Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
DB Pension Plans and DB SERP
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	$ 41	$ 53	$ 50
Interest cost	84	63	83
Settlement loss	(1)	(1)	(1)
Expected return on plan assets	(206)	(208)	(191)
Amortization of
Net loss	40	100	95
Prior service cost (credit)	4	4	1
Settlement loss	9	6	2
Net periodic cost (credit)	(27)	19	41
DB Pension Plans and DB SERP | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	39	51	49
Interest cost	79	59	78
Expected return on plan assets	(194)	(197)	(181)
Amortization of
Net loss	37	96	90
Prior service cost (credit)	4	4	1
Settlement loss	9	6	2
Net periodic cost (credit)	(26)	19	39
OPEB Plan
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	17	18	16
Interest cost	28	23	33
Settlement loss	0	0	0
Expected return on plan assets	(115)	(109)	(100)
Amortization of
Net loss	1	8	15
Prior service cost (credit)	(51)	(53)	(56)
Settlement loss	0	0	0
Net periodic cost (credit)	(120)	(113)	(92)
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	17	17	15
Interest cost	27	23	31
Expected return on plan assets	(107)	(102)	(93)
Amortization of
Net loss	0	8	15
Prior service cost (credit)	(50)	(51)	(54)
Settlement loss	0	0	0
Net periodic cost (credit)	$ (113)	$ (105)	$ (86)