Represents the contribution made by the company to employees defined contribution plans under the profit sharing plan.

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

- Definition

Description of the period of time over which an employees right to contribution plus actual earnings no longer contingent on satisfaction of a service condition.

+ Details

Name:	eqr_DefinedContributionPlanVestingPeriod
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Data Type:	xbrli:integerItemType
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Period Type:	duration

- Definition

Employee Plans.

+ Details

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- Definition

Represents the maximum amount of an employee's contribution to the defined contribution plan that is matched by the company.

+ Details

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Namespace Prefix:	eqr
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the calculation of the discount at which employees can purchase shares under the employee share purchase plan.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation Arrangement By Share Based Payment Award information regarding the Common Shares issued under the Employee Stock Purchase Plan.

+ Details

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Data Type:	xbrli:stringItemType
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- Definition

Represents the range of prices used by employees to purchase common stock under the employee share purchase plan during the year.

+ Details

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Data Type:	us-types:textBlockItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of shares available for purchase under the employee share purchase plan at the balance sheet date that were previously authorized by the board.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of common shares available for purchase under the employee share purchase plan at the balance sheet date.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the maximum amount of common shares common shares an employee can acquire under the employee share purchase plan on an annual basis.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 11

+ Details

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Balance Type:	debit
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- Definition

The cash inflow associated with the amount received from holders to acquire the entity's shares under incentive and share awards other than stock option exercises.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph i

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares newly issued during the reporting period under the plan.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 65

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
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Employee Plans (Details) (USD $)	12 Months Ended
Employee Plans (Details) (USD $)	Dec. 31, 2010 Year Apartmentunit Hector Property LandParcels Project RealEstate	Dec. 31, 2009	Dec. 31, 2008	Jul. 15, 1996
Summary of information regarding the Common Shares issued under the ESPP
Shares issued	157,363	324,394	195,961
Issuance price ranges	$28.26 - $41.16	$14.21 – $24.84	$23.51 – $37.61
Issuance proceeds	$ 5,112,000	$ 5,292,000	$ 6,170,000
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, compensation expense	4,000,000	3,500,000	3,800,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares authorized before amendment				200,000
Employee Plans (Textuals) [Abstract]
Value of common shares that can be acquired by the employee and trustees under employees share purchase plan	100,000
Common Shares available for purchase under the ESPP	3,403,970
Purchase price of common stock	85% of the lesser of: (a) the closing price for a share on the last day of such quarter; and (b) the greater of: (i) the closing price for a share on the first day of such quarter, and (ii) the average closing price for a share for all the business days in the quarter
Minimum eligible compensation percentage for the defined contribution plan (the "401(k) Plan")	3.00%
Defined contribution plan vesting period	5
Contributions by employer under annual discretionary profit sharing contribution plan	0	0	0
Annual discretionary profit sharing contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, compensation expense	$ 0	$ 0	$ 0
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares authorized before amendment	7,000,000