Partners' Equity Of The Parent Company - 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, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator
Net income	$ 974	$ (175)	$ 6,964	$ 276,133	$ 4,020	$ 8,087	$ 7,763	$ 288,240
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(91)			(93)			(331)	(317)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	$ (91)			$ (93)			$ (331)	$ (317)
Denominator
Basic weighted average shares outstanding (in shares)	170,907,018			170,573,028			170,794,585	172,380,410
Contingent securities/Share based compensation (in shares)	1,330,176			453,464			1,283,365	355,026
Diluted weighted average shares outstanding (in shares)	172,237,194			171,026,492			172,077,950	172,735,436
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.01			$ 1.61			$ 0.04	$ 1.66
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.01			$ 1.60			$ 0.04	$ 1.66
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 974	$ (175)	$ 6,964	$ 276,133	$ 4,020	$ 8,087	$ 7,763	$ 288,240
Net (income) loss attributable to noncontrolling interests	2			2			4	(20)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(91)			(93)			(331)	(317)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(91)			(93)			(331)	(317)
Net income (loss) attributable to common unitholders, Basic	885			276,042			7,436	287,903
Net income (loss) attributable to common unitholders, Diluted	$ 885			$ 276,042			$ 7,436	$ 287,903
Denominator
Basic weighted average shares outstanding (in shares)	171,731,001			171,554,662			171,710,387	173,362,044
Contingent securities/Share based compensation (in shares)	1,330,176			453,464			1,283,365	355,026
Diluted weighted average shares outstanding (in shares)	173,061,177			172,008,126			172,993,752	173,717,070
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.01			$ 1.61			$ 0.04	$ 1.66
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.01			$ 1.60			$ 0.04	$ 1.66