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Commitments and Contingencies (Details) (USD $) | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2015 | Apr. 30, 2015 | Dec. 31, 2014
300 properties designed and built in violation of accessibility requirements | 300 eqr_PropertiesDesignedAndBuiltInViolationOfAccessibilityRequirements |  |
Loss Contingency Accrual, Period Increase (Decrease) | $ 1,000,000 us-gaap_LossContingencyAccrualCarryingValuePeriodIncreaseDecrease |  |
Loss Contingency Accrual | 5,000,000 us-gaap_LossContingencyAccrualAtCarryingValue |  |
Projects in various stages of development | 15 eqr_NumberOfProjectsInVariousStagesOfDevelopment |  |
Units in various stages of development | 5,273 eqr_NumberOfUnitsInVariousStagesOfDevelopment |  |
Consolidated Project Under Development Commitment Fund | 1,300,000,000 eqr_ConsolidatedProjectUnderDevelopmentCommitmentFund |  |
Various stages of development with estimated completion dates ranging through September 30, 2017 | Sep. 30, 2017 |  |
Number Of Unconsolidated Projects | 2 eqr_NumberOfUnconsolidatedProjects |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets | 5,968,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets | 130,300,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets |
Investment in Joint Venture | 339,400,000 eqr_InvestmentInJointVenture |  |
Noncontrolling Interests - Partially Owned Properties | 122,661,000 eqr_NoncontrollingInterestsPartiallyOwnedProperties |  | 124,909,000 eqr_NoncontrollingInterestsPartiallyOwnedProperties
Company's Portion [Member] |  |  |
Land purchase price | 76,100,000 eqr_LandPurchasePrice / us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis = eqr_CompanysPortionMember |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets | 102,500,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis = eqr_CompanysPortionMember |  |
Joint Venture Partner [Member] |  |  |
Land purchase price | 57,900,000 eqr_LandPurchasePrice / us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis = eqr_JointVenturePartnerMember |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets | 75,700,000 us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets / us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis = eqr_JointVenturePartnerMember |  |
Noncontrolling Interests - Partially Owned Properties | $ 117,400,000 eqr_NoncontrollingInterestsPartiallyOwnedProperties / us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis = eqr_JointVenturePartnerMember |  |

X
- Definition Represents the company's remaining funding obligation (i.e. total project costs less book value) for consolidated projects that are under development. + References No definition available. + Details
Name: | eqr_ConsolidatedProjectUnderDevelopmentCommitmentFund
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The Company's and the Joint Venture partner's total combined investment in the project. + References No definition available. + Details
Name: | eqr_InvestmentInJointVenture
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the purchase price of land acquired in a joint venture. + References No definition available. + Details
Name: | eqr_LandPurchasePrice
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount of equity interests owned by noncontrolling partners in partially owned properties. + References No definition available. + Details
Name: | eqr_NoncontrollingInterestsPartiallyOwnedProperties
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Total number of open development projects. May include projects that are held for and/or under development, completed and not stabilized or completed and stabilized. These projects are consolidated. + References No definition available. + Details
Name: | eqr_NumberOfProjectsInVariousStagesOfDevelopment
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of unconsolidated open development projects. May include projects that are held for and/or under development, completed and not stabilized or completed and stabilized. + References No definition available. + Details
Name: | eqr_NumberOfUnconsolidatedProjects
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Total number of units that are associated with open development projects. May include projects that are held for and/or under development, completed and not stabilized or completed and stabilized. These units are consolidated. + References No definition available. + Details
Name: | eqr_NumberOfUnitsInVariousStagesOfDevelopment
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of properties that are party to a housing discrimination lawsuit. + References No definition available. + Details
Name: | eqr_PropertiesDesignedAndBuiltInViolationOfAccessibilityRequirements
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the latest completion date for the current projects under development. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of assets acquired at the acquisition date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of increase (decrease) in loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 + Details
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- Details
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Namespace Prefix: |
Data Type: | na
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |