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Equity, Capital and Other Interests - Other - Additional Information (Details) | 9 Months Ended
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Sep. 30, 2019 shares
Equity Capital And Other Interests [Abstract] |
Additional common shares authorized | 13,000,000.0
Stock repurchase program, number of shares authorized to be repurchased | 13,000,000.0
Stock open market repurchased and retired during period, shares | 0
Stock repurchase program, remaining number of shares authorized to be repurchased | 13,000,000.0

X
- Definition Represents the remaining number of shares to be issued into the existing trading market at current market prices as well as through negotiated transactions under the Company's at-the-market share offering program. + References No definition available. + Details
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Balance Type: | na
Period Type: | instant

X
- Definition Represents the Equity of the Parent Company and the Capital of the Operating Partnership as well as the interests of Partially Owned and Limited Partners. + References No definition available. + Details
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Namespace Prefix: | eqr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. + References No definition available. + Details
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Balance Type: | na
Period Type: | instant

X
- Definition The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. + References No definition available. + Details
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Period Type: | instant

X
- Definition Number of shares that have been repurchased and retired during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 + Details
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