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Income Taxes (Narrative) (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2017 USD ($)
Income Taxes [Line Items] |
Increase in deferred tax liabilities | $ 204.5
IPL [Member] |
Income Taxes [Line Items] |
Increase in deferred tax liabilities | 131.7
WPL [Member] |
Income Taxes [Line Items] |
Increase in deferred tax liabilities | $ 63.6

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- Details
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