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Benefit Plans (Expected Benefit Payments) (Details) $ in Millions | Dec. 31, 2020 USD ($)
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Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | $ 94
Expected benefit payments, 2022 | 96
Expected benefit payments, 2023 | 96
Expected benefit payments, 2024 | 96
Expected benefit payments, 2025 | 97
Expected benefit payments, 2026 - 2030 | 472
Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 76
Expected benefit payments, 2022 | 78
Expected benefit payments, 2023 | 79
Expected benefit payments, 2024 | 79
Expected benefit payments, 2025 | 80
Expected benefit payments, 2026 - 2030 | 398
Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 18
Expected benefit payments, 2022 | 18
Expected benefit payments, 2023 | 17
Expected benefit payments, 2024 | 17
Expected benefit payments, 2025 | 17
Expected benefit payments, 2026 - 2030 | 74
IPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 45
Expected benefit payments, 2022 | 45
Expected benefit payments, 2023 | 46
Expected benefit payments, 2024 | 45
Expected benefit payments, 2025 | 45
Expected benefit payments, 2026 - 2030 | 210
IPL [Member] | Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 38
Expected benefit payments, 2022 | 38
Expected benefit payments, 2023 | 39
Expected benefit payments, 2024 | 38
Expected benefit payments, 2025 | 38
Expected benefit payments, 2026 - 2030 | 181
IPL [Member] | Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 7
Expected benefit payments, 2022 | 7
Expected benefit payments, 2023 | 7
Expected benefit payments, 2024 | 7
Expected benefit payments, 2025 | 7
Expected benefit payments, 2026 - 2030 | 29
WPL [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 39
Expected benefit payments, 2022 | 39
Expected benefit payments, 2023 | 39
Expected benefit payments, 2024 | 40
Expected benefit payments, 2025 | 39
Expected benefit payments, 2026 - 2030 | 191
WPL [Member] | Defined Benefit Pension Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 32
Expected benefit payments, 2022 | 32
Expected benefit payments, 2023 | 32
Expected benefit payments, 2024 | 33
Expected benefit payments, 2025 | 33
Expected benefit payments, 2026 - 2030 | 162
WPL [Member] | Other Postretirement Benefits Plans [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Expected benefit payments, 2021 | 7
Expected benefit payments, 2022 | 7
Expected benefit payments, 2023 | 7
Expected benefit payments, 2024 | 7
Expected benefit payments, 2025 | 6
Expected benefit payments, 2026 - 2030 | $ 29

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