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Benefit Plans (Defined Benefit Pension And Other Postretirement Benefits Plans) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2025
Sep. 30, 2024
Defined benefit pension plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 1 $ 1 $ 3 $ 3
Interest cost 11 12 34 34
Expected return on plan assets (13) (14) (40) (41)
Amortization of prior service credit (1) 0 (1) 0
Amortization of actuarial loss 6 6 17 18
Total 4 5 13 14
OPEB Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 1 1 2
Interest cost 2 2 6 6
Expected return on plan assets 0 (2) (3) (4)
Amortization of prior service credit 0 0 0 0
Amortization of actuarial loss 0 0 0 0
Total 2 1 4 4
IPL [Member] | Defined benefit pension plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 1 1 2 2
Interest cost 5 5 15 15
Expected return on plan assets (7) (7) (19) (20)
Amortization of actuarial loss 3 2 7 7
Total 2 1 5 4
IPL [Member] | OPEB Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 0 0 0
Interest cost 0 1 2 3
Expected return on plan assets (1) (1) (3) (3)
Amortization of actuarial loss 0 0 0 0
Total (1) 0 (1) 0
WPL [Member] | Defined benefit pension plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 0 1 1
Interest cost 5 5 15 15
Expected return on plan assets (5) (6) (17) (18)
Amortization of actuarial loss 3 3 8 9
Total 3 2 7 7
WPL [Member] | OPEB Plans [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 0 0 0 0
Interest cost 1 1 2 3
Expected return on plan assets (1) (1) (1) (1)
Amortization of actuarial loss 0 0 0 0
Total $ 0 $ 0 $ 1 $ 2