Real Estate Fund Investments - Schedule of Income from Fund Investment (Details) - Unconsolidated Real Estate Funds [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Property Fund II [Member]
Investment Holdings [Line Items]
Investment income	$ 1	$ 1	$ 1	$ 2
Investment expenses	82	696	278	1,383
Net investment (loss) income	(81)	(695)	(277)	(1,381)
Net realized losses			(15,201)
Net unrealized gains (losses)	17	(33,304)	(4,980)	(31,878)
(Loss) income from real estate fund investments	(64)	(33,999)	(20,458)	(33,259)
Property Fund III [Member]
Investment Holdings [Line Items]
Investment income	1		1,141
Investment expenses	107	86	117	138
Net investment (loss) income	(106)	(86)	1,024	(138)
Net realized losses			(5,253)
Net unrealized gains (losses)	(29)	(11,353)	(3,018)	(10,728)
(Loss) income from real estate fund investments	(135)	(11,439)	(7,247)	(10,866)
Property Fund VII [Member]
Investment Holdings [Line Items]
Investment income	777		962
Investment expenses	560	481	1,036	1,011
Net investment (loss) income	217	(481)	(74)	(1,011)
Net realized losses	(66)		(66)
Net unrealized gains (losses)	(4,456)	11,638	(4,321)	12,744
(Loss) income from real estate fund investments	$ (4,305)	$ 11,157	$ (4,461)	$ 11,733