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. Accumulated Other Comprehensive Income (Loss) [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P. Noncontrolling Interest [Member]	BRANDYWINE OPERATING PARTNERSHIP, L.P. Series E-linked Preferred Stock [Member]
Beginning Balance at Dec. 31, 2016				$ 1,859,642	$ 1,762,764	$ (2,122)	$ 2,150	$ 96,850
Beginning Balance, Shares at Dec. 31, 2016					175,140,760			4,000,000
Net income	$ 48,015		$ 384	48,015	$ 47,990		25
Other comprehensive income	846	$ 839	7	846		846
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	(48)			(48)	$ (48)
Share Issuance from/(to) Deferred Compensation Plan, Shares					1,718
Issuance of LP Units				(499)	$ (499)
Issuance of partnership interest in consolidated real estate ventures	85		85	86			86
Distributions from consolidated real estate ventures	(46)		(46)	(46)			(46)
Share Choice Plan Issuance, Shares					(1,423)
Bonus share issuance	110			110	$ 110
Bonus share issuance, Shares					6,752
Share-based compensation activity	5,907			5,907	$ 5,907
Share-based compensation activity, Shares					333,127
Adjustment of redeemable partnership units to liquidation value at period end				(2,781)	$ (2,781)
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				(84,463)	(84,463)
Ending Balance at Sep. 30, 2017				1,724,706	$ 1,723,767	(1,276)	2,215
Ending Balance, Shares at Sep. 30, 2017					175,477,498
Beginning Balance at Dec. 31, 2017				1,819,682	$ 1,815,411	2,056	2,215
Beginning Balance, Shares at Dec. 31, 2017					178,285,236
Net income	14,579		167	14,579	$ 14,533		46
Other comprehensive income	7,906	$ 7,840	66	7,906		7,906
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
Issuance of partnership interest in consolidated real estate ventures	16		16	16			16
Distributions from consolidated real estate ventures	(54)		$ (54)	(54)			(54)
Share Choice Plan Issuance, Shares					(1,285)
Share-based compensation activity	4,972			4,972	$ 4,972
Share-based compensation activity, Shares					196,151
Adjustment of redeemable partnership units to liquidation value at period end				2,880	$ 2,880
Preferred Share distributions	0			0
Preferred share redemption charge	$ 0			0
Distributions declared to general partnership unitholders				(96,722)	(96,722)
Ending Balance at Sep. 30, 2018				$ 1,753,564	$ 1,741,379	$ 9,962	$ 2,223
Ending Balance, Shares at Sep. 30, 2018					178,602,602