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Plant, Property, and Equipment (Property, Plant and Equipment Table) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
site
Dec. 31, 2013
Dec. 31, 2012
Public Utility, Property, Plant and Equipment [Line Items]      
Construction work in progress $ 1,106us-gaap_ConstructionInProgressGross $ 1,149us-gaap_ConstructionInProgressGross  
Accumulated Depreciation and Amortization (5,415)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment (5,087)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment  
Total plant, property, and equipment 13,412us-gaap_PropertyPlantAndEquipmentNet [1] 12,246us-gaap_PropertyPlantAndEquipmentNet [1]  
Public Utilities, Property Plant and Equipment Additions 1,600cms_PublicUtilitiesPropertyPlantAndEquipmentAdditions 1,300cms_PublicUtilitiesPropertyPlantAndEquipmentAdditions  
Public Utilities, Property Plant and Equipment Disposals 126cms_PublicUtilitiesPropertyPlantAndEquipmentDisposals 156cms_PublicUtilitiesPropertyPlantAndEquipmentDisposals  
Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Capital Leased Assets, Gross 295us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 291us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 285us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
Construction work in progress 1,103us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 1,147us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		  
Less accumulated depreciation and amortization (5,346)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 (5,022)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		  
Total plant, property, and equipment 13,337us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 [1] 12,169us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 [1]  
Public Utilities, Property Plant and Equipment Additions 1,600cms_PublicUtilitiesPropertyPlantAndEquipmentAdditions
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 1,300cms_PublicUtilitiesPropertyPlantAndEquipmentAdditions
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		  
Public Utilities, Property Plant and Equipment Disposals 126cms_PublicUtilitiesPropertyPlantAndEquipmentDisposals
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		 156cms_PublicUtilitiesPropertyPlantAndEquipmentDisposals
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		  
Number of units planned to be retired 10cms_NumberOfUnitsPlannedToBeRetired
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember		    
Electricity Generation Plant, Non-Nuclear [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Generation or Processing 4,544us-gaap_PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricityGenerationPlantNonNuclearMember		 3,992us-gaap_PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricityGenerationPlantNonNuclearMember		  
Electricity Generation Plant, Non-Nuclear [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Generation 22 years    
Electricity Generation Plant, Non-Nuclear [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Generation 125 years    
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Generation or Processing 4,544us-gaap_PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricityGenerationPlantNonNuclearMember		 3,992us-gaap_PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricityGenerationPlantNonNuclearMember		  
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Generation 22 years    
Electricity Generation Plant, Non-Nuclear [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Generation 125 years    
Electric Distribution [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Distribution 6,487us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricDistributionMember		 6,140us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricDistributionMember		  
Electric Distribution [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 23 years    
Electric Distribution [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 75 years    
Electric Distribution [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Distribution 6,487us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricDistributionMember		 6,140us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_ElectricDistributionMember		  
Electric Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 23 years    
Electric Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 75 years    
Electric Other [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 910us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ us-gaap_PublicUtilityAxis
= cms_ElectricOtherMember		 770us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ us-gaap_PublicUtilityAxis
= cms_ElectricOtherMember		  
Electric Other [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 5 years    
Electric Other [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 50 years    
Electric Other [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 910us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_ElectricOtherMember		 770us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_ElectricOtherMember		  
Electric Other [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 5 years    
Electric Other [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 50 years    
Electric Capital Leases [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Capital Leased Assets, Gross 289us-gaap_CapitalLeasedAssetsGross
/ us-gaap_PublicUtilityAxis
= cms_ElectricCapitalLeasesMember		 284us-gaap_CapitalLeasedAssetsGross
/ us-gaap_PublicUtilityAxis
= cms_ElectricCapitalLeasesMember		  
Electric Capital Leases [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Capital Leased Assets, Gross 289us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_ElectricCapitalLeasesMember		 284us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_ElectricCapitalLeasesMember		  
Gas Distribution [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Distribution 3,239us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ us-gaap_PublicUtilityAxis
= us-gaap_GasDistributionMember		 3,015us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ us-gaap_PublicUtilityAxis
= us-gaap_GasDistributionMember		  
Gas Distribution [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 28 years    
Gas Distribution [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 80 years    
Gas Distribution [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Distribution 3,239us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_GasDistributionMember		 3,015us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_GasDistributionMember		  
Gas Distribution [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 28 years    
Gas Distribution [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Distribution 80 years    
Gas Transmission [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Transmission 974us-gaap_PublicUtilitiesPropertyPlantAndEquipmentTransmission
/ us-gaap_PublicUtilityAxis
= us-gaap_GasTransmissionMember		 821us-gaap_PublicUtilitiesPropertyPlantAndEquipmentTransmission
/ us-gaap_PublicUtilityAxis
= us-gaap_GasTransmissionMember		  
Gas Transmission [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Transmission 17 years    
Gas Transmission [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Transmission 75 years    
Gas Transmission [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Transmission 974us-gaap_PublicUtilitiesPropertyPlantAndEquipmentTransmission
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_GasTransmissionMember		 821us-gaap_PublicUtilitiesPropertyPlantAndEquipmentTransmission
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= us-gaap_GasTransmissionMember		  
Gas Transmission [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Transmission 17 years    
Gas Transmission [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Transmission 75 years    
Gas Underground Storage Facilities [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 578us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		 [2] 535us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		 [2]  
Gas Underground Storage Facilities [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 29 years [2]    
Gas Underground Storage Facilities [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 65 years [2]    
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 578us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		 [2] 535us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		 [2]  
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 29 years [2]    
Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 65 years [2]    
Gas Other [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 538us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ us-gaap_PublicUtilityAxis
= cms_GasOtherMember		 465us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ us-gaap_PublicUtilityAxis
= cms_GasOtherMember		  
Gas Other [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 5 years    
Gas Other [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 50 years    
Gas Other [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 538us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasOtherMember		 465us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasOtherMember		  
Gas Other [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 5 years    
Gas Other [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 50 years    
Gas Capital Leases [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Capital Leased Assets, Gross 6us-gaap_CapitalLeasedAssetsGross
/ us-gaap_PublicUtilityAxis
= cms_GasCapitalLeasesMember		 7us-gaap_CapitalLeasedAssetsGross
/ us-gaap_PublicUtilityAxis
= cms_GasCapitalLeasesMember		  
Gas Capital Leases [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Capital Leased Assets, Gross 6us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasCapitalLeasesMember		 7us-gaap_CapitalLeasedAssetsGross
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasCapitalLeasesMember		  
Enterprises IPP [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Plant, property, and equipment, gross 90us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= cms_EnterprisesIppMember		 89us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= cms_EnterprisesIppMember		  
Enterprises IPP [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 3 years    
Enterprises IPP [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 30 years    
Enterprises Other [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Plant, property, and equipment, gross 25us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= cms_EnterprisesOtherMember		 26us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= cms_EnterprisesOtherMember		  
Enterprises Other [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 3 years    
Enterprises Other [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 40 years    
Other [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Other non-utility property 41us-gaap_PropertyPlantAndEquipmentOther
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember		 40us-gaap_PropertyPlantAndEquipmentOther
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember		  
Other [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 1 year    
Other [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 51 years    
Other [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Other non-utility property 15us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember		 15us-gaap_PropertyPlantAndEquipmentOther
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis
= us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember		  
Other [Member] | Consumers Energy Company [Member] | Minimum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 8 years    
Other [Member] | Consumers Energy Company [Member] | Maximum [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Estimated Depreciable Life in Years, Other 51 years    
Base Natural Gas [Member] | Gas Underground Storage Facilities [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment 26us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ cms_BaseNaturalGasAxis
= cms_BaseNaturalGasMember
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		 26us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ cms_BaseNaturalGasAxis
= cms_BaseNaturalGasMember
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		  
Base Natural Gas [Member] | Gas Underground Storage Facilities [Member] | Consumers Energy Company [Member]      
Public Utility, Property, Plant and Equipment [Line Items]      
Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment $ 26us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ cms_BaseNaturalGasAxis
= cms_BaseNaturalGasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		 $ 26us-gaap_PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment
/ cms_BaseNaturalGasAxis
= cms_BaseNaturalGasMember
/ dei_LegalEntityAxis
= cms_ConsumersEnergyCompanyMember
/ us-gaap_PublicUtilityAxis
= cms_GasUndergroundStorageFacilitiesMember		  
[1] For the year ended December 31, 2014, utility plant additions were $1.6 billion and utility plant retirements were $126 million. For the year ended December 31, 2013, utility plant additions were $1.3 billion and utility plant retirements were $156 million.
[2] Underground storage includes base natural gas of $26 million at December 31, 2014 and 2013. Base natural gas is not subject to depreciation.