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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Real Estate Fund Investments -Summary of Consolidated Real Estate Funds (Parenthetical) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Asset management fee income	$ 8,581	$ 7,754
Noncontrolling Interest [Member]
Investment Holdings [Line Items]
Asset management fee income			$ 5,481