v3.26.1
Retirement Benefits (Schedule of Net Benefit Costs) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
DB Pension Plans        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost $ 6 $ 7 $ 12 $ 13
Interest cost 25 27 50 54
Expected return on plan assets (59) (57) (119) (114)
Amortization of:        
Net loss 3 2 7 5
Prior service cost (credit) 1 1 2 2
Settlement loss 2 2 5 5
Net periodic credit (22) (18) (43) (35)
DB Pension Plans | Consumers Energy Company        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 6 6 12 12
Interest cost 24 25 47 51
Expected return on plan assets (56) (54) (112) (108)
Amortization of:        
Net loss 3 3 6 5
Prior service cost (credit) 1 1 2 2
Settlement loss 2 2 5 5
Net periodic credit (20) (17) (40) (33)
OPEB Plan        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 2 2 4 4
Interest cost 9 11 19 22
Expected return on plan assets (31) (28) (62) (56)
Amortization of:        
Net loss 0 1 0 2
Prior service cost (credit) (8) (8) (16) (17)
Settlement loss 0 0 0 0
Net periodic credit (28) (22) (55) (45)
OPEB Plan | Consumers Energy Company        
Defined Benefit Plan, Roll Forwards [Abstract]        
Service cost 2 2 4 4
Interest cost 9 11 19 21
Expected return on plan assets (29) (26) (58) (52)
Amortization of:        
Net loss 0 1 0 2
Prior service cost (credit) (8) (9) (16) (17)
Settlement loss 0 0 0 0
Net periodic credit $ (26) $ (21) $ (51) $ (42)