Restricted Deposits - Restricted Deposits (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Mortgage escrow deposits:
Replacement reserves	$ 10,182	$ 9,877
Mortgage principal reserves/sinking funds	15,360	14,168
Mortgage escrow deposits	25,542	24,045
Restricted cash:
Earnest money on pending acquisitions	3,500
Restricted deposits on real estate investments	302	307
Resident security and utility deposits	31,675	31,412
Other	1,364	1,373
Restricted cash	36,841	33,092
Restricted deposits	$ 62,383	$ 57,137	$ 58,435

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

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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

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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

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
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

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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

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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
-URI http://asc.fasb.org/extlink&oid=121583591&loc=SL98516268-108586

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+ Details

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Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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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

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-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