Employee Plans - Summary of Information Regarding the Common Shares Issued Under the ESPP (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share Based Compensation Aggregate Disclosures [Abstract]
Shares issued	75,414	68,286	63,909
Issuance price ranges, Minimum	$ 47.80	$ 52.79	$ 51.85
Issuance price ranges, Maximum	$ 57.09	$ 58.06	$ 63.37
Issuance proceeds	$ 3,879	$ 3,744	$ 3,686

Represents the maximum price that employees purchase common stock for under the employee purchase plan during the year.

No definition available.

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- Definition

Represents the minimum price that employees purchase common stock for under the employee purchase plan during the year.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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- Definition

Amount of cash inflow from issuance of shares under share-based compensation arrangement, excluding stock option exercises.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=SL79508275-113901

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of share instruments newly issued under a share-based compensation plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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