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Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
--- | --- | ---
Deferred tax liabilities, gross | $ 2,647.7 | $ 2,507.0
Deferred tax assets, valuation allowance | 0 | 1.9
Deferred tax assets, net of valuation allowance | 671.7 | 743.0
Deferred tax liabilities, net of deferred tax assets and valuation allowance | 1,976.0 | 1,764.0
Current deferred tax assets | (136.7) | (170.2)
Non-current deferred tax liabilities | 2,112.7 | 1,934.2
IPL [Member] |  |
Deferred tax assets, gross | (336.0) | (383.4)
Deferred tax liabilities, gross | 1,441.3 | 1,391.4
Deferred tax assets and liabilities, net | 1,105.3 | 1,008.0
Deferred tax liabilities, net of deferred tax assets and valuation allowance | 1,105.3 | 1,008.0
Current deferred tax assets | (87.7) | (79.3)
Non-current deferred tax liabilities | 1,193.0 | 1,087.3
WPL [Member] |  |
Deferred tax assets, gross | (201.6) | (222.8)
Deferred tax liabilities, gross | 1,055.4 | 981.3
Deferred tax assets and liabilities, net | 853.8 | 758.5
Deferred tax liabilities, net of deferred tax assets and valuation allowance | 853.8 | 758.5
Current deferred tax assets | (43.3) | (85.6)
Non-current deferred tax liabilities | 897.1 | 844.1
Property [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 2,316.3 | 2,143.8
Deferred tax assets and liabilities, net | 2,316.3 | 2,143.8
Property [Member] | IPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 1,338.1 | 1,243.9
Deferred tax assets and liabilities, net | 1,338.1 | 1,243.9
Property [Member] | WPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 859.1 | 793.3
Deferred tax assets and liabilities, net | 859.1 | 793.3
Investment In ATC [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 120.7 | 104.3
Deferred tax assets and liabilities, net | 120.7 | 104.3
Investment In ATC [Member] | WPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 120.7 | 104.3
Deferred tax assets and liabilities, net | 120.7 | 104.3
Net operating losses carryforward - state [Member] |  |
Deferred tax assets, gross | (35.3) | (46.8)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (35.3) | (46.8)
Regulatory liability - IPL's tax benefit riders [Member] |  |
Deferred tax assets, gross | (107.8) | (144.6)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (107.8) | (144.6)
Regulatory liability - IPL's tax benefit riders [Member] | IPL [Member] |  |
Deferred tax assets, gross | (107.8) | (144.6)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (107.8) | (144.6)
Federal credit carryforward [Member] |  |
Deferred tax assets, gross | (167.8) | (133.8)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (167.8) | (133.8)
Federal credit carryforward [Member] | IPL [Member] |  |
Deferred tax assets, gross | (52.9) | (37.4)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (52.9) | (37.4)
Federal credit carryforward [Member] | WPL [Member] |  |
Deferred tax assets, gross | (57.1) | (39.4)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (57.1) | (39.4)
Net operating losses carryforward - federal [Member] |  |
Deferred tax assets, gross | (251.9) | (306.0)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (251.9) | (306.0)
Net operating losses carryforward - federal [Member] | IPL [Member] |  |
Deferred tax assets, gross | (111.3) | (131.0)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (111.3) | (131.0)
Net operating losses carryforward - federal [Member] | WPL [Member] |  |
Deferred tax assets, gross | (106.9) | (142.2)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (106.9) | (142.2)
Other [Member] |  |
Deferred tax assets, gross | (108.9) | (113.7)
Deferred tax liabilities, gross | 210.7 | 258.9
Deferred tax assets and liabilities, net | 101.8 | 145.2
Other [Member] | IPL [Member] |  |
Deferred tax assets, gross | (64.0) | (70.4)
Deferred tax liabilities, gross | 103.2 | 147.5
Deferred tax assets and liabilities, net | 39.2 | 77.1
Other [Member] | WPL [Member] |  |
Deferred tax assets, gross | (37.6) | (41.2)
Deferred tax liabilities, gross | 75.6 | 83.7
Deferred tax assets and liabilities, net | 38.0 | 42.5
Subtotal [Member] |  |
Deferred tax assets, gross | (671.7) | (744.9)
Deferred tax liabilities, gross | 2,647.7 | 2,507.0
Deferred tax assets and liabilities, net | $ 1,976.0 | $ 1,762.1

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