Derivative and Other Fair Value Instruments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Fair Value Hedges [Member]
Derivative [Line Items]
Current Notional Balance	$ 315,693
Lowest Possible Notional	315,693
Highest Possible Notional	317,694
Lowest Interest Rate	2.009%
Highest Interest Rate	4.80%
Earliest Maturity Date	2012
Latest Maturity Date	2013
Forward Starting Swaps [Member]
Derivative [Line Items]
Current Notional Balance	200,000
Lowest Possible Notional	200,000
Highest Possible Notional	$ 200,000
Lowest Interest Rate	3.478%
Highest Interest Rate	4.695%
Earliest Maturity Date	2023
Latest Maturity Date	2023

The earliest maturity date on derivatives designated as fair value or cash flow hedging instruments.

No definition available.

Name:	eqr_EarliestMaturityDate
Namespace Prefix:	eqr_
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	instant

- Definition

Highest interest rate on derivatives designated as fair value or cash flow hedging instruments.

+ References

No definition available.

+ Details

Name:	eqr_HighestInterestRate
Namespace Prefix:	eqr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Highest possible notional amount of all derivatives designated as fair value or cash flow hedging instruments. The notional amount relates to a number of currency units, shares, bushels, pounds or other units specified in a derivative instrument.

+ References

No definition available.

+ Details

Name:	eqr_HighestPossibleNotional
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The latest maturity date on derivatives designated as fair value or cash flow hedging instruments.

+ References

No definition available.

+ Details

Name:	eqr_LatestMaturityDate
Namespace Prefix:	eqr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	instant

- Definition

Lowest interest rate on derivatives designated as fair value or cash flow hedging instruments.

+ References

No definition available.

+ Details

Name:	eqr_LowestInterestRate
Namespace Prefix:	eqr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Lowest possible notional amount of all derivatives designated as fair value or cash flow hedging instruments. The notional amount relates to a number of currency units, shares, bushels, pounds or other units specified in a derivative instrument.

+ References

No definition available.

+ Details

Name:	eqr_LowestPossibleNotional
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Aggregate notional amount of all derivatives designated as fair value or cash flow hedging instruments. The notional amount relates to a number of currency units, shares, bushels, pounds, or other units specified in a derivative instrument.

+ References

No definition available.

+ Details

Name:	eqr_NotionalAmountOfHedgeInstruments
Namespace Prefix:	eqr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration