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Fair Value Measurements (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Assets: |  |
Money market fund investments | $ 32 | $ 44
Deferred proceeds | 214 | 188
Liabilities and equity: |  |
Long-term debt (including current maturities) | 8,330 | 8,109
Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 176 | 34
Liabilities and equity: |  |
Derivatives | 9 | 25
Level 1 [Member] |  |
Assets: |  |
Money market fund investments | 32 | 44
Deferred proceeds | 0 | 0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0 | 0
Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Liabilities and equity: |  |
Derivatives | 0 | 0
Level 2 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 8,329 | 8,107
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 146 | 5
Liabilities and equity: |  |
Derivatives | 8 | 25
Level 3 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 214 | 188
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1 | 2
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 30 | 29
Liabilities and equity: |  |
Derivatives | 1 | 0
Carrying Amount [Member] |  |
Assets: |  |
Money market fund investments | 32 | 44
Deferred proceeds | 214 | 188
Liabilities and equity: |  |
Long-term debt (including current maturities) | 7,368 | 6,777
Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 176 | 34
Liabilities and equity: |  |
Derivatives | 9 | 25
IPL [Member] |  |
Assets: |  |
Money market fund investments | 32 | 44
Deferred proceeds | 214 | 188
Liabilities and equity: |  |
Long-term debt (including current maturities) | 4,124 | 4,021
IPL [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 84 | 29
Liabilities and equity: |  |
Derivatives | 4 | 12
IPL [Member] | Level 1 [Member] |  |
Assets: |  |
Money market fund investments | 32 | 44
Deferred proceeds | 0 | 0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0 | 0
IPL [Member] | Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Liabilities and equity: |  |
Derivatives | 0 | 0
IPL [Member] | Level 2 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 4,124 | 4,021
IPL [Member] | Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 65 | 3
Liabilities and equity: |  |
Derivatives | 3 | 12
IPL [Member] | Level 3 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 214 | 188
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0 | 0
IPL [Member] | Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 19 | 26
Liabilities and equity: |  |
Derivatives | 1 | 0
IPL [Member] | Carrying Amount [Member] |  |
Assets: |  |
Money market fund investments | 32 | 44
Deferred proceeds | 214 | 188
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3,643 | 3,345
IPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 84 | 29
Liabilities and equity: |  |
Derivatives | 4 | 12
WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,862 | 2,690
WPL [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 92 | 5
Liabilities and equity: |  |
Derivatives | 5 | 13
WPL [Member] | Level 1 [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0 | 0
WPL [Member] | Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0 | 0
Liabilities and equity: |  |
Derivatives | 0 | 0
WPL [Member] | Level 2 [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,862 | 2,690
WPL [Member] | Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 81 | 2
Liabilities and equity: |  |
Derivatives | 5 | 13
WPL [Member] | Level 3 [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0 | 0
WPL [Member] | Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 11 | 3
Liabilities and equity: |  |
Derivatives | 0 | 0
WPL [Member] | Carrying Amount [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,429 | 2,130
WPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 92 | 5
Liabilities and equity: |  |
Derivatives | $ 5 | $ 13

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