Revenue (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Unbilled receivables	$ 339		$ 339		$ 663
Incentive revenue collection period	24 months		24 months
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Unbilled receivables	$ 339		$ 339		$ 663
Accounts Receivable
Disaggregation of Revenue [Line Items]
Bad debt expense	8	$ 14	17	$ 18
Accounts Receivable | Consumers Energy Company
Disaggregation of Revenue [Line Items]
Bad debt expense	$ 8	$ 14	$ 17	$ 18