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Income Taxes (Narrative) (Details) $ in Millions | 3 Months Ended
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Mar. 31, 2017 USD ($)
Income Taxes [Line Items] |
Increase in deferred tax liabilities | $ 55.7
IPL [Member] |
Income Taxes [Line Items] |
Increase in deferred tax liabilities | 41.4
WPL [Member] |
Income Taxes [Line Items] |
Increase in deferred tax liabilities | $ 13.1

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- Details
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