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Regulatory Matters (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2014 | Dec. 31, 2013
Regulatory Matters [Line Items] |  |
Accrued Power Supply | $ 188 |
Consumers Energy Company [Member] |  |
Regulatory Matters [Line Items] |  |
Reduction of income tax expense | 16 |
Accrued Power Supply | 188 |
Energy optimization incentive requested for exceeding savings targets |  | 18
Electric Utility [Member] | Consumers Energy Company [Member] |  |
Regulatory Matters [Line Items] |  |
Income tax benefits, to be returned to customers | 211 |
Tax benefit, distribution to customers, term | 5 years |
Gas Utility [Member] | Consumers Energy Company [Member] |  |
Regulatory Matters [Line Items] |  |
Income tax benefits, to be returned to customers | 264 |
Tax benefit, distribution to customers, term | 12 years |
Gas Cost Recover (GCR) [Member] | Consumers Energy Company [Member] |  |
Regulatory Matters [Line Items] |  |
Accrued Power Supply | 84 |
Power Supply Cost Recover (PSCR) [Member] | Consumers Energy Company [Member] |  |
Regulatory Matters [Line Items] |  |
Accrued Power Supply | $ 104 |

X
- Definition Underrecoveries of power supply and gas costs that represent amounts that will be recovered from customers within one year of the balance sheet date. + References No definition available. + Details
Name: | cms_AccruedPowerSupply
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Income tax benefits, to be returned to customers + References No definition available. + Details
Name: | cms_IncomeTaxBenefitsToBeReturnedToCustomers
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
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X
- Definition Reduction of income tax expense + References No definition available. + Details
Name: | cms_ReductionOfIncomeTaxExpense
Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
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Namespace Prefix: | cms_
Data Type: | xbrli:stringItemType
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- Definition Energy optimization incentive requested for achieving electric and gas savings targets. + References No definition available. + Details
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Namespace Prefix: | cms_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Income tax benefits, to be returned to customers + References No definition available. + Details
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Namespace Prefix: | cms_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration