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Regulatory Matters (Schedule Of The Components Of Regulatory Assets and Liabilities) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |
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Dec. 31, 2014 | Dec. 31, 2013
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, current | $ 89 us-gaap_RegulatoryAssetsCurrent |  | $ 40 us-gaap_RegulatoryAssetsCurrent |
Regulatory assets, noncurrent | 1,956 us-gaap_RegulatoryAssetsNoncurrent |  | 1,530 us-gaap_RegulatoryAssetsNoncurrent |
Regulatory liabilities | 67 us-gaap_RegulatoryLiabilityCurrent |  | 67 us-gaap_RegulatoryLiabilityCurrent |
Regulatory liabilities, noncurrent | 2,095 us-gaap_RegulatoryLiabilityNoncurrent |  | 2,215 us-gaap_RegulatoryLiabilityNoncurrent |
Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, current | 89 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember | [1] | 40 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember | [1]
Regulatory assets, noncurrent | 1,956 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,530 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Total regulatory asset | 2,045 us-gaap_RegulatoryAssets / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 1,570 us-gaap_RegulatoryAssets / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Regulatory liabilities | 67 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 67 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Regulatory liabilities, noncurrent | 2,095 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 2,215 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Total regulatory liabilities | 2,162 us-gaap_RegulatoryLiabilities / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 2,282 us-gaap_RegulatoryLiabilities / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Cost Of Removal [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory liabilities, noncurrent | 1,673 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_RemovalCostsMember |  | 1,599 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_RemovalCostsMember |
Renewable Energy Plan [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Noncurrent Regulatory Liability, Recovery End Date | 2028 |  |  |
Regulatory liabilities, noncurrent | 131 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_RenewableEnergyProgramMember |  | 159 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_RenewableEnergyProgramMember |
Income Taxes, Net [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Current Regulatory Liability Recovery End Date | 2015 |  |  |
Regulatory liabilities | 64 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_DeferredIncomeTaxChargesMember |  | 64 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_DeferredIncomeTaxChargesMember |
Regulatory liabilities, noncurrent | 103 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_DeferredIncomeTaxChargesMember |  | 157 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_DeferredIncomeTaxChargesMember |
ARO [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory liabilities, noncurrent | 83 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_AssetRetirementObligationCostsMember |  | 93 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_AssetRetirementObligationCostsMember |
Renewable Energy Grant [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Current Regulatory Liability Recovery End Date | 2015 |  |  |
Noncurrent Regulatory Liability, Recovery End Date | 2043 |  |  |
Regulatory liabilities | 2 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = cms_RenewableEnergyGrantMember |  | 2 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = cms_RenewableEnergyGrantMember |
Regulatory liabilities, noncurrent | 63 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = cms_RenewableEnergyGrantMember |  | 65 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = cms_RenewableEnergyGrantMember |
Energy Optimization Plan [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory liabilities, noncurrent | 32 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = cms_EnergyOptimizationPlanMember |  | 31 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = cms_EnergyOptimizationPlanMember |
Postretirement Benefits [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory liabilities, noncurrent |  |  | 98 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_PostretirementBenefitCostsMember |
Other Regulatory Assets And Liabilities [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Current Regulatory Liability Recovery End Date | 2015 |  |  |
Regulatory liabilities | 1 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember |  | 1 us-gaap_RegulatoryLiabilityCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember |
Regulatory liabilities, noncurrent | 10 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember |  | 13 us-gaap_RegulatoryLiabilityNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryLiabilityAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember |
Postretirement Benefits [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, noncurrent | 1,195 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_PostretirementBenefitCostsMember | [1],[2] | 634 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_PostretirementBenefitCostsMember | [1],[2]
Other Securitized Costs [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory Current Asset, End Date for Recovery | 2015 |  |  |
Noncurrent Regulatory Asset Recovery End Date | 2015 |  |  |
Regulatory assets, current | 61 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_SecuritizedCostsMember |  |  |
Regulatory assets, noncurrent |  |  | 129 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_SecuritizedCostsMember |
Costs Of Electric Generating Units To Be Retired And Securitized [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Noncurrent Regulatory Asset Recovery End Date | 2029 | [3],[4] |  |
Regulatory assets, noncurrent | 370 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_CostsOfElectricGeneratingUnitsToBeRetiredAndSecuritizedMember | [3],[4] | 362 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_CostsOfElectricGeneratingUnitsToBeRetiredAndSecuritizedMember | [3],[4]
Manufactured Gas Plant [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, noncurrent | 147 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_ManufacturedGasPlantMember | [2] | 148 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_ManufacturedGasPlantMember | [2]
ARO [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, noncurrent | 139 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_AssetRetirementObligationCostsMember | [2] | 129 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_AssetRetirementObligationCostsMember | [2]
Unamortized Debt Costs [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, noncurrent | 66 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_LossOnReacquiredDebtMember | [2] | 74 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_LossOnReacquiredDebtMember | [2]
Gas Storage Inventory Adjustments [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory assets, noncurrent | 21 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_GasStorageInventoryAdjustmentsMember |  | 23 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_GasStorageInventoryAdjustmentsMember |
Energy Optimization Plan Incentive [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory Current Asset, End Date for Recovery | 2015 |  |  |
Noncurrent Regulatory Asset Recovery End Date | 2016 | [4] |  |
Regulatory assets, current | 17 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_EnergyOptimizationPlanIncentiveMember |  | 17 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_EnergyOptimizationPlanIncentiveMember |
Regulatory assets, noncurrent | 17 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_EnergyOptimizationPlanIncentiveMember | [4] | 18 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_EnergyOptimizationPlanIncentiveMember | [4]
Major Maintenance [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory Current Asset, End Date for Recovery | 2015 | [4] |  |
Noncurrent Regulatory Asset Recovery End Date | 2015 |  |  |
Regulatory assets, current | 8 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_MajorMaintenanceMember | [4] |  |
Regulatory assets, noncurrent |  |  | 10 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_MajorMaintenanceMember |
Cancelled Coal-Fueled Plant Costs [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory Current Asset, End Date for Recovery | 2015 | [3],[4] |  |
Regulatory assets, current | 2 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_CancelledCoalFueledPlantCostsMember | [3],[4] | 5 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_CancelledCoalFueledPlantCostsMember | [3],[4]
Gas Revenue Decoupling Mechanism [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory Current Asset, End Date for Recovery | 2014 |  |  |
Regulatory assets, current |  |  | 17 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = cms_GasRevenueDecouplingMechanismMember |
Other Regulatory Assets And Liabilities [Member] | Consumers Energy Company [Member] |  |  |  |
Regulatory Matters [Line Items] |  |  |  |
Regulatory Current Asset, End Date for Recovery | 2015 |  |  |
Regulatory assets, current | 1 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember |  | 1 us-gaap_RegulatoryAssetsCurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember |
Regulatory assets, noncurrent | $ 1 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember | [3] | $ 3 us-gaap_RegulatoryAssetsNoncurrent / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember / us-gaap_RegulatoryAssetAxis = us-gaap_OtherRegulatoryAssetsLiabilitiesMember | [3]
[1] | This regulatory asset is offset partially by liabilities. The net amount is included in rate base, thereby providing a return.
[2] | These regulatory assets represent incurred costs for which the MPSC has provided, or Consumers expects, recovery without a return on investment.
[3] | These regulatory assets either are included in rate base (or are expected to be included, for costs incurred subsequent to the most recently approved rate case), thereby providing a return on expenditures, or provide a specific return on investment authorized by the MPSC.
[4] | These regulatory assets have arisen from alternative revenue programs and are not associated with incurred costs or capital investments. Therefore, the MPSC has provided for recovery without a return

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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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