Current liabilities that represent obligations to make refunds to customers for fuel costs.

No definition available.

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Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
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- Definition

The amount the MPSC authorized collection from customers.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Authorized recovery, collection period

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
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- Definition

Energy optimization incentive authorized by the MPSC 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

- Definition

Income tax benefits returned to customers

+ References

No definition available.

+ Details

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Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total amount of an accelerated return of income tax benefits to customers per regulatory treatment.

+ References

No definition available.

+ Details

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Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
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- Definition

Net over-/(under-) recovery of expense, including interest, authorized by the MPSC.

+ References

No definition available.

+ Details

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Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Net over-/(under-) recovery of expense, including interest, requested.

+ References

No definition available.

+ Details

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Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of Former Manufactured Gas Plants

+ References

No definition available.

+ Details

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Namespace Prefix:	cms_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of units planned to be retired.

+ References

No definition available.

+ Details

Name:	cms_NumberOfUnitsPlannedToBeRetired
Namespace Prefix:	cms_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percent of energy optimization savings targets achieved during the year.

+ References

No definition available.

+ Details

Name:	cms_PercentOfSavingsTargetAchieved
Namespace Prefix:	cms_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Power generation of cancelled plant

+ References

No definition available.

+ Details

Name:	cms_PowerGenerationOfCancelledPlant
Namespace Prefix:	cms_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash grant received from government during the current period.

+ References

No definition available.

+ Details

Name:	cms_ProceedsFromGovernmentGrant
Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The period reduction to income tax expense due to the accelerated return of income tax benefits to customers per regulatory treatment

+ References

No definition available.

+ Details

Name:	cms_ReductionOfIncomeTaxExpense
Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

- Definition

The period covered related to the accelerated return of income tax benefits to customers per regulatory treatment.

+ References

No definition available.

+ Details

Name:	cms_TaxBenefitDistributionToCustomersTerm
Namespace Prefix:	cms_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Total costs related to electricity produced and sold during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 2

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2(b))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cost of natural gas purchased and associated transportation and storage costs during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_CostOfNaturalGasPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of capitalized fuel costs of a regulated entity that are expected to be recoverable through rate adjustments within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499739&loc=d3e43603-110378

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of capitalized gas costs of a regulated entity that are expected to be recoverable through rate adjustments within one year or the normal operating cycle, if longer.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 405

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=cms_ConsumersEnergyCompanyMember
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Regulatory Matters (Narrative) (Details) (USD $)	12 Months Ended
Regulatory Matters (Narrative) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014	Mar. 31, 2013	Nov. 30, 2014
Public Utilities, General Disclosures [Line Items]
Proceeds from government grant		$ 69,000,000cms_ProceedsFromGovernmentGrant
Accrued Power Supply	27,000,000us-gaap_DeferredFuelCost
Long-term debt	8,016,000,000us-gaap_LongTermDebtNoncurrent	7,101,000,000us-gaap_LongTermDebtNoncurrent
Accrued rate refunds	6,000,000cms_AccruedRateRefunds	12,000,000cms_AccruedRateRefunds
Cost of gas sold	1,493,000,000us-gaap_CostOfNaturalGasPurchases	1,228,000,000us-gaap_CostOfNaturalGasPurchases	1,150,000,000us-gaap_CostOfNaturalGasPurchases
Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Income tax benefits returned to customers	64,000,000
Reduction of income tax expense	39,000,000
Proceeds from government grant		69,000,000
Accrued Power Supply	27,000,000
Energy optimization incentive authorized for exceeding savings targets						18,000,000
Energy optimization incentive requested for exceeding savings targets	17,000,000
Long-term debt	5,154,000,000	4,579,000,000
Recorded liability	2,162,000,000	2,282,000,000
Number of units planned to be retired	10
Accrued rate refunds	6,000,000	12,000,000
Cost of gas sold	1,375,000,000	1,187,000,000	1,110,000,000
Coal-Fueled Electric Generation [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Number of units planned to be retired	7
Gas-Fueled Electric Generation [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Number of units planned to be retired	3
Electric Utility [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Income tax benefits, to be returned to customers	209,000,000
Tax benefit, distribution to customers, term	5 years
Gas Utility [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Income tax benefits, to be returned to customers	260,000,000
Tax benefit, distribution to customers, term	12 years
Gas Cost Recover (GCR) [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Over (under) recovery requested				(84,000,000)
Over (under) recovery authorized by the MPSC					(22,000,000)
Cost of gas sold				900,000,000	900,000,000
Deferred gas costs	27,000,000
Power Supply Cost Recover (PSCR) [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Over (under) recovery requested		10,000,000
Accrued rate refunds	6,000,000
PSCR Cost of Power Sold		1,900,000,000	1,900,000,000
Over (under) recovery authorized by the MPSC			(18,000,000)
Electric Energy Optimization Plan [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Percent of savings target achieved	135.00%
Gas Energy Optimization Plan [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Percent of savings target achieved	129.00%
Cancelled Coal-Fueled Plant Costs [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized recovery, collection period	3 years
Authorized Recovery			14,000,000
Major Maintenance [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized recovery, collection period	6 months
Authorized Recovery						10,000,000
Coal Fueled Electric Generating Units [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Power generation of cancelled plant			830
Manufactured Gas Plant [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized recovery, collection period	10 years
Number of former MGPs	23
Gas Storage Inventory Adjustments [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized recovery, collection period	5 years
Gas Revenue Decoupling Mechanism [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Authorized Recovery		17,000,000
Renewable Energy Grant [Member] \| Consumers Energy Company [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from government grant		$ 69,000,000