Segments Disclosure - Schedule of Reconciliation of NOI to Net (Loss) Income Attributable to Common Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
NOI	$ 107,291	$ 106,590	$ 330,945	$ 315,823
Fee income	3,976	2,085	11,568	5,400
Depreciation and amortization expense	(66,376)	(70,654)	(208,475)	(223,658)
General and administrative expenses	(13,235)	(6,666)	(39,335)	(28,412)
Acquisition and transaction related costs and transfer taxes due in connection with the sale of shares by a former joint venture partner	(282)	(485)	(1,725)	(9,832)
NOI from unconsolidated joint ventures	(3,974)	(4,303)	(12,938)	(12,362)
Income from unconsolidated joint ventures	1,792	1,458	5,291	4,444
Income from real estate fund investments		10,933		30,226
Loss from unconsolidated real estate funds	(1,254)		(2,540)
Interest and other income (loss), net	2,299	(1,763)	5,029	(397)
Interest and debt expense	(38,278)	(42,821)	(113,406)	(126,945)
Unrealized gain on interest rate swaps	12,728	15,772	29,661	49,497
Net income before income taxes	4,687	10,146	4,075	3,784
Income tax (expense) benefit	(218)	(789)	817	(2,706)
Net income	4,469	9,357	4,892	1,078
Consolidated real estate funds	67	(7,936)	819	(16,677)
Consolidated joint ventures	(4,703)	(33)	(10,062)	(964)
Operating Partnership	28	(272)	906	3,239
Net (loss) income attributable to common stockholders	(139)	1,116	(3,445)	(13,324)
Deal Cost [Member]
Segment Reporting Information [Line Items]
Acquisition and transaction related costs and transfer taxes due in connection with the sale of shares by a former joint venture partner	$ (282)	$ (485)	$ (1,725)	(3,960)
Transfer Taxes [Member]
Segment Reporting Information [Line Items]
Acquisition and transaction related costs and transfer taxes due in connection with the sale of shares by a former joint venture partner				$ (5,872)