Partners Equity of the Operating Partnership - Number of Units and Net Income Used to Calculate Basic and Diluted Earnings Per Common Partnership Unit (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator
Net income	$ (43,262)	$ 19,046	$ 14,579	$ 48,015
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(80)	(73)	(280)	(245)
Distribution to preferred shareholders	0	0	0	(2,032)
Preferred share redemption charge	0	0	0	(3,181)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	$ (80)	$ (73)	$ (280)	$ (245)
Denominator
Basic weighted average shares outstanding (in shares)	178,602,622	175,433,657	178,515,993	175,315,581
Contingent securities/Share based compensation (in shares)	0	1,401,365	1,236,551	1,283,751
Diluted weighted average shares outstanding (in shares)	178,602,622	176,835,022	179,752,544	176,599,332
Earnings (loss) per Common Partnership Unit:
Net income (loss) attributable to common shareholders, Basic (USD per share)	$ (0.24)	$ 0.11	$ 0.08	$ 0.24
Net income (loss) attributable to common shareholders, Diluted (USD per share)	$ (0.24)	$ 0.11	$ 0.08	$ 0.24
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ (43,262)	$ 19,046	$ 14,579	$ 48,015
Net income attributable to noncontrolling interests	(20)	(12)	(46)	(25)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(80)	(73)	(280)	(245)
Distribution to preferred shareholders	0	0	0	(2,032)
Preferred share redemption charge	0	0	0	(3,181)
Net income (loss) attributable to common unitholders, Basic	(43,362)	18,961	14,253	42,532
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(80)	(73)	(280)	(245)
Net income (loss) attributable to common unitholders, Diluted	$ (43,362)	$ 18,961	$ 14,253	$ 42,532
Denominator
Basic weighted average shares outstanding (in shares)	180,082,421	176,913,456	179,995,792	176,795,380
Contingent securities/Share based compensation (in shares)	0	1,401,365	1,236,551	1,283,751
Diluted weighted average shares outstanding (in shares)	180,082,421	178,314,821	181,232,343	178,079,131
Earnings (loss) per Common Partnership Unit:
Net income (loss) attributable to common shareholders, Basic (USD per share)	$ (0.24)	$ 0.11	$ 0.08	$ 0.24
Net income (loss) attributable to common shareholders, Diluted (USD per share)	$ (0.24)	$ 0.11	$ 0.08	$ 0.24