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, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator
Net income	$ 6,252	$ 4,583	$ 12,876	$ 44,445	$ 10,835	$ 57,321
Net income attributable to noncontrolling interests, Basic	(47)		(129)		(107)	(504)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(93)		(86)		(212)	(200)
Net income attributable to Common Shareholders of Brandywine Realty Trust	6,112		12,661		10,516	56,617
Net income attributable to noncontrolling interests, Diluted	(47)		(129)		(107)	(504)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(93)		(86)		(212)	(200)
Net income attributable to common shareholders, Diluted	$ 6,112		$ 12,661		$ 10,516	$ 56,617
Denominator
Basic weighted average shares outstanding (in shares)	176,143,206		178,547,555		176,001,071	178,471,960
Basic contingent securities/Share based compensation (in shares)	0		0
Contingent securities/Share based compensation (in shares)	547,618		1,144,781		577,069	1,268,730
Diluted weighted average shares outstanding (in shares)	176,690,824		179,692,336		176,578,140	179,740,690
Earnings per Common Share:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.03		$ 0.07		$ 0.06	$ 0.32
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.03		$ 0.07		$ 0.06	$ 0.31