Investments in Unconsolidated Real Estate Funds - Schedule of Income from Fund Investment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investment Holdings [Line Items]
Net realized losses		$ (839)		$ (665)
Net unrealized losses	$ (270)	202	$ (475)	(26)
Unconsolidated Real Estate Funds [Member] | Property Fund VII [Member]
Investment Holdings [Line Items]
Investment income	4	479	9	1,441
Investment expenses	43	120	163	1,156
Net investment (loss) income	(39)	359	(154)	285
Net realized losses		(3,809)		(3,875)
Net unrealized losses	(3,880)	(4,871)	(6,897)	(9,192)
Loss from real estate fund investments	$ (3,919)	$ (8,321)	$ (7,051)	$ (12,782)