Retirement Benefits (Schedule of Net Benefit Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
DB Pension Plans and DB SERP
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	$ 25	$ 28	$ 29
Interest cost	114	109	112
Expected return on plan assets	(229)	(234)	(220)
Amortization of:
Net loss	11	12	12
Prior service cost (credit)	4	4	4
Settlement loss	11	11	11
Net periodic credit	(64)	(70)	(52)
DB Pension Plans and DB SERP | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	24	27	28
Interest cost	106	102	105
Expected return on plan assets	(215)	(221)	(208)
Amortization of:
Net loss	10	11	11
Prior service cost (credit)	4	4	4
Settlement loss	11	11	11
Net periodic credit	(60)	(66)	(49)
OPEB Plan
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	8	11	12
Interest cost	43	43	44
Expected return on plan assets	(111)	(115)	(103)
Amortization of:
Net loss	3	4	12
Prior service cost (credit)	(34)	(31)	(41)
Settlement loss	0	0	0
Net periodic credit	(91)	(88)	(76)
OPEB Plan | Consumers Energy Company
Defined Benefit Plan, Roll Forwards [Abstract]
Service cost	8	11	11
Interest cost	42	41	42
Expected return on plan assets	(104)	(107)	(95)
Amortization of:
Net loss	3	4	12
Prior service cost (credit)	(33)	(30)	(40)
Settlement loss	0	0	0
Net periodic credit	$ (84)	$ (81)	$ (70)