Partners Equity of the Operating Partnership - 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				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
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(93)		(86)		(212)	(200)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	$ (93)		$ (86)		$ (212)	$ (200)
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 Partnership Unit:
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
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 6,252	$ 4,583	$ 12,876	$ 44,445	$ 10,835	$ 57,321
Net income attributable to noncontrolling interests	(13)		(21)		(47)	(26)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(93)		(86)		(212)	(200)
Net income attributable to common unitholders, Basic	6,146		12,769		10,576	57,095
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(93)		(86)		(212)	(200)
Net income attributable to common unitholders, Diluted	$ 6,146		$ 12,769		$ 10,576	$ 57,095
Denominator
Basic weighted average shares outstanding (in shares)	177,125,064		180,027,354		176,983,433	179,951,759
Basic contingent securities/Share based compensation (in shares)	0		0		0	0
Contingent securities/Share based compensation (in shares)	547,619		1,144,781		577,069	1,268,730
Diluted weighted average shares outstanding (in shares)	177,672,683		181,172,135		177,560,502	181,220,489
Earnings per Common Partnership Unit:
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	$ 0.32