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Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Deferred tax liabilities, property | $ 1,852.7 | $ 2,919.0
Deferred tax liabilities, other | 75.9 | 95.1
Total deferred tax liabilities | 2,015.0 | 3,167.2
Deferred tax assets, federal credit carryforwards | 260.7 | 268.4
Deferred tax assets, net operating losses carryforwards - federal | 174.4 | 173.3
Deferred tax assets, net operating losses carryforwards - state | 41.3 | 32.9
Deferred tax assets, other | 61.8 | 87.9
Subtotal deferred tax assets | 545.6 | 597.2
Deferred tax assets, valuation allowance | (9.0) | (0.2)
Total deferred tax assets | 536.6 | 597.0
Total deferred tax liabilities, net | 1,478.4 | 2,570.2
IPL [Member] |  |
Deferred tax liabilities, property | 1,102.6 | 1,677.0
Deferred tax liabilities, other | 63.4 | 71.4
Total deferred tax liabilities | 1,166.0 | 1,748.4
Deferred tax assets, federal credit carryforwards | 113.1 | 95.9
Deferred tax assets, net operating losses carryforwards - federal | 107.4 | 69.6
Deferred tax assets, net operating losses carryforwards - state | 0.9 | 0.6
Deferred tax assets, other | 27.1 | 35.8
Subtotal deferred tax assets | 255.9 | 236.6
Deferred tax assets, valuation allowance | (0.6) | 0.0
Total deferred tax assets | 255.3 | 236.6
Total deferred tax liabilities, net | 910.7 | 1,511.8
WPL [Member] |  |
Deferred tax liabilities, property | 674.2 | 1,124.5
Deferred tax liabilities, other | 36.5 | 58.8
Total deferred tax liabilities | 710.7 | 1,183.3
Deferred tax assets, federal credit carryforwards | 131.0 | 112.9
Deferred tax assets, net operating losses carryforwards - federal | 43.7 | 75.4
Deferred tax assets, net operating losses carryforwards - state | 0.2 | 0.1
Deferred tax assets, other | 14.7 | 23.6
Subtotal deferred tax assets | 189.6 | 212.0
Deferred tax assets, valuation allowance | (1.3) | (0.3)
Total deferred tax assets | 188.3 | 211.7
Total deferred tax liabilities, net | 522.4 | 971.6
ATC Investment [Member] |  |
Deferred tax liabilities, ATC Investment | 86.4 | 153.1
IPL's tax benefit riders [Member] |  |
Deferred tax assets, regulatory liability - IPL's tax benefit riders | 7.4 | 34.7
IPL's tax benefit riders [Member] | IPL [Member] |  |
Deferred tax assets, regulatory liability - IPL's tax benefit riders | $ 7.4 | $ 34.7

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