v3.25.2
Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Defined benefit pension plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 1 $ 1 $ 2 $ 2
Interest cost 12 11 23 22
Expected return on plan assets (14) (14) (27) (27)
Amortization of actuarial loss 5 6 11 12
Total 4 4 9 9
OPEB Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 1 1 1 1
Interest cost 2 2 4 4
Expected return on plan assets (2) (1) (3) (2)
Amortization of actuarial loss 0 0 0 0
Total 1 2 2 3
IPL [Member] | Defined benefit pension plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 0 1 1
Interest cost 5 5 10 10
Expected return on plan assets (6) (6) (12) (13)
Amortization of actuarial loss 2 3 4 5
Total 1 2 3 3
IPL [Member] | OPEB Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 0 0 0
Interest cost 1 1 2 2
Expected return on plan assets (1) (1) (2) (2)
Amortization of actuarial loss 0 0 0 0
Total 0 0 0 0
WPL [Member] | Defined benefit pension plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 1 1 1 1
Interest cost 5 5 10 10
Expected return on plan assets (6) (6) (12) (12)
Amortization of actuarial loss 2 3 5 6
Total 2 3 4 5
WPL [Member] | OPEB Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 0 0 0
Interest cost 0 1 1 2
Expected return on plan assets 0 0 0 0
Amortization of actuarial loss 0 0 0 0
Total $ 0 $ 1 $ 1 $ 2