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Benefit Plans (Expected Benefit Payments) (Details)
$ in Millions
Dec. 31, 2021
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 $ 103
Expected benefit payments, 2023 100
Expected benefit payments, 2024 99
Expected benefit payments, 2025 99
Expected benefit payments, 2026 99
Expected benefit payments, 2027 - 2031 458
Defined Benefit Pension Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 85
Expected benefit payments, 2023 83
Expected benefit payments, 2024 82
Expected benefit payments, 2025 82
Expected benefit payments, 2026 83
Expected benefit payments, 2027 - 2031 387
Other Postretirement Benefits Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 18
Expected benefit payments, 2023 17
Expected benefit payments, 2024 17
Expected benefit payments, 2025 17
Expected benefit payments, 2026 16
Expected benefit payments, 2027 - 2031 71
IPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 48
Expected benefit payments, 2023 47
Expected benefit payments, 2024 46
Expected benefit payments, 2025 46
Expected benefit payments, 2026 45
Expected benefit payments, 2027 - 2031 202
IPL [Member] | Defined Benefit Pension Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 41
Expected benefit payments, 2023 40
Expected benefit payments, 2024 39
Expected benefit payments, 2025 39
Expected benefit payments, 2026 38
Expected benefit payments, 2027 - 2031 174
IPL [Member] | Other Postretirement Benefits Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 7
Expected benefit payments, 2023 7
Expected benefit payments, 2024 7
Expected benefit payments, 2025 7
Expected benefit payments, 2026 7
Expected benefit payments, 2027 - 2031 28
WPL [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 44
Expected benefit payments, 2023 43
Expected benefit payments, 2024 42
Expected benefit payments, 2025 42
Expected benefit payments, 2026 40
Expected benefit payments, 2027 - 2031 190
WPL [Member] | Defined Benefit Pension Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 37
Expected benefit payments, 2023 36
Expected benefit payments, 2024 35
Expected benefit payments, 2025 35
Expected benefit payments, 2026 34
Expected benefit payments, 2027 - 2031 163
WPL [Member] | Other Postretirement Benefits Plans [Member]  
Defined Benefit Plan Disclosure [Line Items]  
Expected benefit payments, 2022 7
Expected benefit payments, 2023 7
Expected benefit payments, 2024 7
Expected benefit payments, 2025 7
Expected benefit payments, 2026 6
Expected benefit payments, 2027 - 2031 $ 27