Investment in Unconsolidated Real Estate Ventures - Summary of Results of Operations of Real Estate Ventures with Interests (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule Of Equity Method Investments [Line Items]
Equity in loss of Real Estate Ventures		$ (5,723)	$ (7,254)	$ (5,387)	$ (9,323)
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue		56,511	57,710	169,609	157,641
Operating expenses		(27,419)	(27,592)	(77,757)	(81,347)
Provision for impairment			(10,476)		(10,476)
Interest expense, net		(11,670)	(12,102)	(33,771)	(32,019)
Depreciation and amortization		(20,684)	(22,722)	(61,816)	(63,125)
Net loss	[1]	(3,262)	(15,182)	(3,735)	(29,326)
Equity in loss of Real Estate Ventures	[2]	$ (5,723)	$ (7,254)	$ (5,387)	$ (9,323)

[1] The nine-month period ended September 30, 2016 amount includes $7.1 million of acquisition deal costs related to the formation of the MAP Venture.

[2] The three- and nine-month periods ended September 30, 2017 include a $4.8 million other than temporary impairment charge related to the BDN-AI Venture that was recorded during the three months ended September 30, 2017.