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v3.21.1

Leases - Additional Information (Details) | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Residential Apartment Leases [Member] |  |
Operating Leased Assets [Line Items] |  |
Percentage of rental income | 97.00% | 97.00%
Residential Apartment Leases [Member] | Maximum [Member] |  |
Operating Leased Assets [Line Items] |  |
Retail leases term | 12 months |
Non-residential Leases [Member] |  |
Operating Leased Assets [Line Items] |  |
Percentage of rental income | 3.00% | 3.00%
Non-residential Leases [Member] | Maximum [Member] |  |
Operating Leased Assets [Line Items] |  |
Retail leases term | 10 years |
Non-residential Leases [Member] | Minimum [Member] |  |
Operating Leased Assets [Line Items] |  |
Retail leases term | 5 years |

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- Definition Percentage of rental income. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Term of lessor's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=121576215&loc=SL77919359-209981 + Details
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Namespace Prefix: | us-gaap_
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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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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |