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v3.25.3

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Carrying Amount [Member] |  |
Assets: |  |
Money market fund investments | $ 477 | $ 52
Time deposits | 250 | 0
Deferred proceeds | 231 | 163
Liabilities: |  |
Long-term debt (incl. current maturities) | 11,729 | 9,848
Carrying Amount [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 194 | 9
Deferred proceeds | 231 | 163
Liabilities: |  |
Long-term debt (incl. current maturities) | 4,679 | 4,090
Carrying Amount [Member] | WPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 43
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,372 | 3,370
Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 82 | 75
Liabilities: |  |
Derivatives | 48 | 58
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 52 | 48
Liabilities: |  |
Derivatives | 10 | 13
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 30 | 27
Liabilities: |  |
Derivatives | 38 | 45
Money market fund investments | 477 | 52
Time deposits | 250 | 0
Deferred proceeds | 231 | 163
Long-term debt (incl. current maturities) | 11,504 | 9,577
IPL [Member] |  |
Assets: |  |
Money market fund investments | 194 | 9
Deferred proceeds | 231 | 163
Liabilities: |  |
Long-term debt (incl. current maturities) | 4,465 | 3,736
WPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 43
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,287 | 3,170
Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 82 | 75
Liabilities: |  |
Derivatives | 48 | 58
Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 52 | 48
Liabilities: |  |
Derivatives | 10 | 13
Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 30 | 27
Liabilities: |  |
Derivatives | 38 | 45
Level 1 [Member] |  |
Assets: |  |
Money market fund investments | 477 | 52
Time deposits | 0 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 1 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 194 | 9
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 1 [Member] | WPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 43
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Liabilities: |  |
Derivatives | 0 | 0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Liabilities: |  |
Derivatives | 0 | 0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Liabilities: |  |
Derivatives | 0 | 0
Level 2 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Time deposits | 250 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 11,504 | 9,577
Level 2 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 4,465 | 3,736
Level 2 [Member] | WPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,287 | 3,170
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 42 | 48
Liabilities: |  |
Derivatives | 47 | 56
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 21 | 26
Liabilities: |  |
Derivatives | 9 | 11
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 21 | 22
Liabilities: |  |
Derivatives | 38 | 45
Level 3 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Time deposits | 0 | 0
Deferred proceeds | 231 | 163
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 3 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 231 | 163
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 3 [Member] | WPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 40 | 27
Liabilities: |  |
Derivatives | 1 | 2
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 31 | 22
Liabilities: |  |
Derivatives | 1 | 2
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 9 | 5
Liabilities: |  |
Derivatives | $ 0 | $ 0

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