Financings and Capitalization (Major Long-Term Debt Transactions) (Details) $ in Millions	Dec. 31, 2021 USD ($)
First Mortgage Bonds \| 2.650% First Mortgage Bonds Due 2052 \| Consumers Energy Company
Debt Instrument [Line Items]
Principal balance	$ 300
Interest rate	2.65%
Tax Exempt Revenue Bonds \| 0.875% Tax Exempt Revenue Bonds Due 2035 \| Consumers Energy Company
Debt Instrument [Line Items]
Principal balance	$ 35
Interest rate	0.875%
Term loan facility \| Term Loan Facility Due 2021 \| CMS Energy
Debt Instrument [Line Items]
Principal balance	$ 200

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

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