Investments in and Advances to Unconsolidated Real Estate Ventures - Summary of Composition of Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 368,228	$ 261,791
Advances to unconsolidated real estate ventures	80	20
Total investments in and advances to unconsolidated real estate ventures	368,308	261,811
Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	135,801	36,317
Landmark
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	88,494	95,368
CBREI Venture
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 77,062	79,062
Berkshire Group [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	50.00%
Total investments in unconsolidated real estate ventures	$ 33,424	27,761
Brandywine
Schedule of Equity Method Investments [Line Items]
Ownership Interest	30.00%
Total investments in unconsolidated real estate ventures	$ 13,732	13,741
MRP Realty [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	16.70%
CIM/PacLife [Member]
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 10,289	0
JP Morgan
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures		9,296
Other
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 241	$ 246
Minimum \| Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Ownership Interest	55.00%
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 \| Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Ownership Interest	87.30%
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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