Real Estate and Lease Intangibles - Summary of Carrying Amounts of Above and Below Market Ground And Retail Lease Intangibles (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets [Member]
Real Estate [Line Items]
Lease intangible assets	$ 193,178	$ 179,511
Finite-Lived Intangible Assets, Accumulated Amortization	(22,434)	(17,972)
Lease intangible assets, net	170,744	161,539
Assets [Member] \| Ground Lease [Member]
Real Estate [Line Items]
Finite-Lived Intangible Asset, Off-market Lease, Favorable, Gross	191,918	178,251
Assets [Member] \| Retail Site Lease [Member]
Real Estate [Line Items]
Finite-Lived Intangible Asset, Off-market Lease, Favorable, Gross	1,260	1,260
Liability [Member]
Real Estate [Line Items]
Lease Intangible Liabilities	7,670	7,670
Finite Lived Intangible Liabilities Accumulated Amortization	(5,143)	(4,509)
Lease intangible liabilities, net	2,527	3,161
Liability [Member] \| Ground Lease [Member]
Real Estate [Line Items]
Finite-Lived Intangible Liabilities, Off-market Lease, Favorable, Gross	2,400	2,400
Liability [Member] \| Retail Site Lease [Member]
Real Estate [Line Items]
Finite-Lived Intangible Liabilities, Off-market Lease, Favorable, Gross	$ 5,270	$ 5,270

The accumulated amount of amortization of a major finite-lived intangible liabilities class.

No definition available.

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

- Definition

The amount of acquisition cost of a business combination allocated to total lease intangible liabilities that will be amortized.

+ References

No definition available.

+ Details

Name:	eqr_LeaseIntangibleLiabilities
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of acquisition cost of a business combination allocated to total lease intangible liabilities, net of amortization.

+ References

No definition available.

+ Details

Name:	eqr_LeaseIntangibleLiabilitiesnet
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the identifiable intangible asset established upon acquisition based on a favorable difference between the terms of an acquired lease and the current market terms for that lease at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.15)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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

- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

+ Details

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

- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

+ Details

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

- Definition

This element represents a liability associated with the acquisition of an off-market lease when the terms of the lease are unfavorable to the market terms for the lease at the date of acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

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

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_AssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseArrangementTypeAxis=eqr_GroundLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseArrangementTypeAxis=eqr_RetailSiteLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_LiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: