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Plant, Property, and Equipment (Public Utilities Property Plant and Equipment Schedule of Composite Depreciation Rate Table) (Details) (Consumers Energy Company [Member]) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Electric Utility Property [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service | 3.50%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_ElectricUtilityPropertyMember | 3.50%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_ElectricUtilityPropertyMember | 3.20%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_ElectricUtilityPropertyMember
Gas Utility Property [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service | 2.80%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_GasUtilityPropertyMember | 2.80%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_GasUtilityPropertyMember | 2.90%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = cms_GasUtilityPropertyMember
Other property [Member] |  |  |
Public Utility, Property, Plant and Equipment [Line Items] |  |  |
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service | 7.70%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = us-gaap_OtherPropertyMember | 7.00%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = us-gaap_OtherPropertyMember | 7.20%us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDisclosureOfCompositeDepreciationRateForPlantsInService / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_PublicUtilityAxis = us-gaap_OtherPropertyMember

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- Definition Composite depreciation rate for public utility plants in service. + References No definition available. + Details
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