Investments in Unconsolidated Real Estate Funds - Additional Information (Details)	12 Months Ended
Dec. 31, 2020 USD ($) ft²	Jan. 25, 2019 ft²
Investment Holdings [Line Items]
Area of office and retail properties \| ft²	12,900,000
Fund X [Member]
Investment Holdings [Line Items]
Capital commitments \| $	$ 192,000,000
Capital commitments invested \| $	$ 78,791,000
Alternative Investment Fund, Interest Rate	7.80%
Fund VIII [Member]
Investment Holdings [Line Items]
Alternative Investment Fund, Interest Rate	1.30%
Fund VII and VII-H [Member] \| Office Building [Member]
Investment Holdings [Line Items]
Area of office and retail properties \| ft²		65,000

Ownership percentage in investment funds.

No definition available.

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- Definition

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 35
-Paragraph 54B
-URI http://asc.fasb.org/extlink&oid=117332851&loc=SL7495116-110257

+ Details

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- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

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- Definition

Amount of funds committed to investment company from investors.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 205
-Section 50
-Paragraph 25
-URI http://asc.fasb.org/extlink&oid=25866437&loc=d3e10491-115837

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- Definition

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.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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