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. Accumulated Other Comprehensive Income (Loss)	BRANDYWINE OPERATING PARTNERSHIP, L.P. Noncontrolling Interests	BRANDYWINE OPERATING PARTNERSHIP, L.P. General Partner Capital	Cumulative effect of accounting change BRANDYWINE OPERATING PARTNERSHIP, L.P.	Cumulative effect of accounting change BRANDYWINE OPERATING PARTNERSHIP, L.P. General Partner Capital
Beginning balance (in shares) at Dec. 31, 2018							176,873,324
Beginning Balance at Dec. 31, 2018				$ 1,798,508	$ 4,725	$ 2,192	$ 1,791,591	$ (5,336)	$ (5,336)
Net income	$ 4,583		$ 60	4,583		34	$ 4,549
Other comprehensive income (loss)	(2,483)	$ (2,469)	(14)	(2,483)	(2,483)
Deferred compensation obligation (in shares)							(458)
Deferred compensation obligation	0			0
Repurchase and retirement of LP units (in shares)							(1,337,169)
Repurchase and retirement of LP units				(17,281)			$ (17,281)
Repurchase and retirement of Common Shares of Beneficial Interest	22		22	22		22
Share-based compensation activity (in shares)							465,883
Share-based compensation activity	3,677			3,677			$ 3,677
Adjustment of redeemable partnership units to liquidation value at period end				(3,088)			(3,088)
Distributions declared to general partnership unitholders				(33,560)			$ (33,560)
Ending balance (in shares) at Mar. 31, 2019							176,001,580
Ending Balance at Mar. 31, 2019				1,745,042	2,242	2,248	$ 1,740,552
Beginning balance (in shares) at Dec. 31, 2018							176,873,324
Beginning Balance at Dec. 31, 2018				1,798,508	4,725	2,192	$ 1,791,591	$ (5,336)	$ (5,336)
Net income	10,835			10,835
Other comprehensive income (loss)	(7,229)			(7,229)
Ending balance (in shares) at Jun. 30, 2019							176,197,883
Ending Balance at Jun. 30, 2019				1,715,445	(2,504)	2,264	$ 1,715,685
Beginning balance (in shares) at Mar. 31, 2019							176,001,580
Beginning Balance at Mar. 31, 2019				1,745,042	2,242	2,248	$ 1,740,552
Net income	6,252		47	6,252		13	$ 6,239
Other comprehensive income (loss)	(4,746)	(4,720)	(26)	(4,746)	(4,746)
Deferred compensation obligation (in shares)							100,908
Deferred compensation obligation	0			0
Repurchase and retirement of LP units (in shares)							1,245
Repurchase and retirement of LP units				0
Repurchase and retirement of Common Shares of Beneficial Interest	3		3	3		3
Share-based compensation activity (in shares)							94,150
Share-based compensation activity	1,451			1,451			$ 1,451
Adjustment of redeemable partnership units to liquidation value at period end				1,014			1,014
Distributions declared to general partnership unitholders				(33,571)			$ (33,571)
Ending balance (in shares) at Jun. 30, 2019							176,197,883
Ending Balance at Jun. 30, 2019				1,715,445	(2,504)	2,264	$ 1,715,685
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	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)
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	12,107			12,107
Other comprehensive income (loss)	(7,643)			(7,643)
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
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	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)
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