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v3.21.1

Debt - Mortgage Notes Payable - Summary of Certain Interest Rate and Maturity Date Information (Details) - Mortgages [Member] | 3 Months Ended
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Mar. 31, 2021
Debt Instrument [Line Items] |
Weighted Average Interest Rate | 3.18%
Maturity Date Ranges, Start | 2022
Maturity Date Ranges, End | 2061
Minimum [Member] |
Debt Instrument [Line Items] |
Interest Rate Ranges | 0.05%
Maximum [Member] |
Debt Instrument [Line Items] |
Interest Rate Ranges | 4.21%

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- Definition Debt instrument maturity year, end. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

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- Definition Debt instrument maturity year, start. + References No definition available. + Details
Name: | eqr_DebtInstrumentMaturityYearStart
Namespace Prefix: | eqr_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: 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(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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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
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Weighted average interest rate of debt outstanding. + References No definition available. + Details
Name: | us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_MortgagesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |