Financings And Capitalization (Major Long-Term Debt Transactions) (Details)	12 Months Ended
Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Principal Balance	$ 500,000,000
Debt retirement, principal	50,000,000
CMS Energy [Member]
Debt Instrument [Line Items]
Principal Balance	250,000,000
Consumers Energy Company [Member]
Debt Instrument [Line Items]
Principal Balance	250,000,000
Debt retirement, principal	50,000,000
Senior Notes 3.600% Due March 2025 [Member] \| CMS Energy [Member]
Debt Instrument [Line Items]
Principal Balance	$ 250,000,000
Interest rate	3.60%
Debt issuance date	November 2015
Maturity date	November 2025
FMB's 4.100% Due 2045 [Member] \| Consumers Energy Company [Member]
Debt Instrument [Line Items]
Principal Balance	$ 250,000,000
Interest rate	4.10%
Debt issuance date	November 2015
Maturity date	November 2045
FMB's 2.600% Due 2015 [Member] \| Consumers Energy Company [Member]
Debt Instrument [Line Items]
Debt retirement, principal	$ 50,000,000
Interest rate	2.60%
Debt retirement date	October 2015
Maturity date	October 2015

Debt Instrument Issuance Date 2

No definition available.

Name:	cms_DebtInstrumentIssuanceDate2
Namespace Prefix:	cms_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument was partially or fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ References

No definition available.

+ Details

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

- Definition

Maturity date of the debt instrument.

+ References

No definition available.

+ Details

Name:	cms_DebtMaturityDate
Namespace Prefix:	cms_
Data Type:	invest:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

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

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
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- Details

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