Income Taxes (Summary of Significant Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Current income taxes
Federal	$ 34	$ 5	$ 6
State and local	0	1	0
Total current income tax expense	34	6	6
Deferred income taxes
Federal	70	107	4
State and local	76	38	65
Total deferred income tax expense	146	145	69
Deferred income tax credit	(4)	(4)	18
Income tax expense	176	147	93
Consumers Energy Company
Current income taxes
Federal	78	3	(2)
State and local	7	2	8
Total current income tax expense	85	5	6
Deferred income taxes
Federal	51	117	50
State and local	68	43	66
Total deferred income tax expense	119	160	116
Deferred income tax credit	(4)	(4)	18
Income tax expense	$ 200	$ 161	$ 140