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v3.3.1.900

Fair Value Measurements (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Assets: |  |
Deferred proceeds | $ 172.0 | $ 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3,870.5 | 3,802.8
IPL [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,875.0 | 1,775.0
WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,550.0 | 1,580.6
Level 1 [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
Cumulative preferred stock of IPL | 206.6 | 200.2
Level 1 [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
Cumulative preferred stock of IPL | 206.6 | 200.2
Level 1 [Member] | WPL [Member] |  |
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 1 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 0.0 | 0.0
Liabilities and equity: |  |
Derivatives | 0.0 | 0.0
Level 1 [Member] | Commodity Contracts [Member] | WPL [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) | 4,332.4 | 4,414.9
Cumulative preferred stock of IPL | 0.0 | 0.0
Level 2 [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 0.0 | 0.0
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,092.7 | 2,053.0
Cumulative preferred stock of IPL | 0.0 | 0.0
Level 2 [Member] | WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,793.0 | 1,908.9
Level 2 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 2.5 | 2.6
Liabilities and equity: |  |
Derivatives | 16.0 | 19.5
Level 2 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 2.0 | 2.4
Liabilities and equity: |  |
Derivatives | 8.0 | 13.3
Level 2 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 0.5 | 0.2
Liabilities and equity: |  |
Derivatives | 8.0 | 6.2
Level 3 [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3.7 | 3.3
Cumulative preferred stock of IPL | 0.0 | 0.0
Level 3 [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
Cumulative preferred stock of IPL | 0.0 | 0.0
Level 3 [Member] | WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 0.0 | 0.0
Level 3 [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 15.9 | 36.0
Liabilities and equity: |  |
Derivatives | 48.6 | 18.1
Level 3 [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 13.5 | 25.6
Liabilities and equity: |  |
Derivatives | 15.4 | 6.2
Level 3 [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 2.4 | 10.4
Liabilities and equity: |  |
Derivatives | 33.2 | 11.9
Carrying Value [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 3,835.6 | 3,767.3
Cumulative preferred stock of IPL | 200.0 | 200.0
Carrying Value [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,856.9 | 1,758.0
Cumulative preferred stock of IPL | 200.0 | 200.0
Carrying Value [Member] | WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,533.9 | 1,563.1
Carrying Value [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 18.4 | 38.6
Liabilities and equity: |  |
Derivatives | 64.6 | 37.6
Carrying Value [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 15.5 | 28.0
Liabilities and equity: |  |
Derivatives | 23.4 | 19.5
Carrying Value [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 2.9 | 10.6
Liabilities and equity: |  |
Derivatives | 41.2 | 18.1
Fair Value [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 4,336.1 | 4,418.2
Cumulative preferred stock of IPL | 206.6 | 200.2
Fair Value [Member] | IPL [Member] |  |
Assets: |  |
Deferred proceeds | 172.0 | 177.2
Liabilities and equity: |  |
Long-term debt (including current maturities) | 2,092.7 | 2,053.0
Cumulative preferred stock of IPL | 206.6 | 200.2
Fair Value [Member] | WPL [Member] |  |
Liabilities and equity: |  |
Long-term debt (including current maturities) | 1,793.0 | 1,908.9
Fair Value [Member] | Commodity Contracts [Member] |  |
Assets: |  |
Derivatives | 18.4 | 38.6
Liabilities and equity: |  |
Derivatives | 64.6 | 37.6
Fair Value [Member] | Commodity Contracts [Member] | IPL [Member] |  |
Assets: |  |
Derivatives | 15.5 | 28.0
Liabilities and equity: |  |
Derivatives | 23.4 | 19.5
Fair Value [Member] | Commodity Contracts [Member] | WPL [Member] |  |
Assets: |  |
Derivatives | 2.9 | 10.6
Liabilities and equity: |  |
Derivatives | $ 41.2 | $ 18.1

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