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v2.4.1.9

Derivative and Other Fair Value Instruments (Details) (USD $) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Apr. 30, 2015
Derivative [Line Items] |  |
Debt Instrument, Interest Rate, Stated Percentage |  | 6.584%us-gaap_DebtInstrumentInterestRateStatedPercentage
Debt Instrument, Maturity Date | May 01, 2061 |
2.375% Notes [Member] |  |
Derivative [Line Items] |  |
Proceeds from Issuance of Unsecured Debt | 450,000,000 us-gaap_ProceedsFromIssuanceOfUnsecuredDebt / us-gaap_LongtermDebtTypeAxis = eqr_A2.375NotesMember |
Debt Instrument, Interest Rate, Stated Percentage | 2.375%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = eqr_A2.375NotesMember |
Derivative, Variable Interest Rate | 0.61%us-gaap_DerivativeVariableInterestRate / us-gaap_LongtermDebtTypeAxis = eqr_A2.375NotesMember |
Debt Instrument, Maturity Date | Jul. 01, 2019 |
Fair Value Hedging [Member] |  |
Derivative [Line Items] |  |
Current Notional Balance | 450,000,000 invest_DerivativeNotionalAmount / us-gaap_DerivativeByNatureAxis = us-gaap_FairValueHedgingMember |
Lowest Possible Notional | 450,000,000 eqr_LowestPossibleNotional / us-gaap_DerivativeByNatureAxis = us-gaap_FairValueHedgingMember |
Highest Possible Notional | 450,000,000 eqr_HighestPossibleNotional / us-gaap_DerivativeByNatureAxis = us-gaap_FairValueHedgingMember |
Lowest Interest Rate | 2.375%us-gaap_DerivativeLowerFixedInterestRateRange / us-gaap_DerivativeByNatureAxis = us-gaap_FairValueHedgingMember |
Highest Interest Rate | 2.375%us-gaap_DerivativeHigherFixedInterestRateRange / us-gaap_DerivativeByNatureAxis = us-gaap_FairValueHedgingMember |
Earliest Maturity Date | P2019Y0M0D |
Latest Maturity Date | P2019Y0M0D |
Forward Starting Swaps [Member] |  |
Derivative [Line Items] |  |
Current Notional Balance | 450,000,000 invest_DerivativeNotionalAmount / us-gaap_DerivativeByNatureAxis = eqr_ForwardStartingSwapsMember |
Lowest Possible Notional | 450,000,000 eqr_LowestPossibleNotional / us-gaap_DerivativeByNatureAxis = eqr_ForwardStartingSwapsMember |
Highest Possible Notional | 450,000,000 eqr_HighestPossibleNotional / us-gaap_DerivativeByNatureAxis = eqr_ForwardStartingSwapsMember |
Lowest Interest Rate | 1.935%us-gaap_DerivativeLowerFixedInterestRateRange / us-gaap_DerivativeByNatureAxis = eqr_ForwardStartingSwapsMember |
Highest Interest Rate | 3.191%us-gaap_DerivativeHigherFixedInterestRateRange / us-gaap_DerivativeByNatureAxis = eqr_ForwardStartingSwapsMember |
Earliest Maturity Date | P2025Y0M0D |
Latest Maturity Date | P2025Y0M0D |

X
- Definition The earliest maturity date on derivatives designated as fair value or cash flow hedging instruments. + References No definition available. + Details
Name: | eqr_EarliestMaturityDate
Namespace Prefix: | eqr_
Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Highest possible notional amount of all derivatives designated as fair value or cash flow hedging instruments. The notional amount relates to a number of currency units, shares, bushels, pounds or other units specified in a derivative instrument. + References No definition available. + Details
Name: | eqr_HighestPossibleNotional
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The latest maturity date on derivatives designated as fair value or cash flow hedging instruments. + References No definition available. + Details
Name: | eqr_LatestMaturityDate
Namespace Prefix: | eqr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Lowest possible notional amount of all derivatives designated as fair value or cash flow hedging instruments. The notional amount relates to a number of currency units, shares, bushels, pounds or other units specified in a derivative instrument. + References No definition available. + Details
Name: | eqr_LowestPossibleNotional
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Contractual interest rate for funds borrowed, under the 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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + 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 Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentMaturityDate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

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- Definition High end of the range of fixed interest rates when a range is presented for a group of interest rate derivatives. + References No definition available. + Details
Name: | us-gaap_DerivativeHigherFixedInterestRateRange
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Low end of the range of fixed interest rates when a range is presented for a group of interest rate derivatives. + References No definition available. + Details
Name: | us-gaap_DerivativeLowerFixedInterestRateRange
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Variable interest rate in effect as of the balance sheet date related to the interest rate derivative. + References No definition available. + Details
Name: | us-gaap_DerivativeVariableInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfUnsecuredDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_DerivativeByNatureAxis=eqr_ForwardStartingSwapsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_DerivativeByNatureAxis=us-gaap_FairValueHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_LongtermDebtTypeAxis=eqr_A2.375NotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |