Real Estate Fund Investments - Summary of Investment in Unconsolidated Real Estate Funds and Income or Loss from Fund Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Our Share of Investments:
Investments in unconsolidated real estate funds	$ 22,001		$ 22,001		$ 28,173
Loss from unconsolidated real estate funds	(2,411)	$ (960)	(2,123)	$ (1,286)
Net investment income (loss) [Member]
Our Share of Investments:
Loss from unconsolidated real estate funds	71	(68)	124	(607)
Net realized (loss) gain [Member]
Our Share of Investments:
Loss from unconsolidated real estate funds	(5)		174
Net unrealized loss [Member]
Our Share of Investments:
Loss from unconsolidated real estate funds	(324)	(2,807)	(228)	(2,578)
Carried interest [Member]
Our Share of Investments:
Loss from unconsolidated real estate funds	(2,153)	$ 1,915	(2,193)	$ 1,899
Property Funds [Member]
Our Share of Investments:
Investments in unconsolidated real estate funds	16,749		16,749		22,811
Alternative Investment Fund [Member]
Our Share of Investments:
Investments in unconsolidated real estate funds	$ 5,252		$ 5,252		$ 5,362