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									12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator
Net income (loss)	$ 73,844	[1]	$ 19,046	$ 7,698	$ 21,271	$ (12,370)	$ 7,884	$ (1,323)	$ 46,310	$ 121,859	$ 40,501	$ (30,740)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic										(327)	(341)	(329)
Distribution to preferred shareholders										(2,032)	(6,900)	(6,900)
Preferred share redemption charge										(3,181)	0	0
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted										$ (327)	$ (341)	$ (329)
Denominator
Basic weighted average shares outstanding (in shares)										175,484,350	175,018,163	178,162,160
Contingent securities/Share based compensation (in shares)										1,323,816	992,651	0
Diluted weighted average shares outstanding (in shares)										176,808,166	176,010,814	178,162,160
Earnings (loss) per Common Partnership Unit:
Net income (loss) attributable to common shareholders, Basic (USD per share)	$ 0.42		$ 0.11	$ 0.02	$ 0.11	$ (0.08)	$ 0.03	$ (0.02)	$ 0.25	$ 0.66	$ 0.19	$ (0.21)
Net income (loss) attributable to common shareholders, Diluted (USD per share)	$ 0.41		$ 0.11	$ 0.02	$ 0.11	$ (0.08)	$ 0.03	$ (0.02)	$ 0.25	$ 0.65	$ 0.19	$ (0.21)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Numerator
Net income (loss)	$ 73,844	[1]	$ 19,046	$ 7,698	$ 21,271	$ (12,370)	$ 7,884	$ (1,323)	$ 46,310	$ 121,859	$ 40,501	$ (30,740)
Nonforfeitable dividends allocated to unvested restricted shareholders, Basic										(327)	(341)	(329)
Distribution to preferred shareholders										(2,032)	(6,900)	(6,900)
Preferred share redemption charge										(3,181)	0	0
Net (income) loss attributable to noncontrolling interests										(29)	(15)	3
Net income (loss) attributable to common unitholders, Basic										116,290	33,245	(37,966)
Nonforfeitable dividends allocated to unvested restricted shareholders, Diluted										(327)	(341)	(329)
Net income attributable to common unitholders, Diluted										$ 116,290	$ 33,245	$ (37,966)
Denominator
Basic weighted average shares outstanding (in shares)										176,964,149	176,523,800	179,697,262
Contingent securities/Share based compensation (in shares)										1,323,816	992,651	0
Diluted weighted average shares outstanding (in shares)										178,287,965	177,516,451	179,697,262
Earnings (loss) per Common Partnership Unit:
Net income (loss) attributable to common shareholders, Basic (USD per share)	$ 0.42		$ 0.11	$ 0.02	$ 0.11	$ (0.08)	$ 0.03	$ (0.02)	$ 0.25	$ 0.66	$ 0.19	$ (0.21)
Net income (loss) attributable to common shareholders, Diluted (USD per share)	$ 0.41		$ 0.11	$ 0.02	$ 0.11	$ (0.08)	$ 0.03	$ (0.02)	$ 0.25	$ 0.65	$ 0.19	$ (0.21)

[1] The increase in net income for the fourth quarter primarily relates to the gain of $52.2 million from the disposition of eight office properties by the Austin Venture. For further details, see Note 4, "Investment in Unconsolidated Real Estate Ventures."