Investments in Real Estate Entities - Financial Position and Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Assets:
Real estate, net	$ 684,423		$ 684,423		$ 695,077
Other assets	35,006		35,006		39,976
Total assets	719,429		719,429		735,053
Liabilities and partners' capital:
Mortgage notes payable and credit facility	521,950		521,950		523,815
Other liabilities	11,857		11,857		10,540
Partners' capital	185,622		185,622		200,698
Total liabilities and partners' capital	719,429		719,429		$ 735,053
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	21,916	$ 26,789	43,717	$ 55,432
Operating and other expenses	(8,104)	(9,914)	(16,409)	(21,009)
Gain on sale of communities	0	0	0	29,447
Interest expense, net	(5,571)	(6,600)	(11,189)	(13,548)
Depreciation expense	(5,894)	(6,795)	(11,774)	(14,122)
Net income	$ 2,347	$ 3,480	$ 4,345	$ 36,200