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v3.20.2

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Assets: |  |
Money market fund investments | $ 183 | $ 5
Deferred proceeds | 201 | 188
Liabilities: |  |
Long-term debt (incl. current maturities) | 7,851 | 6,920
IPL [Member] |  |
Assets: |  |
Money market fund investments | 183 | 5
Deferred proceeds | 201 | 188
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,987 | 3,489
WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 2,667 | 2,268
Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 48 | 27
Liabilities: |  |
Derivatives | 19 | 38
Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 34 | 22
Liabilities: |  |
Derivatives | 8 | 18
Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 14 | 5
Liabilities: |  |
Derivatives | 11 | 20
Level 1 [Member] |  |
Assets: |  |
Money market fund investments | 183 | 5
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0 | 0
Level 1 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 183 | 5
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 2 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 7,849 | 6,918
Level 2 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 0 | 0
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,987 | 3,489
Level 2 [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 2,667 | 2,268
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 17 | 5
Liabilities: |  |
Derivatives | 18 | 37
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 7 | 3
Liabilities: |  |
Derivatives | 7 | 17
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 10 | 2
Liabilities: |  |
Derivatives | 11 | 20
Level 3 [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 201 | 188
Liabilities: |  |
Long-term debt (incl. current maturities) | 2 | 2
Level 3 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0 | 0
Deferred proceeds | 201 | 188
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 | 31 | 22
Liabilities: |  |
Derivatives | 1 | 1
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 27 | 19
Liabilities: |  |
Derivatives | 1 | 1
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 4 | 3
Liabilities: |  |
Derivatives | 0 | 0
Carrying Amount [Member] |  |
Assets: |  |
Money market fund investments | 183 | 5
Deferred proceeds | 201 | 188
Liabilities: |  |
Long-term debt (incl. current maturities) | 6,581 | 6,190
Carrying Amount [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 183 | 5
Deferred proceeds | 201 | 188
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,344 | 3,147
Carrying Amount [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 2,130 | 1,933
Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 48 | 27
Liabilities: |  |
Derivatives | 19 | 38
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 34 | 22
Liabilities: |  |
Derivatives | 8 | 18
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 14 | 5
Liabilities: |  |
Derivatives | $ 11 | $ 20

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