 31, 2019 (c) Year of Construction Year Acquired Depreciable Life Four Points Centre (11305 Four Points Drive) Austin TX — 7,800 43,581 3,463 7,800 47,044 54,844 1,427 2008 2018 (d) River Place - Building 1 (6500 River Place Boulevard) Austin TX — 2,004 17,680 476 2,004 18,156 20,160 547 2000 2018 (d) River Place - Building 2 (6500 River Place Boulevard) Austin TX — 3,137 29,254 191 3,137 29,445 32,582 816 2000 2018 (d) River Place - Building 3 (6500 River Place Boulevard) Austin TX — 3,064 26,705 12 3,064 26,717 29,781 735 2000 2018 (d) River Place - Building 4 (6500 River Place Boulevard Austin TX — 2,273 18,617 1,001 2,273 19,618 21,891 674 2000 2018 (d) River Place - Building 5 (6500 River Place Boulevard) Austin TX — 1,752 14,315 (24 ) 1,752 14,291 16,043 394 2001 2018 (d) River Place - Building 6 (6500 River Place Boulevard) Austin TX — 1,598 12,945 (24 ) 1,598 12,921 14,519 356 2001 2018 (d) River Place - Building 7 (6500 River Place Boulevard) Austin TX — 1,801 16,486 1,051 1,801 17,537 19,338 586 2002 2018 (d) Quarry Lake II (4516 Seton Center Parkway) Austin TX — 3,970 30,546 821 3,867 31,470 35,337 876 1998 2018 (d) OTHER 10 Foster Avenue Gibbsboro NJ — 244 971 69 244 1,040 1,284 624 1983 1997 (d) 7 Foster Avenue Gibbsboro NJ — 231 921 31 231 952 1,183 549 1983 1997 (d) 2 Foster Avenue Gibbsboro NJ — 185 730 11 185 741 926 741 1974 1997 (d) 4 Foster Avenue Gibbsboro NJ — 183 726 6 183 732 915 732 1974 1997 (d) 1 Foster Avenue Gibbsboro NJ — 93 364 8 93 372 465 372 1972 1997 (d) 5 U.S. Avenue Gibbsboro NJ — 21 81 2 21 83 104 83 1987 1997 (d) 5 Foster Avenue Gibbsboro NJ — 9 32 3 9 35 44 35 1968 1997 (d) Main Street - Plaza 1000 Voorhees NJ — 2,732 10,942 296 2,732 11,238 13,970 11,008 1988 1997 (d) Main Street - Piazza Voorhees NJ — 696 2,802 3,700 704 6,494 7,198 3,515 1990 1997 (d) Main Street - Promenade Voorhees NJ — 532 2,052 312 532 2,364 2,896 1,350 1988 1997 (d) 920 North King Street Wilmington DE — 6,141 21,140 7,969 6,141 29,109 35,250 13,046 1989 2004 (d) 300 Delaware Avenue Wilmington DE — 6,369 13,739 2,638 6,369 16,377 22,746 9,031 1989 2004 (d) Total: $ 315,437 $ 443,949 $ 2,886,455 $ 676,055 $ 489,702 $ 3,516,757 $ 4,006,459 $ 973,318 (a) Excludes the effect of any net interest premium/(discount) and deferred financing costs. (b) Reconciliation of Real Estate: The following table reconciles the real estate investments from January 1, 2017 to December 31, 2019 (in thousands): 2019 2018 2017 Balance at beginning of year $ 3,951,719 $ 3,830,824 $ 3,658,438 Additions: Acquisitions — 509,654 62,587 Capital expenditures and assets placed into service 145,378 129,274 356,857 Less: Dispositions/impairments/placed into redevelopment (50,792 ) (469,517 ) (189,472 ) Retirements (39,846 ) (48,516 ) (57,586 ) Balance at end of year $ 4,006,459 $ 3,951,719 $ 3,830,824 Per consolidated balance sheet $ 4,006,459 $ 3,951,719 $ 3,830,824 The aggregate cost for federal income tax purposes is $3.2 billion as of December 31, 2019 . (c) Reconciliation of Accumulated Depreciation: The following table reconciles the accumulated depreciation on real estate investments from January 1, 2017 to December 31, 2019 (in thousands): 2019 2018 2017 Balance at beginning of year $ 885,407 $ 913,297 $ 885,392 Additions: Depreciation expense 144,131 137,213 154,029 Less: Dispositions/impairments/placed into redevelopment (16,783 ) (117,589 ) (74,178 ) Retirements (39,437 ) (47,514 ) (51,946 ) Balance at end of year $ 973,318 $ 885,407 $ 913,297 Per consolidated balance sheet $ 973,318 $ 885,407 $ 913,297 (d) Depreciation of the buildings and improvements are calculated over lives ranging from the life of the lease to 55 years . (e) Reflects original construction date. Significant improvements were made to 3000 Market Street in 1988 and The Bulletin Building in 2012. (f) Represent leasehold interests in a land parcels acquired through prepaid 99 -year ground leases. Development has not yet commenced on the parcel. Building and improvements represent costs related to parking operations. (g)

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2019
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, 2019 and 2018 , the Company included in its consolidated balance sheets consolidated VIEs having total assets of $392.0 million and $414.3 million , respectively, and total liabilities of $255.6 million and $254.1 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 to twelve months. The Company also considers information obtained about each property as a result of its pre-acquisition due diligence, marketing, and leasing activities in estimating the fair value of the tangible and intangible assets acquired. The Company also uses the information obtained as a result of its pre-acquisition due diligence as part of its consideration of the accounting standard governing asset retirement obligations and when necessary, will record a conditional asset retirement obligation as part of its purchase price. The Company also evaluates tenant relationships on a tenant-specific basis. On most of the Company’s acquisitions, this intangible has not been material and, as a result, no value has been assigned. In the event that a tenant terminates its lease, the unamortized portion of each intangible, including in-place lease values and tenant relationship values, is charged to expense and market rate adjustments (above or below) are recorded to revenue.
Depreciation and Amortization	Depreciation and Amortization The costs of buildings and improvements are depreciated using the straight-line method based on the following useful lives: buildings and improvements ( 5 to 55 years) and tenant improvements (the shorter of (i) the life of the asset ( 1 to 16 years) or (ii) the lease term).
Construction-in-Progress	Construction-in-Progress
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” and “Lease liability - operating leases”, respectively, on the consolidated balance sheet as of December 31, 2019. 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. 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 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	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	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. 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	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	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, 2019 and 2018, 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.
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 $3.2 billion and $3.3 billion for the years ended December 31, 2019 and December 31, 2018 , 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 2019 , 2018 or 2017 . 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, 2019 and December 31, 2018 . 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, 2018, 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 $3.2 billion and $3.3 billion for the years ended December 31, 2019 and December 31, 2018 , 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 Plans
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. Non-financial assets and liabilities recorded at fair value on a non-recurring basis include non-financial assets and liabilities measured at fair value in a purchase price allocation and the impairment. The fair values assigned to the Company's purchase price allocations primarily utilize Level 3 inputs. The fair value assigned to the long-lived assets and equity method investments for which there was impairment recorded utilize Level 3 inputs
Recent Accounting Pronouncements	. New Accounting Pronouncements Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), modifying the principles for the recognition, measurement, presentation, and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification determines whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and lease liability for all leases with a term of greater than twelve months regardless of their classification. Leases with a term of twelve months or less will be accounted for in the same manner as operating leases under ASC 840, Leases. The new standard requires lessors to account for leases using an approach that is substantially equivalent to previous guidance for sales-type leases, direct financing leases, and operating leases. The guidance supersedes previously issued guidance under ASC 840. The Company adopted Topic 842 effective January 1, 2019. In applying the modified retrospective transition method, the Company elected the package of practical expedients available for implementation, which allows for the following: • An entity need not reassess whether any expired or existing contracts are or contain leases; • An entity need not reassess the lease classification for any expired or existing leases; and • An entity need not reassess initial direct costs for any existing leases. Furthermore, the Company elected the optional transition method to make January 1, 2019 the initial application date of the standard. This package of practical expedients allows entities to account for their existing leases for the remainder of their respective lease terms following the previous accounting guidance. The Company also elected to adopt the optional transition practical expedient provided in ASU 2018-01 to not evaluate under Topic 842 for existing or expired land easements prior to the application date to determine if they meet the definition of a lease. The Company also elected to adopt the practical expedient offered in ASU 2018-11 that allows lessors to not allocate the total consideration to lease and nonlease components, such as tenant reimbursements, based on their relative standalone selling prices as the timing and pattern of revenue recognition of the combined single lease component is the same and the leases are classified as operating leases. The Company elected to adopt ASU 2018-20, which allows lessors to not evaluate whether certain sales taxes and other similar taxes are lessor costs or lessee costs. Instead, lessors will account for those costs as if they are lessee costs. All collections from lessees of taxes within the scope of the election are excluded from the consideration of the contract and from variable payments not included in the consideration of the contract. The Company has evaluated all leases for collectability and is recognizing lease payments for certain leases on a cash basis because collectability of substantially all of the lease payments is not probable. As a result, the write off of the accrued rent receivable of $0.7 million was recorded by the Company upon adoption of Topic 842 as a cumulative effect of accounting change adjustment to equity through “Cumulative earnings” on the consolidated balance sheets. While adoption of the practical expedient allows the Company to not revisit the classification of existing leases, the Company measured the present value of the future lease payments for each ground lease agreement for which the Company is the lessor and recognized a right of use asset and lease liability in the aggregate amount of $22.4 million , each as of January 1, 2019. New Accounting Pronouncements Issued but not yet Adopted 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 is effective for the Company on January 1, 2020. The Company has evaluated the impact of this new guidance on reserves for notes receivable, and has concluded that the guidance will not have a material impact on its consolidated financial statements.

ORGANIZATION OF THE PARENT CO_2

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP (Tables)	12 Months Ended
	Dec. 31, 2019
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, as of December 31, 2019 , excludes one development property and four redevelopment properties under construction or committed for construction (collectively, the “Core Properties”). The Properties were comprised of the following as of December 31, 2019 : Number of Properties Rentable Square Feet Office properties 86 15,450,417 Mixed-use properties 4 659,625 Core Properties 90 16,110,042 Development property 1 204,108 Redevelopment properties 4 397,237 The Properties 95 16,711,387

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Schedule of Revision of Previously Issued Financial Statements	Balance sheet impacts (in thousands) : December 31, 2018 Balance Sheet: As previously reported Adjustments As adjusted Assets (Parent Company and Operating Partnership) Operating properties 3,953,319 (1,600 ) 3,951,719 Accumulated depreciation (865,462 ) (19,945 ) (885,407 ) Operating real estate investments, net 3,087,857 (21,545 ) 3,066,312 Total assets 4,098,521 (21,545 ) 4,076,976 Equity (Parent Company) Additional Paid-in Capital 3,200,850 (538 ) 3,200,312 Cumulative Earnings 796,513 (20,888 ) 775,625 Total Brandywine Realty Trust's equity 1,820,253 (21,426 ) 1,798,827 Noncontrolling interests 12,320 (119 ) 12,201 Total beneficiaries' equity 1,832,573 (21,545 ) 1,811,028 Total liabilities and beneficiaries' equity 4,098,521 (21,545 ) 4,076,976 Equity (Operating Partnership) General Partnership Capital 1,813,136 (21,545 ) 1,791,591 Total Brandywine Operating Partnership, L.P.'s equity 1,817,861 (21,545 ) 1,796,316 Total partners' equity 1,820,053 (21,545 ) 1,798,508 Total liabilities and partners' equity 4,098,521 (21,545 ) 4,076,976 Statement of Beneficiaries’ / Partners’ Equity impacts (in thousands): Twelve months ended December 31, 2018 Brandywine Realty Trust As previously reported Adjustments As adjusted Statement of Beneficiaries' Equity: Additional paid-in capital, beginning of period 3,218,564 (487 ) 3,218,077 Cumulative earnings, beginning of period 660,174 (19,081 ) 641,093 Noncontrolling interest, beginning of period 17,420 (162 ) 17,258 Additional paid-in capital, December 31, 2018 3,200,850 (538 ) 3,200,312 Cumulative earnings, December 31, 2018 796,513 (20,888 ) 775,625 Noncontrolling interests, December 31, 2018 12,320 (119 ) 12,201 Brandywine Operating Partnership Statement of Partners' Equity: Partner Capital, beginning of period 1,815,411 (19,727 ) 1,795,684 Partner Capital, December 31, 2018 1,813,136 (21,545 ) 1,791,591 Twelve months ended December 31, 2017 Brandywine Realty Trust As previously reported Adjustments As adjusted Statement of Beneficiaries' Equity: Additional paid-in capital, beginning of period 3,258,870 (484 ) 3,258,386 Cumulative earnings, beginning of period 539,319 (18,405 ) 520,914 Noncontrolling interest, beginning of period 17,093 (160 ) 16,933 Additional paid-in capital, December 31, 2017 3,218,564 (487 ) 3,218,077 Cumulative earnings, December 31, 2017 660,174 (19,081 ) 641,093 Noncontrolling interests, December 31, 2017 17,420 (162 ) 17,258 Brandywine Operating Partnership Statement of Partners' Equity: Partner Capital, beginning of period 1,762,764 (19,049 ) 1,743,715 Partner Capital, December 31, 2017 1,815,411 (19,727 ) 1,795,684
Disaggregation of Revenue	The following is a summary of revenue earned by the Company’s reportable segments (see Note 18, ''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, 2019
Real Estate [Abstract]
Gross Carrying Value of Operating Properties	As of December 31, 2019 and 2018 , the gross carrying value of the operating properties was as follows (in thousands): December 31, 2019 December 31, 2018 Land $ 489,702 $ 487,301 Building and improvements 3,049,395 3,048,889 Tenant improvements 467,362 415,529 Total $ 4,006,459 $ 3,951,719
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, 2019 2018 2017 Development $ 3,047 $ 3,185 $ 4,390 Redevelopment 775 968 319 Tenant Improvements 3,609 2,811 1,354 Total $ 7,431 $ 6,964 $ 6,063
Schedule of Purchase Price Allocation	The purchase price and acquisition-related costs have been allocated as follows (in thousands): July 28, 2017 Building, land and improvements $ 32,004 Intangible assets acquired (a) 2,562 Below market lease liabilities assumed (b) (1,818 ) $ 32,748 (a) Weighted average amortization period of 5.9 years . (b) Weighted average amortization period of 6.0 years . 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. October 13, 2017 Building and improvements $ 30,583 Construction-in-progress 672 Intangible assets acquired (a) 10,575 Below market lease liabilities assumed (b) (4,055 ) $ 37,775 (a) Weighted average amortization period of 7.9 years . (b) Weighted average amortization period of 7.0 years .
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 properties sold during the years ended December 31, 2019, 2018 and 2017 (dollars in thousands): Property/Portfolio Name Disposition Date Location Property Type Rentable Square Feet/ Acres Sales Price Gain/(Loss) on Sale (a) 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 (b) December 21, 2018 Camden, NJ Mixed-use 83,000 45,300 2,570 Rockpoint Portfolio (c) 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 (d) 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 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) November 22, 2017 Newtown Square, PA Office 252,802 42,000 19,642 630 Allendale Road October 31, 2017 King of Prussia, PA Office 150,000 17,500 3,605 50 E. Swedesford Square September 13, 2017 Malvern, PA Land 12.0 acres 7,200 882 Bishop's Gate July 18, 2017 Mount Laurel, NJ Land 49.5 acres 6,000 71 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) (e) June 27, 2017 Marlton, NJ Office 134,794 9,700 (325 ) 7000 Midlantic Drive June 12, 2017 Mount Laurel, NJ Retail 10,784 8,200 1,413 Garza Ranch - Multi-family (d) April 28, 2017 Austin, TX Land 8.4 acres 11,800 1,311 200, 210 & 220 Lake Drive East (Woodland Falls) March 30, 2017 Cherry Hill, NJ Office 215,465 19,000 (249 ) Philadelphia Marine Center (Marine Piers) (f) March 15, 2017 Philadelphia, PA Mixed-use 181,900 21,400 6,498 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) (g) March 13, 2017 Beltsville, MD Office 313,810 9,000 — Gateway Land - Site C February 15, 2017 Richmond, VA Land 4.8 acres 1,100 — 1200 & 1220 Concord Avenue (Concord Airport Plaza) February 2, 2017 Concord, CA Office 350,256 33,100 551 Garza Ranch - Hotel (d) January 30, 2017 Austin, TX Land 1.7 acres 3,500 192 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) 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. (c) 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.” (d) The Company had continuing involvement in these properties through a completion guaranty, which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. 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 sales 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. (e) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million . The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25% , respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy. The loss on sale in the table above represents additional closing costs. (f) On the closing date, the buyer paid $12.0 million in cash and the Company received cash proceeds of $11.2 million , after closing costs and prorations. The $9.4 million balance of the purchase price was due on (a) January 31, 2020 , in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it was appropriate to recognize the sale of the sublease interest in the Marine Piers and to defer the remaining $9.4 million balance due under the purchase and sale agreement until collectability can be determined. During the first quarter of 2019, the tenant at the Marine Piers exercised its option to extend the term of its sublease. As a result, the $9.4 million balance of the purchase price is due on January 15, 2024, and the Company will recognize the additional gain on sale when the gain is realized or realizable. (g) During the twelve months ended 2017, there was a price reduction of $1.7 million under the agreement of sale and additional impairment of $1.7 million was recognized. The summary of the transaction is as follows (in thousands); October 18, 2017 Gross sales price $ 333,250 Debt principal (150,968 ) Debt prepayment penalties (2,120 ) Closing costs and net prorations (7,420 ) Cash to Austin Venture $ 172,742 Company's ownership interest 50 % Cash to the Company $ 86,371 Cash to Austin Venture $ 172,742 Austin Venture basis of sold properties (92,559 ) Austin Venture gain on sale $ 80,183 Company's ownership interest 50 % Company's share of gain $ 40,092 Company's share of gain $ 40,092 Deferred gain from partial sale 12,072 Gain on real estate venture transactions $ 52,164

INVESTMENT IN UNCONSOLIDATED _2

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES (Tables)	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Summary of Financial Position	The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2019 and December 31, 2018 (in thousands): December 31, 2019 MAP Venture Brandywine-AI Venture LLC Other Total Net property 192,582 24,651 617,134 $ 834,367 Other assets (a) 256,453 3,000 82,549 342,002 Other liabilities (a) 266,200 824 23,047 290,071 Debt, net (b) 181,525 — 403,543 585,068 Equity (c) 1,310 26,827 273,093 301,230 December 31, 2018 MAP Venture Brandywine-AI Venture LLC Other Total Net property 198,043 47,043 590,897 835,983 Other assets (a) 65,465 11,206 82,828 159,499 Other liabilities (a) 59,348 2,002 24,331 85,681 Debt, net (b) 180,555 26,020 159,132 365,707 Equity (c) 23,605 30,227 490,262 544,094 (a) The increase is primarily due to the recording of lease related assets and liabilities of $197.1 million and $206.4 million , respectively, for MAP Venture in connection with the adoption of Topic 842. (b) The increase is primarily due to third-party debt financing received by Herndon Innovation Center Venture during 2019. See “Herndon Innovation Center Metro Portfolio Venture” section below for further information. (c) 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.
Investment in Real Estate Ventures and Share of Real Estate Ventures' Income (Loss)	The Company’s investment in Real Estate Ventures as of December 31, 2019 and 2018 , and the Company’s share of the Real Estate Ventures’ income (loss) for the years ended December 31, 2019 and 2018 was as follows (in thousands): Ownership Percentage (a) Carrying Amount Company's Share of Real Estate Venture Income (Loss) Real Estate Venture Debt at 100%, gross 2019 2018 2019 2018 2019 2018 Office Properties Brandywine - AI Venture LLC 50% $ 10,116 $ 11,731 $ (2,800 ) $ (14,559 ) $ — $ 26,111 Herndon Innovation Center Metro Portfolio Venture, LLC 15% 16,446 47,834 (498 ) 83 207,302 — MAP Venture 50% (70 ) 11,173 (6,102 ) (2,155 ) 185,000 185,000 PJP VII 25% (b) — 1,100 190 157 — 3,777 PJP II 30% (b) — 663 81 179 — 2,214 PJP VI 25% (b) — 125 (185 ) 71 — 7,069 Austin Venture 50% (c) — — — 1,687 — — Other 1919 Venture 50% 17,524 19,897 328 253 88,860 88,860 evo at Cira Centre South Venture 50% — — — (358 ) — — Development Properties 4040 Wilson Venture (d) 50% 37,002 37,371 (368 ) (192 ) 114,845 57,288 JBG - 51 N Street (d) 70% 21,531 21,368 (313 ) (137 ) — — JBG - 1250 First Street Office (d) 70% 17,745 17,838 (255 ) (260 ) — — $ 120,294 $ 169,100 $ (9,922 ) $ (15,231 ) $ 596,007 $ 370,319 (a) Ownership percentage represents the Company’s entitlement to residual distributions after payments of priority returns, where applicable. (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) The Company’s purchased its partner’s entire 50% interest in this venture on December 11, 2018. Refer to the "Austin Venture" section below for more information. (d) This entity is a VIE. The following is a summary of the financial position of the Real Estate Ventures as of December 31, 2019 and December 31, 2018 (in thousands): December 31, 2019 MAP Venture Brandywine-AI Venture LLC Other Total Net property 192,582 24,651 617,134 $ 834,367 Other assets (a) 256,453 3,000 82,549 342,002 Other liabilities (a) 266,200 824 23,047 290,071 Debt, net (b) 181,525 — 403,543 585,068 Equity (c) 1,310 26,827 273,093 301,230 December 31, 2018 MAP Venture Brandywine-AI Venture LLC Other Total Net property 198,043 47,043 590,897 835,983 Other assets (a) 65,465 11,206 82,828 159,499 Other liabilities (a) 59,348 2,002 24,331 85,681 Debt, net (b) 180,555 26,020 159,132 365,707 Equity (c) 23,605 30,227 490,262 544,094 (a) The increase is primarily due to the recording of lease related assets and liabilities of $197.1 million and $206.4 million , respectively, for MAP Venture in connection with the adoption of Topic 842. (b) The increase is primarily due to third-party debt financing received by Herndon Innovation Center Venture during 2019. See “Herndon Innovation Center Metro Portfolio Venture” section below for further information. (c) 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, 2019 , 2018 and 2017 (in thousands): Year Ended December 31, 2019 MAP Venture Brandywine-AI Venture LLC Other Total Revenue $ 70,366 $ 6,022 $ 55,970 $ 132,358 Operating expenses (47,362 ) (2,912 ) (21,510 ) (71,784 ) Provision for impairment — (5,664 ) — (5,664 ) Interest expense, net (9,752 ) (698 ) (11,458 ) (21,908 ) Depreciation and amortization (25,413 ) (2,514 ) (25,404 ) (53,331 ) Loss on extinguishment of debt — — (1,231 ) (1,231 ) Net loss $ (12,161 ) $ (5,766 ) $ (3,633 ) $ (21,560 ) Ownership interest % 50 % 50 % Various Various Company's share of net loss $ (6,081 ) $ (2,883 ) $ (901 ) $ (9,865 ) Basis adjustments and other (21 ) 83 (119 ) (57 ) Equity in loss of Real Estate Ventures $ (6,102 ) $ (2,800 ) $ (1,020 ) $ (9,922 ) Year Ended December 31, 2018 MAP Venture Austin Venture Brandywine-AI Venture LLC evo at Cira Centre South Other Total Revenue $ 68,622 $ 53,476 $ 23,515 $ 163 $ 19,550 $ 165,326 Operating expenses (41,056 ) (22,994 ) (10,483 ) (256 ) (7,246 ) (82,035 ) Interest expense, net (12,690 ) (9,083 ) (3,478 ) (123 ) (4,400 ) (29,774 ) Depreciation and amortization (18,891 ) (19,226 ) (8,991 ) (409 ) (6,309 ) (53,826 ) Provision for impairment — — (20,832 ) — — (20,832 ) Loss on extinguishment of debt (334 ) (356 ) (695 ) — — (1,385 ) Net income (loss) $ (4,349 ) $ 1,817 $ (20,964 ) $ (625 ) $ 1,595 $ (22,526 ) Ownership interest % 50 % 50 % 50 % 50 % Various Various Company's share of net income (loss) $ (2,175 ) $ 909 $ (10,482 ) $ (313 ) $ 137 $ (11,924 ) Other than temporary impairment — — (4,076 ) — — (4,076 ) Basis adjustments and other 20 778 (1 ) (45 ) 17 769 Equity in income (loss) of Real Estate Ventures $ (2,155 ) $ 1,687 $ (14,559 ) $ (358 ) $ 154 $ (15,231 ) Year Ended December 31, 2017 MAP Venture Austin Venture Brandywine-AI Venture LLC evo at Cira Centre South Other Total Revenue $ 68,573 $ 85,500 $ 29,500 $ 12,285 $ 20,413 $ 216,271 Operating expenses (40,035 ) (35,997 ) (12,298 ) (3,075 ) (7,935 ) (99,340 ) Interest expense, net (13,677 ) (13,985 ) (4,707 ) (4,092 ) (3,752 ) (40,213 ) Depreciation and amortization (21,202 ) (34,026 ) (11,428 ) (4,512 ) (7,272 ) (78,440 ) Loss on extinguishment of debt — (2,613 ) (811 ) — — (3,424 ) Net income (loss) $ (6,341 ) $ (1,121 ) $ 256 $ 606 $ 1,454 $ (5,146 ) Ownership interest % 50 % 50 % 50 % 50 % Various Company's share of net income (loss) $ (3,171 ) $ (560 ) $ 128 $ 303 $ 1,436 $ (1,864 ) Other than temporary impairment — — (4,844 ) — — (4,844 ) Basis adjustments and other (272 ) (429 ) 251 146 (1,294 ) (1,598 ) Equity in income (loss) of Real Estate Ventures $ (3,443 ) $ (989 ) $ (4,465 ) $ 449 $ 142 $ (8,306 )
Schedule of Maturities of Long-term Debt	As of December 31, 2019 , the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2020 $ — 2021 114,845 2022 — 2023 273,860 2024 207,302 Thereafter — Total principal payments 596,007 Net deferred financing costs (10,939 ) Outstanding indebtedness $ 585,068 As of December 31, 2019 , the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands): 2020 $ 87,226 2021 15,143 2022 256,332 2023 556,736 2024 350,000 Thereafter 878,610 Total principal payments 2,144,047 Net unamortized premiums/(discounts) 10,707 Net deferred financing costs (10,336 ) Outstanding indebtedness $ 2,144,418
Summary of Gain on Sale for Each Land Parcel	The following table summarizes the properties sold during the years ended December 31, 2019, 2018 and 2017 (dollars in thousands): Property/Portfolio Name Disposition Date Location Property Type Rentable Square Feet/ Acres Sales Price Gain/(Loss) on Sale (a) 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 (b) December 21, 2018 Camden, NJ Mixed-use 83,000 45,300 2,570 Rockpoint Portfolio (c) 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 (d) 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 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square) November 22, 2017 Newtown Square, PA Office 252,802 42,000 19,642 630 Allendale Road October 31, 2017 King of Prussia, PA Office 150,000 17,500 3,605 50 E. Swedesford Square September 13, 2017 Malvern, PA Land 12.0 acres 7,200 882 Bishop's Gate July 18, 2017 Mount Laurel, NJ Land 49.5 acres 6,000 71 Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center) (e) June 27, 2017 Marlton, NJ Office 134,794 9,700 (325 ) 7000 Midlantic Drive June 12, 2017 Mount Laurel, NJ Retail 10,784 8,200 1,413 Garza Ranch - Multi-family (d) April 28, 2017 Austin, TX Land 8.4 acres 11,800 1,311 200, 210 & 220 Lake Drive East (Woodland Falls) March 30, 2017 Cherry Hill, NJ Office 215,465 19,000 (249 ) Philadelphia Marine Center (Marine Piers) (f) March 15, 2017 Philadelphia, PA Mixed-use 181,900 21,400 6,498 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton) (g) March 13, 2017 Beltsville, MD Office 313,810 9,000 — Gateway Land - Site C February 15, 2017 Richmond, VA Land 4.8 acres 1,100 — 1200 & 1220 Concord Avenue (Concord Airport Plaza) February 2, 2017 Concord, CA Office 350,256 33,100 551 Garza Ranch - Hotel (d) January 30, 2017 Austin, TX Land 1.7 acres 3,500 192 (a) Gain/(Loss) on Sale is net of closing and other transaction related costs. (b) 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. (c) 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.” (d) The Company had continuing involvement in these properties through a completion guaranty, which required the Company, as developer, to complete certain infrastructure improvements on behalf of the buyers of the land parcels. 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 sales 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. (e) As of March 31, 2017, the Company evaluated the recoverability of the carrying value of its properties that triggered assessment under the undiscounted cash flow model. Based on the Company’s evaluation, it was determined that due to the reduction in the Company’s intended hold period of four properties located in the Other segment, the Company would not recover the carrying values of these properties. Accordingly, the Company recorded impairment charges on these properties of $1.0 million at March 31, 2017, which reduced the aggregate carrying values of the properties from $10.2 million to their estimated fair value of $9.2 million . The Company measured these impairments based on a discounted cash flow analysis, using a hold period of 10 years and residual capitalization rates and discount rates of 9.00% and 9.25% , respectively. The results were comparable to indicative pricing in the market. The assumptions used to determine fair value under the income approach are Level 3 inputs in accordance with the fair value hierarchy. The loss on sale in the table above represents additional closing costs. (f) On the closing date, the buyer paid $12.0 million in cash and the Company received cash proceeds of $11.2 million , after closing costs and prorations. The $9.4 million balance of the purchase price was due on (a) January 31, 2020 , in the event that the tenant at the Marine Piers does not exercise an option it holds to extend the term of the sublease or (b) January 15, 2024, in the event that the tenant does exercise the option to extend the term of the sublease. The Company determined that it was appropriate to recognize the sale of the sublease interest in the Marine Piers and to defer the remaining $9.4 million balance due under the purchase and sale agreement until collectability can be determined. During the first quarter of 2019, the tenant at the Marine Piers exercised its option to extend the term of its sublease. As a result, the $9.4 million balance of the purchase price is due on January 15, 2024, and the Company will recognize the additional gain on sale when the gain is realized or realizable. (g) During the twelve months ended 2017, there was a price reduction of $1.7 million under the agreement of sale and additional impairment of $1.7 million was recognized. The summary of the transaction is as follows (in thousands); October 18, 2017 Gross sales price $ 333,250 Debt principal (150,968 ) Debt prepayment penalties (2,120 ) Closing costs and net prorations (7,420 ) Cash to Austin Venture $ 172,742 Company's ownership interest 50 % Cash to the Company $ 86,371 Cash to Austin Venture $ 172,742 Austin Venture basis of sold properties (92,559 ) Austin Venture gain on sale $ 80,183 Company's ownership interest 50 % Company's share of gain $ 40,092 Company's share of gain $ 40,092 Deferred gain from partial sale 12,072 Gain on real estate venture transactions $ 52,164

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	Lease payments on noncancellable leases at December 31, 2019 are as follows (in thousands): Year Minimum Rent 2020 $ 1,217 2021 1,232 2022 1,248 2023 1,263 2024 1,305 Thereafter 110,452 Total lease payments $ 116,717 Less: Imputed interest 94,163 Present value of operating lease liabilities $ 22,554
Operating Lease Liabilities Maturity Schedule	Lease payments on noncancellable leases at December 31, 2019 are as follows (in thousands): Year Minimum Rent 2020 $ 389,956 2021 369,375 2022 338,435 2023 311,729 2024 280,631 Thereafter 1,234,006
Operating Leases Future Minimum Payments Receivable	Lease payments on noncancellable leases at December 31, 2018, which were determined under ASC 840 and are therefore not adjusted for increases based on CPI, are as follows (in thousands): Year Minimum Rent 2019 $ 1,222 2020 1,222 2021 1,222 2022 1,222 2023 1,222 Thereafter 55,689 Total $ 61,799 Lease payments on noncancellable leases at December 31, 2018, which were determined under under ASC 840 and are therefore not adjusted for increases based on CPI, are as follows (in thousands): Year Minimum Rent 2019 392,058 2020 372,619 2021 349,160 2022 304,445 2023 277,388 Thereafter 1,265,810
Lease Payments and Costs	The table below summarizes the Company’s operating lease cost (in thousands) recognized through “Property operating expenses” on the consolidated statements of operations: Twelve Months Ended December 31, Lease Cost 2019 Fixed lease cost $ 2,100 Variable lease cost 54 Total $ 2,154 Weighted-average remaining lease term (years) 52.7 Weighted-average discount rate 6.3 %

DEFERRED COSTS (Tables)

DEFERRED COSTS (Tables)	12 Months Ended
	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure	As of December 31, 2019 and 2018 , the Company’s deferred costs were comprised of the following (in thousands): 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 December 31, 2018 Total Cost Accumulated Amortization Deferred Costs, net Leasing costs $ 144,831 $ (56,846 ) $ 87,985 Financing costs - Revolving Credit Facility 6,298 (3,208 ) 3,090 Total $ 151,129 $ (60,054 ) $ 91,075

INTANGIBLE ASSETS (Tables)

INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets and Liabilities	As of December 31, 2019 and 2018 , the Company’s intangible assets were comprised of the following (in thousands): 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 December 31, 2018 Total Cost Accumulated Amortization Intangible Assets, net Intangible assets, net: In-place lease value $ 181,887 $ (53,376 ) $ 128,511 Tenant relationship value 9,564 (8,551 ) 1,013 Above market leases acquired 4,966 (3,142 ) 1,824 Total intangible assets, net $ 196,417 $ (65,069 ) $ 131,348 Total Cost Accumulated Amortization Intangible Liabilities, net Intangible liabilities, net: Below market leases acquired $ 49,655 $ (17,872 ) $ 31,783
Summary of Amortization for Intangible Assets and Liabilities	As of December 31, 2019 , the Company’s annual amortization for its intangible assets/liabilities, assuming no early lease terminations, are as follows (dollars in thousands): Assets Liabilities 2020 $ 27,813 $ 5,270 2021 17,887 3,856 2022 12,067 2,263 2023 9,236 1,722 2024 6,317 1,434 Thereafter 11,531 7,718 Total $ 84,851 $ 22,263

DEBT OBLIGATIONS (Tables)

DEBT OBLIGATIONS (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Consolidated debt obligations	The following table sets forth information regarding the Company’s consolidated debt obligations outstanding at December 31, 2019 and 2018 (in thousands): December 31, 2019 December 31, 2018 Effective Maturity Date MORTGAGE DEBT: Two Logan Square $ 81,103 $ 82,805 3.98% May 2020 Four Tower Bridge 9,291 9,526 4.50% (a) February 2021 One Commerce Square 116,571 120,183 3.64% April 2023 Two Commerce Square 108,472 110,518 4.51% April 2023 Principal balance outstanding 315,437 323,032 Plus: fair market value premium (discount), net (1,383 ) (1,759 ) Less: deferred financing costs (242 ) (404 ) Mortgage indebtedness $ 313,812 $ 320,869 UNSECURED DEBT $600 million Unsecured Credit Facility $ — $ 92,500 LIBOR + 1.10% July 2022 Seven-Year Term Loan - Swapped to fixed 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 350,000 250,000 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 350,000 250,000 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 1,721,110 Plus: original issue premium (discount), net 12,090 (4,096 ) Less: deferred financing costs (10,094 ) (9,837 ) Total unsecured indebtedness $ 1,830,606 $ 1,707,177 Total Debt Obligations $ 2,144,418 $ 2,028,046 (a) Assumed upon acquisition of the related property on January 5, 2018. The interest rate reflects the market rate at the time of acquisition.
Schedule of Maturities of Long-term Debt	As of December 31, 2019 , the aggregate principal payments of recourse and non-recourse debt payable to third-parties are as follows (in thousands): 2020 $ — 2021 114,845 2022 — 2023 273,860 2024 207,302 Thereafter — Total principal payments 596,007 Net deferred financing costs (10,939 ) Outstanding indebtedness $ 585,068 As of December 31, 2019 , the Company’s aggregate scheduled principal payments of debt obligations, excluding amortization of discounts and premiums, are as follows (in thousands): 2020 $ 87,226 2021 15,143 2022 256,332 2023 556,736 2024 350,000 Thereafter 878,610 Total principal payments 2,144,047 Net unamortized premiums/(discounts) 10,707 Net deferred financing costs (10,336 ) Outstanding indebtedness $ 2,144,418

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 December 31, 2018 Carrying Amount (a) Fair Value Carrying Amount (a) Fair Value Unsecured notes payable $ 1,503,435 $ 1,591,830 $ 1,288,024 $ 1,262,570 Variable rate debt $ 327,171 $ 309,947 $ 419,153 $ 402,924 Mortgage notes payable $ 313,812 $ 317,031 $ 320,869 $ 318,515 Notes receivable $ 44,430 $ 43,322 $ 47,771 $ 47,747 (a) The carrying amounts presented in the table above are net of deferred financing costs of $8.7 million and $7.9 million for unsecured notes payable, $1.4 million and $2.0 million for variable rate debt and $0.2 million and $0.4 million for mortgage notes payable as of December 31, 2019 and December 31, 2018 , respectively.

DERIVATIVE FINANCIAL INSTRUME_2

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 and December 31, 2018 . 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 12/31/2019 12/31/2018 12/31/2019 12/31/2018 Assets Swap Interest Rate Cash Flow (a) $ — $ 25,774 3.090 % January 6, 2012 October 30, 2019 $ — $ 183 Liabilities Swap Interest Rate Cash Flow (b) $ 250,000 $ 250,000 2.868 % October 8, 2015 October 8, 2022 $ (562 ) $ 7,008 Swap Interest Rate Cash Flow (b) $ 25,774 $ 25,774 3.300 % December 22, 2011 January 30, 2021 (94 ) 292 $ 275,774 $ 301,548 (a) On October 30, 2019, the interest rate hedge contract for this swap expired. (b) Hedging unsecured variable rate debt.

BENEFICIARIES' EQUITY OF THE _2

BENEFICIARIES' EQUITY OF THE PARENT COMPANY (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Earnings Per Share (EPS), Basic and Diluted	The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year Ended December 31, 2019 2018 2017 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 34,529 $ 34,529 $ 135,472 $ 135,472 $ 121,177 $ 121,177 Net income attributable to noncontrolling interests (262 ) (262 ) (954 ) (954 ) (1,004 ) (1,004 ) Nonforfeitable dividends allocated to unvested restricted shareholders (396 ) (396 ) (369 ) (369 ) (327 ) (327 ) Distribution to preferred shareholders — — — — (2,032 ) (2,032 ) Preferred share redemption charge — — — — (3,181 ) (3,181 ) Net income attributable to common shareholders $ 33,871 $ 33,871 $ 134,149 $ 134,149 $ 114,633 $ 114,633 Denominator Weighted-average shares outstanding 176,132,941 176,132,941 178,519,748 178,519,748 175,484,350 175,484,350 Contingent securities/Share based compensation — 553,872 — 1,121,744 — 1,323,816 Weighted-average shares outstanding 176,132,941 176,686,813 178,519,748 179,641,492 175,484,350 176,808,166 Earnings per Common Share: Net income attributable to common shareholders $ 0.19 $ 0.19 $ 0.75 $ 0.75 $ 0.65 $ 0.65 The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year Ended December 31, 2019 2018 2017 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 34,529 $ 34,529 $ 135,472 $ 135,472 $ 121,177 $ 121,177 Net income attributable to noncontrolling interests (69 ) (69 ) (55 ) (55 ) (29 ) (29 ) Nonforfeitable dividends allocated to unvested restricted unitholders (396 ) (396 ) (369 ) (369 ) (327 ) (327 ) Preferred unit dividends — — — — (2,032 ) (2,032 ) Preferred unit redemption charge — — — — (3,181 ) (3,181 ) Net income attributable to common unitholders $ 34,064 $ 34,064 $ 135,048 $ 135,048 $ 115,608 $ 115,608 Denominator Weighted-average units outstanding 177,114,932 177,114,932 179,959,370 179,959,370 176,964,149 176,964,149 Contingent securities/Share based compensation — 553,872 — 1,121,744 — 1,323,816 Total weighted-average units outstanding 177,114,932 177,668,804 179,959,370 181,081,114 176,964,149 178,287,965 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 0.19 $ 0.19 $ 0.75 $ 0.75 $ 0.65 $ 0.65

PARTNER'S EQUITY OF THE PAREN_2

PARTNER'S EQUITY OF THE PARENT COMPANY (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Earnings Per Share (EPS), Basic and Diluted	The following tables detail the number of shares and net income used to calculate basic and diluted earnings per share (in thousands, except share and per share amounts; results may not add due to rounding): Year Ended December 31, 2019 2018 2017 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 34,529 $ 34,529 $ 135,472 $ 135,472 $ 121,177 $ 121,177 Net income attributable to noncontrolling interests (262 ) (262 ) (954 ) (954 ) (1,004 ) (1,004 ) Nonforfeitable dividends allocated to unvested restricted shareholders (396 ) (396 ) (369 ) (369 ) (327 ) (327 ) Distribution to preferred shareholders — — — — (2,032 ) (2,032 ) Preferred share redemption charge — — — — (3,181 ) (3,181 ) Net income attributable to common shareholders $ 33,871 $ 33,871 $ 134,149 $ 134,149 $ 114,633 $ 114,633 Denominator Weighted-average shares outstanding 176,132,941 176,132,941 178,519,748 178,519,748 175,484,350 175,484,350 Contingent securities/Share based compensation — 553,872 — 1,121,744 — 1,323,816 Weighted-average shares outstanding 176,132,941 176,686,813 178,519,748 179,641,492 175,484,350 176,808,166 Earnings per Common Share: Net income attributable to common shareholders $ 0.19 $ 0.19 $ 0.75 $ 0.75 $ 0.65 $ 0.65 The following tables detail the number of units and net income used to calculate basic and diluted earnings per common partnership unit (in thousands, except unit and per unit amounts; results may not add due to rounding): Year Ended December 31, 2019 2018 2017 Basic Diluted Basic Diluted Basic Diluted Numerator Net income $ 34,529 $ 34,529 $ 135,472 $ 135,472 $ 121,177 $ 121,177 Net income attributable to noncontrolling interests (69 ) (69 ) (55 ) (55 ) (29 ) (29 ) Nonforfeitable dividends allocated to unvested restricted unitholders (396 ) (396 ) (369 ) (369 ) (327 ) (327 ) Preferred unit dividends — — — — (2,032 ) (2,032 ) Preferred unit redemption charge — — — — (3,181 ) (3,181 ) Net income attributable to common unitholders $ 34,064 $ 34,064 $ 135,048 $ 135,048 $ 115,608 $ 115,608 Denominator Weighted-average units outstanding 177,114,932 177,114,932 179,959,370 179,959,370 176,964,149 176,964,149 Contingent securities/Share based compensation — 553,872 — 1,121,744 — 1,323,816 Total weighted-average units outstanding 177,114,932 177,668,804 179,959,370 181,081,114 176,964,149 178,287,965 Earnings per Common Partnership Unit: Net income attributable to common unitholders $ 0.19 $ 0.19 $ 0.75 $ 0.75 $ 0.65 $ 0.65

SHARE BASED COMPENSATION, 401(K

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Option Activity	Options outstanding as of December 31, 2019 and changes during the year-ended December 31, 2019 were as follows: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at January 1, 2019 964,359 $ 9.13 1.3 Exercised (629,798 ) $ 7.67 $ 4,967.7 Outstanding at December 31, 2019 334,561 $ 11.88 1.0 $ 1,295.9 Vested/Exercisable at December 31, 2019 334,561 $ 11.88 1.0 $ 1,295.9
Company's Restricted Share Activity	The following table summarizes the Company’s restricted share activity during the year-ended December 31, 2019 : Shares Weighted Average Grant Date Fair Value Aggregate Intrinsic Value (in thousands) Non-vested at January 1, 2019 466,439 $ 14.93 $ 70.7 Granted 278,442 $ 15.51 $ 65.6 Vested (248,607 ) $ 13.68 $ 538.3 Forfeited (17,130 ) $ 15.66 $ 1.6 Non-vested at December 31, 2019 479,144 $ 15.90 $ 44.7
Schedule of Restricted Performance Share Units Plan	The table below presents certain information as to unvested RPSU awards. RPSU Grant 3/1/2017 2/28/2018 2/21/2019 Total (Amounts below in shares, unless otherwise noted) Non-vested at January 1, 2019 169,525 206,025 — 375,550 Units Granted — — 213,728 213,728 Units Vested (8,420 ) — — (8,420 ) Units Cancelled (1,935 ) (15,729 ) (7,659 ) (25,323 ) Non-vested at December 31, 2019 159,170 190,296 206,069 555,535 Measurement Period Commencement Date 1/1/2017 1/1/2018 1/1/2019 Measurement Period End Date 12/31/2019 12/31/2020 12/31/2021 Units Granted 174,854 209,193 213,728 Fair Value of Units on Grant Date (in thousands) $ 3,735 $ 4,276 $ 4,627

DISTRIBUTIONS (Tables)

DISTRIBUTIONS (Tables)	12 Months Ended
	Dec. 31, 2019
Distributions [Abstract]
Schedule of Dividends Payable	The following table provides the tax characteristics of the 2019 , 2018 and 2017 distributions paid: Years ended December 31, 2019 2018 2017 (in thousands, except per share amounts) Common Share Distributions: Ordinary income $ 0.62 $ 0.55 $ 0.38 Capital gain — — 0.26 Non-taxable distributions 0.14 0.17 — Distributions per share $ 0.76 $ 0.72 $ 0.64 Percentage classified as ordinary income 81.00 % 76.20 % 60.00 % Percentage classified as capital gain — % — % 40.00 % Percentage classified as non-taxable distribution 19.00 % 23.80 % — % Preferred Share Distributions: Total distributions paid $ — $ — $ 2,032 Percentage classified as ordinary income — % — % 60.00 % Percentage classified as capital gain — % — % 40.00 % Percentage classified as non-taxable distribution — % — % — %

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 (in thousands): Parent Company Cash Flow Hedges Balance at January 1, 2017 $ (1,745 ) Change in fair market value during year 2,948 Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests (34 ) Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 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 ) Operating Partnership Cash Flow Hedges Balance at January 1, 2017 $ (2,122 ) Change in fair market value during year 2,948 Amortization of interest rate contracts reclassified from comprehensive income to interest expense 1,230 Balance at December 31, 2017 $ 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 )

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Real Estate Investments, Net Operating Income and Unconsolidated Real Estate Ventures of Reportable Segments	The following tables provide selected asset information and results of operations of the Company’s reportable segments as of and for the three years ended December 31, 2019 , 2018 and 2017 (in thousands): Real estate investments, at cost: December 31, 2019 December 31, 2018 December 31, 2017 Philadelphia CBD $ 1,726,299 $ 1,670,388 $ 1,643,296 Pennsylvania Suburbs 1,003,890 1,002,937 957,272 Austin, Texas (a) 721,255 667,698 163,653 Metropolitan Washington, D.C. (b) 468,035 524,190 978,257 Other 86,980 86,506 88,346 Operating Properties $ 4,006,459 $ 3,951,719 $ 3,830,824 Corporate Right of use asset - operating leases, net (c) $ 21,656 $ — $ — Construction-in-progress $ 180,718 $ 150,263 $ 121,188 Land held for development (d) $ 96,124 $ 86,401 $ 98,242 Prepaid leasehold interests in land held for development, net (e) $ 39,592 $ 39,999 $ — (a) Refer to Note 3, ''Real Estate Investments ,” for details related to the Company's acquisition of DRA Advisors' ownership interest in the Austin Venture in December 2018. (b) Refer to Note 4, ''Investment in Unconsolidated Real Estate Ventures .” for details of the Company's transaction with the Herndon Innovation Center Metro Portfolio Venture, LLC in December 2018. (c) Refer to Note 2, ''Summary of Significant Accounting Policies ,” for further information on the impact of adoption of Topic 842. (d) Does not include 35.2 acres, 37.9 acres, and 13.1 acres of land classified as held for sale as of December 31, 2019, 2018, and 2017, respectively. Refer to Note 3, ''Real Estate Investments ,” for further information. (e) Includes leasehold interests in prepaid 99 -year ground leases at 3025 and 3001-3003 JFK Boulevard, in Philadelphia, Pennsylvania as of December 31, 2019 and December 31, 2018 . Refer to Note 3, ''Real Estate Investments ,” for further information. Year Ended December 31, 2019 2018 2017 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 Philadelphia CBD $ 263,769 $ (100,219 ) $ 163,550 $ 256,717 $ (99,449 ) $ 157,268 $ 226,673 $ (88,818 ) $ 137,855 Pennsylvania Suburbs 141,084 (47,418 ) 93,666 138,279 (49,433 ) 88,846 139,785 (47,845 ) 91,940 Austin, Texas 104,157 (38,285 ) 65,872 38,665 (16,739 ) 21,926 34,301 (15,456 ) 18,845 Metropolitan Washington, D.C. 51,498 (23,455 ) 28,043 90,308 (34,072 ) 56,236 92,024 (35,014 ) 57,010 Other 14,558 (9,328 ) 5,230 16,757 (11,888 ) 4,869 18,347 (11,749 ) 6,598 Corporate 5,351 (7,141 ) (1,790 ) 3,619 (6,518 ) (2,899 ) 9,363 (7,193 ) 2,170 Operating properties $ 580,417 $ (225,846 ) $ 354,571 $ 544,345 $ (218,099 ) $ 326,246 $ 520,493 $ (206,075 ) $ 314,418 (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, 2019 December 31, 2018 December 31, 2017 2019 2018 2017 Philadelphia CBD $ 17,524 $ 19,897 $ 39,939 $ 328 $ (105 ) $ 255 Pennsylvania Suburbs — — 3,503 — — 631 Metropolitan Washington, D.C. (a) 102,840 136,142 119,817 (4,234 ) (15,065 ) (5,044 ) MAP Venture (70 ) 11,173 15,450 (6,102 ) (2,155 ) (3,443 ) Other — 1,888 1,939 86 407 285 Austin, Texas (b) — — 13,973 — 1,687 (990 ) Total $ 120,294 $ 169,100 $ 194,621 $ (9,922 ) $ (15,231 ) $ (8,306 ) (a) Refer to Note 4, ''Investment in Unconsolidated Real Estate Ventures ," for details of the Company's transaction with the Herndon Innovation Center Metro Portfolio Venture, LLC in December 2018. (b) Refer to Note 3, ''Real Estate Investments ," for details related to the Company's acquisition of DRA Advisors' ownership interest in the Austin Venture in December 2018.
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, 2019 2018 2017 Net income $ 34,529 $ 135,472 $ 121,177 Plus: Interest expense 81,512 78,199 81,886 Interest expense - amortization of deferred financing costs 2,768 2,498 2,435 Depreciation and amortization 210,005 176,000 180,323 General and administrative expenses 32,156 27,802 28,538 Equity in loss of Real Estate Ventures 9,922 15,231 8,306 Provision for impairment — 71,707 3,057 Loss on early extinguishment of debt — 105 3,933 Less: Interest income 2,318 4,703 1,113 Income tax (provision) benefit (12 ) (423 ) 628 Net gain on disposition of real estate 356 2,932 32,017 Net gain on sale of undepreciated real estate 2,020 3,040 953 Net gain on real estate venture transactions 11,639 142,233 80,526 Gain on promoted interest in unconsolidated real estate venture — 28,283 — Consolidated net operating income $ 354,571 $ 326,246 $ 314,418

SUMMARY OF QUARTERLY RESULTS _2

SUMMARY OF QUARTERLY RESULTS (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following is a summary of quarterly financial information as of and for the years ended December 31, 2019 and 2018 (in thousands, except per share data): Brandywine Realty Trust 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 2019 Total revenue $ 143,896 $ 144,151 $ 145,331 $ 147,039 Net income 4,583 6,252 6,820 16,874 (d) Net income allocated to Common Shares 4,404 6,112 6,679 16,676 Basic earnings per Common Share $ 0.03 $ 0.03 $ 0.04 $ 0.09 Diluted earnings per Common Share $ 0.03 $ 0.03 $ 0.04 $ 0.09 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,445 12,876 (43,522 ) (a) 121,673 (c) Net income (loss) allocated to Common Shares 43,956 12,661 (43,260 ) 120,792 Basic earnings (loss) per Common Share $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Share $ 0.24 $ 0.07 $ (0.24 ) $ 0.67 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) Driven by a $56.9 million impairment charge related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, ''Real Estate Investments ,” for further information. (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, ''Real Estate Investments ,” for further information on this transaction. (c) Increase primarily relates to gains of $103.8 million and $28.3 million , recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, ''Real Estate Investments ." (d) Increase primarily related to a gain of $8.0 million recorded in the "Net gains on real estate venture transactions" within the Company's consolidated statement of operations from the sale of three PJP Ventures properties. For further details, see Note 4, "Investment in Unconsolidated Joint Ventures." Brandywine Operating Partnership, L.P. 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 2019 Total revenue $ 143,896 $ 144,151 $ 145,331 $ 147,039 Net income 4,583 6,252 6,820 16,874 (d) Net income attributable to Common Partnership Unitholders 4,430 6,146 6,716 16,772 Basic earnings per Common Partnership Unit $ 0.03 $ 0.03 $ 0.04 $ 0.09 Diluted earnings per Common Partnership Unit $ 0.03 $ 0.03 $ 0.04 $ 0.09 2018 Total revenue $ 136,358 $ 133,786 $ 134,998 $ 139,203 (b) Net income (loss) 44,445 12,876 (43,522 ) (a) 121,673 (c) Net income (loss) attributable to Common Partnership Unitholders 44,326 12,769 (43,622 ) 121,575 Basic earnings (loss) per Common Partnership Unit $ 0.25 $ 0.07 $ (0.24 ) $ 0.68 Diluted earnings (loss) per Common Partnership Unit $ 0.24 $ 0.07 $ (0.24 ) $ 0.67 The summation of quarterly earnings per share amounts does not necessarily equal the full year amounts due to rounding. (a) Driven by a $56.9 million impairment charge related to eight office properties in the Company’s Metropolitan Washington, D.C. segment. See Note 3, ''Real Estate Investments ,” for further information. (b) The increase in fourth quarter revenues primarily relates to the acquisition of the Austin Portfolio, located in Austin, Texas, on December 11, 2018. See Note 3, ''Real Estate Investments ,” for further information on this transaction. (c) Increase primarily relates to gains of $103.8 million and $28.3 million , recorded in the “Net gain on real estate venture transactions” and “Gain on promoted interest in unconsolidated real estate venture” captions within the Company’s consolidated statements of operations, respectively, from the Austin Portfolio transaction. For further details, see Note 3, ''Real Estate Investments ." (d) Increase primarily related to a gain of $8.0 million recorded in the "Net gains on real estate venture transactions" within the Company's consolidated statement of operations from the sale of three PJP Ventures properties. For further details, see Note 4, "Investment in Unconsolidated Joint Ventures."

ORGANIZATION OF THE PARENT CO_3

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Narrative (Details)	12 Months Ended
	Dec. 31, 2019aft²parcelinvestmentproperty
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	95
Area of real estate property	16,711,387
Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	16,700,000
Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Undeveloped parcels of land | a	234.7
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	24,300,000
Wholly-owned Management Company Subsidiaries | Wholly Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	16,700,000
Wholly-owned Management Company Subsidiaries | Partially Owned Properties
Organization of The Parent Company and The Operating Partnership [Line Items]
Area of real estate property	7,600,000
Development
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	1
Redevelopment
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of Properties | property	4
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%
Unconsolidated Real Estate Ventures | Parent Company
Organization of The Parent Company and The Operating Partnership [Line Items]
Number of unconsolidated investments In real estate ventures | investment	7

ORGANIZATION OF THE PARENT CO_4

ORGANIZATION OF THE PARENT COMPANY AND THE OPERATING PARTNERSHIP - Summary of Properties (Details)	Dec. 31, 2019ft²property
Real Estate Properties [Line Items]
Number of Properties | property	95
Rentable Square Feet | ft²	16,711,387
Office Properties
Real Estate Properties [Line Items]
Number of Properties | property	86
Rentable Square Feet | ft²	15,450,417
Mixed-use Properties
Real Estate Properties [Line Items]
Number of Properties | property	4
Rentable Square Feet | ft²	659,625
Core Properties
Real Estate Properties [Line Items]
Number of Properties | property	90
Rentable Square Feet | ft²	16,110,042
Development Property
Real Estate Properties [Line Items]
Number of Properties | property	1
Rentable Square Feet | ft²	204,108
Redevelopment Properties
Real Estate Properties [Line Items]
Number of Properties | property	4
Rentable Square Feet | ft²	397,237

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revised Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating properties	$ 4,006,459	$ 3,951,719
Accumulated depreciation	(973,318)	(885,407)	$ (913,297)
Operating real estate investments, net	3,054,797	3,066,312
Total assets	4,075,969	4,076,976
Additional paid-in-capital	3,192,158	3,200,312
Cumulative earnings	804,556	775,625
Total Brandywine Realty Trust's equity	1,677,877	1,798,827
Noncontrolling interests	10,426	12,201
Total beneficiaries' equity	1,688,303	1,811,028	$ 1,826,870	$ 1,864,388
Total liabilities and equity	$ 4,075,969	4,076,976
Total Brandywine Operating Partnership, L.P.'s equity		1,796,316
Total partners' equity		1,798,508
As previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating properties		3,953,319
Accumulated depreciation		(865,462)
Operating real estate investments, net		3,087,857
Total assets		4,098,521
Additional paid-in-capital		3,200,850
Cumulative earnings		796,513
Total Brandywine Realty Trust's equity		1,820,253
Noncontrolling interests		12,320
Total beneficiaries' equity		1,832,573
Total liabilities and equity		4,098,521
Total Brandywine Operating Partnership, L.P.'s equity		1,817,861
Total partners' equity		1,820,053
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating properties		(1,600)
Accumulated depreciation		(19,945)
Operating real estate investments, net		(21,545)
Total assets		(21,545)
Additional paid-in-capital		(538)
Cumulative earnings		(20,888)
Total Brandywine Realty Trust's equity		(21,426)
Noncontrolling interests		(119)
Total beneficiaries' equity		(21,545)
Total liabilities and equity		(21,545)
Total Brandywine Operating Partnership, L.P.'s equity		(21,545)
Total partners' equity		(21,545)
General Partner Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General Partnership Capital; 176,480,095 and 176,873,324 units issued and outstanding as of December 31, 2019 and December 31, 2018, respectively		1,791,591
General Partner Capital | As previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General Partnership Capital; 176,480,095 and 176,873,324 units issued and outstanding as of December 31, 2019 and December 31, 2018, respectively		1,813,136
General Partner Capital | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General Partnership Capital; 176,480,095 and 176,873,324 units issued and outstanding as of December 31, 2019 and December 31, 2018, respectively		$ (21,545)

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revised Statements of Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity	$ 1,688,303	$ 1,811,028	$ 1,826,870	$ 1,864,388
Total partners' equity		1,798,508
Additional Paid-in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity	3,192,158	3,200,312	3,218,077	3,258,386
Cumulative Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity	804,556	775,625	641,093	520,914
Noncontrolling Interests
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity	10,426	12,201	17,258	16,933
As previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		1,832,573
Total partners' equity		1,820,053
As previously reported | Additional Paid-in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		3,200,850	3,218,564	3,258,870
As previously reported | Cumulative Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		796,513	660,174	539,319
As previously reported | Noncontrolling Interests
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		12,320	17,420	17,093
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		(21,545)
Total partners' equity		(21,545)
Adjustments | Additional Paid-in Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		(538)	(487)	(484)
Adjustments | Cumulative Earnings
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		(20,888)	(19,081)	(18,405)
Adjustments | Noncontrolling Interests
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total beneficiaries' equity		(119)	(162)	(160)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total partners' equity	1,672,915	1,798,508	1,799,955	1,840,593
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Noncontrolling Interests
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total partners' equity	1,091	2,192	2,215	2,150
BRANDYWINE OPERATING PARTNERSHIP, L.P. | General Partner Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total partners' equity	$ 1,674,539	1,791,591	1,795,684	1,743,715
BRANDYWINE OPERATING PARTNERSHIP, L.P. | General Partner Capital | As previously reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total partners' equity		1,813,136	1,815,411	1,762,764
BRANDYWINE OPERATING PARTNERSHIP, L.P. | General Partner Capital | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total partners' equity		$ (21,545)	$ (19,727)	$ (19,049)

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revised Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ 16,676	$ 6,679	$ 6,112	$ 4,404	$ 120,792	$ (43,260)	$ 12,661	$ 43,956	$ 34,267	$ 134,518	$ 120,173
Basic earnings per Common Share (in dollars per shares)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.68	$ (0.24)	$ 0.07	$ 0.25	$ 0.19	$ 0.75	$ 0.65
Diluted earnings (loss) per Common Share (in dollars per shares)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.67	$ (0.24)	$ 0.07	$ 0.24	$ 0.19	$ 0.75	$ 0.65
Prior Period Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net income (loss)										$ 1,800	$ 700
Earnings per share, basic and diluted (in usd per share)										$ (0.01)
Basic earnings per Common Share (in dollars per shares)											$ (0.01)
Diluted earnings (loss) per Common Share (in dollars per shares)											$ 0

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Principles of Consolidation (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Total assets	$ 4,075,969	$ 4,076,976
Liabilities	2,387,666	2,265,948
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets	392,000	414,300
Liabilities	$ 255,600	$ 254,100

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Depreciation and Amortization, Construction-in-Progress, and Ground Leases (Details)	12 Months Ended
	Dec. 31, 2019
Minimum
Construction in Progress [Line Items]
Buildings and improvements useful life	5 years
Tenant improvements useful lives	1 year
Maximum
Construction in Progress [Line Items]
Buildings and improvements useful life	55 years
Tenant improvements useful lives	16 years

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Impairment or Disposal of Long-Lived Assets (Details)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Disposition of assets, holding period	10 years

SUMMARY OF SIGNIFICANT ACCOU_10

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deferred Costs (Details)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Remaining lease period - minimum	1 year
Remaining lease period - maximum	16 years

SUMMARY OF SIGNIFICANT ACCOU_11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenue	$ 147,039	$ 145,331	$ 144,151	$ 143,896	$ 139,203	$ 134,998	$ 133,786	$ 136,358	$ 580,417	$ 544,345	$ 520,493
Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									411,524
Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									114,224
Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									525,748
Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									8,857
Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									20,060
Rents
Disaggregation of Revenue [Line Items]
Total revenue									554,665
Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									19,626
Other income
Disaggregation of Revenue [Line Items]
Total revenue									6,126
Philadelphia CBD
Disaggregation of Revenue [Line Items]
Total revenue									263,769
Philadelphia CBD | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									178,481
Philadelphia CBD | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									58,580
Philadelphia CBD | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									237,061
Philadelphia CBD | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									3,745
Philadelphia CBD | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									18,665
Philadelphia CBD | Rents
Disaggregation of Revenue [Line Items]
Total revenue									259,471
Philadelphia CBD | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									876
Philadelphia CBD | Other income
Disaggregation of Revenue [Line Items]
Total revenue									3,422
Pennsylvania Suburbs
Disaggregation of Revenue [Line Items]
Total revenue									141,084
Pennsylvania Suburbs | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									125,969
Pennsylvania Suburbs | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									14,282
Pennsylvania Suburbs | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									140,251
Pennsylvania Suburbs | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									(12)
Pennsylvania Suburbs | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									174
Pennsylvania Suburbs | Rents
Disaggregation of Revenue [Line Items]
Total revenue									140,413
Pennsylvania Suburbs | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									43
Pennsylvania Suburbs | Other income
Disaggregation of Revenue [Line Items]
Total revenue									628
Austin, Texas
Disaggregation of Revenue [Line Items]
Total revenue									104,157
Austin, Texas | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									62,232
Austin, Texas | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									34,748
Austin, Texas | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									96,980
Austin, Texas | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									4,638
Austin, Texas | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									165
Austin, Texas | Rents
Disaggregation of Revenue [Line Items]
Total revenue									101,783
Austin, Texas | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									1,956
Austin, Texas | Other income
Disaggregation of Revenue [Line Items]
Total revenue									418
Metropolitan DC
Disaggregation of Revenue [Line Items]
Total revenue									51,498
Metropolitan DC | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									39,420
Metropolitan DC | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									4,029
Metropolitan DC | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									43,449
Metropolitan DC | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									0
Metropolitan DC | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									824
Metropolitan DC | Rents
Disaggregation of Revenue [Line Items]
Total revenue									44,273
Metropolitan DC | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									6,922
Metropolitan DC | Other income
Disaggregation of Revenue [Line Items]
Total revenue									303
Other
Disaggregation of Revenue [Line Items]
Total revenue									14,558
Other | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									7,834
Other | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									3,080
Other | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									10,914
Other | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									486
Other | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									232
Other | Rents
Disaggregation of Revenue [Line Items]
Total revenue									11,632
Other | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									2,915
Other | Other income
Disaggregation of Revenue [Line Items]
Total revenue									11
Corporate
Disaggregation of Revenue [Line Items]
Total revenue									5,351
Corporate | Fixed rent
Disaggregation of Revenue [Line Items]
Total revenue									(2,412)
Corporate | Variable rent
Disaggregation of Revenue [Line Items]
Total revenue									(495)
Corporate | Total lease revenue
Disaggregation of Revenue [Line Items]
Total revenue									(2,907)
Corporate | Amortization of deferred market rents
Disaggregation of Revenue [Line Items]
Total revenue									0
Corporate | Daily parking & hotel flexible stay
Disaggregation of Revenue [Line Items]
Total revenue									0
Corporate | Rents
Disaggregation of Revenue [Line Items]
Total revenue									(2,907)
Corporate | Third party management fees, labor reimbursement and leasing
Disaggregation of Revenue [Line Items]
Total revenue									6,914
Corporate | Other income
Disaggregation of Revenue [Line Items]
Total revenue									$ 1,344

SUMMARY OF SIGNIFICANT ACCOU_12

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Income Taxes (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Distributable income minimum percentage	90.00%
Tax basis of assets, cost for income tax purposes	$ 3.2	$ 3.3
Federal excise tax if sufficient taxable income is not distributed within prescribed time limits	4.00%
Excise tax equal to annual amount	4.00%
Excise tax, if sum of ordinary income	85.00%
Excise tax, if net capital gain exceeds cash distributions and certain taxes paid	95.00%
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Income Tax Contingency [Line Items]
Tax basis of assets, cost for income tax purposes	$ 3.2	$ 3.3

SUMMARY OF SIGNIFICANT ACCOU_13

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - New Accounting Pronouncements Adopted (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change		$ (5,336)
Right of use asset - operating leases, net	$ 21,656		$ 0	$ 0
Lease Liability - operating leases	$ 22,554		$ 0
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change		(700)
Right of use asset - operating leases, net		22,400
Lease Liability - operating leases		$ 22,400

REAL ESTATE INVESTMENTS - Gross

REAL ESTATE INVESTMENTS - Gross Carrying Value of Operating Properties (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Real Estate [Abstract]
Land	$ 489,702	$ 487,301
Building and improvements	3,049,395	3,048,889
Tenant improvements	467,362	415,529
Total	$ 4,006,459	$ 3,951,719

REAL ESTATE INVESTMENTS - Capit

REAL ESTATE INVESTMENTS - Capitalized Construction Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 7,431	$ 6,964	$ 6,063
Development
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	3,047	3,185	4,390
Redevelopment
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	775	968	319
Tenant Improvements
Property, Plant and Equipment [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 3,609	$ 2,811	$ 1,354

REAL ESTATE INVESTMENTS - Acqui

REAL ESTATE INVESTMENTS - Acquisitions (Textual) (Details) $ in Thousands	Dec. 19, 2018USD ($)ft²	Dec. 11, 2018USD ($)ft²property	Jun. 29, 2018USD ($)ft²	Mar. 22, 2018USD ($)	Jan. 05, 2018USD ($)ft²	Oct. 13, 2017USD ($)ft²	Jul. 28, 2017USD ($)ft²	Dec. 31, 2019USD ($)ft²property	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)ft²property	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings																	$ 7,431	$ 6,964	$ 6,063
Number of properties | property								95									95
Area of real estate property | ft²								16,711,387									16,711,387
Gain on promoted interest in unconsolidated real estate venture																	$ 0	28,283	0
Net gain from remeasurement of investment in real estate ventures																	11,639	142,233	80,526
Prepaid leasehold interests in land held for development, net								$ 39,592				$ 39,999				$ 0	39,592	39,999	0	$ 39,999
Capitalized transaction costs																	15,485	18,407	17,657
Net income (loss)								$ 16,676	$ 6,679	$ 6,112	$ 4,404	$ 120,792	$ (43,260)	$ 12,661	$ 43,956		$ 34,267	134,518	120,173
Office Properties
Business Acquisition [Line Items]
Number of properties | property								86									86
Area of real estate property | ft²								15,450,417									15,450,417
Seven Tower Bridge
Business Acquisition [Line Items]
Sale of ownership interest percentage					20.00%
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
Working capital obtained	368
Aggregate cash payment	$ 39,037
Service and other 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
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
Working capital obtained		24,865
Gain on promoted interest in unconsolidated real estate venture		28,300
Net gain from remeasurement of investment in real estate ventures		103,800
Aggregate cash payment		$ 117,348
Percentage of ownership interests		50.00%
Service and other revenue																	3,400
Net income (loss)																	$ 1,300
3025 JFK Boulevard
Business Acquisition [Line Items]
Lease agreement term			99 years														99 years
Prepaid leasehold interests in land held for development, net			$ 15,000
Capitalized transaction costs			300
3025 JFK Boulevard | Other Assets
Business Acquisition [Line Items]
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
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%
Mortgage debt assumed repaid at settlement					$ 0
Working capital obtained					(1,379)
Aggregate cash payment					$ 0
Percentage of ownership interest after non-monetary exchange transaction					100.00%
Fair value of unencumbered acquisition related costs, to tangible and intangible assets and liabilities					$ 23,600
Service and other revenue																	$ 2,800
Net income (loss)																	300
Four Tower Bridge | Conshohocken | Pennsylvania
Business Acquisition [Line Items]
Area of real estate property | ft²					86,021
Real estate property debt					$ 9,700
Bulletin Building
Business Acquisition [Line Items]
Rentable square feet | ft²						282,709
Gross purchase value of office property						$ 35,000
Lease agreement term						99 years
Service and other revenue																1,200
Net income (loss)																$ 400
3000 Market Street
Business Acquisition [Line Items]
Gross purchase value of office property							$ 32,700
Service and other revenue																				800
Net income (loss)																				$ 500
3000 Market Street | Office Properties
Business Acquisition [Line Items]
Area of real estate property | ft²							58,587
Development
Business Acquisition [Line Items]
Capitalized interest																	$ 3,200	$ 3,600	$ 3,100

REAL ESTATE INVESTMENTS - Purch

REAL ESTATE INVESTMENTS - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 19, 2018	Dec. 11, 2018	Jan. 05, 2018
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

REAL ESTATE INVESTMENTS - Pur_2

REAL ESTATE INVESTMENTS - Purchase Price Allocation (Additional Information) (Details) - USD ($) $ in Thousands	Dec. 11, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 05, 2018
Business Acquisition [Line Items]
Outstanding principal balances on mortgage debt assumed		$ 313,812	$ 320,869
Repayments of mortgage debt assumed		$ 7,595	$ 122,180	$ 4,931
Mortgage Debt Assumed - at Fair Value
Business Acquisition [Line Items]
Repayments of mortgage debt assumed	$ 115,500
Four Tower Bridge | Mortgage Debt Assumed - at Fair Value
Business Acquisition [Line Items]
Outstanding principal balances on mortgage debt assumed					$ 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 - Summa

REAL ESTATE INVESTMENTS - Summary of Acquisitions (Details) - USD ($) $ in Thousands	Oct. 13, 2017	Jul. 28, 2017
Bulletin Building
Building and improvements	$ 30,583
Construction-in-progress	672
Intangible assets acquired	10,575
Below market lease liabilities assumed	(4,055)
Total encumbered acquisition value	$ 37,775
3000 Market Street
Building and improvements		$ 32,004
Intangible assets acquired		2,562
Below market lease liabilities assumed		(1,818)
Total encumbered acquisition value		$ 32,748
Intangible Assets Acquired | Bulletin Building
Weighted average amortization period	7 years 10 months 24 days
Intangible Assets Acquired | 3000 Market Street
Weighted average amortization period		5 years 10 months 24 days
Below Market Lease | Bulletin Building
Weighted average amortization period	7 years
Below Market Lease | 3000 Market Street
Weighted average amortization period		6 years

REAL ESTATE INVESTMENTS - Sum_2

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

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

Nov. 22, 2017USD ($)a

Oct. 31, 2017USD ($)a

Sep. 13, 2017USD ($)a

Jul. 18, 2017USD ($)a

Jun. 27, 2017USD ($)ft²

Jun. 12, 2017USD ($)ft²

Apr. 28, 2017USD ($)a

Mar. 30, 2017USD ($)ft²

Mar. 15, 2017USD ($)ft²

Mar. 13, 2017USD ($)ft²

Feb. 15, 2017USD ($)a

Feb. 02, 2017USD ($)ft²

Jan. 30, 2017USD ($)a

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

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

Gain (Loss) on Sale

$ 356

$ 2,932

$ 32,017

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)

Office Properties | 11, 14, 15, 17 and 18 Campus Boulevard (Newtown Square)

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

Rentable square feet | a

252,802

Sales Price

$ 42,000

Gain (Loss) on Sale

$ 19,642

Office Properties | 630 Allendale Road

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

Rentable square feet | a

150,000

Sales Price

$ 17,500

Gain (Loss) on Sale

$ 3,605

Office Properties | Two, Four A, Four B and Five Eves Drive (Evesham Corporate Center)

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

Rentable square feet | ft²

134,794

Sales Price

$ 9,700

Gain (Loss) on Sale

$ (325)

Office Properties | 200, 210 & 220 Lake Drive East (Woodland Falls)

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

Rentable square feet | ft²

215,465

Sales Price

$ 19,000

Gain (Loss) on Sale

$ (249)

Office Properties | 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton)

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

Rentable square feet | ft²

313,810

Sales Price

$ 9,000

Gain (Loss) on Sale

$ 0

Office Properties | 1200 & 1220 Concord Avenue (Concord Airport Plaza)

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

Rentable square feet | ft²

350,256

Sales Price

$ 33,100

Gain (Loss) on Sale

$ 551

Land

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

Gain (Loss) on Sale

1,000

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 | 50 E. Swedesford Square

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

Acres | a

12

Sales Price

$ 7,200

Gain (Loss) on Sale

$ 882

Land | Bishops Gate

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

Acres | a

49.5

Sales Price

$ 6,000

Gain (Loss) on Sale

$ 71

Land | Garza Ranch - Multi-family

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

Acres | a

8.4

Sales Price

$ 11,800

Gain (Loss) on Sale

$ 1,311

$ 3,000

Land | Gateway Land - Site C

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

Acres | a

4.8

Sales Price

$ 1,100

Gain (Loss) on Sale

$ 0

Land | Garza Ranch - Hotel

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

Acres | a

1.7

Sales Price

$ 3,500

Gain (Loss) on Sale

$ 192

Retail Properties | 7000 Midlantic Drive

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

Rentable square feet | ft²

10,784

Sales Price

$ 8,200

Gain (Loss) on Sale

$ 1,413

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

Mixed-use Properties | Philadelphia Marine Center (Marine Piers)

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

Rentable square feet | ft²

181,900

Sales Price

$ 21,400

Gain (Loss) on Sale

$ 6,498

REAL ESTATE INVESTMENTS - Sum_3

REAL ESTATE INVESTMENTS - Summary of Office Properties Sold (Additional Information) (Details) $ in Thousands	Mar. 15, 2017USD ($)	Sep. 30, 2018USD ($)	Mar. 31, 2017USD ($)property	Dec. 31, 2019USD ($)property	Dec. 31, 2018USD ($)property	Dec. 31, 2017USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on disposition of real estate				$ 356	$ 2,932	$ 32,017
Number of Properties | property				95
Building and improvements				$ 3,049,395	3,048,889
Proceeds from the sale of properties				41,795	$ 324,090	171,860
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
Philadelphia Marine Center (Marine Piers)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payment by cash on purchases	$ 12,000
Proceeds from the sale of properties	11,200
Balance payment on purchase price	$ 9,400
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
Other
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Properties | property			4		1
Impairment of properties held for use			$ 1,000		$ 14,800
Carrying value of real estate prior to impairment				10,200	$ 52,800
Impairment hold period			10 years		10 years
Other | Impairment on Held for Use Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Building and improvements				9,200	$ 38,000
Other | Residual Capitalization Rates
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale			0.0900		0.075
Other | Discount Rates
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Measurement input for impairment on assets held for sale			0.0925		0.095
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
Land | 11700, 11710, 11720 & 11740 Beltsville Drive (Calverton)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price reduction						1,700
Provision for impairment on assets held for sale						$ 1,700

REAL ESTATE INVESTMENTS - Held

REAL ESTATE INVESTMENTS - Held for Sale and Use Impairment (Narrative) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)property	Dec. 31, 2019USD ($)aft²property	Dec. 31, 2018USD ($)aproperty
Number of properties | property		95
Building and improvements		$ 3,049,395	$ 3,048,889
Assets held for sale, net		7,349	11,599
Land Held For Development | Assets Held-for-sale
Assets held for sale, net		$ 7,300	$ 11,600
Acres | a		35.2	37.9
Other
Number of properties | property	4		1
Impairment of properties held for use	$ 1,000		$ 14,800
Carrying value of real estate prior to impairment		$ 10,200	$ 52,800
Impairment hold period	10 years		10 years
Impairment on Held for Use Properties | Other
Building and improvements		$ 9,200	$ 38,000
Residual Capitalization Rates | Other
Measurement input for impairment on assets held for sale	0.0900		0.075
Discount Rates | Other
Measurement input for impairment on assets held for sale	0.0925		0.095
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
Office Properties | Metropolitan Washington, D.C. - Office | Assets Held-for-sale
Impairment hold period		10 years
Number of properties sold | property		8
Rentable square feet | ft²		1,293,197
Provision for impairment on assets held for sale		$ 56,900

INVESTMENT IN UNCONSOLIDATED _3

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details) $ in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2019USD ($)aft²investmentapartment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	$ 120,294	$ 169,100	$ 194,621
Accounts receivable	16,363	16,394
Real Estate Venture
Schedule of Equity Method Investments [Line Items]
Accounts receivable	800
Real Estate Venture | Management Fees
Schedule of Equity Method Investments [Line Items]
Service and other revenue	4,300	6,300	6,400
Real Estate Venture | Leasing Commission Income
Schedule of Equity Method Investments [Line Items]
Service and other revenue	1,700	$ 2,500	$ 4,500
Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
Investment in Real Estate Ventures, equity method	$ 120,300
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 | Six Real Estate Ventures | Office Properties
Schedule of Equity Method Investments [Line Items]
Number of unconsolidated investments In real estate ventures | investment	3
Rentable square feet | ft²	5.4
Unconsolidated Real Estate Ventures | Two Real Estate Ventures | Land Held For Development
Schedule of Equity Method Investments [Line Items]
Number of unconsolidated investments In real estate ventures | investment	2
Acres | a	1.4
Unconsolidated Real Estate Ventures | One Real Estate Venture | Land Under Active Development
Schedule of Equity Method Investments [Line Items]
Number of unconsolidated investments In real estate ventures | investment	1
Acres | a	1.3
Unconsolidated Real Estate Ventures | Two Other Real Estate Ventures | Residential Tower
Schedule of Equity Method Investments [Line Items]
Number of unconsolidated investments In real estate ventures | investment	1
Number of property units | apartment	321
Parent Company | Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
Number of unconsolidated investments In real estate ventures | investment	7

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, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 11, 2018	Aug. 01, 2018	Jun. 26, 2018	May 29, 2015	Jul. 31, 2013
Schedule of Equity Method Investments [Line Items]
Carrying Amount	$ 120,294	$ 169,100	$ 194,621
Company's Share of Real Estate Venture Income (Loss)	(9,922)	(15,231)	$ (8,306)
Real Estate Venture Debt at 100%, gross	$ 596,007	$ 370,319
Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%
Carrying Amount	$ 10,116	$ 11,731
Company's Share of Real Estate Venture Income (Loss)	(2,800)	(14,559)	$ (4,465)
Real Estate Venture Debt at 100%, gross	$ 0	26,111
Herndon Innovation Center Metro Portfolio Venture, LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	15.00%
Carrying Amount	$ 16,446	47,834
Company's Share of Real Estate Venture Income (Loss)	(498)	83
Real Estate Venture Debt at 100%, gross	$ 207,302	$ 0
MAP Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%
Carrying Amount	$ (70)	$ 11,173
Company's Share of Real Estate Venture Income (Loss)	(6,102)	(2,155)	$ (3,443)
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	1,100
Company's Share of Real Estate Venture Income (Loss)	190	157
Real Estate Venture Debt at 100%, gross	$ 0	3,777
PJP Two
Schedule of Equity Method Investments [Line Items]
Ownership percentage	30.00%
Carrying Amount	$ 0	663
Company's Share of Real Estate Venture Income (Loss)	81	179
Real Estate Venture Debt at 100%, gross	$ 0	2,214
PJP VI
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Carrying Amount	$ 0	125
Company's Share of Real Estate Venture Income (Loss)	(185)	71
Real Estate Venture Debt at 100%, gross	$ 0	7,069
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%
Carrying Amount	$ 0	0
Company's Share of Real Estate Venture Income (Loss)	0	1,687
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	$ 17,524	19,897
Company's Share of Real Estate Venture Income (Loss)	328	253
Real Estate Venture Debt at 100%, gross	$ 88,860	$ 88,860
Evo at Cira Centre South Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%	50.00%	50.00%
Carrying Amount	$ 0	$ 0
Company's Share of Real Estate Venture Income (Loss)	0	(358)	$ 449
Real Estate Venture Debt at 100%, gross	$ 0	0
4040 Wilson Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%							50.00%
Carrying Amount	$ 37,002	37,371
Company's Share of Real Estate Venture Income (Loss)	(368)	(192)
Real Estate Venture Debt at 100%, gross	$ 114,845	57,288
JBG 51 N 50 Patterson
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%
Carrying Amount	$ 21,531	21,368
Company's Share of Real Estate Venture Income (Loss)	(313)	(137)
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	$ 17,745	17,838
Company's Share of Real Estate Venture Income (Loss)	(255)	(260)
Real Estate Venture Debt at 100%, gross	$ 0	$ 0
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage				50.00%
Percentage of ownership interests				50.00%

INVESTMENT IN UNCONSOLIDATED _5

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Summary of Financial Position of Real Estate Ventures (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Net property	$ 834,367	$ 835,983
Other assets	342,002	159,499
Other liabilities	290,071	85,681
Debt, net	585,068	365,707
Equity	301,230	544,094
Right of use asset - operating leases, net	21,656	0	$ 0
Lease Liability - operating leases	22,554	0
MAP Venture
Schedule of Equity Method Investments [Line Items]
Net property	192,582	198,043
Other assets	256,453	65,465
Other liabilities	266,200	59,348
Debt, net	181,525	180,555
Equity	1,310	23,605
Right of use asset - operating leases, net	197,100
Lease Liability - operating leases	206,400
Brandywine-AI Ventures LLC
Schedule of Equity Method Investments [Line Items]
Net property	24,651	47,043
Other assets	3,000	11,206
Other liabilities	824	2,002
Debt, net	0	26,020
Equity	26,827	30,227
Other
Schedule of Equity Method Investments [Line Items]
Net property	617,134	590,897
Other assets	82,549	82,828
Other liabilities	23,047	24,331
Debt, net	403,543	159,132
Equity	$ 273,093	$ 490,262

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures	$ (9,922)	$ (15,231)	$ (8,306)
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Revenue		53,476	85,500
Operating expenses		(22,994)	(35,997)
Provision for impairment		0
Interest expense, net		(9,083)	(13,985)
Depreciation and amortization		(19,226)	(34,026)
Loss on extinguishment of debt		(356)	(2,613)
Net income (loss)		$ 1,817	$ (1,121)
Ownership percentage		50.00%	50.00%
Company's share of net income (loss)		$ 909	$ (560)
Other-than-temporary impairment		0	0
Basis adjustments and other		778	(429)
Equity in income (loss) of Real Estate Ventures		1,687	(989)
MAP Venture
Schedule of Equity Method Investments [Line Items]
Revenue	70,366	68,622	68,573
Operating expenses	(47,362)	(41,056)	(40,035)
Provision for impairment	0	0
Interest expense, net	(9,752)	(12,690)	(13,677)
Depreciation and amortization	(25,413)	(18,891)	(21,202)
Loss on extinguishment of debt	0	(334)	0
Net income (loss)	$ (12,161)	$ (4,349)	$ (6,341)
Ownership percentage	50.00%	50.00%	50.00%
Company's share of net income (loss)	$ (6,081)	$ (2,175)	$ (3,171)
Other-than-temporary impairment		0	0
Basis adjustments and other	(21)	20	(272)
Equity in income (loss) of Real Estate Ventures	(6,102)	(2,155)	(3,443)
Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Revenue	6,022	23,515	29,500
Operating expenses	(2,912)	(10,483)	(12,298)
Provision for impairment	(5,664)	(20,832)
Interest expense, net	(698)	(3,478)	(4,707)
Depreciation and amortization	(2,514)	(8,991)	(11,428)
Loss on extinguishment of debt	0	(695)	(811)
Net income (loss)	$ (5,766)	$ (20,964)	$ 256
Ownership percentage	50.00%	50.00%	50.00%
Company's share of net income (loss)	$ (2,883)	$ (10,482)	$ 128
Other-than-temporary impairment		(4,076)	(4,844)
Basis adjustments and other	83	(1)	251
Equity in income (loss) of Real Estate Ventures	$ (2,800)	(14,559)	(4,465)
Evo at Cira Centre South Venture
Schedule of Equity Method Investments [Line Items]
Revenue		163	12,285
Operating expenses		(256)	(3,075)
Provision for impairment		0
Interest expense, net		(123)	(4,092)
Depreciation and amortization		(409)	(4,512)
Loss on extinguishment of debt		0	0
Net income (loss)		$ (625)	$ 606
Ownership percentage	50.00%	50.00%	50.00%
Company's share of net income (loss)		$ (313)	$ 303
Other-than-temporary impairment		0	0
Basis adjustments and other		(45)	146
Equity in income (loss) of Real Estate Ventures	$ 0	(358)	449
Other
Schedule of Equity Method Investments [Line Items]
Revenue	55,970	19,550	20,413
Operating expenses	(21,510)	(7,246)	(7,935)
Provision for impairment	0	0
Interest expense, net	(11,458)	(4,400)	(3,752)
Depreciation and amortization	(25,404)	(6,309)	(7,272)
Loss on extinguishment of debt	(1,231)	0	0
Net income (loss)	(3,633)	1,595	1,454
Company's share of net income (loss)	(901)	137	1,436
Other-than-temporary impairment		0	0
Basis adjustments and other	(119)	17	(1,294)
Equity in income (loss) of Real Estate Ventures	(1,020)	154	142
Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
Revenue	132,358	165,326	216,271
Operating expenses	(71,784)	(82,035)	(99,340)
Provision for impairment	(5,664)	(20,832)
Interest expense, net	(21,908)	(29,774)	(40,213)
Depreciation and amortization	(53,331)	(53,826)	(78,440)
Loss on extinguishment of debt	(1,231)	(1,385)	(3,424)
Net income (loss)	(21,560)	(22,526)	(5,146)
Company's share of net income (loss)	(9,865)	(11,924)	(1,864)
Other-than-temporary impairment		(4,076)	(4,844)
Basis adjustments and other	(57)	769	(1,598)
Equity in income (loss) of Real Estate Ventures	$ (9,922)	$ (15,231)	$ (8,306)

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, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
2020	$ 87,226
2021	15,143
2022	256,332
2023	556,736
2024	350,000
Thereafter	878,610
Total principal payments	596,007	$ 370,319
Net deferred financing costs	(10,336)
Outstanding indebtedness	585,068	$ 365,707
Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
2020	0
2021	114,845
2022	0
2023	273,860
2024	207,302
Thereafter	0
Total principal payments	596,007
Net deferred financing costs	(10,939)
Outstanding indebtedness	$ 585,068

INVESTMENT IN UNCONSOLIDATED _8

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - PJP Ventures (Details) $ in Thousands	Oct. 29, 2019USD ($)ft²property	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²		16,711,387
Proceeds from the sale of properties		$ 41,795	$ 324,090	$ 171,860
Net gain on real estate venture transactions		$ 11,639	$ 142,233	$ 80,526
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 _9

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 ($)	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²						16,711,387
Proceeds from the sale of properties						$ 41,795,000	$ 324,090,000	$ 171,860,000
Net gain on disposition of real estate						$ 356,000	$ 2,932,000	$ 32,017,000
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_10

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Austin Venture (Details) $ in Thousands	Dec. 11, 2018USD ($)ft²property	Oct. 18, 2017USD ($)ft²property	Oct. 17, 2017USD ($)property	Dec. 31, 2019USD ($)ft²property	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Oct. 16, 2013USD ($)ft²property
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²				16,711,387
Real estate ventures aggregate indebtedness to third parties				$ 596,007	$ 370,319
Net gain on real estate venture transactions				$ 11,639	$ 142,233	$ 80,526
Number of Properties | property				95
Austin Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership percentage		50.00%
Number of properties sold | property		8	7
Rentable square feet | ft²		1,164,496
Gross sales price		$ 333,250
Real estate ventures aggregate indebtedness to third parties		150,968	$ 151,000
Proceeds from divestiture of businesses, net of cash divested		86,400
Net gain on real estate venture transactions		40,092
Deferred gain on sale		$ 12,072
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]
Number of properties contributed to a joint venture | property									7
Area of real estate property | ft²									1,398,826
Aggregate gross sales price of a joint venture									$ 330,000
Equity method investment, agreement to pay future capital expenditures							$ 4,400	$ 800	$ 5,200
DRA Advisors LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage				50.00%
DRA Austin Venture
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²	1,570,123
Ownership percentage	50.00%
Net gain on real estate venture transactions	$ 103,800
Aggregate purchase price	$ 535,100
Number of Properties | property	12

INVESTMENT IN UNCONSOLIDATED_11

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Summary of Transaction (Details) - USD ($) $ in Thousands	Oct. 18, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 17, 2017
Schedule of Equity Method Investments [Line Items]
Debt principal		$ (596,007)	$ (370,319)
Proceeds from sale		(9,730)	(60,346)	$ (145,416)
Company's share of gain		$ 11,639	$ 142,233	$ 80,526
Austin Joint Venture
Schedule of Equity Method Investments [Line Items]
Gross sales price	$ 333,250
Debt principal	(150,968)				$ (151,000)
Debt prepayment penalties	(2,120)
Closing costs and net prorations	(7,420)
Proceeds from sale	$ (172,742)
Ownership percentage	50.00%
Cash to the Company	$ 86,371
Austin Venture basis of sold properties	(92,559)
Austin Venture gain on sale	80,183
Company's share of gain	40,092
Deferred gain on sale	12,072
Gain on real estate venture transactions	$ 52,164

INVESTMENT IN UNCONSOLIDATED_12

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Brandywine - AI Venture (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)property	Dec. 31, 2018USD ($)ft²property	Dec. 31, 2017USD ($)ft²
Schedule of Equity Method Investments [Line Items]
Outstanding indebtedness	$ 2,144,418	$ 2,028,046
Net gain on real estate venture transactions	11,639	142,233	$ 80,526
Encumbrances	315,437
Proceeds from real estate venture sales	$ 9,730	60,346	145,416
Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Other-than-temporary impairment		$ 4,076	$ 4,844
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
Number of properties sold | property		3
Gross sales price		$ 107,000
Encumbrances		66,500
Debt prepayment penalty		700
Gross proceeds from sale		34,800
Proceeds from real estate venture sales		17,400
Fairview Properties
Schedule of Equity Method Investments [Line Items]
Other-than-temporary impairment		4,100
Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Number of office properties owned | property	1
Impairment of properties held for use	$ 5,600	$ 20,800
Impairment hold period		10 years
7101 Washington Avenue | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Rentable square feet | ft²			230,904
Net gain on real estate venture transactions			$ 13,800
Encumbrances			37,400
Debt prepayment penalty			800
Gross proceeds from sale			63,600
Proceeds from real estate venture sales			105,700
Other-than-temporary impairment			$ 4,800
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
Net gain on real estate venture transactions	2,200
Residual Capitalization Rates | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input		0.080
Residual Capitalization Rates | 7101 Washington Avenue | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input			0.075
Minimum | Discount Rates | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input		0.090
Minimum | Discount Rates | 7101 Washington Avenue | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input			0.078
Maximum | Discount Rates | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input		0.095
Maximum | Discount Rates | 7101 Washington Avenue | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Measurement input			0.085
Brandywine Realty Trust | Fairview Properties | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Impairment of properties held for use	$ 2,800	$ 10,400
Brandywine Realty Trust | 7101 Washington Avenue | Brandywine - AI Venture LLC
Schedule of Equity Method Investments [Line Items]
Proceeds from real estate venture sales			$ 31,800

INVESTMENT IN UNCONSOLIDATED_13

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - MAP Venture (Details) $ in Thousands	Jan. 01, 2019USD ($)	Aug. 01, 2018USD ($)	Dec. 31, 2019USD ($)property	Dec. 31, 2018USD ($)	Feb. 04, 2016ft²
Schedule of Equity Method Investments [Line Items]
Real estate ventures aggregate indebtedness to third parties			$ 596,007	$ 370,319
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%
Cumulative effect on retained earnings	$ 9,200		$ 4,600
Real estate ventures aggregate indebtedness to third parties		$ 180,800	$ 185,000	$ 185,000
Variable Interest Entity, Not Primary Beneficiary | MAP Venture
Schedule of Equity Method Investments [Line Items]
Number of office properties owned | property			58
Rentable square feet | ft²					3,924,783
Secured Debt | MAP Venture
Schedule of Equity Method Investments [Line Items]
Debt instrument, face amount		$ 185,000
Variable interest rate		2.45%
Maximum | Secured Debt | MAP Venture
Schedule of Equity Method Investments [Line Items]
Effective interest rate		6.00%

INVESTMENT IN UNCONSOLIDATED_14

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - 1919 Ventures (Details) $ in Thousands	Jun. 26, 2018USD ($)	Oct. 27, 2014ft²storyapartmentcar	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Schedule of Equity Method Investments [Line Items]
Outstanding indebtedness			$ 585,068	$ 365,707
1919 Ventures
Schedule of Equity Method Investments [Line Items]
Number of floors of a building | story		29
Square foot of contemporary glass tower development | ft²		455,000
Number of luxury apartments | apartment		321
Square feet of commercial space | ft²		24,000
Number of car structured parking facility | car		215
Note receivable	$ 44,400
Loan interest rate	4.00%
Repayment of construction loan	$ 88,800
Construction loan, principal amount	88,600
Accrued interest on construction loan	200
LCOR/CalSTRS | 1919 Ventures
Schedule of Equity Method Investments [Line Items]
Outstanding indebtedness	44,400
Other Assets | 1919 Ventures
Schedule of Equity Method Investments [Line Items]
Note receivable	$ 44,400

INVESTMENT IN UNCONSOLIDATED_15

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Four Tower Bridge Acquisition (Details) $ in Thousands	Jan. 05, 2018USD ($)ft²	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²		16,711,387
Net gain on real estate venture transactions		$ 11,639	$ 142,233	$ 80,526
Four Tower Bridge
Schedule of Equity Method Investments [Line Items]
Ownership percentage	35.00%
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%
Pennsylvania | Conshohocken | Four Tower Bridge
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²	86,021
Real estate property debt	$ 9,700

INVESTMENT IN UNCONSOLIDATED_16

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - evo at Cira Centre South Venture (Details) $ in Thousands	Jan. 10, 2018USD ($)housing_unit	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Proceeds from real estate venture sales		$ 9,730	$ 60,346	$ 145,416
Net gain on real estate venture transactions		$ 11,639	$ 142,233	$ 80,526
Evo At Cira Disposition [Member]
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
Proceeds from real estate venture sales	43,000
Cost of equity method investment	17,300
Net gain on real estate venture transactions	25,700
Philadelphia [Member] | Pennsylvania | Evo At Cira Disposition [Member]
Schedule of Equity Method Investments [Line Items]
Development costs contemplated debt financing	$ 110,900

INVESTMENT IN UNCONSOLIDATED_17

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - The Parc at Plymouth Meeting Venture (Details)	Jan. 31, 2017USD ($)housing_unit	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Proceeds from real estate venture sales		$ 9,730,000	$ 60,346,000	$ 145,416,000
Net gain on real estate venture transactions		$ 11,639,000	$ 142,233,000	$ 80,526,000
TB-BDN Plymouth Apartments
Schedule of Equity Method Investments [Line Items]
Sale of ownership interest percentage	50.00%
Gross sales price	$ 100,500,000
Allocated gross sales value of ownership interest, percentage	50.00%
Number of properties sold | housing_unit	398
Guarantee obligations cancelled	$ 3,200,000
Proceeds from real estate venture sales	27,200,000
Net gain on real estate venture transactions	14,600,000
TB-BDN Plymouth Apartments | Unconsolidated Real Estate Ventures
Schedule of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures	12,600,000
Pennsylvania | TB-BDN Plymouth Apartments
Schedule of Equity Method Investments [Line Items]
Development costs contemplated debt financing	$ 54,000,000

INVESTMENT IN UNCONSOLIDATED_18

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - JGB Ventures (Details) - a	Dec. 31, 2019	May 29, 2015
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		0.5
JBG 51 N 50 Patterson
Schedule of Equity Method Investments [Line Items]
Ownership percentage	70.00%
Area owned by real estate venture of undeveloped parcels of land		0.9
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 ($)aft²property	Dec. 31, 2019USD ($)ft²property	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Area of real estate property | ft²		16,711,387
Number of Properties | property		95
Cash paid to acquire real estate ventures		$ 2,181	$ 0	$ 0
Advanced under the construction loan		$ 253	$ 908	6,638
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		$ 114,800
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

LEASES - Lessor Accounting Matu

LEASES - Lessor Accounting Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020	$ 389,956
2021	369,375
2022	338,435
2023	311,729
2024	280,631
Thereafter	$ 1,234,006
Operating Leases, Future Minimum Payments Receivable [Abstract]
2019		$ 392,058
2020		372,619
2021		349,160
2022		304,445
2023		277,388
Thereafter		$ 1,265,810

LEASES - Lease Cost (Details)

LEASES - Lease Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Fixed lease cost	$ 2,100
Variable lease cost	54
Total	$ 2,154
Weighted-average remaining lease term (years)	52 years 8 months 12 days
Weighted-average discount rate	6.30%

LEASES - Narrative (Details)

LEASES - Narrative (Details)	12 Months Ended
	Dec. 31, 2019lease
Lessee, Lease, Description [Line Items]
Number of ground leases considered operating lease	6
Minimum
Lessee, Lease, Description [Line Items]
Lease terms	9 years
Maximum
Lessee, Lease, Description [Line Items]
Lease terms	65 years

LEASES - Lessee Accounting Matu

LEASES - Lessee Accounting Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020	$ 1,217
2021	1,232
2022	1,248
2023	1,263
2024	1,305
Thereafter	110,452
Total lease payments	116,717
Less: Imputed interest	94,163
Lease Liability - operating leases	$ 22,554	$ 0
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019		1,222
2020		1,222
2021		1,222
2022		1,222
2023		1,222
Thereafter		55,689
Total		$ 61,799

DEFERRED COSTS - Deferred Costs

DEFERRED COSTS - Deferred Costs (Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs [Line Items]
Leasing costs, Total Cost	$ 156,619	$ 144,831
Total Cost	162,918	151,129
Leasing costs, Accumulated Amortization	(63,257)	(56,846)
Total, Accumulated Amortization	(67,358)	(60,054)
Leasing costs, Deferred Costs, net	93,362	87,985
Financing costs, Deferred Costs, net	10,336
Deferred Costs	95,560	91,075
Revolving Credit Facility
Deferred Costs [Line Items]
Financing costs, Total Cost	6,299	6,298
Financing costs, Accumulated Amortization	(4,101)	(3,208)
Financing costs, Deferred Costs, net	$ 2,198	$ 3,090

DEFERRED COSTS - Narrative (Det

DEFERRED COSTS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs (Textual) [Abstract]
Capitalized internal direct leasing costs	$ 1.7	$ 3.9	$ 4.6

INTANGIBLE ASSETS - Intangible

INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Intangible Assets [Line Items]
Intangible assets, total cost	$ 177,581	$ 196,417
Intangible assets, accumulated amortization	(92,730)	(65,069)
Intangible assets, net	84,851	131,348
Acquired lease intangibles, net	22,263	31,783
Below market leases acquired
Intangible Assets [Line Items]
Acquired lease intangibles, gross	44,757	49,655
Acquired lease intangibles, accumulated amortization	(22,494)	(17,872)
Acquired lease intangibles, net	22,263	31,783
In-place lease value
Intangible Assets [Line Items]
Intangible assets, total cost	167,357	181,887
Intangible assets, accumulated amortization	(84,123)	(53,376)
Intangible assets, net	83,234	128,511
Tenant relationship value
Intangible Assets [Line Items]
Intangible assets, total cost	5,268	9,564
Intangible assets, accumulated amortization	(4,815)	(8,551)
Intangible assets, net	453	1,013
Above market leases acquired
Intangible Assets [Line Items]
Intangible assets, total cost	4,956	4,966
Intangible assets, accumulated amortization	(3,792)	(3,142)
Intangible assets, net	$ 1,164	$ 1,824

INTANGIBLE ASSETS - Narrative (

INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Tenant Move-Outs Prior to End of the Lease Term
Finite-Lived Intangible Assets [Line Items]
Intangible assets written off through accelerated amortization	$ 4.5	$ 0.7	$ 0.6
Tenant Move-Outs
Finite-Lived Intangible Assets [Line Items]
Intangible assets written off through accelerated amortization	$ 2.2

INTANGIBLE ASSETS - Annual Amor

INTANGIBLE ASSETS - Annual Amortization of Intangible Assets, Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
2020	$ 27,813
2021	17,887
2022	12,067
2023	9,236
2024	6,317
Thereafter	11,531
Intangible assets, net	84,851	$ 131,348
Liabilities
2020	5,270
2021	3,856
2022	2,263
2023	1,722
2024	1,434
Thereafter	7,718
Acquired lease intangibles, net	$ 22,263	$ 31,783

DEBT OBLIGATIONS - Consolidated

DEBT OBLIGATIONS - Consolidated Debt Obligations Outstanding (Details) - USD ($) $ in Thousands	Dec. 13, 2018	Dec. 12, 2018	Dec. 31, 2019	Dec. 31, 2018
Consolidated debt obligations
Plus: premiums/(discounts), net			$ 10,707
Net deferred financing costs			(10,336)
Total Debt Obligations			2,144,418	$ 2,028,046
Secured Debt
Consolidated debt obligations
Long-term debt, gross			315,437	323,032
Plus: premiums/(discounts), net			(1,383)	(1,759)
Net deferred financing costs			(242)	(404)
Total mortgage indebtedness			313,812	320,869
Secured Debt | Two Logan Square
Consolidated debt obligations
Long-term debt, gross			$ 81,103	82,805
Effective interest rate			3.98%
Secured Debt | Four Tower Bridge
Consolidated debt obligations
Long-term debt, gross			$ 9,291	9,526
Effective interest rate			4.50%
Secured Debt | One Commerce Square
Consolidated debt obligations
Long-term debt, gross			$ 116,571	120,183
Effective interest rate			3.64%
Secured Debt | Two Commerce Square
Consolidated debt obligations
Long-term debt, gross			$ 108,472	110,518
Effective interest rate			4.51%
Unsecured Debt
Consolidated debt obligations
Long-term debt, gross			$ 1,828,610	1,721,110
Plus: premiums/(discounts), net			12,090	(4,096)
Net deferred financing costs			(10,094)	(9,837)
Total unsecured indebtedness			1,830,606	1,707,177
Unsecured Debt | $600 million Unsecured Credit Facility
Consolidated debt obligations
Long-term debt, gross			0	92,500
Unsecured Debt | Seven-Year Term Loan - Swapped to fixed
Consolidated debt obligations
Long-term debt, gross	$ 250,000		$ 250,000	250,000
Effective interest rate	2.87%		2.87%
Unsecured Debt | $350.0M 3.95% Guaranteed Notes due 2023
Consolidated debt obligations
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
Long-term debt, gross			$ 350,000	250,000
Effective interest rate			3.78%
Unsecured Debt | $450.0M 3.95% Guaranteed Notes due 2027
Consolidated debt obligations
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
Long-term debt, gross			$ 350,000	250,000
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, 2018	Dec. 12, 2018	Jul. 17, 2018USD ($)extension	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)shares	Dec. 31, 2017shares	Oct. 10, 2019USD ($)
Debt Instrument [Line Items]
Line of credit				$ 0	$ 92,500,000
Repurchased and retired (in shares) | shares				1,337,169	1,729,278	0
Guaranteed Notes Due 2024
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage							4.10%
Debt instrument, face amount							$ 100,000,000
Debt instrument, premium, percentage of face amount							106.315%
Debt instrument, unamortized premium				$ 5,300,000
Guaranteed Notes Due 2029
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage							4.55%
Debt instrument, face amount							$ 100,000,000
Debt instrument, premium, percentage of face amount							110.058%
Debt instrument, unamortized premium				$ 8,500,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, weighted average interest rate				3.52%	3.24%
Line of credit				$ 0	$ 92,500,000
Interest expense borrowings				$ 4,400,000	$ 1,000,000
Revolving Credit Facility | 2018 Credit Facility
Debt Instrument [Line Items]
Debt instrument, number of extensions | extension			2
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 | Seven-Year Term Loan - Swapped to fixed
Debt Instrument [Line Items]
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]
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 of Debt Obligation, Excluding Amortization of Discounts and Premiums (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2020	$ 87,226
2021	15,143
2022	256,332
2023	556,736
2024	350,000
Thereafter	878,610
Total principal payments	2,144,047
Net unamortized premiums/(discounts)	10,707
Net deferred financing costs	(10,336)
Outstanding indebtedness	$ 2,144,418	$ 2,028,046

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Financial Instruments for which Estimates of Fair Value Differ from Carrying Amounts (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage notes payable, net	$ 313,812	$ 320,869
Deferred financing costs, net	10,336
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable	44,430	47,771
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable, fair value	43,322	47,747
Unsecured notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs, net	10,094	9,837
Unsecured notes payable | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured notes payable	1,503,435	1,288,024
Deferred financing costs, net	8,700	7,900
Unsecured notes payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	1,591,830	1,262,570
Variable rate debt | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Variable rate debt	327,171	419,153
Deferred financing costs, net	1,400	2,000
Variable rate debt | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	309,947	402,924
Mortgage notes payable | Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage notes payable, net	313,812	320,869
Deferred financing costs, net	200	400
Mortgage notes payable | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	$ 317,031	$ 318,515

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Jun. 26, 2018
Third Party
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Note receivable		$ 3.4
1919 Ventures
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage loan			$ 44.4
Ownership percentage	50.00%		50.00%
Note receivable			$ 44.4

DERIVATIVE FINANCIAL INSTRUME_3

DERIVATIVE FINANCIAL INSTRUMENTS - Terms and Fair Values of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative, notional amount	$ 275,774	$ 301,548
3.090% Interest Rate Swap Maturing October 30, 2019 | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	$ 0	25,774
Derivative, fixed interest rate	3.09%
Derivative asset, fair value, gross asset	$ 0	(183)
3.718% 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	$ (562)	(7,008)
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	$ (94)	$ (292)

DERIVATIVE FINANCIAL INSTRUME_4

DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details) - customer	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Rental Revenue | Customer Concentration Risk
Derivatives, Fair Value [Line Items]
Number of tenant accounted for 10% or more of the Company's rents	0	0	0

LIMITED PARTNERS' NONCONTROLL_2

LIMITED PARTNERS' NONCONTROLLING INTERESTS IN THE PARENT COMPANY (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Noncontrolling Interest [Abstract]
Aggregate amount related to non-controlling interests classified within equity	$ 9.3	$ 10.1
Settlement value of non controlling interest in operating partnership	$ 15.5	$ 12.6

BENEFICIARIES' EQUITY OF THE _3

BENEFICIARIES' EQUITY OF THE PARENT COMPANY - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator
Net income	$ 16,874	$ 6,820	$ 6,252	$ 4,583	$ 121,673	$ (43,522)	$ 12,876	$ 44,445	$ 34,529	$ 135,472	$ 121,177
Net income attributable to noncontrolling interests, Basic									(262)	(954)	(1,004)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic									(396)	(369)	(327)
Distribution to preferred shareholders									0	0	(2,032)
Preferred share redemption charge									0	0	(3,181)
Net income attributable to Common Shareholders/ Unitholders of Brandywine Realty Trust									33,871	134,149	114,633
Net income attributable to noncontrolling interests, Diluted									(262)	(954)	(1,004)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted									(396)	(369)	(327)
Net income attributable to common shareholders, Diluted									$ 33,871	$ 134,149	$ 114,633
Denominator
Basic weighted average shares outstanding (in shares)									176,132,941	178,519,748	175,484,350
Contingent securities/Share based compensation (in shares)									553,872	1,121,744	1,323,816
Diluted weighted average shares outstanding (in shares)									176,686,813	179,641,492	176,808,166
Earnings per Common Share:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.68	$ (0.24)	$ 0.07	$ 0.25	$ 0.19	$ 0.75	$ 0.65
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.67	$ (0.24)	$ 0.07	$ 0.24	$ 0.19	$ 0.75	$ 0.65

BENEFICIARIES' EQUITY OF THE _4

BENEFICIARIES' EQUITY OF THE PARENT COMPANY - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 11, 2019	Apr. 11, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 03, 2019	Jan. 10, 2017
Class of Stock [Line Items]
Dividends, common stock	$ 33,800
Preferred shares authorized (in shares)			20,000,000
Preferred shares outstanding (in shares)			0
Preferred share redemption charge			$ 0	$ 0	$ 3,181
Repurchased and retired (in shares)			1,337,169	1,729,278	0
Share price (in usd per share)			$ 12.92	$ 12.64
Repurchased and retired, value			$ 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	$ 416	$ 51,225
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	23,311	2,858,991
Weighted average price per share (usd per share)				$ 18.04	$ 18.19
Cash proceeds, net of issuance costs				$ 400	$ 51,200
Common shares remain available for issuance (in shares)			13,117,698
Maximum
Class of Stock [Line Items]
Authorized amount						$ 150,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends, common stock	$ 33,800
Preferred share redemption charge			$ 0	0	3,181
Repurchase program, number of common units retired for each common share repurchased (in units)			1
Cash proceeds, net of issuance costs			$ 0	$ 416	$ 51,225
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Series E Preferred Stock
Class of Stock [Line Items]
Redemption outstanding shares (in shares)		4,000,000
Redemption price per share (in usd per share)		$ 25.51
Accrued dividends paid in cash		$ 2,000
Preferred share redemption charge		$ 3,200
Dividend Declared
Class of Stock [Line Items]
Dividends payable, amount per share (in usd per share)	$ 0.19
Dividend Declared | BRANDYWINE OPERATING PARTNERSHIP, L.P.
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	982,871	1,479,799

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	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator
Net income	$ 16,874	$ 6,820	$ 6,252	$ 4,583	$ 121,673	$ (43,522)	$ 12,876	$ 44,445	$ 34,529	$ 135,472	$ 121,177
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic									(396)	(369)	(327)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted									(396)	(369)	(327)
Preferred Share distributions									0	0	(2,032)
Preferred share redemption charge									$ 0	$ 0	$ (3,181)
Denominator
Basic weighted average shares outstanding (in shares)									176,132,941	178,519,748	175,484,350
Contingent securities/Share based compensation (in shares)									553,872	1,121,744	1,323,816
Diluted weighted average shares outstanding (in shares)									176,686,813	179,641,492	176,808,166
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.68	$ (0.24)	$ 0.07	$ 0.25	$ 0.19	$ 0.75	$ 0.65
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.67	$ (0.24)	$ 0.07	$ 0.24	$ 0.19	$ 0.75	$ 0.65
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 16,874	$ 6,820	$ 6,252	$ 4,583	$ 121,673	$ (43,522)	$ 12,876	$ 44,445	$ 34,529	$ 135,472	$ 121,177
Net income attributable to noncontrolling interests									(69)	(55)	(29)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic									(396)	(369)	(327)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted									(396)	(369)	(327)
Preferred Share distributions									0	0	(2,032)
Preferred share redemption charge									0	0	(3,181)
Net income attributable to common unitholders, Basic									34,064	135,048	115,608
Net income attributable to common unitholders, Diluted									$ 34,064	$ 135,048	$ 115,608
Denominator
Basic weighted average shares outstanding (in shares)									177,114,932	179,959,370	176,964,149
Contingent securities/Share based compensation (in shares)									553,872	1,121,744	1,323,816
Diluted weighted average shares outstanding (in shares)									177,668,804	181,081,114	178,287,965
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.68	$ (0.24)	$ 0.07	$ 0.25	$ 0.19	$ 0.75	$ 0.65
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.67	$ (0.24)	$ 0.07	$ 0.24	$ 0.19	$ 0.75	$ 0.65

PARTNER'S EQUITY OF THE PAREN_4

PARTNER'S EQUITY OF THE PARENT COMPANY - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 11, 2019	Apr. 11, 2017	Jan. 10, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 03, 2019
Earnings Per Common Partnership Unit [Line Items]
Dividends, common stock	$ 33,800
Preferred share redemption charge				$ 0	$ 0	$ 3,181
Repurchased and retired (in shares)				1,337,169	1,729,278	0
Share price (in usd per share)				$ 12.92	$ 12.64
Repurchased and retired, value				$ 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
Upfront costs						$ 499
Cash proceeds, net of issuance costs				$ 0	$ 416	$ 51,225
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	23,311	2,858,991
Weighted average price per share (usd per share)					$ 18.04	$ 18.19
Cash proceeds, net of issuance costs					$ 400	$ 51,200
Common shares remain available for issuance (in shares)				13,117,698
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)				$ 15.75	$ 12.87	$ 18.19
Limited partners' capital account, units outstanding (in units)				981,634	982,871	1,479,799
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Earnings Per Common Partnership Unit [Line Items]
Preferred units, outstanding (in units)				0	0
Dividends, common stock	$ 33,800
Preferred share redemption charge				$ 0	$ 0	$ 3,181
Repurchase program, number of mirror unit of operating partnership retired for each common share repurchased				1
Cash proceeds, net of issuance costs				$ 0	$ 416	$ 51,225
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Dividend Declared
Earnings Per Common Partnership Unit [Line Items]
Dividends payable, amount per share (in usd per share)	$ 0.19
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Series E Preferred Stock
Earnings Per Common Partnership Unit [Line Items]
Redemption outstanding shares (in shares)		4,000,000
Redemption price per share (in usd per share)		$ 25.51
Accrued dividends paid in cash		$ 2,000
Preferred share redemption charge		$ 3,200

SHARE BASED COMPENSATION, 401_2

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Narrative (Details) - USD ($)	Feb. 21, 2019	Feb. 01, 2019	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation arrangement by share-based payment award, options, outstanding, number				334,561	964,359
Defined contribution plan, maximum annual contribution per employee, percent				100.00%
Defined contribution plan, employer discretionary contribution amount				$ 400,000	$ 500,000	$ 400,000
Number of shares to be issued under deferred compensation plan included in total shares outstanding				1,100,000	1,000,000
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				$ 0	$ 0	0
Share-based compensation expense, capitalized				0	0	0
Restricted Share Rights Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				3,900,000	3,600,000	2,800,000
Share-based compensation expense, capitalized				$ 300,000	$ 600,000	400,000
Restricted share rights outstanding (in shares)				479,144	466,439
Weighted average grant date fair value (in dollars per shares)				$ 15.90	$ 14.93
Unrecognized compensation expenses				$ 2,200,000
Weighted average period over which options will be recognized				1 year 18 days
Granted (in shares)	196,667			278,442
Number of restricted share right will get settled for common share	1
Accumulated service period for voluntary termination			15 years
Voluntary termination of employment age limit			57 years
Restricted Share Rights Awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				2 years
Restricted Share Rights Awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				3 years
Restricted Performance Share Units Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense				$ 4,200,000	$ 3,900,000	3,400,000
Share-based compensation expense, capitalized				$ 600,000	1,100,000	800,000
Restricted share rights outstanding (in shares)	37,472			233,890
Intrinsic value of awards				$ 3,700,000
Weighted average grant date fair value (in dollars per shares)				$ 15.61
Vesting period				3 years
Unrecognized compensation expenses				$ 2,000,000
Weighted average period over which options will be recognized				1 year 8 months 12 days
Common shares issued for share based compensation		147,111
Dividends payable, amount per share (in usd per share)		$ 0.19
Performance earning potential				200.00%
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				1,250,000
Stock issued during period, value, employee stock purchase plan				$ 500,000	$ 500,000	$ 400,000
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, 2019	Dec. 31, 2018
Shares
Outstanding at beginning of year (in shares)	964,359
Exercised (in shares)	(629,798)
Outstanding at end of year, shares (in shares)	334,561	964,359
Vested/Exercisable at end of year (in shares)	334,561
Weighted Average Exercise Price
Outstanding at beginning of year, Weighted Average Exercise Price (in dollars per shares)	$ 9.13
Exercised, Weighted Average Exercise Price (in dollars per shares)	7.67
Outstanding at end of year, Weighted Average Exercise price (in dollars per shares)	11.88	$ 9.13
Vested/Exercisable at end of period, Weighted Average Exercise Price (in dollars per shares)	$ 11.88
Weighted Average Remaining Contractual Term (in years)	1 year	1 year 3 months 18 days
Vested/Exercisable at end of period, Weighted Average Remaining Contractual Term (in years)	1 year
Exercised, Aggregated Intrinsic Value	$ 4,967,700
Outstanding, Aggregate Intrinsic Value	1,295,900
Vested/Exercisable at end of year, Aggregate Intrinsic Value	$ 1,295,900

SHARE BASED COMPENSATION, 401_4

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Restricted Share Activity (Details) - USD ($)	Feb. 21, 2019	Dec. 31, 2019
Restricted Performance Share Units Plan
Shares
Ending balance (in shares)	37,472	233,890
Weighted Average Grant Date Fair Value
Non-vested at end of year, Weighted Average Grant Date Fair Value (in dollars per shares)		$ 15.61
Restricted Share Rights Awards
Shares
Beginning balance (in shares)		466,439
Granted (in shares)	196,667	278,442
Vested (in shares)		(248,607)
Forfeited (in shares)		(17,130)
Ending balance (in shares)		479,144
Weighted Average Grant Date Fair Value
Non-vested at beginning of year, Weighted Average Grant Date Fair Value (in dollars per shares)		$ 14.93
Granted, Weighted Average Grant Date Fair Value (in dollars per shares)		15.51
Vested, Weighted Average Grant Date Fair Value (in dollars per shares)		13.68
Forfeited, Weighted Average Grant Date Fair Value (in dollars per shares)		15.66
Non-vested at end of year, Weighted Average Grant Date Fair Value (in dollars per shares)		$ 15.90
Non-vested at beginning of year, Aggregate Intrinsic Value		$ 70,700
Granted, Aggregate Intrinsic Value		65,600
Vested, Aggregate Intrinsic Value		538,300
Forfeited, Aggregate Intrinsic Value		1,600
Non-vested at end of year, Aggregate Intrinsic Value		$ 44,700
Executive Officers | Restricted Performance Share Units Plan
Shares
Beginning balance (in shares)		375,550
Granted (in shares)		213,728
Vested (in shares)		(8,420)
Forfeited (in shares)		(25,323)
Ending balance (in shares)		555,535
February 22, 2016 RSPU Grant | Executive Officers | Restricted Performance Share Units Plan
Shares
Beginning balance (in shares)		169,525
Granted (in shares)		0
Vested (in shares)		(8,420)
Forfeited (in shares)		(1,935)
Ending balance (in shares)		159,170
March 01, 2017 RSPU Grant | Executive Officers | Restricted Performance Share Units Plan
Shares
Beginning balance (in shares)		206,025
Granted (in shares)		0
Vested (in shares)		0
Forfeited (in shares)		(15,729)
Ending balance (in shares)		190,296
February 28, 2018 RSPU Grant | Executive Officers | Restricted Performance Share Units Plan
Shares
Beginning balance (in shares)		0
Granted (in shares)		213,728
Vested (in shares)		0
Forfeited (in shares)		(7,659)
Ending balance (in shares)		206,069

SHARE BASED COMPENSATION, 401_5

SHARE BASED COMPENSATION, 401(K) PLAN AND DEFERRED COMPENSATION - Restricted Performance Share Units (Details) - Restricted Performance Share Units Plan - USD ($) $ in Thousands	Feb. 21, 2019	Feb. 28, 2018	Mar. 01, 2017	Feb. 22, 2016	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ending balance (in shares)	37,472				233,890
Executive Officers
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)					375,550
Granted (in shares)					213,728
Units Cancelled (in shares)					(25,323)
Ending balance (in shares)					555,535
Total number of shares authorized for issuance (in shares)		213,728	209,193	174,854
Fair Value of Units on Grant Date		$ 4,627	$ 4,276	$ 3,735
Executive Officers | February 22, 2016 RSPU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)					169,525
Granted (in shares)					0
Units Cancelled (in shares)					(1,935)
Ending balance (in shares)					159,170
Executive Officers | March 01, 2017 RSPU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)					206,025
Granted (in shares)					0
Units Cancelled (in shares)					(15,729)
Ending balance (in shares)					190,296
Executive Officers | February 28, 2018 RSPU Grant
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares)					0
Granted (in shares)					213,728
Units Cancelled (in shares)					(7,659)
Ending balance (in shares)					206,069

DISTRIBUTIONS (Details)

DISTRIBUTIONS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Distributions [Abstract]
Common share distributions payments of ordinary dividends (in usd per share)	$ 0.62	$ 0.55	$ 0.38
Common share distributions capital gain (in usd per share)	0	0	0.26
Common share distributions non-taxable distributions (in usd per share)	0.14	0.17	0
Common stock dividends per share paid (in usd per share)	$ 0.76	$ 0.72	$ 0.64
Percentage of distributions classified as ordinary income	81.00%	76.20%	60.00%
Percentage of distributions classified as capital gain	0.00%	0.00%	40.00%
Percentage of distributions classified as non-taxable distributions	19.00%	23.80%	0.00%
Dividends, preferred stock	$ 0	$ 0	$ 2,032
Percentage of preferred distributions classified as ordinary income	0.00%	0.00%	60.00%
Percentage of preferred distributions classified as capital gain	0.00%	0.00%	40.00%
Percentage of preferred distributions classified as non-taxable distributions	0.00%	0.00%	0.00%

INCOME TAXES AND TAX CREDIT T_2

INCOME TAXES AND TAX CREDIT TRANSACTIONS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accruals for tax uncertainties	$ 0	$ 0
Deferred income tax expense (benefit)	100,000	300,000	$ (600,000)
Current income tax expense (benefit)	$ (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, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Beneficiaries' Equity, Beginning Balance		$ 1,811,028	$ 1,826,870	$ 1,864,388
Partners' Equity, Beginning Balance		1,798,508
Unrealized gain (loss) on derivative financial instruments		(8,210)	1,478	2,948
Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests		41	(39)	(34)
Amortization of interest rate contracts reclassified from comprehensive income to interest expense	[1]	770	1,191	1,230
Beneficiaries' Equity, Ending Balance		1,688,303	1,811,028	1,826,870
Partners' Equity, Ending Balance			1,798,508
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Partners' Equity, Beginning Balance		1,798,508	1,799,955	1,840,593
Unrealized gain (loss) on derivative financial instruments		(8,210)	1,478	2,948
Amortization of interest rate contracts reclassified from comprehensive income to interest expense	[1]	770	1,191	1,230
Partners' Equity, Ending Balance		1,672,915	1,798,508	1,799,955
Accumulated Other Comprehensive Income (Loss)
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Beneficiaries' Equity, Beginning Balance		5,029	2,399	(1,745)
Beneficiaries' Equity, Ending Balance		(2,370)	5,029	2,399
Accumulated Other Comprehensive Income (Loss) | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Partners' Equity, Beginning Balance		4,725	2,056	(2,122)
Partners' Equity, Ending Balance		$ (2,715)	$ 4,725	$ 2,056
[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, 2019USD ($)
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

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Details)	Apr. 02, 2015USD ($)	Sep. 30, 2004USD ($)	Dec. 31, 2019USD ($)aft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness			$ 596,007,000	$ 370,319,000
Agreed holding period (not to sell) for properties acquired as part of the TRC acquisition			15 years
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	$ 2,000,000		$ 1,970,000
Fair value of contingent consideration	1,600,000
Interest expense	$ 2,000,000
Drexel Square
Property Subject to or Available for Operating Lease [Line Items]
Required spending in capital improvements to property			8,500,000
Estimated potential additional contribution obligation			$ 2,800,000
Two Logan Square
Property Subject to or Available for Operating Lease [Line Items]
Leased area of building | ft²			708,844
Amount to be paid if the Company takes fee title to Two Logan Square upon foreclosure of related mortgage			$ 2,900,000
Liability related to acquisition of TRC		$ 700,000	2,900,000
One Commerce Square
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation			125,000,000
Two Commerce Square
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation			100,000,000
Mortgage Lenders
Property Subject to or Available for Operating Lease [Line Items]
Associated letter of credit			0
Unconsolidated Real Estate Ventures
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness			596,007,000
4040 Wilson Venture
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness			114,845,000	$ 57,288,000
Secured construction loan with total borrowing capacity					$ 150,000,000
4040 Wilson Venture | 4040 Wilson Venture
Property Subject to or Available for Operating Lease [Line Items]
Secured construction loan with total borrowing capacity			150,000,000
Guarantees, maximum exposure amount			$ 41,300,000
Radnor PA Property
Property Subject to or Available for Operating Lease [Line Items]
Rentable square feet | ft²			170,000
Acres | a			7.8
Building purchase price			$ 20,300,000
Land purchase price			11,300,000
Payments for deposit on real estate investment			$ 1,000,000

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details)	12 Months Ended
	Dec. 31, 2019segment
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) $ in Thousands	Jun. 29, 2018USD ($)	Dec. 31, 2019USD ($)a	Dec. 31, 2018USD ($)a	Dec. 31, 2017USD ($)a
Segment Reporting Information [Line Items]
Operating properties		$ 4,006,459	$ 3,951,719	$ 3,830,824
Right of use asset - operating leases, net		21,656	0	0
Construction-in-progress		180,718	150,263	121,188
Land held for development		96,124	86,401	98,242
Prepaid leasehold interests in land held for development, net		$ 39,592	$ 39,999	$ 0
Held for Sale Properties Included in Continuing Operations | Land Held For Development
Segment Reporting Information [Line Items]
Acres | a		35.2	37.9	13.1
3025 JFK Boulevard
Segment Reporting Information [Line Items]
Prepaid leasehold interests in land held for development, net	$ 15,000
Lease agreement term	99 years	99 years
Philadelphia CBD
Segment Reporting Information [Line Items]
Operating properties		$ 1,726,299	$ 1,670,388	$ 1,643,296
Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Operating properties		1,003,890	1,002,937	957,272
Austin, Texas
Segment Reporting Information [Line Items]
Operating properties		721,255	667,698	163,653
Metropolitan DC
Segment Reporting Information [Line Items]
Operating properties		468,035	524,190	978,257
Other
Segment Reporting Information [Line Items]
Operating properties		$ 86,980	$ 86,506	$ 88,346

SEGMENT INFORMATION - Net Opera

SEGMENT INFORMATION - Net Operating Income of Company's Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 147,039	$ 145,331	$ 144,151	$ 143,896	$ 139,203	$ 134,998	$ 133,786	$ 136,358	$ 580,417	$ 544,345	$ 520,493
Operating expenses									(225,846)	(218,099)	(206,075)
Net operating income (loss)									354,571	326,246	314,418
Philadelphia CBD
Segment Reporting Information [Line Items]
Total revenue									263,769
Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Total revenue									141,084
Austin, Texas
Segment Reporting Information [Line Items]
Total revenue									104,157
Metropolitan DC
Segment Reporting Information [Line Items]
Total revenue									51,498
Operating Segments | Philadelphia CBD
Segment Reporting Information [Line Items]
Total revenue									263,769	256,717	226,673
Operating expenses									(100,219)	(99,449)	(88,818)
Net operating income (loss)									163,550	157,268	137,855
Operating Segments | Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Total revenue									141,084	138,279	139,785
Operating expenses									(47,418)	(49,433)	(47,845)
Net operating income (loss)									93,666	88,846	91,940
Operating Segments | Austin, Texas
Segment Reporting Information [Line Items]
Total revenue									104,157	38,665	34,301
Operating expenses									(38,285)	(16,739)	(15,456)
Net operating income (loss)									65,872	21,926	18,845
Operating Segments | Metropolitan DC
Segment Reporting Information [Line Items]
Total revenue									51,498	90,308	92,024
Operating expenses									(23,455)	(34,072)	(35,014)
Net operating income (loss)									28,043	56,236	57,010
Operating Segments | Other
Segment Reporting Information [Line Items]
Total revenue									14,558	16,757	18,347
Operating expenses									(9,328)	(11,888)	(11,749)
Net operating income (loss)									5,230	4,869	6,598
Corporate
Segment Reporting Information [Line Items]
Total revenue									5,351	3,619	9,363
Operating expenses									(7,141)	(6,518)	(7,193)
Net operating income (loss)									$ (1,790)	$ (2,899)	$ 2,170

SEGMENT INFORMATION - Unconsoli

SEGMENT INFORMATION - Unconsolidated Real Estate Ventures of Company's Reportable Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	$ 120,294	$ 169,100	$ 194,621
Equity in loss of Real Estate Ventures	(9,922)	(15,231)	(8,306)
Philadelphia CBD
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	17,524	19,897	39,939
Equity in loss of Real Estate Ventures	328	(105)	255
Pennsylvania Suburbs
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	0	0	3,503
Equity in loss of Real Estate Ventures	0	0	631
Metropolitan DC
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	102,840	136,142	119,817
Equity in loss of Real Estate Ventures	(4,234)	(15,065)	(5,044)
MAP Venture
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	(70)	11,173	15,450
Equity in loss of Real Estate Ventures	(6,102)	(2,155)	(3,443)
Other
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	0	1,888	1,939
Equity in loss of Real Estate Ventures	86	407	285
Austin, Texas
Segment Reporting Information [Line Items]
Investment in Real Estate Ventures, equity method	0	0	13,973
Equity in loss of Real Estate Ventures	$ 0	$ 1,687	$ (990)

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation of Consolidated Net Income (Loss) to Consolidated NOI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting [Abstract]
Net income	$ 16,874	$ 6,820	$ 6,252	$ 4,583	$ 121,673	$ (43,522)	$ 12,876	$ 44,445	$ 34,529	$ 135,472	$ 121,177
Plus:
Interest expense									81,512	78,199	81,886
Interest expense - amortization of deferred financing costs									2,768	2,498	2,435
Depreciation and amortization									210,005	176,000	180,323
General and administrative expenses									32,156	27,802	28,538
Equity in loss of Real Estate Ventures									9,922	15,231	8,306
Provision for impairment									0	71,707	3,057
Loss on early extinguishment of debt									0	105	3,933
Less:
Interest income									2,318	4,703	1,113
Income tax (provision) benefit									(12)	(423)	628
Net gain on disposition of real estate									356	2,932	32,017
Net gain on sale of undepreciated real estate									2,020	3,040	953
Net gain on real estate venture transactions									11,639	142,233	80,526
Gain on promoted interest in unconsolidated real estate venture									0	28,283	0
Consolidated net operating income									$ 354,571	$ 326,246	$ 314,418

SUMMARY OF QUARTERLY RESULTS _3

SUMMARY OF QUARTERLY RESULTS (UNAUDITED) (Details) $ / shares in Units, $ in Thousands	Dec. 11, 2018USD ($)	Dec. 31, 2019USD ($)$ / shares	Sep. 30, 2019USD ($)$ / shares	Jun. 30, 2019USD ($)$ / shares	Mar. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares	Sep. 30, 2018USD ($)property$ / shares	Jun. 30, 2018USD ($)$ / shares	Mar. 31, 2018USD ($)$ / shares	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)$ / shares
Quarterly Financial Information [Line Items]
Total revenue		$ 147,039	$ 145,331	$ 144,151	$ 143,896	$ 139,203	$ 134,998	$ 133,786	$ 136,358	$ 580,417	$ 544,345	$ 520,493
Net income (loss)		16,874	6,820	6,252	4,583	121,673	(43,522)	12,876	44,445	34,529	135,472	121,177
Net income (loss) allocated to common equity holders		$ 16,676	$ 6,679	$ 6,112	$ 4,404	$ 120,792	$ (43,260)	$ 12,661	$ 43,956	$ 34,267	$ 134,518	$ 120,173
Basic earnings per Common Share (in dollars per shares) | $ / shares		$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.68	$ (0.24)	$ 0.07	$ 0.25	$ 0.19	$ 0.75	$ 0.65
Diluted earnings (loss) per Common Share (in dollars per shares) | $ / shares		$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.67	$ (0.24)	$ 0.07	$ 0.24	$ 0.19	$ 0.75	$ 0.65
Net gain on real estate venture transactions										$ 11,639	$ 142,233	$ 80,526
Gain on promoted interest in unconsolidated real estate venture										0	28,283	0
DRA Austin Venture
Quarterly Financial Information [Line Items]
Net income (loss) allocated to common equity holders										1,300
Net gain on real estate venture transactions	$ 103,800
Gain on promoted interest in unconsolidated real estate venture	$ 28,300
PJP II, PJP VII, And PJP VII
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions		$ 8,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Total revenue		147,039	$ 145,331	$ 144,151	$ 143,896	$ 139,203	$ 134,998	$ 133,786	$ 136,358	580,417	544,345	520,493
Net income (loss)		16,874	6,820	6,252	4,583	121,673	(43,522)	12,876	44,445	$ 34,529	$ 135,472	$ 121,177
Net income (loss) allocated to common equity holders		$ 16,772	$ 6,716	$ 6,146	$ 4,430	$ 121,575	$ (43,622)	$ 12,769	$ 44,326
Basic earnings per Common Share (in dollars per shares) | $ / shares		$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.68	$ (0.24)	$ 0.07	$ 0.25	$ 0.19	$ 0.75	$ 0.65
Diluted earnings (loss) per Common Share (in dollars per shares) | $ / shares		$ 0.09	$ 0.04	$ 0.03	$ 0.03	$ 0.67	$ (0.24)	$ 0.07	$ 0.24	$ 0.19	$ 0.75	$ 0.65
Net gain on real estate venture transactions										$ 11,639	$ 142,233	$ 80,526
Gain on promoted interest in unconsolidated real estate venture										$ 0	$ 28,283	$ 0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | DRA Austin Venture
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions						$ 103,800
Gain on promoted interest in unconsolidated real estate venture						$ 28,300
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Metropolitan Washington, D.C. - Office
Quarterly Financial Information [Line Items]
Provision for impairment on assets held for sale							$ 56,900
Number of properties contributed to a joint venture | property							8
BRANDYWINE OPERATING PARTNERSHIP, L.P. | PJP II, PJP VII, And PJP VII
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions		$ 8,000

Schedule II - Valuation and Q_2

Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 12,919	$ 17,112	$ 16,116
Additions	0	1,775	1,912
Deductions	4,944	5,968	916
Balance at End of Year	$ 7,975	$ 12,919	$ 17,112

Schedule III - Real Estate an_2

Schedule III - Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 315,437
Initial Cost [Abstract]
Land	443,949
Buildings and Improvements	2,886,455
Net Improvements (Retirements) Since Acquisition	676,055
Carrying Amount at Which Carried [Abstract]
Land	489,702
Buildings and Improvements	3,516,757
Total	4,006,459	$ 3,951,719	$ 3,830,824	$ 3,658,438
Accumulated Depreciation at December 31, 2019	973,318	885,407	$ 913,297	$ 885,392
Pennsylvania | 400 Berwyn Park
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,657
Buildings and Improvements		4,462
Net Improvements (Retirements) Since Acquisition		12,841
Carrying Amount at Which Carried [Abstract]
Land		2,657
Buildings and Improvements		17,303
Total		19,960
Accumulated Depreciation at December 31, 2019		7,583
Pennsylvania | 300 Berwyn Park
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,206
Buildings and Improvements		13,422
Net Improvements (Retirements) Since Acquisition		4,145
Carrying Amount at Which Carried [Abstract]
Land		2,206
Buildings and Improvements		17,567
Total		19,773
Accumulated Depreciation at December 31, 2019		10,516
Pennsylvania | 1050 Westlakes Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,611
Buildings and Improvements		10,445
Net Improvements (Retirements) Since Acquisition		2,210
Carrying Amount at Which Carried [Abstract]
Land		2,611
Buildings and Improvements		12,655
Total		15,266
Accumulated Depreciation at December 31, 2019		6,238
Pennsylvania | 1200 Swedesford Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,595
Buildings and Improvements		11,809
Net Improvements (Retirements) Since Acquisition		490
Carrying Amount at Which Carried [Abstract]
Land		2,595
Buildings and Improvements		12,299
Total		14,894
Accumulated Depreciation at December 31, 2019		6,848
Pennsylvania | 200 Berwyn Park
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,533
Buildings and Improvements		9,460
Net Improvements (Retirements) Since Acquisition		1,574
Carrying Amount at Which Carried [Abstract]
Land		1,533
Buildings and Improvements		11,034
Total		12,567
Accumulated Depreciation at December 31, 2019		6,569
Pennsylvania | 1180 Swedesford Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,086
Buildings and Improvements		8,342
Net Improvements (Retirements) Since Acquisition		2,865
Carrying Amount at Which Carried [Abstract]
Land		2,086
Buildings and Improvements		11,207
Total		13,293
Accumulated Depreciation at December 31, 2019		5,802
Pennsylvania | 100 Berwyn Park
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,180
Buildings and Improvements		7,290
Net Improvements (Retirements) Since Acquisition		1,419
Carrying Amount at Which Carried [Abstract]
Land		1,180
Buildings and Improvements		8,709
Total		9,889
Accumulated Depreciation at December 31, 2019		5,252
Pennsylvania | 1160 Swedesford Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,781
Buildings and Improvements		7,124
Net Improvements (Retirements) Since Acquisition		6,810
Carrying Amount at Which Carried [Abstract]
Land		2,045
Buildings and Improvements		13,670
Total		15,715
Accumulated Depreciation at December 31, 2019		6,698
Pennsylvania | 1100 Cassett Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,695
Buildings and Improvements		6,779
Net Improvements (Retirements) Since Acquisition		1,730
Carrying Amount at Which Carried [Abstract]
Land		1,695
Buildings and Improvements		8,509
Total		10,204
Accumulated Depreciation at December 31, 2019		4,044
Pennsylvania | Six Tower Bridge (181 Washington Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		6,927
Buildings and Improvements		14,722
Net Improvements (Retirements) Since Acquisition		2,511
Carrying Amount at Which Carried [Abstract]
Land		6,237
Buildings and Improvements		17,923
Total		24,160
Accumulated Depreciation at December 31, 2019		3,803
Pennsylvania | 52 Swedesford Square
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		4,241
Buildings and Improvements		16,579
Net Improvements (Retirements) Since Acquisition		5,193
Carrying Amount at Which Carried [Abstract]
Land		4,241
Buildings and Improvements		21,772
Total		26,013
Accumulated Depreciation at December 31, 2019		11,511
Pennsylvania | 640 Freedom Business Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,015
Buildings and Improvements		20,098
Net Improvements (Retirements) Since Acquisition		4,832
Carrying Amount at Which Carried [Abstract]
Land		414
Buildings and Improvements		25,531
Total		25,945
Accumulated Depreciation at December 31, 2019		14,251
Pennsylvania | 620 Freedom Business Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		666
Buildings and Improvements		13,118
Net Improvements (Retirements) Since Acquisition		1,826
Carrying Amount at Which Carried [Abstract]
Land		270
Buildings and Improvements		15,340
Total		15,610
Accumulated Depreciation at December 31, 2019		8,836
Pennsylvania | 1000 First Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		0
Buildings and Improvements		13,708
Net Improvements (Retirements) Since Acquisition		3,211
Carrying Amount at Which Carried [Abstract]
Land		0
Buildings and Improvements		16,919
Total		16,919
Accumulated Depreciation at December 31, 2019		10,766
Pennsylvania | 1060 First Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		0
Buildings and Improvements		13,665
Net Improvements (Retirements) Since Acquisition		4,169
Carrying Amount at Which Carried [Abstract]
Land		0
Buildings and Improvements		17,834
Total		17,834
Accumulated Depreciation at December 31, 2019		11,055
Pennsylvania | 630 Freedom Business Center Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		666
Buildings and Improvements		13,251
Net Improvements (Retirements) Since Acquisition		3,259
Carrying Amount at Which Carried [Abstract]
Land		273
Buildings and Improvements		16,903
Total		17,176
Accumulated Depreciation at December 31, 2019		9,861
Pennsylvania | 1020 First Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		0
Buildings and Improvements		10,744
Net Improvements (Retirements) Since Acquisition		3,931
Carrying Amount at Which Carried [Abstract]
Land		0
Buildings and Improvements		14,675
Total		14,675
Accumulated Depreciation at December 31, 2019		9,089
Pennsylvania | 1040 First Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		0
Buildings and Improvements		14,142
Net Improvements (Retirements) Since Acquisition		5,080
Carrying Amount at Which Carried [Abstract]
Land		0
Buildings and Improvements		19,222
Total		19,222
Accumulated Depreciation at December 31, 2019		12,076
Pennsylvania | 610 Freedom Business Center Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		485
Buildings and Improvements		9,602
Net Improvements (Retirements) Since Acquisition		2,676
Carrying Amount at Which Carried [Abstract]
Land		198
Buildings and Improvements		12,565
Total		12,763
Accumulated Depreciation at December 31, 2019		6,976
Pennsylvania | 650 Park Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,916
Buildings and Improvements		4,378
Net Improvements (Retirements) Since Acquisition		(4,378)
Carrying Amount at Which Carried [Abstract]
Land		1,916
Buildings and Improvements		0
Total		1,916
Accumulated Depreciation at December 31, 2019		0
Pennsylvania | 600 Park Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,012
Buildings and Improvements		4,048
Net Improvements (Retirements) Since Acquisition		385
Carrying Amount at Which Carried [Abstract]
Land		1,012
Buildings and Improvements		4,433
Total		5,445
Accumulated Depreciation at December 31, 2019		2,647
Pennsylvania | 933 First Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,127
Buildings and Improvements		20,794
Net Improvements (Retirements) Since Acquisition		(1,125)
Carrying Amount at Which Carried [Abstract]
Land		3,127
Buildings and Improvements		19,669
Total		22,796
Accumulated Depreciation at December 31, 2019		2,216
Pennsylvania | 500 North Gulph Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,303
Buildings and Improvements		5,201
Net Improvements (Retirements) Since Acquisition		21,017
Carrying Amount at Which Carried [Abstract]
Land		1,303
Buildings and Improvements		26,218
Total		27,521
Accumulated Depreciation at December 31, 2019		1,202
Pennsylvania | 401 Plymouth Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		6,199
Buildings and Improvements		16,131
Net Improvements (Retirements) Since Acquisition		15,831
Carrying Amount at Which Carried [Abstract]
Land		6,199
Buildings and Improvements		31,962
Total		38,161
Accumulated Depreciation at December 31, 2019		15,355
Pennsylvania | Metroplex (4000 Chemical Road)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		4,373
Buildings and Improvements		24,546
Net Improvements (Retirements) Since Acquisition		399
Carrying Amount at Which Carried [Abstract]
Land		4,373
Buildings and Improvements		24,945
Total		29,318
Accumulated Depreciation at December 31, 2019		7,701
Pennsylvania | 610 West Germantown Pike
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,651
Buildings and Improvements		14,514
Net Improvements (Retirements) Since Acquisition		3,285
Carrying Amount at Which Carried [Abstract]
Land		3,651
Buildings and Improvements		17,799
Total		21,450
Accumulated Depreciation at December 31, 2019		8,669
Pennsylvania | 600 West Germantown Pike
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,652
Buildings and Improvements		15,288
Net Improvements (Retirements) Since Acquisition		2,717
Carrying Amount at Which Carried [Abstract]
Land		3,652
Buildings and Improvements		18,005
Total		21,657
Accumulated Depreciation at December 31, 2019		8,124
Pennsylvania | 630 West Germantown Pike
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,558
Buildings and Improvements		14,743
Net Improvements (Retirements) Since Acquisition		2,714
Carrying Amount at Which Carried [Abstract]
Land		3,558
Buildings and Improvements		17,457
Total		21,015
Accumulated Depreciation at December 31, 2019		7,906
Pennsylvania | 620 West Germantown Pike
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,572
Buildings and Improvements		14,435
Net Improvements (Retirements) Since Acquisition		1,498
Carrying Amount at Which Carried [Abstract]
Land		3,572
Buildings and Improvements		15,933
Total		19,505
Accumulated Depreciation at December 31, 2019		7,042
Pennsylvania | 660 West Germantown Pike
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,694
Buildings and Improvements		5,487
Net Improvements (Retirements) Since Acquisition		20,715
Carrying Amount at Which Carried [Abstract]
Land		5,405
Buildings and Improvements		24,491
Total		29,896
Accumulated Depreciation at December 31, 2019		6,850
Pennsylvania | 351 Plymouth Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		1,043
Buildings and Improvements		555
Net Improvements (Retirements) Since Acquisition		0
Carrying Amount at Which Carried [Abstract]
Land		1,043
Buildings and Improvements		555
Total		1,598
Accumulated Depreciation at December 31, 2019		205
Pennsylvania | 150 Radnor Chester Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		11,925
Buildings and Improvements		36,986
Net Improvements (Retirements) Since Acquisition		10,142
Carrying Amount at Which Carried [Abstract]
Land		11,897
Buildings and Improvements		47,156
Total		59,053
Accumulated Depreciation at December 31, 2019		22,504
Pennsylvania | One Radnor Corporate Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		7,323
Buildings and Improvements		28,613
Net Improvements (Retirements) Since Acquisition		22,885
Carrying Amount at Which Carried [Abstract]
Land		7,323
Buildings and Improvements		51,498
Total		58,821
Accumulated Depreciation at December 31, 2019		30,974
Pennsylvania | 201 King of Prussia Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		8,956
Buildings and Improvements		29,811
Net Improvements (Retirements) Since Acquisition		2,871
Carrying Amount at Which Carried [Abstract]
Land		8,949
Buildings and Improvements		32,689
Total		41,638
Accumulated Depreciation at December 31, 2019		19,061
Pennsylvania | 555 Lancaster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		8,014
Buildings and Improvements		16,508
Net Improvements (Retirements) Since Acquisition		20,204
Carrying Amount at Which Carried [Abstract]
Land		8,609
Buildings and Improvements		36,117
Total		44,726
Accumulated Depreciation at December 31, 2019		18,535
Pennsylvania | Four Radnor Corporate Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		5,406
Buildings and Improvements		21,390
Net Improvements (Retirements) Since Acquisition		12,770
Carrying Amount at Which Carried [Abstract]
Land		5,705
Buildings and Improvements		33,861
Total		39,566
Accumulated Depreciation at December 31, 2019		15,781
Pennsylvania | Five Radnor Corporate Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		6,506
Buildings and Improvements		25,525
Net Improvements (Retirements) Since Acquisition		8,209
Carrying Amount at Which Carried [Abstract]
Land		6,578
Buildings and Improvements		33,662
Total		40,240
Accumulated Depreciation at December 31, 2019		12,120
Pennsylvania | Three Radnor Corporate Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		4,773
Buildings and Improvements		17,961
Net Improvements (Retirements) Since Acquisition		1,273
Carrying Amount at Which Carried [Abstract]
Land		4,791
Buildings and Improvements		19,216
Total		24,007
Accumulated Depreciation at December 31, 2019		9,598
Pennsylvania | Two Radnor Corporate Center
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,937
Buildings and Improvements		15,484
Net Improvements (Retirements) Since Acquisition		3,163
Carrying Amount at Which Carried [Abstract]
Land		3,942
Buildings and Improvements		18,642
Total		22,584
Accumulated Depreciation at December 31, 2019		9,853
Pennsylvania | 130 Radnor Chester Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,573
Buildings and Improvements		8,338
Net Improvements (Retirements) Since Acquisition		3,188
Carrying Amount at Which Carried [Abstract]
Land		2,567
Buildings and Improvements		11,532
Total		14,099
Accumulated Depreciation at December 31, 2019		6,716
Pennsylvania | 170 Radnor Chester Road
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		2,514
Buildings and Improvements		8,147
Net Improvements (Retirements) Since Acquisition		1,751
Carrying Amount at Which Carried [Abstract]
Land		2,509
Buildings and Improvements		9,903
Total		12,412
Accumulated Depreciation at December 31, 2019		4,375
Pennsylvania | 200 N. Radnor Chester Rd.
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,366
Buildings and Improvements		0
Net Improvements (Retirements) Since Acquisition		3,653
Carrying Amount at Which Carried [Abstract]
Land		3,366
Buildings and Improvements		3,653
Total		7,019
Accumulated Depreciation at December 31, 2019		772
Pennsylvania | 101 West Elm Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		6,251
Buildings and Improvements		25,209
Net Improvements (Retirements) Since Acquisition		3,853
Carrying Amount at Which Carried [Abstract]
Land		6,251
Buildings and Improvements		29,062
Total		35,313
Accumulated Depreciation at December 31, 2019		10,721
Pennsylvania | 1 West Elm Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		0
Initial Cost [Abstract]
Land		3,557
Buildings and Improvements		14,249
Net Improvements (Retirements) Since Acquisition		3,376
Carrying Amount at Which Carried [Abstract]
Land		3,557
Buildings and Improvements		17,625
Total		21,182
Accumulated Depreciation at December 31, 2019		6,823
Pennsylvania | Four Tower Bridge (200 Barr Harbor Drive)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances		9,291
Initial Cost [Abstract]
Land		6,000
Buildings and Improvements		14,734
Net Improvements (Retirements) Since Acquisition		336
Carrying Amount at Which Carried [Abstract]
Land		6,000
Buildings and Improvements		15,070
Total		21,070
Accumulated Depreciation at December 31, 2019		$ 761
Philadelphia CBD | Cira Centre (2929 Arch Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	208,570
Net Improvements (Retirements) Since Acquisition	(17,837)
Carrying Amount at Which Carried [Abstract]
Land	12,586
Buildings and Improvements	178,147
Total	190,733
Accumulated Depreciation at December 31, 2019	62,966
Philadelphia CBD | Three Logan Square (1717 Arch Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	98,188
Net Improvements (Retirements) Since Acquisition	75,116
Carrying Amount at Which Carried [Abstract]
Land	25,195
Buildings and Improvements	148,109
Total	173,304
Accumulated Depreciation at December 31, 2019	40,161
Philadelphia CBD | Two Commerce Square (2001 Market Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	108,472
Initial Cost [Abstract]
Land	15,323
Buildings and Improvements	120,200
Net Improvements (Retirements) Since Acquisition	33,693
Carrying Amount at Which Carried [Abstract]
Land	15,323
Buildings and Improvements	153,893
Total	169,216
Accumulated Depreciation at December 31, 2019	27,952
Philadelphia CBD | One Logan Square (130 North 18th Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	14,496
Buildings and Improvements	107,736
Net Improvements (Retirements) Since Acquisition	30,019
Carrying Amount at Which Carried [Abstract]
Land	14,473
Buildings and Improvements	137,778
Total	152,251
Accumulated Depreciation at December 31, 2019	62,425
Philadelphia CBD | Two Logan Square (100 North 18th Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	81,103
Initial Cost [Abstract]
Land	16,066
Buildings and Improvements	100,255
Net Improvements (Retirements) Since Acquisition	20,061
Carrying Amount at Which Carried [Abstract]
Land	16,066
Buildings and Improvements	120,316
Total	136,382
Accumulated Depreciation at December 31, 2019	49,266
Philadelphia CBD | One Commerce Square (2005 Market Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	116,571
Initial Cost [Abstract]
Land	15,161
Buildings and Improvements	105,021
Net Improvements (Retirements) Since Acquisition	32,326
Carrying Amount at Which Carried [Abstract]
Land	15,160
Buildings and Improvements	137,348
Total	152,508
Accumulated Depreciation at December 31, 2019	25,304
Philadelphia CBD | Cira Centre South Garage (129 South 30th Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	76,008
Net Improvements (Retirements) Since Acquisition	26,832
Carrying Amount at Which Carried [Abstract]
Land	6,905
Buildings and Improvements	95,935
Total	102,840
Accumulated Depreciation at December 31, 2019	19,682
Philadelphia CBD | 1900 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	7,768
Buildings and Improvements	17,263
Net Improvements (Retirements) Since Acquisition	63,292
Carrying Amount at Which Carried [Abstract]
Land	7,768
Buildings and Improvements	80,555
Total	88,323
Accumulated Depreciation at December 31, 2019	15,492
Philadelphia CBD | 3020 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	21,417
Net Improvements (Retirements) Since Acquisition	8,272
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	29,689
Total	29,689
Accumulated Depreciation at December 31, 2019	10,492
Philadelphia CBD | 618-634 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	13,365
Buildings and Improvements	5,791
Net Improvements (Retirements) Since Acquisition	2,176
Carrying Amount at Which Carried [Abstract]
Land	13,365
Buildings and Improvements	7,967
Total	21,332
Accumulated Depreciation at December 31, 2019	5,975
Philadelphia CBD | FMC Tower at Cira Centre South (2929 Walnut Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	400,294
Net Improvements (Retirements) Since Acquisition	13,296
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	413,590
Total	413,590
Accumulated Depreciation at December 31, 2019	47,285
Philadelphia CBD | 2100 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	18,827
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	6,433
Carrying Amount at Which Carried [Abstract]
Land	18,854
Buildings and Improvements	6,406
Total	25,260
Accumulated Depreciation at December 31, 2019	1,027
Philadelphia CBD | 3000 Market Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	18,924
Buildings and Improvements	13,080
Net Improvements (Retirements) Since Acquisition	1,039
Carrying Amount at Which Carried [Abstract]
Land	18,924
Buildings and Improvements	14,119
Total	33,043
Accumulated Depreciation at December 31, 2019	2,979
Philadelphia CBD | The Bulletin Building (3025 Market Street)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	24,377
Net Improvements (Retirements) Since Acquisition	13,353
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	37,730
Total	37,730
Accumulated Depreciation at December 31, 2019	2,086
Philadelphia CBD | 3001-3003 JFK Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	111
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	111
Total	111
Accumulated Depreciation at December 31, 2019	10
Philadelphia CBD | 3025 JFK Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	0
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	0
Total	0
Accumulated Depreciation at December 31, 2019	0
Metropolitan DC | 6600 Rockledge Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	37,421
Net Improvements (Retirements) Since Acquisition	9,270
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	46,691
Total	46,691
Accumulated Depreciation at December 31, 2019	14,871
Metropolitan DC | 2340 Dulles Corner Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	16,345
Buildings and Improvements	65,379
Net Improvements (Retirements) Since Acquisition	524
Carrying Amount at Which Carried [Abstract]
Land	16,129
Buildings and Improvements	66,119
Total	82,248
Accumulated Depreciation at December 31, 2019	22,150
Metropolitan DC | 1676 International Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	18,437
Buildings and Improvements	97,538
Net Improvements (Retirements) Since Acquisition	(962)
Carrying Amount at Which Carried [Abstract]
Land	18,785
Buildings and Improvements	96,228
Total	115,013
Accumulated Depreciation at December 31, 2019	25,451
Metropolitan DC | 8260 Greensboro Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	7,952
Buildings and Improvements	33,964
Net Improvements (Retirements) Since Acquisition	4,955
Carrying Amount at Which Carried [Abstract]
Land	8,102
Buildings and Improvements	38,769
Total	46,871
Accumulated Depreciation at December 31, 2019	11,152
Metropolitan DC | 2273 Research Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	5,167
Buildings and Improvements	31,110
Net Improvements (Retirements) Since Acquisition	5,799
Carrying Amount at Which Carried [Abstract]
Land	5,237
Buildings and Improvements	36,839
Total	42,076
Accumulated Depreciation at December 31, 2019	11,928
Metropolitan DC | 2275 Research Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	5,059
Buildings and Improvements	29,668
Net Improvements (Retirements) Since Acquisition	7,588
Carrying Amount at Which Carried [Abstract]
Land	5,154
Buildings and Improvements	37,161
Total	42,315
Accumulated Depreciation at December 31, 2019	13,308
Metropolitan DC | 2277 Research Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	4,649
Buildings and Improvements	26,952
Net Improvements (Retirements) Since Acquisition	18,853
Carrying Amount at Which Carried [Abstract]
Land	4,733
Buildings and Improvements	45,721
Total	50,454
Accumulated Depreciation at December 31, 2019	17,093
Metropolitan DC | 8521 Leesburg Pike
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	4,316
Buildings and Improvements	30,885
Net Improvements (Retirements) Since Acquisition	7,145
Carrying Amount at Which Carried [Abstract]
Land	4,397
Buildings and Improvements	37,949
Total	42,346
Accumulated Depreciation at December 31, 2019	11,925
Austin, Texas | 11501 Burnet Road - Building 1
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	3,755
Buildings and Improvements	22,702
Net Improvements (Retirements) Since Acquisition	115
Carrying Amount at Which Carried [Abstract]
Land	3,755
Buildings and Improvements	22,817
Total	26,572
Accumulated Depreciation at December 31, 2019	3,193
Austin, Texas | 11501 Burnet Road - Building 2
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,732
Buildings and Improvements	16,305
Net Improvements (Retirements) Since Acquisition	1,551
Carrying Amount at Which Carried [Abstract]
Land	2,732
Buildings and Improvements	17,856
Total	20,588
Accumulated Depreciation at December 31, 2019	2,920
Austin, Texas | 11501 Burnet Road - Building 3
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	3,688
Buildings and Improvements	22,348
Net Improvements (Retirements) Since Acquisition	94
Carrying Amount at Which Carried [Abstract]
Land	3,688
Buildings and Improvements	22,442
Total	26,130
Accumulated Depreciation at December 31, 2019	3,161
Austin, Texas | 11501 Burnet Road - Building 4
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,614
Buildings and Improvements	15,740
Net Improvements (Retirements) Since Acquisition	75
Carrying Amount at Which Carried [Abstract]
Land	2,614
Buildings and Improvements	15,815
Total	18,429
Accumulated Depreciation at December 31, 2019	2,242
Austin, Texas | 11501 Burnet Road - Building 5
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	3,689
Buildings and Improvements	22,354
Net Improvements (Retirements) Since Acquisition	118
Carrying Amount at Which Carried [Abstract]
Land	3,689
Buildings and Improvements	22,472
Total	26,161
Accumulated Depreciation at December 31, 2019	3,207
Austin, Texas | 11501 Burnet Road - Building 6
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,676
Buildings and Improvements	15,972
Net Improvements (Retirements) Since Acquisition	13,973
Carrying Amount at Which Carried [Abstract]
Land	2,676
Buildings and Improvements	29,945
Total	32,621
Accumulated Depreciation at December 31, 2019	3,408
Austin, Texas | 11501 Burnet Road - Building 8
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	1,400
Buildings and Improvements	7,422
Net Improvements (Retirements) Since Acquisition	1,547
Carrying Amount at Which Carried [Abstract]
Land	1,400
Buildings and Improvements	8,969
Total	10,369
Accumulated Depreciation at December 31, 2019	1,172
Austin, Texas | 11501 Burnet Road - Parking Garage
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	0
Buildings and Improvements	19,826
Net Improvements (Retirements) Since Acquisition	63
Carrying Amount at Which Carried [Abstract]
Land	0
Buildings and Improvements	19,889
Total	19,889
Accumulated Depreciation at December 31, 2019	3,628
Austin, Texas | Four Points Centre 3, 11120 Four Points Drive
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	1,140
Buildings and Improvements	0
Net Improvements (Retirements) Since Acquisition	40,564
Carrying Amount at Which Carried [Abstract]
Land	1,140
Buildings and Improvements	40,564
Total	41,704
Accumulated Depreciation at December 31, 2019	1,511
Austin, Texas | One Barton Skyway (1501 South MoPac Expressway)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	10,496
Buildings and Improvements	47,670
Net Improvements (Retirements) Since Acquisition	113
Carrying Amount at Which Carried [Abstract]
Land	10,495
Buildings and Improvements	47,784
Total	58,279
Accumulated Depreciation at December 31, 2019	1,378
Austin, Texas | Two Barton Skyway (1601 South MoPac Expressway)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	10,849
Buildings and Improvements	53,868
Net Improvements (Retirements) Since Acquisition	2,828
Carrying Amount at Which Carried [Abstract]
Land	10,848
Buildings and Improvements	56,697
Total	67,545
Accumulated Depreciation at December 31, 2019	1,810
Austin, Texas | Three Barton Skyway (1221 South MoPac Expressway)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	10,374
Buildings and Improvements	47,624
Net Improvements (Retirements) Since Acquisition	184
Carrying Amount at Which Carried [Abstract]
Land	10,373
Buildings and Improvements	47,809
Total	58,182
Accumulated Depreciation at December 31, 2019	1,343
Austin, Texas | Four Barton Skyway (1301 South MoPac Expressway)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	13,301
Buildings and Improvements	57,041
Net Improvements (Retirements) Since Acquisition	(40)
Carrying Amount at Which Carried [Abstract]
Land	13,300
Buildings and Improvements	57,002
Total	70,302
Accumulated Depreciation at December 31, 2019	1,583
Austin, Texas | Four Points Centre (11305 Four Points Drive)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	7,800
Buildings and Improvements	43,581
Net Improvements (Retirements) Since Acquisition	3,463
Carrying Amount at Which Carried [Abstract]
Land	7,800
Buildings and Improvements	47,044
Total	54,844
Accumulated Depreciation at December 31, 2019	1,427
Austin, Texas | River Place - Building 1 (6500 River Place Boulevard)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,004
Buildings and Improvements	17,680
Net Improvements (Retirements) Since Acquisition	476
Carrying Amount at Which Carried [Abstract]
Land	2,004
Buildings and Improvements	18,156
Total	20,160
Accumulated Depreciation at December 31, 2019	547
Austin, Texas | River Place - Building 2 (6500 River Place Boulevard)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	3,137
Buildings and Improvements	29,254
Net Improvements (Retirements) Since Acquisition	191
Carrying Amount at Which Carried [Abstract]
Land	3,137
Buildings and Improvements	29,445
Total	32,582
Accumulated Depreciation at December 31, 2019	816
Austin, Texas | River Place - Building 3 (6500 River Place Boulevard)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	3,064
Buildings and Improvements	26,705
Net Improvements (Retirements) Since Acquisition	12
Carrying Amount at Which Carried [Abstract]
Land	3,064
Buildings and Improvements	26,717
Total	29,781
Accumulated Depreciation at December 31, 2019	735
Austin, Texas | River Place - Building 4 (6500 River Place Boulevard
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,273
Buildings and Improvements	18,617
Net Improvements (Retirements) Since Acquisition	1,001
Carrying Amount at Which Carried [Abstract]
Land	2,273
Buildings and Improvements	19,618
Total	21,891
Accumulated Depreciation at December 31, 2019	674
Austin, Texas | River Place - Building 5 (6500 River Place Boulevard)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	1,752
Buildings and Improvements	14,315
Net Improvements (Retirements) Since Acquisition	(24)
Carrying Amount at Which Carried [Abstract]
Land	1,752
Buildings and Improvements	14,291
Total	16,043
Accumulated Depreciation at December 31, 2019	394
Austin, Texas | River Place - Building 6 (6500 River Place Boulevard)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	1,598
Buildings and Improvements	12,945
Net Improvements (Retirements) Since Acquisition	(24)
Carrying Amount at Which Carried [Abstract]
Land	1,598
Buildings and Improvements	12,921
Total	14,519
Accumulated Depreciation at December 31, 2019	356
Austin, Texas | River Place - Building 7 (6500 River Place Boulevard)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	1,801
Buildings and Improvements	16,486
Net Improvements (Retirements) Since Acquisition	1,051
Carrying Amount at Which Carried [Abstract]
Land	1,801
Buildings and Improvements	17,537
Total	19,338
Accumulated Depreciation at December 31, 2019	586
Austin, Texas | Quarry Lake II (4516 Seton Center Parkway)
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	3,970
Buildings and Improvements	30,546
Net Improvements (Retirements) Since Acquisition	821
Carrying Amount at Which Carried [Abstract]
Land	3,867
Buildings and Improvements	31,470
Total	35,337
Accumulated Depreciation at December 31, 2019	876
Other | 10 Foster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	244
Buildings and Improvements	971
Net Improvements (Retirements) Since Acquisition	69
Carrying Amount at Which Carried [Abstract]
Land	244
Buildings and Improvements	1,040
Total	1,284
Accumulated Depreciation at December 31, 2019	624
Other | 7 Foster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	231
Buildings and Improvements	921
Net Improvements (Retirements) Since Acquisition	31
Carrying Amount at Which Carried [Abstract]
Land	231
Buildings and Improvements	952
Total	1,183
Accumulated Depreciation at December 31, 2019	549
Other | 2 Foster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	185
Buildings and Improvements	730
Net Improvements (Retirements) Since Acquisition	11
Carrying Amount at Which Carried [Abstract]
Land	185
Buildings and Improvements	741
Total	926
Accumulated Depreciation at December 31, 2019	741
Other | 4 Foster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	183
Buildings and Improvements	726
Net Improvements (Retirements) Since Acquisition	6
Carrying Amount at Which Carried [Abstract]
Land	183
Buildings and Improvements	732
Total	915
Accumulated Depreciation at December 31, 2019	732
Other | 1 Foster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	93
Buildings and Improvements	364
Net Improvements (Retirements) Since Acquisition	8
Carrying Amount at Which Carried [Abstract]
Land	93
Buildings and Improvements	372
Total	465
Accumulated Depreciation at December 31, 2019	372
Other | 5 U.S. Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	21
Buildings and Improvements	81
Net Improvements (Retirements) Since Acquisition	2
Carrying Amount at Which Carried [Abstract]
Land	21
Buildings and Improvements	83
Total	104
Accumulated Depreciation at December 31, 2019	83
Other | 5 Foster Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	9
Buildings and Improvements	32
Net Improvements (Retirements) Since Acquisition	3
Carrying Amount at Which Carried [Abstract]
Land	9
Buildings and Improvements	35
Total	44
Accumulated Depreciation at December 31, 2019	35
Other | Main Street-Plaza 1000
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	2,732
Buildings and Improvements	10,942
Net Improvements (Retirements) Since Acquisition	296
Carrying Amount at Which Carried [Abstract]
Land	2,732
Buildings and Improvements	11,238
Total	13,970
Accumulated Depreciation at December 31, 2019	11,008
Other | Main Street-Piazza
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	696
Buildings and Improvements	2,802
Net Improvements (Retirements) Since Acquisition	3,700
Carrying Amount at Which Carried [Abstract]
Land	704
Buildings and Improvements	6,494
Total	7,198
Accumulated Depreciation at December 31, 2019	3,515
Other | Main Street-Promenade
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	532
Buildings and Improvements	2,052
Net Improvements (Retirements) Since Acquisition	312
Carrying Amount at Which Carried [Abstract]
Land	532
Buildings and Improvements	2,364
Total	2,896
Accumulated Depreciation at December 31, 2019	1,350
Other | 920 North King Street
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	6,141
Buildings and Improvements	21,140
Net Improvements (Retirements) Since Acquisition	7,969
Carrying Amount at Which Carried [Abstract]
Land	6,141
Buildings and Improvements	29,109
Total	35,250
Accumulated Depreciation at December 31, 2019	13,046
Other | 300 Delaware Avenue
Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost [Abstract]
Land	6,369
Buildings and Improvements	13,739
Net Improvements (Retirements) Since Acquisition	2,638
Carrying Amount at Which Carried [Abstract]
Land	6,369
Buildings and Improvements	16,377
Total	22,746
Accumulated Depreciation at December 31, 2019	$ 9,031

Schedule III - Real Estate an_3

Schedule III - Real Estate and Accumulated Depreciation (Reconciliations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at the Beginning of the Year	$ 3,951,719	$ 3,830,824	$ 3,658,438
Additions:
Acquisitions	0	509,654	62,587
Capital expenditures and assets placed into service	145,378	129,274	356,857
Less:
Dispositions/impairments/placed into redevelopment	(50,792)	(469,517)	(189,472)
Retirements	(39,846)	(48,516)	(57,586)
Balance at the end of the year	4,006,459	3,951,719	3,830,824
Operating properties	4,006,459	3,951,719	3,830,824
Tax basis of assets, cost for income tax purposes	3,200,000	3,300,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	885,407	913,297	885,392
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense	144,131	137,213	154,029
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions/impairments/placed into redevelopment	(16,783)	(117,589)	(74,178)
Retirements	(39,437)	(47,514)	(51,946)
Balance at the end of the year	973,318	885,407	913,297
Per consolidated balance sheet	$ 973,318	$ 885,407	$ 913,297
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

Uncategorized Items - bdn10k123

Label	Element	Value
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (5,336,000)
Subsidiaries [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(5,336,000)
Subsidiaries [Member] | General Partner [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (5,336,000)