Beneficiaries Equity of the Parent Company - 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
	Mar. 31, 2021	Mar. 31, 2020
Numerator
Net income	$ 6,964	$ 8,087
Net income attributable to noncontrolling interests, Basic	(43)	(65)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(146)	(131)
Net income attributable to noncontrolling interests, Diluted	(43)	(65)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(146)	(131)
Net income attributable to Common Shareholders of Brandywine Realty Trust	6,775	7,891
Net income attributable to common shareholders, Diluted	$ 6,775	$ 7,891
Denominator
Basic weighted average shares outstanding (in shares)	170,624,741	176,069,968
Contingent securities/Share based compensation (in shares)	1,011,379	583,491
Diluted weighted average shares outstanding (in shares)	171,636,120	176,653,459
Earnings per Common Share:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.04	$ 0.04
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.04	$ 0.04