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Real Estate and Accumulated Depreciation - Overall Summary and Encumbrances Reconciliation (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Overall summary of real estate and accumulated depreciation |  |  |
Accumulated Depreciation | $ (5,432,805,000)us-gaap_RealEstateAccumulatedDepreciation | $ (4,807,709,000)us-gaap_RealEstateAccumulatedDepreciation | $ (4,912,221,000)us-gaap_RealEstateAccumulatedDepreciation
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract] |  |  |
Number of Properties Encumbered | 35 eqr_NumberOfPropertiesEncumbered |  |
Changes in total real estate |  |  |
Balance, beginning of year | 26,800,948,000 us-gaap_RealEstateGrossAtCarryingValue | 21,008,429,000 us-gaap_RealEstateGrossAtCarryingValue | 20,407,946,000 us-gaap_RealEstateGrossAtCarryingValue
Acquisitions and development | 1,121,423,000 eqr_RealEstateAcquisitionsAndDevelopment | 9,273,492,000 eqr_RealEstateAcquisitionsAndDevelopment | 1,250,633,000 eqr_RealEstateAcquisitionsAndDevelopment
Improvements | 191,243,000 us-gaap_RealEstateImprovements | 139,950,000 us-gaap_RealEstateImprovements | 161,460,000 us-gaap_RealEstateImprovements
Dispositions and other | (438,231,000)eqr_RealEstateDispositionsAndOther | (3,620,923,000)eqr_RealEstateDispositionsAndOther | (811,610,000)eqr_RealEstateDispositionsAndOther
Balance, end of year | 27,675,383,000 us-gaap_RealEstateGrossAtCarryingValue | 26,800,948,000 us-gaap_RealEstateGrossAtCarryingValue | 21,008,429,000 us-gaap_RealEstateGrossAtCarryingValue
Changes in accumulated depreciation |  |  |
Balance, beginning of year | (4,807,709,000)us-gaap_RealEstateAccumulatedDepreciation | (4,912,221,000)us-gaap_RealEstateAccumulatedDepreciation | (4,539,583,000)us-gaap_RealEstateAccumulatedDepreciation
Depreciation | 758,861,000 us-gaap_SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense | 1,013,353,000 us-gaap_SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense | 684,992,000 us-gaap_SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense
Dispositions and other | (133,765,000)eqr_RealEstateAccumulatedDepreciationDispositionsAndOther | (1,117,865,000)eqr_RealEstateAccumulatedDepreciationDispositionsAndOther | (312,354,000)eqr_RealEstateAccumulatedDepreciationDispositionsAndOther
Balance, end of year | (5,432,805,000)us-gaap_RealEstateAccumulatedDepreciation | (4,807,709,000)us-gaap_RealEstateAccumulatedDepreciation | (4,912,221,000)us-gaap_RealEstateAccumulatedDepreciation
EQR-Fanwell 2007 LP [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 300,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_EqrFanwell2007LpMember |  |
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract] |  |  |
Number of Properties Encumbered | 5 eqr_NumberOfPropertiesEncumbered / dei_LegalEntityAxis = eqr_EqrFanwell2007LpMember |  |
EQR-Fanwell 2007 LP [Member] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 0 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_EqrFanwell2007LpMember / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
EQR-Fanwell 2007 LP [Member] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 300,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_EqrFanwell2007LpMember / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |
EQR-Wellfan 2008 LP [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 550,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_EqrWellfan2008LpMember |  |
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract] |  |  |
Number of Properties Encumbered | 12 eqr_NumberOfPropertiesEncumbered / dei_LegalEntityAxis = eqr_EqrWellfan2008LpMember |  |
EQR-Wellfan 2008 LP [Member] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 0 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_EqrWellfan2008LpMember / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
EQR-Wellfan 2008 LP [Member] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 550,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_EqrWellfan2008LpMember / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |
Fannie Mae Pool 3 [Domain] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 474,179,543 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_FannieMaePool3Domain |  |
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract] |  |  |
Number of Properties Encumbered | 5 eqr_NumberOfPropertiesEncumbered / dei_LegalEntityAxis = eqr_FannieMaePool3Domain |  |
Fannie Mae Pool 3 [Domain] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 24,840,581 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_FannieMaePool3Domain / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
Fannie Mae Pool 3 [Domain] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 449,338,962 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_FannieMaePool3Domain / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |
Archstone Master Property [Domain] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 800,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_ArchstoneMasterPropertyDomain |  |
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract] |  |  |
Number of Properties Encumbered | 13 eqr_NumberOfPropertiesEncumbered / dei_LegalEntityAxis = eqr_ArchstoneMasterPropertyDomain |  |
Archstone Master Property [Domain] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 0 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_ArchstoneMasterPropertyDomain / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
Archstone Master Property [Domain] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 800,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_ArchstoneMasterPropertyDomain / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |
Individual Property Encumbrances [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 2,962,335,468 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_IndividualPropertyEncumbrancesMember |  |
Individual Property Encumbrances [Member] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 335,638,681 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_IndividualPropertyEncumbrancesMember / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
Individual Property Encumbrances [Member] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 2,626,696,787 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / dei_LegalEntityAxis = eqr_IndividualPropertyEncumbrancesMember / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |
EQR-Wholly Owned Unencumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 263 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
Units | 69,217 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
Investment in Real Estate, Gross | 18,538,492,146 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
Accumulated Depreciation | (3,650,524,741)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
Investment in Real Estate Net | 14,887,967,405 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
Encumbrances | 0 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (3,650,524,741)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedUnencumberedMember |  |
EQR-Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 104 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Units | 29,923 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Investment in Real Estate, Gross | 8,113,776,123 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Accumulated Depreciation | (1,587,799,207)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Investment in Real Estate Net | 6,525,976,916 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Encumbrances | 4,726,035,749 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (1,587,799,207)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrWhollyOwnedEncumberedMember |  |
Wholly Owned Properties [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 367 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
Units | 99,140 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
Investment in Real Estate, Gross | 26,652,268,269 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
Accumulated Depreciation | (5,238,323,948)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
Investment in Real Estate Net | 21,413,944,321 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
Encumbrances | 4,726,035,749 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (5,238,323,948)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_WhollyOwnedPropertiesMember |  |
EQR-Partially Owned Unencumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 8 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
Units | 1,505 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
Investment in Real Estate, Gross | 575,092,221 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
Accumulated Depreciation | (77,534,358)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
Investment in Real Estate Net | 497,557,863 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
Encumbrances | 0 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (77,534,358)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedUnencumberedMember |  |
EQR-Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 11 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Units | 2,266 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Investment in Real Estate, Gross | 448,022,434 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Accumulated Depreciation | (116,947,029)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Investment in Real Estate Net | 331,075,405 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Encumbrances | 360,479,262 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (116,947,029)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EqrPartiallyOwnedEncumberedMember |  |
Partially Owned Properties [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 19 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Units | 3,771 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Investment in Real Estate, Gross | 1,023,114,655 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Accumulated Depreciation | (194,481,387)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Investment in Real Estate Net | 828,633,268 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Encumbrances | 360,479,262 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (194,481,387)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = us-gaap_PartiallyOwnedPropertiesMember |  |
Unencumbered Properties [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 271 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Units | 70,722 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Investment in Real Estate, Gross | 19,113,584,367 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Accumulated Depreciation | (3,728,059,099)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Investment in Real Estate Net | 15,385,525,268 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Encumbrances | 0 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (3,728,059,099)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_UnencumberedPropertiesMember |  |
Encumbered Properties [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 115 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Units | 32,189 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Investment in Real Estate, Gross | 8,561,798,557 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Accumulated Depreciation | (1,704,746,236)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Investment in Real Estate Net | 6,857,052,321 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Encumbrances | 5,086,515,011 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (1,704,746,236)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_EncumberedPropertiesMember |  |
Total Consolidated Investment in Real Estate [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Properties | 386 eqr_RealEstateAndAccumulatedDepreciationProperties / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Units | 102,911 eqr_RealEstateAndAccumulatedDepreciationUnits / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Investment in Real Estate, Gross | 27,675,382,924 eqr_RealEstateAndAccumulatedDepreciationCarryingAmountOfLandBuildingsAndFurnituresAndFixtures / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Accumulated Depreciation | (5,432,805,335)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Investment in Real Estate Net | 22,242,577,589 eqr_InvestmentInRealEstateNet / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Encumbrances | 5,086,515,011 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Changes in accumulated depreciation |  |  |
Balance, end of year | (5,432,805,335)us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember |  |
Total Consolidated Investment in Real Estate [Member] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 360,479,262 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
Total Consolidated Investment in Real Estate [Member] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 4,726,035,749 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_TotalConsolidatedInvestmentInRealEstateMember / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |
Portfolio Entity Encumbrances [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 2,124,179,543 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_PortfolioEntityEncumbrancesMember |  |
Portfolio Entity Encumbrances [Member] | Partially Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | 24,840,581 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_PortfolioEntityEncumbrancesMember / us-gaap_StatementEquityComponentsAxis = eqr_PartiallyOwnedEncumberedMember |  |
Portfolio Entity Encumbrances [Member] | Wholly Owned Encumbered [Member] |  |  |
Overall summary of real estate and accumulated depreciation |  |  |
Encumbrances | $ 2,099,338,962 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = eqr_PortfolioEntityEncumbrancesMember / us-gaap_StatementEquityComponentsAxis = eqr_WhollyOwnedEncumberedMember |  |

X
- Definition The net book value of each property at the end of the period. + References No definition available. + Details
Name: | eqr_InvestmentInRealEstateNet
Namespace Prefix: | eqr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the number of rental properties encumbered by a lien or mortgage. + References No definition available. + Details
Name: | eqr_NumberOfPropertiesEncumbered
Namespace Prefix: | eqr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

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- Definition The amount of depreciation expense related to dispositions that has been reclassified to discontinued operations. + References No definition available. + Details
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