Segment Information - Summary of Certain Balance Sheet Data by Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Real estate, at cost	$ 5,851,533	$ 5,775,519
Investments in and advances to unconsolidated real estate ventures	542,983	543,026
Total assets (1)	6,139,813	5,986,251
Operating Segments \| Commercial Segment
Segment Reporting Information [Line Items]
Real estate, at cost	3,450,039	3,415,294
Investments in and advances to unconsolidated real estate ventures	398,849	396,199
Total assets (1)	3,570,707	3,361,122
Operating Segments \| Multifamily
Segment Reporting Information [Line Items]
Real estate, at cost	2,016,514	1,998,297
Investments in and advances to unconsolidated real estate ventures	107,162	107,882
Total assets (1)	1,697,302	1,682,872
Other
Segment Reporting Information [Line Items]
Real estate, at cost	384,980	361,928
Investments in and advances to unconsolidated real estate ventures	36,972	38,945
Total assets (1)	$ 871,804	$ 942,257

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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=119400593&loc=d3e572229-122910

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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.

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