v3.25.2
Retirement Benefits (Schedule of Net Benefit Costs) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
DB Pension Plans        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost $ 7 $ 7 $ 13 $ 14
Interest cost 27 26 54 52
Expected return on plan assets (57) (59) (114) (118)
Amortization of:        
Net loss 2 3 5 6
Prior service cost (credit) 1 1 2 2
Settlement loss 2 2 5 5
Net periodic credit (18) (20) (35) (39)
DB Pension Plans | Consumers Energy Company        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 6 6 12 13
Interest cost 25 25 51 49
Expected return on plan assets (54) (55) (108) (110)
Amortization of:        
Net loss 3 2 5 5
Prior service cost (credit) 1 1 2 2
Settlement loss 2 2 5 5
Net periodic credit (17) (19) (33) (36)
OPEB Plan        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 2 3 4 6
Interest cost 11 11 22 22
Expected return on plan assets (28) (29) (56) (58)
Amortization of:        
Net loss 1 1 2 2
Prior service cost (credit) (8) (8) (17) (16)
Settlement loss 0 0 0 0
Net periodic credit (22) (22) (45) (44)
OPEB Plan | Consumers Energy Company        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 2 3 4 6
Interest cost 11 10 21 20
Expected return on plan assets (26) (27) (52) (54)
Amortization of:        
Net loss 1 1 2 2
Prior service cost (credit) (9) (8) (17) (15)
Settlement loss 0 0 0 0
Net periodic credit $ (21) $ (21) $ (42) $ (41)