Derivative and Other Fair Value Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2011
Fair Value Hedges [Member]
Derivative Instrument Table
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 Instrument Table
Current Notional Balance	950,000
Lowest Possible Notional	950,000
Highest Possible Notional	$ 950,000
Lowest Interest Rate	3.478%
Highest Interest Rate	4.695%
Earliest Maturity Date	2021
Latest Maturity Date	2023

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.

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- 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.

+ Details

Name:	eqr_LowestPossibleNotional
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
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- Definition

Schedule of derivative instruments.

+ Details

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- Definition

High end of the range of fixed interest rates when a range is presented for a group of interest rate derivatives.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The high end of the range of time remaining until maturity when a range is presented for a group of derivatives.

+ Details

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Namespace Prefix:	us-gaap
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Balance Type:	na
Period Type:	instant

- Definition

High end of the range of variable interest rates when a range is presented for a group of interest rate derivatives.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

Low end of the range of fixed interest rates when a range is presented for a group of interest rate derivatives.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

The low end of the range of time remaining until maturity when a range is presented for a group of derivatives.

+ Details

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- Definition

Low end of the range of variable interest rates when a range is presented for a group of interest rate derivatives.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

Aggregate notional amount of all derivatives designated as 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Notional Amount
-URI http://asc.fasb.org/extlink&oid=6519104

+ Details

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Balance Type:	debit
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Notional Amount
-URI http://asc.fasb.org/extlink&oid=6519104

+ Details

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