Debt - Notes - Summary of Notes Activity (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Notes, net beginning balance	$ 5,335,536
Proceeds	497,470
Amortization of premiums/ discounts	1,865	$ 2,043
Notes, net ending balance	5,833,483
Fixed Rate Debt [Member] \| Unsecured – Public [Member]
Debt Instrument [Line Items]
Notes, net beginning balance	5,335,536
Proceeds	497,470
Amortization of premiums/ discounts	1,865
Amortization of deferred financing costs, net	(1,388)
Notes, net ending balance	$ 5,833,483

Amount of amortization of other deferred financing costs associated with notes payable, net.

No definition available.

Name:	eqr_AmortizationOfDeferredFinancingCostsNotesPayableNet
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The component of interest expense representing the noncash expenses charged against earnings in the period to amortize debt discount and premium associated with the unsecured notes during the period.

+ References

No definition available.

+ Details

Name:	eqr_AmortizationOfDiscountsAndPremiumsOnDebtNotesNet
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_NotesPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from borrowings supported by a written promise to pay an obligation that is uncollateralized (where debt is not backed by the pledge of collateral).

+ 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 (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromUnsecuredNotesPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LongtermDebtTypeAxis=eqr_FixedRateDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=eqr_UnsecuredPublicMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: