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
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Our Share of Investments:
Investments in unconsolidated real estate funds	$ 23,913		$ 28,173
Income (loss) from unconsolidated real estate funds	288	$ (326)
Net investment (loss) income [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	53	(539)
Net realized gains [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	179
Net unrealized income (loss) [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	96	229
Carried interest [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	(40)	(16)
Property Funds [Member]
Our Share of Investments:
Investments in unconsolidated real estate funds	19,250		22,811
Income (loss) from unconsolidated real estate funds	210	(345)
Property Funds [Member] | Net investment (loss) income [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	(7)	(569)
Property Funds [Member] | Net realized gains [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	179
Property Funds [Member] | Net unrealized income (loss) [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	78	240
Property Funds [Member] | Carried interest [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	(40)	(16)
Alternative Investment Fund [Member]
Our Share of Investments:
Investments in unconsolidated real estate funds	4,663		$ 5,362
Income (loss) from unconsolidated real estate funds	78	19
Alternative Investment Fund [Member] | Net investment (loss) income [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	60	30
Alternative Investment Fund [Member] | Net unrealized income (loss) [Member]
Our Share of Investments:
Income (loss) from unconsolidated real estate funds	$ 18	$ (11)