Investments in Unconsolidated Real Estate Funds - Schedule of Income from Fund Investment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investment Holdings [Line Items]
Net realized losses		$ (5)		$ 174
Net unrealized losses	$ (73)	(324)	$ (205)	(228)
Unconsolidated Real Estate Funds [Member] | Property Fund VII [Member]
Investment Holdings [Line Items]
Investment income	5	777	5	962
Investment expenses	76	560	120	1,036
Net investment (loss) income	(71)	217	(115)	(74)
Net realized losses		(66)		(66)
Net unrealized losses	(1,138)	(4,456)	(3,017)	(4,321)
Loss from real estate fund investments	$ (1,209)	$ (4,305)	$ (3,132)	$ (4,461)