Investments in Partially Owned Entities - Consolidated Variable Interest Entities ("VIEs") - Additional Information (Details) $ in Thousands	Sep. 30, 2019 USD ($) Property ApartmentUnit	Dec. 31, 2018 USD ($)
Variable Interest Entity [Line Items]
Properties \| Property	308
Apartment units \| ApartmentUnit	80,299
Total assets	$ 21,054,056	$ 20,394,209
Total liabilities	$ 10,152,058	9,615,454
Consolidated VIE [Member]
Variable Interest Entity [Line Items]
Properties \| Property	17
Apartment units \| ApartmentUnit	3,535
Total assets	$ 711,500	713,600
Total liabilities	$ 325,500	$ 313,900
Consolidated VIE [Member] \| Consolidated Joint Venture [Member]
Variable Interest Entity [Line Items]
Ownership Percentage	90.00%
Consolidated VIE [Member] \| General Partner and Developer [Member] \| Consolidated Joint Venture [Member]
Variable Interest Entity [Line Items]
Ownership Percentage	10.00%

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
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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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- Definition

Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

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- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

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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.

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