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Debt - Line of Credit and Commercial Paper - Additional Information (Details) - USD ($) | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Nov. 04, 2019 | Nov. 03, 2019 | Nov. 01, 2019 | Oct. 31, 2019
Line of Credit Facility [Line Items] |  |  |  |  |  |
Debt instrument, maturity date | Nov. 01, 2024 |  |  |  |  |
Commercial paper balance outstanding | $ 415,000,000.0 | $ 1,000,000,000.0 | $ 1,000,000,000.0 | $ 500,000,000.0 |  |
Commercial Paper [Member] |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Weighted average interest rates | 1.72% | 2.42% |  |  |  |
Weighted average amount outstanding | $ 276,600,000 | $ 434,400,000 |  |  |  |
Commercial paper weighted average days outstanding | 45 days | 40 days |  |  |  |
Unsecured Revolving Credit Facility [Member] |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Unsecured revolving credit facility | $ 2,500,000,000 | $ 2,500,000,000 |  |  | $ 2,500,000,000 | $ 2,000,000,000.0
Ability to increase LOC facility | $ 750,000,000.0 |  |  |  |  |
Debt instrument, basis spread on variable rate | 0.775% |  |  |  |  |
Percentage points of line of credit facility commitment fee | 0.125% |  |  |  |  |
Commercial paper balance outstanding | $ 415,000,000 | $ 1,000,000,000 |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |  |  |
Weighted average interest rates | 1.47% | 3.12% |  |  |  |

X
- Definition Represents the amount by which available borrowings on the unsecured revolving credit facility may be increased. The available borrowings may be increased by adding additional banks to the facility or obtaining the agreement of existing banks to increase their commitments. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Commercial Paper Weighted average period outstanding. + References No definition available. + Details
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Balance Type: | na
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X
- Definition Percentage points of line of credit facility commitment fee. + References No definition available. + Details
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Balance Type: | na
Period Type: | duration

X
- Definition Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(13)(2)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 3: 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(19)(a)(3)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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Balance Type: | credit
Period Type: | instant

X
- Definition Percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Weighted average interest rate of debt outstanding. + References No definition available. + Details
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- Definition Average amount borrowed under the credit facility during the period. + References No definition available. + Details
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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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X
- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + 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 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Details
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- Details
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