Disclosure of the amount of the entity's issued liability supported by a third-party credit enhancement.

No definition available.

Name:	cms_DebtInstrumentSupportedByThirdPartyCreditEnhancement
Namespace Prefix:	cms_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	cms_FinancialInstrumentsLineItems
Namespace Prefix:	cms_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

+ Details

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

- Details

Name:	dei_LegalEntityAxis=cms_ConsumersEnergyCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Jan. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Financial Instruments [Line Items]
Portion of long-term debt supported by third-party credit enhancements		$ 103	$ 103
Consumers Energy Company [Member]
Financial Instruments [Line Items]
Portion of long-term debt supported by third-party credit enhancements		103	103
Gain on CMS Energy common stock	9
DB SERP [Member]
Financial Instruments [Line Items]
Company contributions		25
DB SERP [Member] \| Consumers Energy Company [Member]
Financial Instruments [Line Items]
Company contributions		$ 17