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v3.19.3.a.u2

Fair Value Measurements (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Assets: |  |
Deferred proceeds | $ 187.7 | $ 119.4
Liabilities and equity: |  |
Long-term debt (including current maturities) | 6,919.9 | 5,860.8
Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 26.8 | 28.3
Liabilities and equity: |  |
Derivatives | 37.6 | 23.3
Level 1 [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities and equity: |  |
Derivatives | 0.0 | 0.0
Level 2 [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 6,917.9 | 5,858.4
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 4.8 | 8.9
Liabilities and equity: |  |
Derivatives | 36.8 | 16.1
Level 3 [Member] |  |
Assets: |  |
Deferred proceeds | 187.7 | 119.4
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2.0 | 2.4
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 22.0 | 19.4
Liabilities and equity: |  |
Derivatives | 0.8 | 7.2
Carrying Amount [Member] |  |
Assets: |  |
Deferred proceeds | 187.7 | 119.4
Liabilities and equity: |  |
Long-term debt (including current maturities) | 6,190.2 | 5,502.8
Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 26.8 | 28.3
Liabilities and equity: |  |
Derivatives | 37.6 | 23.3
IPL [Member] |  |
Assets: |  |
Deferred proceeds | 187.7 | 119.4
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3,489.1 | 2,691.2
IPL [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 22.3 | 17.7
Liabilities and equity: |  |
Derivatives | 17.4 | 11.2
IPL [Member] | Level 1 [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
IPL [Member] | Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities and equity: |  |
Derivatives | 0.0 | 0.0
IPL [Member] | Level 2 [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3,489.1 | 2,691.2
IPL [Member] | Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 2.8 | 4.0
Liabilities and equity: |  |
Derivatives | 16.6 | 6.5
IPL [Member] | Level 3 [Member] |  |
Assets: |  |
Deferred proceeds | 187.7 | 119.4
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
IPL [Member] | Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 19.5 | 13.7
Liabilities and equity: |  |
Derivatives | 0.8 | 4.7
IPL [Member] | Carrying Amount [Member] |  |
Assets: |  |
Deferred proceeds | 187.7 | 119.4
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3,147.3 | 2,552.3
IPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 22.3 | 17.7
Liabilities and equity: |  |
Derivatives | 17.4 | 11.2
WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,268.2 | 2,043.7
WPL [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 4.5 | 10.6
Liabilities and equity: |  |
Derivatives | 20.2 | 12.1
WPL [Member] | Level 1 [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
WPL [Member] | Level 1 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities and equity: |  |
Derivatives | 0.0 | 0.0
WPL [Member] | Level 2 [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,268.2 | 2,043.7
WPL [Member] | Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 2.0 | 4.9
Liabilities and equity: |  |
Derivatives | 20.2 | 9.6
WPL [Member] | Level 3 [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
WPL [Member] | Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 2.5 | 5.7
Liabilities and equity: |  |
Derivatives | 0.0 | 2.5
WPL [Member] | Carrying Amount [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,932.7 | 1,834.9
WPL [Member] | Carrying Amount [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 4.5 | 10.6
Liabilities and equity: |  |
Derivatives | $ 20.2 | $ 12.1

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