Segments - Schedule of Reconciliation of NOI to Net (Loss) Income Attributable to Common Stockholders (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting [Abstract]
NOI	$ 123,154,000	$ 110,665,000	$ 362,655,000	$ 335,950,000
Fee income	4,079,000	5,834,000	12,953,000	19,838,000
Depreciation and amortization expense	(64,610,000)	(66,515,000)	(194,541,000)	(198,143,000)
General and administrative expenses	(14,452,000)	(14,470,000)	(44,278,000)	(44,624,000)
Transaction related costs	(450,000)	(274,000)	(863,000)	(1,051,000)
NOI from unconsolidated joint ventures	(4,448,000)	(4,993,000)	(13,757,000)	(14,774,000)
Income from unconsolidated joint ventures	472,000	671,000	2,931,000	19,143,000
Loss from unconsolidated real estate funds	(188,000)	(3,930,000)	(268,000)	(6,053,000)
Interest and other income (loss), net	2,778,000	(17,668,000)	6,888,000	(11,982,000)
Interest and debt expense	(37,105,000)	(35,733,000)	(109,996,000)	(107,568,000)
Loss on early extinguishment of debt				(7,877,000)
Real estate impairment loss			(46,000,000)
Gain on sale of real estate	36,845,000		36,845,000	133,989,000
Unrealized gain on interest rate swaps				1,802,000
Net income (loss) before income taxes	46,075,000	(26,413,000)	12,569,000	118,650,000
Income tax (expense) benefit	(1,814,000)	1,010,000	(2,171,000)	(4,242,000)
Net income (loss)	44,261,000	(25,403,000)	10,398,000	114,408,000
Consolidated joint ventures	(2,713,000)	14,217,000	(5,520,000)	11,029,000
Consolidated real estate fund	(86,000)	(114,000)	(668,000)	(20,195,000)
Operating Partnership	(3,931,000)	1,086,000	(381,000)	(12,068,000)
Net income (loss) attributable to common stockholders	$ 37,531,000	$ (10,214,000)	$ 3,829,000	$ 93,174,000