Contingencies and Commitments (Guarantees) (Details) $ in Millions	6 Months Ended
Jun. 30, 2021 USD ($)
Variable Interest Entity, Primary Beneficiary \| Aviator Wind Class B Membership
Guarantees And Other Contingencies [Line Items]
Ownership percentage	49.00%
Guarantees
Guarantees And Other Contingencies [Line Items]
Expiration Date	indefinite
Maximum Obligation	$ 30
Carrying Amount	$ 0
Guarantees \| Consumers Energy Company
Guarantees And Other Contingencies [Line Items]
Expiration Date	indefinite
Maximum Obligation	$ 30
Carrying Amount	$ 0
Indemnification Agreement From Purchase Of Variable Interest Entity
Guarantees And Other Contingencies [Line Items]
Expiration Date	indefinite
Maximum Obligation	$ 331
Carrying Amount	$ 0
Indemnity Obligations From Stock And Asset Sales Agreements
Guarantees And Other Contingencies [Line Items]
Expiration Date	indefinite
Maximum Obligation	$ 153
Carrying Amount	2
Tax And Other Indemnity Obligations \| Consumers Energy Company
Guarantees And Other Contingencies [Line Items]
Carrying Amount	$ 1

Guarantees And Other Contingencies [Line Items]

No definition available.

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

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

+ Details

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

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

+ Details

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

- Definition

Describe the approximate term of the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

+ Details

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

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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