Summary of Quarterly Results (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
Quarterly Financial Information [Line Items]
Total revenue	$ 133,344	[1]	$ 128,438	$ 127,791	$ 130,920	$ 132,086	$ 129,694	$ 127,181	$ 136,502	$ 520,493	$ 525,463	$ 602,631
Net income (loss)	73,844	[2]	19,046	7,698	21,271	(12,370)	7,884	(1,323)	46,310	121,859	40,501	(30,740)
Net income (loss) allocated to Common Shares/ Partnership Unitholders	$ 73,137		$ 18,803	$ 4,092	$ 19,278	$ (14,058)	$ 6,022	$ (3,105)	$ 44,091	$ 120,850	$ 40,191	$ (30,401)
Basic earnings (loss) per Common Shares/Partnership Unitholders	$ 0.42		$ 0.11	$ 0.02	$ 0.11	$ (0.08)	$ 0.03	$ (0.02)	$ 0.25	$ 0.66	$ 0.19	$ (0.21)
Diluted earnings (loss) per Common Share/ Partnership Unitholders	$ 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.
Quarterly Financial Information [Line Items]
Total revenue	$ 133,344	[1]	$ 128,438	$ 127,791	$ 130,920	$ 132,086	$ 129,694	$ 127,181	$ 136,502	$ 520,493	$ 525,463	$ 602,631
Net income (loss)	73,844	[2]	19,046	7,698	21,271	(12,370)	7,884	(1,323)	46,310	121,859	40,501	(30,740)
Net income (loss) allocated to Common Shares/ Partnership Unitholders	$ 73,758		$ 18,961	$ 4,129	$ 19,442	$ (14,176)	$ 6,074	$ (3,131)	$ 44,478	$ 121,830	$ 40,486	$ (30,737)
Basic earnings (loss) per Common Shares/Partnership Unitholders	$ 0.42		$ 0.11	$ 0.02	$ 0.11	$ (0.08)	$ 0.03	$ (0.02)	$ 0.25	$ 0.66	$ 0.19	$ (0.21)
Diluted earnings (loss) per Common Share/ Partnership Unitholders	$ 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 fourth quarter revenues primarily relates to the operating performance of 1900 Market Street in Philadelphia, Pennsylvania and the acquisition of One Drexel Plaza in Philadelphia, Pennsylvania.

[2] 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."