Consolidated Statements of Partners' Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest - Consolidated Real Estate Ventures	BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P. Accumulated Other Comprehensive Income (Loss)	BRANDYWINE OPERATING PARTNERSHIP, L.P. Noncontrolling Interest - Consolidated Real Estate Ventures	BRANDYWINE OPERATING PARTNERSHIP, L.P. General Partner Capital
Beginning balance (in shares) at Dec. 31, 2019							176,480,095
Beginning Balance at Dec. 31, 2019				$ 1,672,915	$ (2,715)	$ 1,091	$ 1,674,539
Net income (loss)	$ 8,087		$ 65	8,087		12	$ 8,075
Other comprehensive income (loss)	(7,869)	$ (7,825)	(44)	(7,869)	(7,869)
Deferred compensation obligation (in shares)							(12,376)
Deferred compensation obligation	(193)			(193)			$ (193)
Repurchase and retirement of LP units (in shares)							(5,644,200)
Repurchase and retirement of LP units				(53,858)			$ (53,858)
Share-based compensation activity (in shares)							142,468
Share-based compensation activity	2,031			2,031			$ 2,031
Adjustment of redeemable partnership units to liquidation value at period end				5,220			5,220
Distributions declared to general partnership unitholders				(32,500)			$ (32,500)
Ending balance (in shares) at Mar. 31, 2020							170,965,987
Ending Balance at Mar. 31, 2020				1,593,833	(10,584)	1,103	$ 1,603,314
Beginning balance (in shares) at Dec. 31, 2019							176,480,095
Beginning Balance at Dec. 31, 2019				1,672,915	(2,715)	1,091	$ 1,674,539
Net income (loss)	288,240			288,240
Other comprehensive income (loss)	(6,415)			(6,415)
Ending balance (in shares) at Sep. 30, 2020							170,572,964
Ending Balance at Sep. 30, 2020				1,805,832	(9,130)	72	$ 1,814,890
Beginning balance (in shares) at Mar. 31, 2020							170,965,987
Beginning Balance at Mar. 31, 2020				1,593,833	(10,584)	1,103	$ 1,603,314
Net income (loss)	4,020		24	4,020		10	$ 4,010
Other comprehensive income (loss)	226	225	1	226	226
Deferred compensation obligation (in shares)							(44,827)
Deferred compensation obligation	(11)			(11)			$ (11)
Repurchase and retirement of LP units (in shares)							(604,283)
Repurchase and retirement of LP units				(6,141)			$ (6,141)
Share-based compensation activity (in shares)							166,628
Share-based compensation activity	1,668			1,668			$ 1,668
Adjustment of redeemable partnership units to liquidation value at period end				(743)			(743)
Distributions declared to general partnership unitholders				(32,540)			$ (32,540)
Ending balance (in shares) at Jun. 30, 2020							170,573,159
Ending Balance at Jun. 30, 2020				1,560,312	(10,358)	1,113	$ 1,569,557
Net income (loss)	276,133		1,612	276,133		(2)	$ 276,135
Other comprehensive income (loss)	1,228	1,221	7	1,228	1,228
Deferred compensation obligation (in shares)							(195)
Deferred compensation obligation	(2)			(2)			$ (2)
Distributions from consolidated real estate ventures	(22)		(22)	(22)		(22)
Share-based compensation activity	1,263			1,263			1,263
Impact of deconsolidation of real estate venture	(1,017)		(1,017)	(1,017)		(1,017)
Adjustment of redeemable partnership units to liquidation value at period end				400			400
Distributions declared to general partnership unitholders				(32,463)			$ (32,463)
Ending balance (in shares) at Sep. 30, 2020							170,572,964
Ending Balance at Sep. 30, 2020				1,805,832	(9,130)	72	$ 1,814,890
Beginning balance (in shares) at Dec. 31, 2020							170,572,964
Beginning Balance at Dec. 31, 2020				1,793,082	(7,935)	72	$ 1,800,945
Net income (loss)	6,964		43	6,964		(1)	$ 6,965
Other comprehensive income (loss)	1,098	1,092	6	1,098	1,098
Deferred compensation obligation (in shares)							(18,058)
Deferred compensation obligation	(198)			(198)			$ (198)
Share-based compensation activity (in shares)							108,345
Share-based compensation activity	2,502			2,502			$ 2,502
Adjustment of redeemable partnership units to liquidation value at period end				(1,294)			(1,294)
Distributions declared to general partnership unitholders				(32,573)			$ (32,573)
Ending balance (in shares) at Mar. 31, 2021							170,663,251
Ending Balance at Mar. 31, 2021				1,769,581	(6,837)	71	$ 1,776,347
Beginning balance (in shares) at Dec. 31, 2020							170,572,964
Beginning Balance at Dec. 31, 2020				1,793,082	(7,935)	72	$ 1,800,945
Net income (loss)	7,763			7,763
Other comprehensive income (loss)	3,245			3,245
Ending balance (in shares) at Sep. 30, 2021							171,126,257
Ending Balance at Sep. 30, 2021				1,714,307	(4,690)	68	$ 1,718,929
Beginning balance (in shares) at Mar. 31, 2021							170,663,251
Beginning Balance at Mar. 31, 2021				1,769,581	(6,837)	71	$ 1,776,347
Net income (loss)	(175)		(8)	(175)		(1)	(174)
Other comprehensive income (loss)	1,048	1,042	6	1,048	1,048
Deferred compensation obligation	0
Repurchase and retirement of LP units				(2,334)			(2,334)
Issuance of partnership interest in consolidated real estate ventures	2,289		2,289	2,289			$ 2,289
Share-based compensation activity (in shares)							237,240
Share-based compensation activity	690			690			$ 690
Adjustment of redeemable partnership units to liquidation value at period end				1,066			1,066
Distributions declared to general partnership unitholders				(32,562)			$ (32,562)
Ending balance (in shares) at Jun. 30, 2021							170,900,491
Ending Balance at Jun. 30, 2021				1,739,603	(5,789)	70	$ 1,745,322
Net income (loss)	974		7	974		(2)	$ 976
Other comprehensive income (loss)	1,099	$ 1,094	5	1,099	1,099
Issuance of LP Units (in shares)							226,695
Issuance of LP Units	3,052						$ 3,052
Issuance of partnership interest in consolidated real estate ventures	476		$ 476	476			$ 476
Share-based compensation activity (in shares)							(929)
Share-based compensation activity	$ 1,585			1,585			$ 1,585
Adjustment of redeemable partnership units to liquidation value at period end				124			124
Distributions declared to general partnership unitholders				(32,606)			$ (32,606)
Ending balance (in shares) at Sep. 30, 2021							171,126,257
Ending Balance at Sep. 30, 2021				$ 1,714,307	$ (4,690)	$ 68	$ 1,718,929