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Asset Retirement Obligations (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Asset Retirement Obligations [Line Items]    
Asset Retirement Obligations Assumed Market Risk Premium 5.00%cms_AssetRetirementObligationsAssumedMarketRiskPremium 5.00%cms_AssetRetirementObligationsAssumedMarketRiskPremium
Hypothetical Asset Retirement Obligations Liability Increase $ 17cms_HypotheticalAssetRetirementObligationsLiabilityIncrease $ 16cms_HypotheticalAssetRetirementObligationsLiabilityIncrease
ARO Liability, at beginning of period 325us-gaap_AssetRetirementObligation 312us-gaap_AssetRetirementObligation
Incurred 9us-gaap_AssetRetirementObligationLiabilitiesIncurred (3)us-gaap_AssetRetirementObligationLiabilitiesIncurred
Settled (12)us-gaap_AssetRetirementObligationLiabilitiesSettled [1] (6)us-gaap_AssetRetirementObligationLiabilitiesSettled [1]
Accretion 18us-gaap_AssetRetirementObligationAccretionExpense 18us-gaap_AssetRetirementObligationAccretionExpense
Cash flow Revisions   4us-gaap_AssetRetirementObligationRevisionOfEstimate
ARO Liability, end of period 340us-gaap_AssetRetirementObligation 325us-gaap_AssetRetirementObligation
ARO Cash payments 12us-gaap_AssetRetirementObligationCashPaidToSettle 6us-gaap_AssetRetirementObligationCashPaidToSettle
Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
Asset Retirement Obligations Assumed Market Risk Premium 5.00%cms_AssetRetirementObligationsAssumedMarketRiskPremium
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
5.00%cms_AssetRetirementObligationsAssumedMarketRiskPremium
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Hypothetical Asset Retirement Obligations Liability Increase 17cms_HypotheticalAssetRetirementObligationsLiabilityIncrease
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
16cms_HypotheticalAssetRetirementObligationsLiabilityIncrease
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
ARO Liability, at beginning of period 324us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
311us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Incurred 9us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
(3)us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Settled (12)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1] (6)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1]
Accretion 18us-gaap_AssetRetirementObligationAccretionExpense
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
18us-gaap_AssetRetirementObligationAccretionExpense
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Cash flow Revisions   4us-gaap_AssetRetirementObligationRevisionOfEstimate
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
ARO Liability, end of period 339us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
324us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
ARO Cash payments 12us-gaap_AssetRetirementObligationCashPaidToSettle
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
6us-gaap_AssetRetirementObligationCashPaidToSettle
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Close Gas Treating Plant and Gas Wells [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 1us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CloseGasTreatingPlantAndGasWellsMember
1us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CloseGasTreatingPlantAndGasWellsMember
Incurred     
Settled    [1]  
Accretion     
Cash flow Revisions      
ARO Liability, end of period 1us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CloseGasTreatingPlantAndGasWellsMember
1us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CloseGasTreatingPlantAndGasWellsMember
Coal Ash Disposal Areas [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 118us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
114us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Settled (3)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1] (1)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1]
Accretion 5us-gaap_AssetRetirementObligationAccretionExpense
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
5us-gaap_AssetRetirementObligationAccretionExpense
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Cash flow Revisions     
ARO Liability, end of period 120us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
118us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_CoalAshDisposalAreasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Asbestos Abatement [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 49us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
43us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Settled (1)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1] (1)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1]
Accretion 3us-gaap_AssetRetirementObligationAccretionExpense
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
3us-gaap_AssetRetirementObligationAccretionExpense
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Cash flow Revisions   4us-gaap_AssetRetirementObligationRevisionOfEstimate
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
ARO Liability, end of period 51us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
49us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_AsbestosAbatementMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Gas Distribution Cut, Purge, Cap [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 154us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
151us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Incurred 6us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
(3)us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Settled (8)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1] (4)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1]
Accretion 10us-gaap_AssetRetirementObligationAccretionExpense
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
10us-gaap_AssetRetirementObligationAccretionExpense
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Cash flow Revisions     
ARO Liability, end of period 162us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
154us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_GasDistributionCutPurgeCapMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Wind Park [Member] | Consumers Energy Company [Member]    
Asset Retirement Obligations [Line Items]    
ARO Liability, at beginning of period 3us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_WindFarmMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
3us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_WindFarmMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Incurred 3us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_WindFarmMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
 
Settled    [1]  
Accretion     
Cash flow Revisions      
ARO Liability, end of period $ 6us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_WindFarmMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
$ 3us-gaap_AssetRetirementObligation
/ cms_AssetRetirementObligationsCategoriesAxis
= cms_WindFarmMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
[1] Cash payments of $12 million in 2014 and $6 million in 2013 were included in other current and non-current assets and liabilities as a component of net cash provided by operating activities on CMS Energy’s and Consumers’ consolidated statements of cash flow.