Financings and Capitalization (Major Long-Term Debt Transactions) (Details) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($)
Debt Instrument [Line Items]
Principal balance	$ 1,395
Debt retirement, principal	780
Consumers Energy Company
Debt Instrument [Line Items]
Principal balance	300
Debt retirement, principal	300
First mortgage bonds due February 2050 \| Consumers Energy Company
Debt Instrument [Line Items]
Principal balance	$ 300
Interest Rate	3.75%
Debt issuance date	May 2019
Maturity Date	February 2050
First mortgage bonds due April 2020 \| Consumers Energy Company
Debt Instrument [Line Items]
Debt retirement, principal	$ 300
Interest Rate	5.65%
Debt retirement date	May 2019
Maturity Date	April 2020
CMS Energy Corporation
Debt Instrument [Line Items]
Principal balance	$ 1,095
Debt retirement, principal	480
CMS Energy Corporation \| Term loan facility due December 2019
Debt Instrument [Line Items]
Principal balance	300
Debt retirement, principal	$ 300
Debt issuance date	January 2019
Debt retirement date	February 2019
Maturity Date	December 2019
CMS Energy Corporation \| 5.875% Junior Subordinated Notes due 2079
Debt Instrument [Line Items]
Principal balance	$ 630
Interest Rate	5.875%
Debt issuance date	February 2019
Maturity Date	March 2079
CMS Energy Corporation \| Term loan facility due June 2020
Debt Instrument [Line Items]
Principal balance	$ 165
Debt issuance date	June 2019
Maturity Date	June 2020
Effective interest rate	2.845%
CMS Energy Corporation \| Term loan facility due April 2019
Debt Instrument [Line Items]
Debt retirement, principal	$ 180
Debt retirement date	February 2019
Maturity Date	April 2019
London Interbank Offered Rate (LIBOR) \| CMS Energy Corporation \| Term loan facility due June 2020
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%

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- 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

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- Definition

Maturity date of the debt instrument.

+ References

No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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- Definition

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

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- 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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- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

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