Summary of Quarterly Results (Parenthetical) (Details) $ in Thousands		3 Months Ended		12 Months Ended
	Dec. 11, 2018 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($) property	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions				$ 142,233	$ 80,526	$ 20,000
Gain on promoted interest in unconsolidated real estate venture				28,283	0	0
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions				142,233	80,526	20,000
Gain on promoted interest in unconsolidated real estate venture				$ 28,283	$ 0	$ 0
DRA Austin Venture [Member]
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions	$ 103,800	$ 103,800
Gain on promoted interest in unconsolidated real estate venture	$ 28,300	28,300
DRA Austin Venture [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Net gain on real estate venture transactions		103,800
Gain on promoted interest in unconsolidated real estate venture		$ 28,300
Metropolitan Washington, D.C. - Office [Member]
Quarterly Financial Information [Line Items]
Provision for impairment on assets held for sale			$ 56,900
Number of properties contributed to a joint venture | property			8
Metropolitan Washington, D.C. - Office [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Quarterly Financial Information [Line Items]
Provision for impairment on assets held for sale			$ 56,900
Number of properties contributed to a joint venture | property			8