Income Taxes (Significant Components Of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current income taxes
Federal	$ (1)	$ (35)	$ (31)
State and local	1	(2)	28
Total current income tax expense	0	(37)	(3)
Deferred income taxes
Federal	49	100	84
State and local	49	57	29
Total deferred income tax expense	98	157	113
Deferred income tax credit	(3)	(5)	21
Income tax expense	95	115	131
Consumers Energy Company
Current income taxes
Federal	(13)	3	107
State and local	15	(7)	41
Total current income tax expense	2	(4)	148
Deferred income taxes
Federal	103	115	(10)
State and local	54	67	26
Total deferred income tax expense	157	182	16
Deferred income tax credit	(3)	(5)	21
Income tax expense	$ 156	$ 173	$ 185