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]
Beginning Balance at Dec. 31, 2015				$ 1,929,977	$ 1,836,692	$ 96,850	$ (5,597)	$ 2,032
Beginning Balance, Shares at Dec. 31, 2015					174,688,568	4,000,000
Net income	$ 40,501		$ 310	40,501	$ 40,486			15
Other comprehensive income	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	0		(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	0		297	0	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	121,859		1,009	121,859	$ 121,830			29
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, 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 ventures	$ (48)		(48)	$ (48)				(48)
Share Choice Plan Issuance, Shares	0			0	(1,423)
Bonus share issuance	$ 110			$ 110	$ 110
Bonus share issuance, Shares					6,752
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	0		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	$ 0	2,056	2,215
Ending Balance, Shares at Dec. 31, 2017					178,285,236	0
Net income	137,289		965	137,289	$ 137,234			55
Other comprehensive income	2,669	$ 2,630	39	2,669			2,669
Share Issuance from/(to) Deferred Compensation Plan	(111)			(111)	$ (111)
Share Issuance from/(to) Deferred Compensation Plan, Shares					99,189
Issuance of LP Units				416	$ 416
Issuance of LP Units, Shares					23,311
Repurchase and retirement of LP units				(21,858)	$ (21,858)
Repurchase and retirement of LP units, Shares					(1,729,278)
Issuance of partnership interest in consolidated real estate venture	16		16	16				16
Distributions from consolidated real estate ventures	$ (94)		(94)	$ (94)				(94)
Share Choice Plan Issuance, Shares	0			0	(1,285)
Share-based compensation activity	$ 5,843			$ 5,843	$ 5,843
Share-based compensation activity, Shares					196,151
Reallocation of Noncontrolling Interest	0		$ 2,003
Redemption value of limited partnership units				6,369	$ 6,369
Preferred Share distributions	0			0
Preferred share redemption charge	$ 0			0
Distributions declared to general partnership unitholders				(130,168)	(130,168)
Ending Balance at Dec. 31, 2018				$ 1,820,053	$ 1,813,136	$ 0	$ 4,725	$ 2,192
Ending Balance, Shares at Dec. 31, 2018					176,873,324	0