Investments in Affiliates - Investments in Affiliates (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	$ 38,682	$ 38,469	$ 36,410
Joint Venture Unconsolidated \| Equity Method investments in Real Estate Affiliates [Member]
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	29,829	29,472	26,883
Joint Venture Unconsolidated \| Other Affiliates [Member]
Investments In And Advances To Affiliates [Line Items]
Investments in affiliates	$ 8,853	$ 8,997	$ 9,527

Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant