v3.25.4
Retirement Benefits (Schedule of Funded Status of Retirement Benefit Plans) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
DB Pension Plans      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of period $ 2,094 $ 2,195  
Service cost 25 28  
Interest cost 109 104  
Plan amendments 0 0  
Actuarial loss (gain) 53 (91)  
Benefits paid (158) (142)  
Benefit obligation at end of period 2,123 2,094 $ 2,195
Defined Benefit Plan, Roll Forwards [Abstract]      
Plan assets at fair value at beginning of period 2,964 3,004  
Actual return on plan assets 371 102  
Company contribution 0 0  
Actual benefits paid (158) (142)  
Plan assets at fair value at end of period 3,177 2,964 3,004
Funded status 1,054 870  
DB Pension Plans | Consumers Energy Company      
Defined Benefit Plan, Roll Forwards [Abstract]      
Funded status 1,000 836  
DB SERP      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of period 105 114  
Service cost 0 0  
Interest cost 5 5  
Plan amendments 0 0  
Actuarial loss (gain) 4 (4)  
Benefits paid (10) (10)  
Benefit obligation at end of period 104 105 114
Defined Benefit Plan, Roll Forwards [Abstract]      
Plan assets at fair value at beginning of period 0 0  
Actual return on plan assets 0 0  
Company contribution 10 10  
Actual benefits paid (10) (10)  
Plan assets at fair value at end of period 0 0 0
Funded status (104) (105)  
DB SERP | Consumers Energy Company      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of period 76 83  
Service cost 0 0  
Interest cost 4 4  
Plan amendments 0 0  
Actuarial loss (gain) 3 (4)  
Benefits paid (7) (7)  
Benefit obligation at end of period 76 76 83
Defined Benefit Plan, Roll Forwards [Abstract]      
Plan assets at fair value at beginning of period 0 0  
Actual return on plan assets 0 0  
Company contribution 7 7  
Actual benefits paid (7) (7)  
Plan assets at fair value at end of period 0 0 0
Funded status (76) (76)  
OPEB Plan      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of period 831 900  
Service cost 8 11 12
Interest cost 43 43 44
Plan amendments 0 (25)  
Actuarial loss (gain) 2 (40)  
Benefits paid (54) (58)  
Benefit obligation at end of period 830 831 900
Defined Benefit Plan, Roll Forwards [Abstract]      
Plan assets at fair value at beginning of period 1,588 1,559  
Actual return on plan assets 197 86  
Company contribution 0 0  
Actual benefits paid (52) (57)  
Plan assets at fair value at end of period 1,733 1,588 1,559
Funded status 903 757  
OPEB Plan | Consumers Energy Company      
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]      
Benefit obligation at beginning of period 801 867  
Service cost 8 11 11
Interest cost 42 41 42
Plan amendments 0 (24)  
Actuarial loss (gain) 1 (38)  
Benefits paid (51) (56)  
Benefit obligation at end of period 801 801 867
Defined Benefit Plan, Roll Forwards [Abstract]      
Plan assets at fair value at beginning of period 1,479 1,453  
Actual return on plan assets 184 80  
Company contribution 0 0  
Actual benefits paid (50) (54)  
Plan assets at fair value at end of period 1,613 1,479 $ 1,453
Funded status $ 812 $ 678