Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		$ (1,745)
Reclassification of realized losses on derivative financial instruments to operations, net	[1]	1,230	$ 1,104	$ 420
Balance at December 31,		2,399	(1,745)
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		(2,122)
Reclassification of realized losses on derivative financial instruments to operations, net	[2]	1,230	1,104	420
Balance at December 31,		2,056	(2,122)
Accumulated Other Comprehensive Income (Loss) [Member]
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		(1,745)	(5,192)	(4,607)
Change in fair market value during year		2,948	2,371	(1,010)
Allocation of unrealized (gains)/losses on derivative financial instruments to noncontrolling interests		(34)	(28)	5
Reclassification of realized losses on derivative financial instruments to operations, net		1,230	1,104	420
Balance at December 31,		2,399	(1,745)	(5,192)
Accumulated Other Comprehensive Income (Loss) [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Schedule of Accumulated other comprehensive income (loss) [Line Items]
Balance at January 1		(2,122)	(5,597)	(5,007)
Change in fair market value during year		2,948	2,371	(1,010)
Reclassification of realized losses on derivative financial instruments to operations, net		1,230	1,104	420
Balance at December 31,		$ 2,056	$ (2,122)	$ (5,597)

[1] Amounts reclassified from comprehensive income to interest expense within the Consolidated Statements of Operations.

[2] Amounts reclassified from comprehensive income to interest expense within the Consolidated Statement of Operations.