Investments in Real Estate Entities (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	$ 101,615	$ 131,901	$ 173,578
Operating and other expenses	(38,566)	(50,945)	(67,962)
Gain on sale of communities	136,333	196,749	98,899
Interest expense, net	(27,104)	(45,886)	(45,517)
Depreciation expense	(25,914)	(34,471)	(45,324)
Net income	146,364	197,348	113,674
Schedule of Equity Method Investments [Line Items]
Loss (gain) on extinguishment of debt, net	25,472	7,075	(26,736)
Funds [Member]
Schedule of Equity Method Investments [Line Items]
Loss (gain) on extinguishment of debt, net	1,591	12,659	4,481
Fund II
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of communities	26,322	41,501	$ 29,726
Equity in income of unconsolidated entities relating to the Company's recognition of promoted interest	$ 26,742	$ 7,985