BENEFICIARIES' EQUITY OF THE PARENT COMPANY - Schedule of Number of Shares and Net Income Used to Calculate Basic and Diluted Earnings per Share (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
Net (income) loss attributable to noncontrolling interests, Basic	82			(37)			140	(59)
Net (income) loss attributable to noncontrolling interests, Diluted	82			(37)			140	(59)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(159)			(105)			(433)	(351)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(159)			(105)			(433)	(351)
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	(21,713)			13,336			(39,942)	23,820
Net income (loss) attributable to common shareholders, diluted	$ (21,713)			$ 13,336			$ (39,942)	$ 23,820
Denominator
Basic weighted average shares outstanding (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 Share:
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