Restricted Deposits - Restricted Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Mortgage escrow deposits:
Replacement reserves	$ 11,156	$ 9,877
Mortgage principal reserves/sinking funds	19,104	14,168
Mortgage escrow deposits	30,260	24,045
Restricted cash:
Tax-deferred (1031) exchange proceeds	166,362
Earnest money on pending acquisitions	2,000
Restricted deposits on real estate investments	284	307
Resident security and utility deposits	35,663	31,412
Other	1,835	1,373
Restricted cash	206,144	33,092
Restricted deposits	$ 236,404	$ 57,137	$ 71,246

Earnest money on pending acquisitions.

No definition available.

Name:	eqr_EarnestMoneyOnPendingAcquisitions
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The designation of funds furnished by a borrower to a lender to assure future payments of the borrower's real estate taxes, insurance and replacement reserve obligations with respect to a mortgaged property. Escrow deposits may be made for a variety of other purposes such as earnest money and contingent payments.

+ References

No definition available.

+ Details

Name:	eqr_EscrowDepositsForMortgageAndReplacementReserves
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Mortgage escrow deposits.

+ References

No definition available.

+ Details

Name:	eqr_MortgageEscrowDepositsAbstract
Namespace Prefix:	eqr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Other cash and cash items not otherwise listed in the existing taxonomy that are pledged or subject to withdrawal restrictions.

+ References

No definition available.

+ Details

Name:	eqr_OtherRestrictedCash
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Restricted cash and cash items pertaining to security deposits and utility deposits from residents.

+ References

No definition available.

+ Details

Name:	eqr_ResidentSecurityAndUtilityDeposits
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Restricted cash and cash items primarily pertaining to deposits held by a joint venture to collateralize construction guarantees or miscellaneous deposits held in escrow that were assumed in conjunction with a business combination.

+ References

No definition available.

+ Details

Name:	eqr_RestrictedDepositsOnRealEstateInvestments
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Restricted cash and cash items pertaining to "like-kind" exchanges (i.e. the proceeds from the previous sale of a property are used in part or in whole to acquire a new (replacement) property).

+ References

No definition available.

+ Details

Name:	eqr_TaxDeferredExchangeProceeds
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Cumulative amount paid into a fund, which is used to retire the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
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-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123465755&loc=d3e1835-112601

+ Details

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

- Definition

This element represents those amounts set aside for the repair and replacement of real or personal property in the foreseen future. Such amount may be funded from sales revenue (for example; timeshare sales) or operating revenues; in a lump sum or installments (such as monthly); as per internal policy (for example: hotel operators), as required by contractual agreement (for example: sales contract); or by the terms of debt agreements.

+ References

+ Details

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

- Definition

Amount of cash restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
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+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_RestrictedCashAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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+ Details

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