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Share Incentive Plans - Information Regarding Options Outstanding and Exercisable (Parenthetical) (Details) | Dec. 31, 2018 $ / shares
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Share Based Compensation [Abstract] |
Market value of common shares | $ 66.01

X
- Definition Represents the closing share price of the company's stock on the balance sheet date. + References No definition available. + Details
Name: | eqr_MarketValueOfCommonShares
Namespace Prefix: | eqr_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration