Notes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2010	Dec. 31, 2009	Apr. 12, 2010
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Net Principal Balance	$ 5,185,180	$ 4,609,124
Rate of unconsolidated debt		5.60%
Interest rate range from minimum		0.0020
Interest rate range to maximum		0.12465
Life period of extension option	one year
Number of extension option	1		2
Fixed Rate Public or Private Notes [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Net Principal Balance	4,375,860	3,771,700
Interest rate range from minimum	0.0385	0.0385
Interest rate range to maximum	0.0757	0.0757
Weighted Average Interest Rate	5.78%	5.93%
Maturity Date Ranges Minimum	2011	2011
Maturity Date Ranges Maximum	2026	2026
Floating Rate Public or Private Notes [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Net Principal Balance	809,320	801,824
Weighted Average Interest Rate	1.72%	1.37%
Maturity Date Ranges Minimum	2011	2010
Maturity Date Ranges Maximum	2013	2013
Fixed Rate Tax- Exempt Bonds [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Net Principal Balance		$ 35,600
Weighted Average Interest Rate		0.37%
Maturity Date		2,028

Represents the date at which the unsecured notes are scheduled to be fully repaid.

Name:	eqr_DebtInstrumentMaturityYear
Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the length of time the maturity date for a loan can be extended, the end of which would require fuel repayment of the loan.

+ Details

Name:	eqr_ExtensionOptionLongTermDebt
Namespace Prefix:	eqr
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of extension options available to extend the maturity date of the loan (i.e. where the loan is required to be fully repaid).

+ Details

Name:	eqr_ExtensionOptionLongTermDebtNumber
Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the weighted average interest rate on unsecured debt during the period.

+ Details

Name:	eqr_WeightedAverageInterestRate
Namespace Prefix:	eqr
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Interest rate stated in the contractual debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum
Namespace Prefix:	us-gaap
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum
Namespace Prefix:	us-gaap
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

When presenting a range of maturity dates, the latest date when the outstanding debt instruments are required to be repaid. May be presented in a variety of ways (for example: year only, month and year, day, month and year, and number of years).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

+ Details

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Namespace Prefix:	us-gaap
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

When presenting a range of maturity dates, the earliest date when the outstanding debt instruments are required to be repaid. May be presented in a variety of ways (for example: year only, month and year, day, month and year, and number of years).

+ References

+ Details

Name:	us-gaap_DebtInstrumentMaturityDateRangeStart
Namespace Prefix:	us-gaap
Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of outstanding principal due under the debt instrument at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number APB14-1

-Paragraph 31

-Subparagraph b

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongTermDebtAbstract
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Period Type:	duration