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Benefit Plans (Accumulated Benefit Obligations) (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Pension Plans, Defined Benefit [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligations | $ 824 | $ 857
Plans with accumulated benefit obligations in excess of plan assets: |  |
Accumulated benefit obligations | 824 | 857
Fair value of plan assets | 715 | 732
Plans with projected benefit obligations in excess of plan assets: |  |
Projected benefit obligations | 841 | 876
Fair value of plan assets | 715 | 732
Other Postretirement Benefits Plans [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligations | 148 | 160
Plans with accumulated benefit obligations in excess of plan assets: |  |
Accumulated benefit obligations | 148 | 160
Fair value of plan assets | 80 | 83
IPL [Member] | Pension Plans, Defined Benefit [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligations | 362 | 377
Plans with accumulated benefit obligations in excess of plan assets: |  |
Accumulated benefit obligations | 362 | 377
Fair value of plan assets | 340 | 352
Plans with projected benefit obligations in excess of plan assets: |  |
Projected benefit obligations | 372 | 387
Fair value of plan assets | 340 | 352
IPL [Member] | Other Postretirement Benefits Plans [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligations | 59 | 65
Plans with accumulated benefit obligations in excess of plan assets: |  |
Accumulated benefit obligations |  | 65
Fair value of plan assets |  | 61
WPL [Member] | Pension Plans, Defined Benefit [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligations | 358 | 373
Plans with accumulated benefit obligations in excess of plan assets: |  |
Accumulated benefit obligations | 358 | 373
Fair value of plan assets | 303 | 306
Plans with projected benefit obligations in excess of plan assets: |  |
Projected benefit obligations | 365 | 381
Fair value of plan assets | 303 | 306
WPL [Member] | Other Postretirement Benefits Plans [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligations | 56 | 61
Plans with accumulated benefit obligations in excess of plan assets: |  |
Accumulated benefit obligations | 56 | 61
Fair value of plan assets | $ 13 | $ 14

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