Financings and Capitalization (First Mortgage Bond Purchase) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Principal (In Millions)	$ 3,556
Unamortized discounts	(30)	$ (30)
Unamortized issuance costs	(135)	(120)
Long-term debt	14,508	13,122
Gain on debt extinguishment		0	$ 0
Interest on long-term debt	616	509	481
Consumers Energy Company
Debt Instrument [Line Items]
Principal (In Millions)	2,671
Unamortized discounts	(28)	(27)
Unamortized issuance costs	(73)	(67)
Long-term debt	10,037	9,192
Interest on long-term debt	415	325	294
Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	431
Long-term debt	424	0
CMS Energy
Debt Instrument [Line Items]
Principal (In Millions)	800
Long-term debt	4,471	3,930
Interest on long-term debt	201	$ 181	$ 183
First mortgage bonds
Debt Instrument [Line Items]
Gain on debt extinguishment	131
First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	431
Unamortized discounts	(3)
Unamortized issuance costs	(4)
Long-term debt	424
First mortgage bonds | CMS Energy
Debt Instrument [Line Items]
Payment for purchase of first mortgage bonds	$ 293
First mortgage bonds due 2060 | First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Interest rate	2.50%
First mortgage bonds due 2060 | First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	$ 163
First mortgage bonds due 2052 | First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Interest rate	2.65%
First mortgage bonds due 2052 | First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	$ 106
First mortgage bonds due 2050 | First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Interest rate	3.75%
First mortgage bonds due 2050 | First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	$ 23
First mortgage bonds due 2050 | First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Interest rate	3.10%
First mortgage bonds due 2050 | First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	$ 52
First mortgage bonds due 2051 | First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Interest rate	3.50%
First mortgage bonds due 2051 | First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	$ 27
First mortgage bonds due 2048 | First mortgage bonds | Consumers Energy Company
Debt Instrument [Line Items]
Interest rate	4.05%
First mortgage bonds due 2048 | First mortgage bonds | Consumers Energy Company | Related Party
Debt Instrument [Line Items]
Principal (In Millions)	$ 60
Repurchased Debt | First mortgage bonds
Debt Instrument [Line Items]
Interest on long-term debt	$ 5