Schedule III - Real Estate and Accumulated Depreciation-Encumbrances Reconciliation (Details)	Dec. 31, 2017 USD ($) Property
Total Consolidated Investment in Real Estate [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	$ 3,618,721,998
EQR-Wellfan 2008 LP [Member]
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered \| Property	10
Overall summary of real estate and accumulated depreciation
Encumbrances	$ 549,547,007
Archstone Master Property [Domain]
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered \| Property	13
Overall summary of real estate and accumulated depreciation
Encumbrances	$ 797,306,782
Portfolio Entity Encumbrances [Member]
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered \| Property	23
Overall summary of real estate and accumulated depreciation
Encumbrances	$ 1,346,853,789
Individual Property Encumbrances [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	$ 2,271,868,209

Represents the number of rental properties encumbered by a lien or mortgage.

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Overall summary of real estate and accumulated depreciation.

+ References

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Real Estate and Accumulated Depreciation Encumbrances Reconciliation.

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- Definition

Amount of lien or mortgage outstanding on real estate investment properties for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 970
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28)
-URI http://asc.fasb.org/extlink&oid=6590653&loc=d3e638233-123024

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule III)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

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