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Real Estate - Additional Information (Details) - Assets [Member] | 3 Months Ended
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Mar. 31, 2021 USD ($)
Real estate acquired | $ 0
Real estate sold | $ 0

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- Definition Real estate acquired. + References No definition available. + Details
Name: | eqr_RealEstateAcquired
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Amount of real estate investments sold for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 970 -SubTopic 360 -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Footnote 4)) -URI http://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024 + Details
Name: | us-gaap_RealEstateCostOfRealEstateSold
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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