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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator
Net income (loss)	$ (175)	$ 6,964	$ 4,020	$ 8,087	$ 6,789	$ 12,107
Net (income) loss attributable to noncontrolling interests, Basic	8		(24)		(35)	(89)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(94)		(93)		(240)	(224)
Net (income) loss attributable to noncontrolling interests, Diluted	8		(24)		(35)	(89)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(94)		(93)		(240)	(224)
Net income (loss) attributable to Common Shareholders of Brandywine Realty Trust	(261)		3,903		6,514	11,794
Net income (loss) attributable to common shareholders, Diluted	$ (261)		$ 3,903		$ 6,514	$ 11,794
Denominator
Basic weighted average shares outstanding (in shares)	170,848,894		170,518,095		170,737,437	173,294,031
Contingent securities/Share based compensation (in shares)	0		251,983		1,258,682	311,917
Diluted weighted average shares outstanding (in shares)	170,848,894		170,770,078		171,996,119	173,605,948
Earnings per Common Share:
Net income attributable to common shareholders, Basic (USD per share)	$ 0		$ 0.02		$ 0.04	$ 0.07
Net income attributable to common shareholders, Diluted (USD per share)	$ 0		$ 0.02		$ 0.04	$ 0.07