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v3.19.3

Fair Value Measurements (Fair Value Measurements) (Details) - USD ($) $ in Millions | Sep. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Assets: |  |
Money market fund investments | $ 174.4 | $ 0.0
Deferred proceeds | 237.0 | 119.4
Liabilities: |  |
Long-term debt (incl. current maturities) | 7,018.4 | 5,860.8
IPL [Member] |  |
Assets: |  |
Money market fund investments | 173.7 | 0.0
Deferred proceeds | 237.0 | 119.4
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,537.0 | 2,691.2
WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 2,314.1 | 2,043.7
Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 30.3 | 28.3
Liabilities: |  |
Derivatives | 31.8 | 23.3
Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 23.3 | 17.7
Liabilities: |  |
Derivatives | 13.4 | 11.2
Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 7.0 | 10.6
Liabilities: |  |
Derivatives | 18.4 | 12.1
Level 1 [Member] |  |
Assets: |  |
Money market fund investments | 174.4 | 0.0
Deferred proceeds | 0.0 | 0.0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0.0 | 0.0
Level 1 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 173.7 | 0.0
Deferred proceeds | 0.0 | 0.0
Liabilities: |  |
Long-term debt (incl. current maturities) | 0.0 | 0.0
Level 1 [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 0.0 | 0.0
Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities: |  |
Derivatives | 0.0 | 0.0
Level 1 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities: |  |
Derivatives | 0.0 | 0.0
Level 1 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities: |  |
Derivatives | 0.0 | 0.0
Level 2 [Member] |  |
Assets: |  |
Money market fund investments | 0.0 | 0.0
Deferred proceeds | 0.0 | 0.0
Liabilities: |  |
Long-term debt (incl. current maturities) | 7,016.4 | 5,858.4
Level 2 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0.0 | 0.0
Deferred proceeds | 0.0 | 0.0
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,537.0 | 2,691.2
Level 2 [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 2,314.1 | 2,043.7
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 8.1 | 8.9
Liabilities: |  |
Derivatives | 31.3 | 16.1
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 4.8 | 4.0
Liabilities: |  |
Derivatives | 12.9 | 6.5
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 3.3 | 4.9
Liabilities: |  |
Derivatives | 18.4 | 9.6
Level 3 [Member] |  |
Assets: |  |
Money market fund investments | 0.0 | 0.0
Deferred proceeds | 237.0 | 119.4
Liabilities: |  |
Long-term debt (incl. current maturities) | 2.0 | 2.4
Level 3 [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 0.0 | 0.0
Deferred proceeds | 237.0 | 119.4
Liabilities: |  |
Long-term debt (incl. current maturities) | 0.0 | 0.0
Level 3 [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 0.0 | 0.0
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 22.2 | 19.4
Liabilities: |  |
Derivatives | 0.5 | 7.2
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 18.5 | 13.7
Liabilities: |  |
Derivatives | 0.5 | 4.7
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 3.7 | 5.7
Liabilities: |  |
Derivatives | 0.0 | 2.5
Carrying Amount [Member] |  |
Assets: |  |
Money market fund investments | 174.4 | 0.0
Deferred proceeds | 237.0 | 119.4
Liabilities: |  |
Long-term debt (incl. current maturities) | 6,191.9 | 5,502.8
Carrying Amount [Member] | IPL [Member] |  |
Assets: |  |
Money market fund investments | 173.7 | 0.0
Deferred proceeds | 237.0 | 119.4
Liabilities: |  |
Long-term debt (incl. current maturities) | 3,146.8 | 2,552.3
Carrying Amount [Member] | WPL [Member] |  |
Liabilities: |  |
Long-term debt (incl. current maturities) | 1,932.3 | 1,834.9
Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 30.3 | 28.3
Liabilities: |  |
Derivatives | 31.8 | 23.3
Carrying Amount [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 23.3 | 17.7
Liabilities: |  |
Derivatives | 13.4 | 11.2
Carrying Amount [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 7.0 | 10.6
Liabilities: |  |
Derivatives | $ 18.4 | $ 12.1

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