Schedule III - Real Estate and Accumulated Depreciation - Summary of Changes in Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in total real estate
Balance, beginning of year	$ 27,533,607	$ 26,511,022	$ 26,026,896
Acquisitions and development	298,847	1,704,320	855,254
Improvements	154,433	180,944	192,661
Dispositions and other	(783,562)	(862,679)	(563,789)
Balance, end of year	$ 27,203,325	$ 27,533,607	$ 26,511,022

Gross amount at which new acquisitions and development properties are carried at the end of the period.

No definition available.

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Period Type:	duration

- Definition

Gross amount at which dispositions are removed from the balance sheet for properties sold during the year.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount, before accumulated depreciation, of real estate investment by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. Excludes real estate not held as investment or interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 970
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column E))
-URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in real estate investments related to improvements for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 970
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Footnote 4))
-URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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