PARTNERS' EQUITY OF THE PARENT COMPANY - Schedule of 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, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator
Net income (loss)	$ (21,636)	$ (12,737)	$ (5,276)	$ 13,478	$ 4,651	$ 6,101	$ (39,649)	$ 24,230
Nonforfeitable dividends allocated to unvested restricted unitholders, Basic	(159)			(105)			(433)	(351)
Nonforfeitable dividends allocated to unvested restricted unitholders, Diluted	$ (159)			$ (105)			$ (433)	$ (351)
Denominator
Weighted average units outstanding, basic (in shares)	172,097,661			171,569,807			171,912,552	171,464,936
Contingent securities/Share based compensation (in shares)	0			582,449			0	970,217
Weighted average shares outstanding, diluted (in shares)	172,097,661			172,152,256			171,912,552	172,435,153
Earnings (loss) per Common Partnership Unit:
Net income attributable to common shareholders, Basic (in dollars per share)	$ (0.13)			$ 0.08			$ (0.23)	$ 0.14
Net income attributable to common shareholders, Diluted (in dollars per share)	$ (0.13)			$ 0.08			$ (0.23)	$ 0.14
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income (loss)	$ (21,636)	$ (12,737)	$ (5,276)	$ 13,478	$ 4,651	$ 6,101	$ (39,649)	$ 24,230
Net loss attributable to noncontrolling interests	20			1			21	5
Nonforfeitable dividends allocated to unvested restricted unitholders, Basic	(159)			(105)			(433)	(351)
Nonforfeitable dividends allocated to unvested restricted unitholders, Diluted	(159)			(105)			(433)	(351)
Net income attributable to common unitholders, Basic	(21,775)			13,374			(40,061)	23,884
Net income attributable to common unitholders, Diluted	$ (21,775)			$ 13,374			$ (40,061)	$ 23,884
Denominator
Weighted average units outstanding, basic (in shares)	172,614,128			172,086,274			172,429,019	172,019,701
Contingent securities/Share based compensation (in shares)	0			582,449			0	970,217
Weighted average shares outstanding, diluted (in shares)	172,614,128			172,668,723			172,429,019	172,989,918
Earnings (loss) per Common Partnership Unit:
Net income attributable to common shareholders, Basic (in dollars per share)	$ (0.13)			$ 0.08			$ (0.23)	$ 0.14
Net income attributable to common shareholders, Diluted (in dollars per share)	$ (0.13)			$ 0.08			$ (0.23)	$ 0.14