Segments - Schedule of Reconciliation of NOI to Net (Loss) Income Attributable to Common Stockholders (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting [Abstract]
NOI	$ 122,933,000	$ 114,753,000	$ 239,501,000	$ 225,285,000
Fee income	5,409,000	4,448,000	8,874,000	14,004,000
Depreciation and amortization expense	(64,775,000)	(68,636,000)	(129,931,000)	(131,628,000)
General and administrative expenses	(17,195,000)	(16,573,000)	(29,826,000)	(30,154,000)
Transaction related costs	(293,000)	(502,000)	(413,000)	(777,000)
NOI from unconsolidated joint ventures	(4,569,000)	(4,958,000)	(9,309,000)	(9,781,000)
Income from unconsolidated joint ventures	2,521,000	16,535,000	2,459,000	18,472,000
Loss from unconsolidated real estate funds	(14,000)	(2,411,000)	(80,000)	(2,123,000)
Interest and other income, net	2,094,000	2,486,000	4,110,000	5,686,000
Interest and debt expense	(36,809,000)	(34,817,000)	(72,891,000)	(71,835,000)
Loss on early extinguishment of debt		(5,162,000)		(7,877,000)
Real estate impairment loss	(46,000,000)		(46,000,000)
Gain on sale of real estate		133,989,000		133,989,000
Unrealized gain on interest rate swaps				1,802,000
Net (loss) income before income taxes	(36,698,000)	139,152,000	(33,506,000)	145,063,000
Income tax benefit (expense)	120,000	(970,000)	(357,000)	(5,252,000)
Net (loss) income	(36,578,000)	138,182,000	(33,863,000)	139,811,000
Consolidated joint ventures	(1,752,000)	(1,897,000)	(2,807,000)	(3,188,000)
Consolidated real estate fund	(152,000)	(20,169,000)	(582,000)	(20,081,000)
Operating Partnership	3,666,000	(13,100,000)	3,550,000	(13,154,000)
Net (loss) income attributable to common stockholders	$ (34,816,000)	$ 103,016,000	$ (33,702,000)	$ 103,388,000