Retirement Benefits (Schedule Of Net Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
DB Pension Plans
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	$ 7	$ 9	$ 22	$ 32
Interest cost	27	21	80	59
Expected return on plan assets	(55)	(51)	(165)	(155)
Amortization of
Net loss	2	5	8	32
Prior service cost (credit)	1	1	3	3
Settlement loss	3	2	8	6
Net periodic credit	(15)	(13)	(44)	(23)
DB Pension Plans | Volatility Mechanism
Amortization of
Deferred costs (credits)			(9)
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	7	9	21	32
Interest cost	24	20	75	56
Expected return on plan assets	(52)	(48)	(156)	(147)
Amortization of
Net loss	3	5	8	30
Prior service cost (credit)	1	1	3	3
Settlement loss	3	2	8	6
Net periodic credit	(14)	(11)	(41)	(20)
OPEB Plan
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	2	4	8	13
Interest cost	11	7	33	21
Expected return on plan assets	(26)	(29)	(77)	(87)
Amortization of
Net loss	3	0	9	1
Prior service cost (credit)	(10)	(12)	(31)	(38)
Settlement loss	0	0	0	0
Net periodic credit	(20)	(30)	(58)	(90)
OPEB Plan | Volatility Mechanism
Amortization of
Deferred costs (credits)			17
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	2	4	8	13
Interest cost	10	6	31	20
Expected return on plan assets	(23)	(26)	(71)	(80)
Amortization of
Net loss	3	0	9	0
Prior service cost (credit)	(10)	(13)	(30)	(38)
Settlement loss	0	0	0	0
Net periodic credit	$ (18)	$ (29)	$ (53)	$ (85)