Revenue (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Bad debt expense	$ 10	$ 7	$ 30	$ 24
Unbilled receivables	381		381		$ 584
Consumers Energy Company
Disaggregation of Revenue [Line Items]
Bad debt expense	10	$ 7	30	$ 24
Unbilled receivables	$ 381		$ 381		$ 584