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	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator
Net income	$ 12,366	$ 307,326	$ 34,529
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(421)	(410)	(396)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	$ (421)	$ (410)	$ (396)
Denominator
Basic weighted average shares outstanding (in shares)	170,878,185	171,926,079	176,132,941
Contingent securities/Share based compensation (in shares)	1,395,055	390,997	553,872
Diluted weighted average shares outstanding (in shares)	172,273,240	172,317,076	176,686,813
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (in dollars per share)	$ 0.07	$ 1.77	$ 0.19
Net income attributable to common shareholders, Diluted (in dollars per share)	$ 0.07	$ 1.77	$ 0.19
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 12,366	$ 307,326	$ 34,529
Net income attributable to noncontrolling interests	3	(20)	(69)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(421)	(410)	(396)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(421)	(410)	(396)
Net income attributable to common unitholders, Basic	11,948	306,896	34,064
Net income attributable to common unitholders, Diluted	$ 11,948	$ 306,896	$ 34,064
Denominator
Basic weighted average shares outstanding (in shares)	171,770,843	172,907,713	177,114,932
Contingent securities/Share based compensation (in shares)	1,395,055	390,997	553,872
Diluted weighted average shares outstanding (in shares)	173,165,898	173,298,710	177,668,804
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (in dollars per share)	$ 0.07	$ 1.77	$ 0.19
Net income attributable to common shareholders, Diluted (in dollars per share)	$ 0.07	$ 1.77	$ 0.19