Retirement Benefits (Schedule of Net Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
DB Pension Plans
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	$ 7	$ 7	$ 21	$ 22
Interest cost	26	27	78	80
Expected return on plan assets	(58)	(55)	(176)	(165)
Amortization of:
Net loss	3	2	9	8
Prior service cost (credit)	1	1	3	3
Settlement loss	3	3	8	8
Net periodic credit	(18)	(15)	(57)	(44)
DB Pension Plans | Volatility Mechanism
Amortization of:
Deferred credits			12
DB Pension Plans | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	7	7	20	21
Interest cost	25	24	74	75
Expected return on plan assets	(56)	(52)	(166)	(156)
Amortization of:
Net loss	3	3	8	8
Prior service cost (credit)	1	1	3	3
Settlement loss	3	3	8	8
Net periodic credit	(17)	(14)	(53)	(41)
OPEB Plan
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	2	2	8	8
Interest cost	10	11	32	33
Expected return on plan assets	(28)	(26)	(86)	(77)
Amortization of:
Net loss	1	3	3	9
Prior service cost (credit)	(7)	(10)	(23)	(31)
Settlement loss	0	0	0	0
Net periodic credit	(22)	(20)	(66)	(58)
OPEB Plan | Volatility Mechanism
Amortization of:
Deferred credits			8
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	2	2	8	8
Interest cost	11	10	31	31
Expected return on plan assets	(26)	(23)	(80)	(71)
Amortization of:
Net loss	1	3	3	9
Prior service cost (credit)	(8)	(10)	(23)	(30)
Settlement loss	0	0	0	0
Net periodic credit	$ (20)	$ (18)	$ (61)	$ (53)