Subsequent Events - Additional Information (Details) $ in Thousands		3 Months Ended
Apr. 01, 2020 USD ($) Property ApartmentUnit DerivativeInstrument	Mar. 31, 2020 USD ($)
Subsequent Event [Line Items]
Debt instrument, maturity date		Nov. 01, 2024
Repayments of long-term debt		$ 1,941
Subsequent Event \| Forward Starting Swaps [Member]
Subsequent Event [Line Items]
Payments for settlement of derivative instruments	$ 1,200
Forward starting swaps settled \| DerivativeInstrument	2
Property/Apartment [Member] \| Subsequent Event
Subsequent Event [Line Items]
Number of properties sold \| Property	1
Number of self managed apartments \| ApartmentUnit	138
Amount of property sold	$ 108,000
Mortgages [Member] \| Subsequent Event
Subsequent Event [Line Items]
Proceeds from issuance of long-term debt	$ 495,000
Debt instrument, maturity date	May 01, 2030
Debt instrument, interest rate, stated percentage	2.60%
Mortgages [Member] \| Subsequent Event \| Forward Starting Swaps [Member]
Subsequent Event [Line Items]
Debt instrument face amount	$ 495,000
4.747% Mortgage [Member] \| Subsequent Event
Subsequent Event [Line Items]
Debt instrument, maturity date	May 01, 2021
Debt instrument, interest rate, stated percentage	4.747%
Repayments of long-term debt	$ 91,500

Amount of property sold.

No definition available.

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

- Definition

Number of derivative instrument settled.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of properties sold.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of self managed apartments.

+ References

No definition available.

+ Details

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Namespace Prefix:	eqr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 45
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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+ Details

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Data Type:	num:percentItemType
Balance Type:	na
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
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+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The cash outflow for a financial contract that meets the hedge criteria as either cash flow hedge, fair value hedge or hedge of net investment in foreign operations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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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Namespace Prefix:
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- Details

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- Details

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- Details

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