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Benefit Plans (Expected Benefit Payments) (Details)
$ in Millions
Dec. 31, 2023
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 $ 90
Expected benefit payments, 2025 90
Expected benefit payments, 2026 90
Expected benefit payments, 2027 91
Expected benefit payments, 2028 90
Expected benefit payments, 2029 - 2033 408
Defined Benefit Pension Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 73
Expected benefit payments, 2025 73
Expected benefit payments, 2026 74
Expected benefit payments, 2027 75
Expected benefit payments, 2028 75
Expected benefit payments, 2029 - 2033 343
Other Postretirement Benefits Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 17
Expected benefit payments, 2025 17
Expected benefit payments, 2026 16
Expected benefit payments, 2027 16
Expected benefit payments, 2028 15
Expected benefit payments, 2029 - 2033 65
IPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 41
Expected benefit payments, 2025 41
Expected benefit payments, 2026 41
Expected benefit payments, 2027 39
Expected benefit payments, 2028 39
Expected benefit payments, 2029 - 2033 176
IPL [Member] | Defined Benefit Pension Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 34
Expected benefit payments, 2025 34
Expected benefit payments, 2026 34
Expected benefit payments, 2027 33
Expected benefit payments, 2028 33
Expected benefit payments, 2029 - 2033 151
IPL [Member] | Other Postretirement Benefits Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 7
Expected benefit payments, 2025 7
Expected benefit payments, 2026 7
Expected benefit payments, 2027 6
Expected benefit payments, 2028 6
Expected benefit payments, 2029 - 2033 25
WPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 39
Expected benefit payments, 2025 39
Expected benefit payments, 2026 37
Expected benefit payments, 2027 37
Expected benefit payments, 2028 37
Expected benefit payments, 2029 - 2033 170
WPL [Member] | Defined Benefit Pension Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 32
Expected benefit payments, 2025 32
Expected benefit payments, 2026 31
Expected benefit payments, 2027 31
Expected benefit payments, 2028 31
Expected benefit payments, 2029 - 2033 146
WPL [Member] | Other Postretirement Benefits Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2024 7
Expected benefit payments, 2025 7
Expected benefit payments, 2026 6
Expected benefit payments, 2027 6
Expected benefit payments, 2028 6
Expected benefit payments, 2029 - 2033 $ 24