Consolidated Statements of Partners' Equity - USD ($) $ in Thousands	Total	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P.	BRANDYWINE OPERATING PARTNERSHIP, L.P. General Partner Capital [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P. Series E-linked Preferred Stock [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P. Accumulated Other Comprehensive Income (Loss) [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P. Noncontrolling Interest [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P. Partners Equity [Member]
Beginning Balance at Dec. 31, 2014				$ 2,134,755	$ 2,041,902	$ 96,850	$ (5,007)	$ 1,010
Beginning Balance, Shares at Dec. 31, 2014					179,293,160	4,000,000
Net income (loss)	$ (30,740)		$ (339)	(30,740)	$ (30,740)			3	$ (30,737)
Other comprehensive income (loss)	(590)	$ (585)	(5)	(590)			(590)
Share Issuance from/(to) Deferred Compensation Plan	(2)			(2)	$ (2)
Share Issuance from/(to) Deferred Compensation Plan, Shares					88,146
Repurchase and retirement of LP units				(67,430)	$ (67,430)
Repurchase and retirement of LP units, Shares					(5,209,437)
Issuance of partnership interest in consolidated real estate venture				1,025				1,025
Bonus share issuance	125			125	$ 125
Bonus share issuance, Shares					8,447
Share Choice Plan Issuance, Shares					(1,423)
Share-based compensation activity	5,097			5,097	$ 5,097
Share-based compensation activity, Shares					509,675
Adjustment of redeemable partnership units to liquidation value at period end				1,533	$ 1,533
Reallocation of Noncontrolling Interest			(93)		6			(6)
Preferred Share distributions	(6,900)			(6,900)	(6,900)
Preferred share redemption charge	0			0
Distributions declared to general partnership unitholders				(106,899)	(106,899)
Ending Balance at Dec. 31, 2015				1,929,977	$ 1,836,692	$ 96,850	(5,597)	2,032
Ending Balance, Shares at Dec. 31, 2015					174,688,568	4,000,000
Net income (loss)	40,501		310	40,501	$ 40,486			15
Other comprehensive income (loss)	3,475	3,447	28	3,475			3,475
Share Issuance from/(to) Deferred Compensation Plan	(47)			(47)	$ (47)
Share Issuance from/(to) Deferred Compensation Plan, Shares					(8,311)
Issuance of partnership interest in consolidated real estate venture	108		108	109				109
Conversion of LP Units to Common Shares			(875)	875	$ 875
Conversion of LP Units to Common Shares, Shares					55,303
Share-based compensation activity	5,764			5,763	$ 5,763
Share-based compensation activity, Shares					405,200
Adjustment of redeemable partnership units to liquidation value at period end				(2,622)	$ (2,622)
Reallocation of Noncontrolling Interest			297		6			(6)
Redemption value of limited partnership units				(875)	(875)
Preferred Share distributions	(6,900)			(6,900)	(6,900)
Preferred share redemption charge	0			0
Distributions declared to general partnership unitholders				(110,614)	(110,614)
Ending Balance at Dec. 31, 2016				1,859,642	$ 1,762,764	$ 96,850	(2,122)	2,150
Ending Balance, Shares at Dec. 31, 2016					175,140,760	4,000,000
Net income (loss)	121,859		1,009	121,859	$ 121,830			29
Other comprehensive income (loss)	4,178	$ 4,144	34	4,178			4,178
Redemption of Preferred Mirror Units				(96,850)		$ (96,850)
Redemption of Preferred Mirror Units, Shares						(4,000,000)
Share Issuance from/(to) Deferred Compensation Plan	(768)			(768)	$ (768)
Share Issuance from/(to) Deferred Compensation Plan, Shares					(52,971)
Issuance of LP Units				50,726	$ 50,726
Issuance of LP Units, 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)
Bonus share issuance	110			110	$ 110
Bonus share issuance, Shares					6,752
Share Choice Plan Issuance, Shares					(1,423)
Share-based compensation activity	6,697			6,697	$ 6,697
Share-based compensation activity, Shares					333,127
Adjustment of redeemable partnership units to liquidation value at period end				(4,100)	$ (4,099)			(1)
Reallocation of Noncontrolling Interest			$ 224
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)
Ending Balance at Dec. 31, 2017				$ 1,819,682	$ 1,815,411		$ 2,056	$ 2,215
Ending Balance, Shares at Dec. 31, 2017					178,285,236