Investments in and Advances to Unconsolidated Real Estate Ventures - Summary of Composition of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 261,791	$ 45,776
Advances to unconsolidated real estate ventures	20	0
Total investments in and advances to unconsolidated real estate ventures	261,811	45,776
Landmark
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	95,368	0
CBREI Venture
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 79,062	0
Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Ownership Interest	55.00%
Total investments in unconsolidated real estate ventures	$ 36,317	36,312
Brandywine
Schedule of Equity Method Investments [Line Items]
Ownership Interest	30.00%
Total investments in unconsolidated real estate ventures	$ 13,741	0
Berkshire Group
Schedule of Equity Method Investments [Line Items]
Ownership Interest	50.00%
Total investments in unconsolidated real estate ventures	$ 27,761	0
JP Morgan
Schedule of Equity Method Investments [Line Items]
Ownership Interest	5.00%
Total investments in unconsolidated real estate ventures	$ 9,296	9,335
Other
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 246	$ 129
Minimum \| Landmark
Schedule of Equity Method Investments [Line Items]
Ownership Interest	1.80%
Minimum \| CBREI Venture
Schedule of Equity Method Investments [Line Items]
Ownership Interest	5.00%
Maximum \| Landmark
Schedule of Equity Method Investments [Line Items]
Ownership Interest	49.00%
Maximum \| CBREI Venture
Schedule of Equity Method Investments [Line Items]
Ownership Interest	64.00%

Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures, Advances

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- Definition

Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures, Excluding Advances

+ References

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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