Consolidated Statements of Partners' Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests	General Partner Capital	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
Beginning Balance at Dec. 31, 2017					$ 1,799,955	$ 2,056	$ 2,215	$ 1,795,684
Beginning balance (in shares) at Dec. 31, 2017								178,285,236
Net income (loss)	$ 44,445		$ 375		44,445		5	$ 44,440
Other comprehensive income (loss)	5,008	$ 4,966	42		5,008	5,008
Share Issuance from/(to) Deferred Compensation Plan	0				0
Share Issuance from/(to) Deferred Compensation Plan (in shares)								66,830
Issuance of LP Units					416			$ 416
Issuance of LP Units (in shares)								23,311
Issuance of partnership interest in consolidated real estate ventures	15		15		15		15
Distributions from consolidated real estate ventures	(54)		(54)		(54)		(54)
Share Choice Plan issuance (in shares)								(1,285)
Share-based compensation activity	3,076				3,075			$ 3,075
Share-based compensation activity (in shares)								68,425
Adjustment of redeemable partnership units to liquidation value at period end					3,604			$ 3,604
Distributions declared to general partnership unitholders					(32,259)			(32,259)
Ending Balance at Mar. 31, 2018					1,824,205	7,064	2,181	$ 1,814,960
Ending balance (in shares) at Mar. 31, 2018								178,442,517
Beginning Balance at Dec. 31, 2017					1,799,955	2,056	2,215	$ 1,795,684
Beginning balance (in shares) at Dec. 31, 2017								178,285,236
Net income (loss)	13,799				13,799
Other comprehensive income (loss)	7,906				7,906
Ending Balance at Sep. 30, 2018					1,733,055	9,962	2,223	$ 1,720,870
Ending balance (in shares) at Sep. 30, 2018								178,602,602
Beginning Balance at Mar. 31, 2018					1,824,205	7,064	2,181	$ 1,814,960
Beginning balance (in shares) at Mar. 31, 2018								178,442,517
Net income (loss)	12,876		129		12,876		21	$ 12,855
Other comprehensive income (loss)	1,871	1,856	15		1,871	1,871
Share Issuance from/(to) Deferred Compensation Plan	(111)				(111)			$ (111)
Share Issuance from/(to) Deferred Compensation Plan (in shares)								34,230
Issuance of partnership interest in consolidated real estate ventures	(4)		(4)		(4)		(4)
Share-based compensation activity	1,139				1,140			$ 1,140
Share-based compensation activity (in shares)								127,726
Adjustment of redeemable partnership units to liquidation value at period end					(1,991)			$ (1,991)
Distributions declared to general partnership unitholders					(32,230)			(32,230)
Ending Balance at Jun. 30, 2018					1,805,756	8,935	2,198	$ 1,794,623
Ending balance (in shares) at Jun. 30, 2018								178,604,473
Net income (loss)	(43,522)		(342)		(43,522)		20	$ (43,542)
Other comprehensive income (loss)	1,027	1,018	9		1,027	1,027
Share Issuance from/(to) Deferred Compensation Plan	0				0
Share Issuance from/(to) Deferred Compensation Plan (in shares)								(1,871)
Issuance of partnership interest in consolidated real estate ventures	5		5		5		5
Share-based compensation activity	758				758			$ 758
Adjustment of redeemable partnership units to liquidation value at period end					1,264			1,264
Distributions declared to general partnership unitholders					(32,233)			(32,233)
Ending Balance at Sep. 30, 2018					1,733,055	9,962	2,223	$ 1,720,870
Ending balance (in shares) at Sep. 30, 2018								178,602,602
Beginning Balance at Dec. 31, 2018	1,798,508			$ 1,791,591	1,798,508	4,725	2,192	$ 1,791,591
Beginning balance (in shares) at Dec. 31, 2018								176,873,324
Net income (loss)	4,583		60		4,583		34	$ 4,549
Other comprehensive income (loss)	(2,483)	(2,469)	(14)		(2,483)	(2,483)
Share Issuance from/(to) Deferred Compensation Plan	0				0
Share Issuance from/(to) Deferred Compensation Plan (in shares)								(458)
Repurchase and retirement of LP units					(17,281)			$ (17,281)
Repurchase and retirement of LP units (in shares)								(1,337,169)
Issuance of partnership interest in consolidated real estate ventures	22		22		22		22
Share-based compensation activity	3,677				3,677			$ 3,677
Share-based compensation activity (in shares)								465,883
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 at Mar. 31, 2019					1,745,042	2,242	2,248	$ 1,740,552
Ending balance (in shares) at Mar. 31, 2019								176,001,580
Beginning Balance at Dec. 31, 2018	1,798,508			$ 1,791,591	1,798,508	4,725	2,192	$ 1,791,591
Beginning balance (in shares) at Dec. 31, 2018								176,873,324
Net income (loss)	17,655				17,655
Other comprehensive income (loss)	(8,627)				(8,627)
Ending Balance at Sep. 30, 2019					1,687,709	(3,902)	2,277	$ 1,689,334
Ending balance (in shares) at Sep. 30, 2019								176,194,918
Beginning Balance at Mar. 31, 2019					1,745,042	2,242	2,248	$ 1,740,552
Beginning balance (in shares) at Mar. 31, 2019								176,001,580
Net income (loss)	6,252		47		6,252		13	$ 6,239
Other comprehensive income (loss)	(4,746)	(4,720)	(26)		(4,746)	(4,746)
Share Issuance from/(to) Deferred Compensation Plan	0				0
Share Issuance from/(to) Deferred Compensation Plan (in shares)								100,908
Repurchase and retirement of LP units					0
Repurchase and retirement of LP units (in shares)								1,245
Issuance of partnership interest in consolidated real estate ventures	3		3		3		3
Share-based compensation activity	1,451				1,451			$ 1,451
Share-based compensation activity (in shares)								94,150
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 at Jun. 30, 2019					1,715,445	(2,504)	2,264	$ 1,715,685
Ending balance (in shares) at Jun. 30, 2019								176,197,883
Net income (loss)	6,820		48		6,820		11	$ 6,809
Other comprehensive income (loss)	(1,398)	$ (1,390)	(8)		(1,398)	(1,398)
Share Issuance from/(to) Deferred Compensation Plan	0				0
Share Issuance from/(to) Deferred Compensation Plan (in shares)								(2,965)
Issuance of partnership interest in consolidated real estate ventures	2		$ 2		2		2
Share-based compensation activity	$ 1,105				1,105			$ 1,105
Adjustment of redeemable partnership units to liquidation value at period end					(695)			(695)
Distributions declared to general partnership unitholders					(33,570)			(33,570)
Ending Balance at Sep. 30, 2019					$ 1,687,709	$ (3,902)	$ 2,277	$ 1,689,334
Ending balance (in shares) at Sep. 30, 2019								176,194,918