v3.26.3
Retirement Benefits (Schedule of Net Benefit Costs) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
DB Pension Plans        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost $ 6 $ 6 $ 18 $ 19
Interest cost 25 27 75 81
Expected return on plan assets (60) (57) (179) (171)
Amortization of:        
Net loss 4 3 11 8
Prior service cost (credit) 0 1 2 3
Settlement loss 3 3 8 8
Net periodic credit (22) (17) (65) (52)
DB Pension Plans | Consumers Energy Company        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 6 6 18 18
Interest cost 24 26 71 77
Expected return on plan assets (57) (54) (169) (162)
Amortization of:        
Net loss 4 2 10 7
Prior service cost (credit) 0 1 2 3
Settlement loss 3 3 8 8
Net periodic credit (20) (16) (60) (49)
OPEB Plan        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 2 2 6 6
Interest cost 10 10 29 32
Expected return on plan assets (31) (27) (93) (83)
Amortization of:        
Net loss 0 0 0 2
Prior service cost (credit) (8) (8) (24) (25)
Settlement loss 0 0 0 0
Net periodic credit (27) (23) (82) (68)
OPEB Plan | Consumers Energy Company        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 2 2 6 6
Interest cost 9 11 28 32
Expected return on plan assets (29) (26) (87) (78)
Amortization of:        
Net loss 0 0 0 2
Prior service cost (credit) (7) (8) (23) (25)
Settlement loss 0 0 0 0
Net periodic credit $ (25) $ (21) $ (76) $ (63)