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Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions | Mar. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Carrying Amount [Member] |  |
Assets: |  |
Money market fund investments | $ 10 | $ 45
Deferred proceeds | 184 | 216
Liabilities: |  |
Long-term debt (incl. current maturities) | 9,333 | 9,034
Carrying Amount [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 6 | 45
Deferred proceeds | 184 | 216
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,945 | 3,945
Carrying Amount [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,367 | 3,070
Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 56 | 88
Liabilities: |  |
Derivatives | 94 | 98
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 34 | 54
Liabilities: |  |
Derivatives | 30 | 30
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 22 | 34
Liabilities: |  |
Derivatives | 64 | 68
Carrying Amount [Member] | Interest Rate Swap [Member] |  |
Assets: |  |
Derivatives | 3 | 1
Money market fund investments | 10 | 45
Deferred proceeds | 184 | 216
Liabilities: |  |
Long-term debt (incl. current maturities) | 9,051 | 8,677
IPL [Member] |  |
Assets: |  |
Money market fund investments | 6 | 45
Deferred proceeds | 184 | 216
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,607 | 3,664
WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,176 | 2,933
Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 56 | 88
Liabilities: |  |
Derivatives | 94 | 98
Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 34 | 54
Liabilities: |  |
Derivatives | 30 | 30
Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 22 | 34
Liabilities: |  |
Derivatives | 64 | 68
Interest Rate Swap [Member] |  |
Assets: |  |
Derivatives | 3 | 1
Level 1 [Member] |  |
Assets: |  |
Money market fund investments | 10 | 45
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 1 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 6 | 45
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 1 [Member] | WPL [Member] |  |
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 1 [Member] | Interest Rate Swap [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Level 2 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 9,051 | 8,677
Level 2 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,607 | 3,664
Level 2 [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,176 | 2,933
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 46 | 59
Liabilities: |  |
Derivatives | 91 | 93
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 26 | 30
Liabilities: |  |
Derivatives | 27 | 25
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 20 | 29
Liabilities: |  |
Derivatives | 64 | 68
Level 2 [Member] | Interest Rate Swap [Member] |  |
Assets: |  |
Derivatives | 3 | 1
Level 3 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 184 | 216
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 3 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 184 | 216
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 3 [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 10 | 29
Liabilities: |  |
Derivatives | 3 | 5
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 8 | 24
Liabilities: |  |
Derivatives | 3 | 5
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 2 | 5
Liabilities: |  |
Derivatives | 0 | 0
Level 3 [Member] | Interest Rate Swap [Member] |  |
Assets: |  |
Derivatives | $ 0 | $ 0

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