Segments Disclosure - Schedule of Reconciliation of NOI to Net Income (Loss) Attributable to Common Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
NOI	$ 112,670	$ 107,645	$ 223,654	$ 209,233
Fee income	4,175	1,780	7,592	3,315
Depreciation and amortization expense	(67,287)	(79,421)	(142,099)	(153,004)
General and administrative expenses	(12,139)	(9,133)	(26,100)	(21,746)
Transfer taxes due in connection with the sale of shares by a former joint venture partner	(508)	(8,208)	(1,443)	(9,347)
NOI from unconsolidated joint ventures	(4,536)	(4,278)	(8,964)	(8,059)
Income from unconsolidated joint ventures	2,003	2,011	3,499	2,986
Income from real estate fund investments		14,072		19,293
Loss from unconsolidated real estate funds	(960)		(1,286)
Interest and other income, net	1,030	512	2,730	1,366
Interest and debt expense	(38,009)	(42,236)	(75,128)	(84,124)
Unrealized gain on interest rate swaps	10,073	21,747	16,933	33,725
Net income (loss) before income taxes	6,512	4,491	(612)	(6,362)
Income tax benefit (expense)	1,398	(1,343)	1,035	(1,917)
Net income (loss)	7,910	3,148	423	(8,279)
Consolidated real estate funds	78	(6,532)	752	(8,741)
Consolidated joint ventures	(4,107)	(2,472)	(5,359)	(931)
Operating Partnership	(693)	1,147	878	3,511
Net income (loss) attributable to common stockholders	3,188	(4,709)	(3,306)	(14,440)
Deal Cost [Member]
Segment Reporting Information [Line Items]
Transfer taxes due in connection with the sale of shares by a former joint venture partner	$ (508)	(2,336)	$ (1,443)	(3,475)
Transfer Taxes [Member]
Segment Reporting Information [Line Items]
Transfer taxes due in connection with the sale of shares by a former joint venture partner		$ (5,872)		$ (5,872)