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, 2018	Mar. 31, 2017
Numerator
Net income	$ 44,705	$ 21,271
Net income attributable to noncontrolling interests, Basic	(376)	(169)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic	(114)	(99)
Distribution to preferred shareholders	0	(1,725)
Net income attributable to Common Shareholders of Brandywine Realty Trust	44,215	19,278
Net income attributable to noncontrolling interests, Diluted	(376)	(169)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted	(114)	(99)
Net income attributable to common shareholders, Diluted	$ 44,215	$ 19,278
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 Share:
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