Contingencies And Commitments (Guarantees) (Details) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($)
Guarantees
Guarantees And Other Contingencies [Line Items]
Guarantee Description	Guarantees
Expiration Date	indefinite
Maximum Obligation	$ 36
Carrying Amount	$ 0
Guarantees \| Consumers Energy Company
Guarantees And Other Contingencies [Line Items]
Guarantee Description	Guarantee
Expiration Date	indefinite
Maximum Obligation	$ 30
Carrying Amount	$ 0
Indemnity Obligations From Stock And Asset Sales Agreements
Guarantees And Other Contingencies [Line Items]
Guarantee Description	Indemnity obligations from stock and asset sales agreements
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=118943654&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsCurrentCarryingValue
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=118943654&loc=d3e12069-110248

+ Details

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

- Definition

Describes how and under what circumstances or in connection with which transaction the guarantee or each group of similar guarantees was given and the objective of the guarantee.

+ 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)(2)
-URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12069-110248

+ Details

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

- 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=118943654&loc=d3e12069-110248

+ Details

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

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_GuaranteeTypeOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_IndemnificationGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=cms_TaxAndOtherIndemnityObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: