Financings And Capitalization (Major Long-Term Debt Transactions) (Details) - First Mortgage Bonds - 2.650% First Mortgage Bonds Due 2052 - Consumers Energy Company $ in Millions	Sep. 30, 2021 USD ($)
Debt Instrument [Line Items]
Principal Balance	$ 300
Interest rate	2.65%

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

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