Subsequent Events - Additional Information (Details) $ in Thousands		6 Months Ended
Jul. 01, 2019 USD ($) Property ApartmentUnit	Jun. 30, 2019 USD ($) Property ApartmentUnit
Subsequent Event [Line Items]
Properties acquired \| Property		6
Property Units acquired \| ApartmentUnit		1,644
Purchase Price		$ 650,882
Debt instrument, maturity date		Jan. 10, 2022
Subsequent Event \| Mortgages Debt [Member]
Subsequent Event [Line Items]
Repayments of long-term debt	$ 84,500
Debt instrument, interest rate, stated percentage	4.79%
Debt instrument, maturity date	Apr. 01, 2053
Prepayment penalty charges	$ 3,400
Subsequent Event \| 2.375% Notes [Member]
Subsequent Event [Line Items]
Debt instrument, interest rate, stated percentage	2.375%
Repayments of unsecured debt	$ 450,000
Debt instrument, basis spread on variable rate	0.61%
Subsequent Event \| 2.375% Notes [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Subsequent Event [Line Items]
Debt instrument, description of variable rate basis	90-Day LIBOR plus 0.61%
Subsequent Event \| Fannie Mae Pool 3 [Member] \| Mortgages Debt [Member]
Subsequent Event [Line Items]
Repayments of long-term debt	$ 500,000
Debt instrument, interest rate, stated percentage	5.78%
Debt instrument, maturity date	Jul. 01, 2020
Property/Apartment [Member] \| Subsequent Event
Subsequent Event [Line Items]
Properties acquired \| Property	2
Property Units acquired \| ApartmentUnit	549
Purchase Price	$ 192,900
Number of properties sold \| Property	1
Number of self managed apartments \| ApartmentUnit	298
Amount of property sold	$ 117,000
Land Parcels [Member]
Subsequent Event [Line Items]
Purchase Price		$ 16,232
Land Parcels [Member] \| Subsequent Event
Subsequent Event [Line Items]
Properties acquired \| Property	1
Purchase Price	$ 3,600
Number of properties sold \| Property	1
Amount of property sold	$ 1,900

Amount of property sold.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of properties sold.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
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Balance Type:	na
Period Type:	duration

- Definition

Number of self managed apartments.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

Total number of property or properties acquired from unaffiliated third parties during the period.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Total number of units associated with the property or properties acquired from unaffiliated third parties during the period.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Amount of assets acquired at the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

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Period Type:	instant

- 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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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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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
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-Topic 210
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+ Details

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Period Type:	instant

- 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
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+ Details

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- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
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+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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+ Details

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Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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- Details

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- Details

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