Segment Information - Summary of Certain Balance Sheet Data by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Real estate, at cost	$ 5,940,655	$ 5,775,519
Investments in unconsolidated real estate ventures	463,026	543,026
Total assets (1)	6,277,324	5,986,251
Operating Segments \| Commercial Segment
Segment Reporting Information [Line Items]
Real estate, at cost	3,506,113	3,415,294
Investments in unconsolidated real estate ventures	330,111	396,199
Total assets (1)	3,473,426	3,361,122
Operating Segments \| Multifamily
Segment Reporting Information [Line Items]
Real estate, at cost	2,034,045	1,998,297
Investments in unconsolidated real estate ventures	108,110	107,882
Total assets (1)	1,798,714	1,682,872
Other
Segment Reporting Information [Line Items]
Real estate, at cost	400,497	361,928
Investments in unconsolidated real estate ventures	24,805	38,945
Total assets (1)	$ 1,005,184	$ 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))
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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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