Revenue (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Bad debt expense	$ 34	$ 50	$ 22
Unbilled receivables	494	663
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Bad debt expense	34	50	22
Regulatory liability	3,950	3,900
Unbilled receivables	494	663
Consumers Energy Company | Contributions to assistance programs
Disaggregation of Revenue [Line Items]
Regulatory liability	10
Consumers Energy Company | Voluntary refund mechanism
Disaggregation of Revenue [Line Items]
Regulatory liability		22
Consumers Energy Company | Reserve for customer refunds
Disaggregation of Revenue [Line Items]
Regulatory liability	15
Accounts Receivable
Disaggregation of Revenue [Line Items]
Bad debt expense	34	50	22
Accounts Receivable | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Bad debt expense	$ 34	$ 50	$ 22