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Derivative and Other Fair Value Instruments - Summary of Consolidated Derivative Instruments (Details) | 12 Months Ended
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Dec. 31, 2018 USD ($)
Fair Value Hedges [Member] |
Derivative [Line Items] |
Current Notional Balance | $ 450,000,000
Maturity Date | 2019
Fair Value Hedges [Member] | Minimum [Member] |
Derivative [Line Items] |
Interest Rate | 2.375%
Fair Value Hedges [Member] | Maximum [Member] |
Derivative [Line Items] |
Interest Rate | 2.375%
Forward Starting Swaps [Member] |
Derivative [Line Items] |
Current Notional Balance | $ 500,000,000
Maturity Date | 2029
Forward Starting Swaps [Member] | Minimum [Member] |
Derivative [Line Items] |
Interest Rate | 2.2665%
Forward Starting Swaps [Member] | Maximum [Member] |
Derivative [Line Items] |
Interest Rate | 3.1163%

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- Definition Maturity date, derivative. + References No definition available. + Details
Name: | eqr_MaturityDateDerivative
Namespace Prefix: | eqr_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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Namespace Prefix: | invest_
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Balance Type: | na
Period Type: | instant

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- Definition Fixed interest rate related to the interest rate derivative. + References No definition available. + Details
Name: | us-gaap_DerivativeFixedInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- 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
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Balance Type: | na
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- Details
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Balance Type: |
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- Details
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Period Type: |

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- Details
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- Details
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Namespace Prefix: |
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Balance Type: |
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