Real Estate Fund Investments - Summary of Investment in Property Funds and an Alternative Investment Fund and Income or Loss from Fund Investments (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Our Share of Investments:
Investments in unconsolidated real estate funds	$ 7,253	$ 28,173
(Loss) income from unconsolidated real estate funds	(6,143)	(498)
Net realized loss	(72,134)
Net unrealized loss	(6,266)	14,275
Net investment (loss) income [Member]
Our Share of Investments:
(Loss) income from unconsolidated real estate funds	236	(324)
Net realized loss [Member]
Our Share of Investments:
Net realized loss	(126)
Net unrealized loss [Member]
Our Share of Investments:
Net unrealized loss	(663)	(1,706)
Carried interest [Member]
Our Share of Investments:
(Loss) income from unconsolidated real estate funds	(5,590)	1,532
Property Funds [Member]
Our Share of Investments:
Investments in unconsolidated real estate funds	2,429	22,811
Alternative Investment Fund [Member]
Our Share of Investments:
Investments in unconsolidated real estate funds	$ 4,824	$ 5,362

Equity method investment summarized financial information realized gain (losses) net.

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- Definition

Equity method investment summarized financial information unrealized gain (losses) net.

+ References

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its real estate fund investments to which equity method of accounting is applied.

+ References

No definition available.

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The carrying amount of investments in unconsolidated real estate and other joint ventures not separately presented. This includes direct and indirect investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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