Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
DB Pension Plans
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	$ 12	$ 14
Interest cost	18	15
Expected return on plan assets	(52)	(52)
Amortization of
Net loss	17	25
Prior service cost (credit)	1	1
Settlement loss	2	1
Net periodic cost (credit)	(2)	4
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	12	13
Interest cost	16	14
Expected return on plan assets	(49)	(49)
Amortization of
Net loss	16	25
Prior service cost (credit)	1	1
Settlement loss	2	1
Net periodic cost (credit)	(2)	5
OPEB Plan
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	4	4
Interest cost	7	6
Expected return on plan assets	(29)	(27)
Amortization of
Net loss	0	2
Prior service cost (credit)	(12)	(13)
Settlement loss	0	0
Net periodic cost (credit)	(30)	(28)
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	4	4
Interest cost	7	6
Expected return on plan assets	(27)	(25)
Amortization of
Net loss	0	2
Prior service cost (credit)	(12)	(13)
Settlement loss	0	0
Net periodic cost (credit)	$ (28)	$ (26)