Investments in Real Estate Entities - Financial Position and Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Assets:
Real estate, net	$ 731,006		$ 731,006		$ 695,077
Other assets	90,712		90,712		39,976
Total assets	821,718		821,718		735,053
Liabilities and partners' capital:
Mortgage notes payable and credit facility	492,965		492,965		523,815
Other liabilities	16,583		16,583		10,540
Partners' capital	312,170		312,170		200,698
Total liabilities and partners' capital	821,718		821,718		$ 735,053
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	24,535	$ 24,568	68,324	$ 79,999
Operating and other expenses	(8,749)	(9,378)	(26,066)	(30,386)
Gain on sale of communities	30,597	107,067	30,597	136,514
Interest expense, net	(5,938)	(7,867)	(17,130)	(21,415)
Depreciation expense	(6,288)	(5,938)	(18,704)	(20,059)
Net income	$ 34,157	$ 108,452	$ 37,021	$ 144,653