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Stock-Based Compensation (Schedule Of Compensation Cost For Share-Based Payment Arrangements, Allocation Of Share-Based Compensation Costs By Plan) (Details) (Restricted Stock [Member], USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value $ 16us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue $ 10us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue $ 10us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
Allocated Share-based Compensation Expense 14us-gaap_AllocatedShareBasedCompensationExpense 14us-gaap_AllocatedShareBasedCompensationExpense 12us-gaap_AllocatedShareBasedCompensationExpense
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense 5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense 5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense 5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized 13us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized    
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition 1 year 10 months 24 days    
Consumers Energy Company [Member]
      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value 15us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 8us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Allocated Share-based Compensation Expense 13us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 14us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 11us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense 5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 5us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 4us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized $ 13us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		    
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition 1 year 10 months 24 days