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Income Taxes (Schedule Of Impacts Of the Tax Cuts and Jobs Act of 2017) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($)
Income Tax [Line Items] |
Other current assets | $ 0.0
Investments, ATC Investment | (75.0)
Other assets, regulatory assets | (387.6)
Other assets, deferred charges and other | 41.0
Total Tax Reform impact on assets | (421.6)
Other liabilities, deferred tax liabilities | (1,331.9)
Other liabilities, regulatory liabilities | 885.9
Other liabilities, other | 6.3
Total Tax Reform impact on liabilities | (439.7)
Income tax expense (benefit) | (18.1)
IPL [Member] |
Income Tax [Line Items] |
Other current assets | 4.7
Investments, ATC Investment | 0.0
Other assets, regulatory assets | (375.0)
Other assets, deferred charges and other | 0.0
Total Tax Reform impact on assets | (370.3)
Other liabilities, deferred tax liabilities | (757.2)
Other liabilities, regulatory liabilities | 390.7
Other liabilities, other | 0.0
Total Tax Reform impact on liabilities | (366.5)
Income tax expense (benefit) | 3.8
WPL [Member] |
Income Tax [Line Items] |
Other current assets | (1.4)
Investments, ATC Investment | 0.0
Other assets, regulatory assets | (12.7)
Other assets, deferred charges and other | 0.0
Total Tax Reform impact on assets | (14.1)
Other liabilities, deferred tax liabilities | (523.8)
Other liabilities, regulatory liabilities | 495.2
Other liabilities, other | 0.0
Total Tax Reform impact on liabilities | (28.6)
Income tax expense (benefit) | $ (14.5)

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