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Asset Retirement Obligations (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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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 | $ 17 cms_HypotheticalAssetRetirementObligationsLiabilityIncrease |  | $ 16 cms_HypotheticalAssetRetirementObligationsLiabilityIncrease |
ARO Liability, at beginning of period | 325 us-gaap_AssetRetirementObligation |  | 312 us-gaap_AssetRetirementObligation |
Incurred | 9 us-gaap_AssetRetirementObligationLiabilitiesIncurred |  | (3)us-gaap_AssetRetirementObligationLiabilitiesIncurred |
Settled | (12)us-gaap_AssetRetirementObligationLiabilitiesSettled | [1] | (6)us-gaap_AssetRetirementObligationLiabilitiesSettled | [1]
Accretion | 18 us-gaap_AssetRetirementObligationAccretionExpense |  | 18 us-gaap_AssetRetirementObligationAccretionExpense |
Cash flow Revisions |  |  | 4 us-gaap_AssetRetirementObligationRevisionOfEstimate |
ARO Liability, end of period | 340 us-gaap_AssetRetirementObligation |  | 325 us-gaap_AssetRetirementObligation |
ARO Cash payments | 12 us-gaap_AssetRetirementObligationCashPaidToSettle |  | 6 us-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 | 17 cms_HypotheticalAssetRetirementObligationsLiabilityIncrease / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 16 cms_HypotheticalAssetRetirementObligationsLiabilityIncrease / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
ARO Liability, at beginning of period | 324 us-gaap_AssetRetirementObligation / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 311 us-gaap_AssetRetirementObligation / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Incurred | 9 us-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 | 18 us-gaap_AssetRetirementObligationAccretionExpense / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 18 us-gaap_AssetRetirementObligationAccretionExpense / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Cash flow Revisions |  |  | 4 us-gaap_AssetRetirementObligationRevisionOfEstimate / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
ARO Liability, end of period | 339 us-gaap_AssetRetirementObligation / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 324 us-gaap_AssetRetirementObligation / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
ARO Cash payments | 12 us-gaap_AssetRetirementObligationCashPaidToSettle / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 6 us-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 | 1 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_CloseGasTreatingPlantAndGasWellsMember |  | 1 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_CloseGasTreatingPlantAndGasWellsMember |
Incurred |  |  |  |
Settled |  | [1] |  |
Accretion |  |  |  |
Cash flow Revisions |  |  |  |
ARO Liability, end of period | 1 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_CloseGasTreatingPlantAndGasWellsMember |  | 1 us-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 | 118 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_CoalAshDisposalAreasMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 114 us-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 | 5 us-gaap_AssetRetirementObligationAccretionExpense / cms_AssetRetirementObligationsCategoriesAxis = cms_CoalAshDisposalAreasMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 5 us-gaap_AssetRetirementObligationAccretionExpense / cms_AssetRetirementObligationsCategoriesAxis = cms_CoalAshDisposalAreasMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Cash flow Revisions |  |  |  |
ARO Liability, end of period | 120 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_CoalAshDisposalAreasMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 118 us-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 | 49 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_AsbestosAbatementMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 43 us-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 | 3 us-gaap_AssetRetirementObligationAccretionExpense / cms_AssetRetirementObligationsCategoriesAxis = cms_AsbestosAbatementMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 3 us-gaap_AssetRetirementObligationAccretionExpense / cms_AssetRetirementObligationsCategoriesAxis = cms_AsbestosAbatementMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Cash flow Revisions |  |  | 4 us-gaap_AssetRetirementObligationRevisionOfEstimate / cms_AssetRetirementObligationsCategoriesAxis = cms_AsbestosAbatementMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
ARO Liability, end of period | 51 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_AsbestosAbatementMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 49 us-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 | 154 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_GasDistributionCutPurgeCapMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 151 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_GasDistributionCutPurgeCapMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Incurred | 6 us-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 | 10 us-gaap_AssetRetirementObligationAccretionExpense / cms_AssetRetirementObligationsCategoriesAxis = cms_GasDistributionCutPurgeCapMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 10 us-gaap_AssetRetirementObligationAccretionExpense / cms_AssetRetirementObligationsCategoriesAxis = cms_GasDistributionCutPurgeCapMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Cash flow Revisions |  |  |  |
ARO Liability, end of period | 162 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_GasDistributionCutPurgeCapMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 154 us-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 | 3 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_WindFarmMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | 3 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_WindFarmMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |
Incurred | 3 us-gaap_AssetRetirementObligationLiabilitiesIncurred / cms_AssetRetirementObligationsCategoriesAxis = cms_WindFarmMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  |  |
Settled |  | [1] |  |
Accretion |  |  |  |
Cash flow Revisions |  |  |  |
ARO Liability, end of period | $ 6 us-gaap_AssetRetirementObligation / cms_AssetRetirementObligationsCategoriesAxis = cms_WindFarmMember / dei_LegalEntityAxis = cms_ConsumersEnergyCompanyMember |  | $ 3 us-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.

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- Definition Market risk premium assumed to estimate increase in liability of an asset retirement obligation. No market risk premium was included in ARO fair value estimates because reasonable estimates of market risk premiums could not be made. + References No definition available. + Details
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- Definition Hypothetical increase in liability of an asset retirement obligation for which a risk premium could not be reasonably estimated. + References No definition available. + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Asset Retirement Obligation -URI http://asc.fasb.org/extlink&oid=6505190 + Details
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of cash paid during the period to settle an asset retirement obligation. Amounts paid to settle an asset retirement obligation are generally included in the operating section of the Statement of Cash Flows. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 17 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3367-108585 + Details
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- Definition Amount of asset retirement obligations incurred during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Amount of the Increase or Decrease in the amount of the asset retirement obligation during the current period for changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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