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Employee Plans (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Summary of information regarding the Common Shares issued under the ESPP |  |  |
Shares issued | 68,807 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod | 73,468 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod | 110,054 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Employee Share Purchase Plan Issuance Price Minimum | $ 45.90 eqr_EmployeeSharePurchasePlanIssuancePriceMinimum | $ 44.26 eqr_EmployeeSharePurchasePlanIssuancePriceMinimum | $ 46.33 eqr_EmployeeSharePurchasePlanIssuancePriceMinimum
Employee Share Purchase Plan Issuance Price Maximum | $ 55.95 eqr_EmployeeSharePurchasePlanIssuancePriceMaximum | $ 48.17 eqr_EmployeeSharePurchasePlanIssuancePriceMaximum | $ 51.78 eqr_EmployeeSharePurchasePlanIssuancePriceMaximum
Issuance proceeds | $ 3,392,000 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans | $ 3,401,000 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans | $ 5,399,000 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans
Value of common shares that can be acquired by the employee and trustees under employees share purchase plan | 100,000 eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardValueOfCommonSharesThatCanBeAcquiredByEmployeeAndTrusteesUnderEmployeesSharePurchasePlan |  |
Number of common shares authorized after amendment | 7,000,000 eqr_Sharebasedcompensationarrangementbysharebasedpaymentawardnumberofsharesauthorizedafteramendment |  |
Number of common shares authorized before amendment | 2,000,000 eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedBeforeAmendment |  |
Common Shares available for purchase under the ESPP | 3,038,534 eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForPurchaseUnderEmployeeSharePurchasePlan |  |
Purchase price of common stock | 85.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate |  |
Minimum eligible compensation percentage for the defined contribution plan (the "401(k) Plan") | 4.00%eqr_MaximumEligibleCompensationPercentageForDefinedContributionPlanByEmployer | 3.00%eqr_MaximumEligibleCompensationPercentageForDefinedContributionPlanByEmployer |
Defined contribution plan vesting period | 5 eqr_DefinedContributionPlanVestingPeriod |  |
Defined contribution plan, compensation expense | $ 5,200,000 us-gaap_DefinedContributionPlanCostRecognized | $ 4,200,000 us-gaap_DefinedContributionPlanCostRecognized | $ 4,400,000 us-gaap_DefinedContributionPlanCostRecognized

X
- Definition Description of the period of time over which an employee's right to contribution plus actual earnings is no longer contingent on satisfaction of a service condition. + References No definition available. + Details
Name: | eqr_DefinedContributionPlanVestingPeriod
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the maximum price that employees purchase common stock for under the employee purchase plan during the year. + References No definition available. + Details
Name: | eqr_EmployeeSharePurchasePlanIssuancePriceMaximum
Namespace Prefix: | eqr_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the minimum price that employees purchase common stock for under the employee purchase plan during the year. + References No definition available. + Details
Name: | eqr_EmployeeSharePurchasePlanIssuancePriceMinimum
Namespace Prefix: | eqr_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the maximum amount of an employee's contribution to the defined contribution plan that is matched by the company. + References No definition available. + Details
Name: | eqr_MaximumEligibleCompensationPercentageForDefinedContributionPlanByEmployer
Namespace Prefix: | eqr_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardInformationRegardingCommonSharesIssuedUnderEmployeeSharePurchasePlanAbstract
Namespace Prefix: | eqr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of shares authorized for purchase under the employee share purchase plan after the most recent amendment. + References No definition available. + Details
Name: | eqr_Sharebasedcompensationarrangementbysharebasedpaymentawardnumberofsharesauthorizedafteramendment
Namespace Prefix: | eqr_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of shares available for purchase under the employee share purchase plan that were initially authorized by the board. + References No definition available. + Details
Name: | eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedBeforeAmendment
Namespace Prefix: | eqr_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of common shares available for purchase under the employee share purchase plan at the balance sheet date. + References No definition available. + Details
Name: | eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForPurchaseUnderEmployeeSharePurchasePlan
Namespace Prefix: | eqr_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the maximum value of common shares an employee can acquire under the employee share purchase plan on an annual basis. + References No definition available. + Details
Name: | eqr_ShareBasedCompensationArrangementByShareBasedPaymentAwardValueOfCommonSharesThatCanBeAcquiredByEmployeeAndTrusteesUnderEmployeesSharePurchasePlan
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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 Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. + References No definition available. + Details
Name: | us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Discount rate from fair value on purchase date that participants pay for shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of share instruments newly issued under a share-based compensation plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration