Income Taxes (Reconciliation Of Beginning And Ending Uncertain Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 25	$ 23	$ 19
Additions for current-year tax positions	2	1	1
Additions for prior-year tax positions	0	3	3
Reductions for prior-year tax positions	0	(2)	0
Balance at end of period	27	25	23
Consumers Energy Company
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	31	34	28
Additions for current-year tax positions	3	1	1
Additions for prior-year tax positions	0	4	5
Reductions for prior-year tax positions	0	(8)	0
Balance at end of period	$ 34	$ 31	$ 34