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
	Mar. 31, 2018	Mar. 31, 2017
Numerator
Net income	$ 44,705	$ 21,271
Distribution to preferred shareholders	0	(1,725)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(114)	(99)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	$ (114)	$ (99)
Denominator
Basic weighted average shares outstanding (in shares)	178,395,525	175,176,964
Contingent securities/Share based compensation (in shares)	1,392,786	1,024,908
Diluted weighted average shares outstanding (in shares)	179,788,311	176,201,872
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.25	$ 0.11
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.25	$ 0.11
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income	$ 44,705	$ 21,271
Net income attributable to noncontrolling interests	(5)	(5)
Distribution to preferred shareholders	0	(1,725)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(114)	(99)
Net income attributable to common unitholders, Basic	44,586	19,442
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(114)	(99)
Net income attributable to common unitholders, Diluted	$ 44,586	$ 19,442
Denominator
Basic weighted average shares outstanding (in shares)	179,875,324	176,656,763
Contingent securities/Share based compensation (in shares)	1,392,786	1,024,908
Diluted weighted average shares outstanding (in shares)	181,268,110	177,681,671
Earnings per Common Partnership Unit:
Net income attributable to common shareholders, Basic (USD per share)	$ 0.25	$ 0.11
Net income attributable to common shareholders, Diluted (USD per share)	$ 0.25	$ 0.11