Financings and Capitalization (First Mortgage Bond Purchase) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Payment for purchase of first mortgage bonds			$ 884	$ 789
Interest on long-term debt	$ 204	$ 176	590	519
Consumers Energy Company
Debt Instrument [Line Items]
Payment for purchase of first mortgage bonds			100	322
Interest on long-term debt	135	123	388	364
First mortgage bonds
Debt Instrument [Line Items]
Gain on extinguishment of debt		20	72	90
First mortgage bonds | Consumers Energy Company | Repurchased Debt
Debt Instrument [Line Items]
Interest on long-term debt	$ 8	5	21	13
First mortgage bonds | Related Party
Debt Instrument [Line Items]
Principal (In Millions)		69	184	311
Payment for purchase of first mortgage bonds		$ 49	$ 109	$ 218