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Income Taxes (Narrative) (Details) (Consumers Energy Company [Member], USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015
Income Tax Benefits [Line Items] |
Reduction of income tax expense | $ 14 cms_ReductionOfIncomeTaxExpense
Electric Utility [Member] |
Income Tax Benefits [Line Items] |
Income tax benefits, to be returned to customers | 209 cms_IncomeTaxBenefitsToBeReturnedToCustomers / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_ElectricUtilityMember
Tax benefit, distribution to customers, term | 5 years
Gas Utility [Member] |
Income Tax Benefits [Line Items] |
Income tax benefits, to be returned to customers | $ 260 cms_IncomeTaxBenefitsToBeReturnedToCustomers / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_GasUtilityMember
Tax benefit, distribution to customers, term | 12 years

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- Definition The total amount of an accelerated return of income tax benefits to customers per regulatory treatment. + References No definition available. + Details
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