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Leases (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Leases [Line Items] |  |  |
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges | $ 20 | $ 20 | $ 21
Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Finance Lease Term | 15 years |  |
Finance Leases Lessee Balance Sheet Assets Amortization And Interest Charges | $ 20 | $ 20 | $ 21
Coal-Carrying Railcars [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Operating leases without extension provisions, remaining term | 10 years |  |
Operating leases with extension provisions, remaining term | 13 years |  |
Gas Transportation Pipeline into Karn [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Capital Lease Term | 15 years |  |
Capital Lease Remaining Term | 8 years |  |
Gas Transportation Pipeline into Zeeland [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Capital Lease Remaining Term | 4 years |  |
Capital lease renewal term | 5 years |  |
Minimum [Member] | Coal-Carrying Railcars [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Operating leases, term | 3 years |  |
Minimum [Member] | Long-term PPAs [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Lease term | 2 years |  |
Maximum [Member] | Coal-Carrying Railcars [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Operating leases, term | 15 years |  |
Maximum [Member] | Vehicle Fleet Operations [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Capital Lease Term | 120 months |  |
Maximum [Member] | Long-term PPAs [Member] | Consumers Energy Company [Member] |  |  |
Leases [Line Items] |  |  |
Lease term | 19 years |  |

X
- Definition Remaining term of a capital lease contract before expiration. + References No definition available. + Details
Name: | cms_CapitalLeaseRemainingTerm
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Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Capital lease renewal term + References No definition available. + Details
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Namespace Prefix: | cms_
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Balance Type: | na
Period Type: | duration

X
- Definition Term of capital lease contract. + References No definition available. + Details
Name: | cms_CapitalLeaseTerm
Namespace Prefix: | cms_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortization and interest charges under the financing. + References No definition available. + Details
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Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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X
- Definition Term of finance lease contract. + References No definition available. + Details
Name: | cms_FinanceLeaseTerm
Namespace Prefix: | cms_
Data Type: | xbrli:durationItemType
Balance Type: | na
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X
- Details
Name: | cms_LeasesLineItems
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Data Type: | xbrli:stringItemType
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X
- Definition Lease term + References No definition available. + Details
Name: | cms_LeaseTerm
Namespace Prefix: | cms_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Time period remaining over which operating leases are expiring with extension provisions in the contracts. + References No definition available. + Details
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- Definition Time period remaining over which operating leases are expiring without extension provisions in the contracts. + References No definition available. + Details
Name: | cms_OperatingLeasesWithoutExtensionProvisionsRemainingTerm
Namespace Prefix: | cms_
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X
- Definition Term of the lessor's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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