v2.4.0.6

Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
--- | --- | ---
Deferred tax liabilities, gross | $ 2,507.0 | $ 2,320.4
Deferred tax assets, valuation allowance | 1.9 | 1.2
Deferred tax assets, net of valuation allowance | 743.0 | 751.0
Deferred tax liabilities, net of deferred tax assets and valuation allowance | 1,764.0 | 1,569.4
Other current assets | (170.2) | (22.8)
Deferred income taxes | 1,934.2 | 1,592.2
IPL [Member] |  |
Deferred tax assets, gross | (383.4) | (396.5)
Deferred tax liabilities, gross | 1,391.4 | 1,319.9
Deferred tax assets and liabilities, net | 1,008.0 | 923.4
Deferred tax liabilities, net of deferred tax assets and valuation allowance | 1,008.0 | 923.4
Other current assets | (79.3) | (13.5)
Deferred income taxes | 1,087.3 | 936.9
WPL [Member] |  |
Deferred tax assets, gross | (222.8) | (208.1)
Deferred tax liabilities, gross | 981.3 | 874.6
Deferred tax assets and liabilities, net | 758.5 | 666.5
Deferred tax liabilities, net of deferred tax assets and valuation allowance | 758.5 | 666.5
Other current assets | (85.6) | (6.0)
Deferred income taxes | 844.1 | 672.5
Property [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 2,143.8 | 1,926.4
Deferred tax assets and liabilities, net | 2,143.8 | 1,926.4
Property [Member] | IPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 1,243.9 | 1,134.1
Deferred tax assets and liabilities, net | 1,243.9 | 1,134.1
Property [Member] | WPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 793.3 | 697.1
Deferred tax assets and liabilities, net | 793.3 | 697.1
Investment In ATC [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 104.3 | 93.8
Deferred tax assets and liabilities, net | 104.3 | 93.8
Investment In ATC [Member] | WPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 104.3 | 93.8
Deferred tax assets and liabilities, net | 104.3 | 93.8
Pension And Other Postretirement Benefits Obligations [Member] | IPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 64.9 | 67.6
Deferred tax assets and liabilities, net | 64.9 | 67.6
Pension And Other Postretirement Benefits Obligations [Member] | WPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 46.4 | 49.6
Deferred tax assets and liabilities, net | 46.4 | 49.6
Deferred Portion of Tax Gain On IPL's Electric Transmission Assets Sale [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 50.7 | 75.5
Deferred tax assets and liabilities, net | 50.7 | 75.5
Deferred Portion of Tax Gain On IPL's Electric Transmission Assets Sale [Member] | IPL [Member] |  |
Deferred tax assets, gross | 0 | 0
Deferred tax liabilities, gross | 50.7 | 75.5
Deferred tax assets and liabilities, net | 50.7 | 75.5
Net Operating Losses Carryforward - State [Member] |  |
Deferred tax assets, gross | (46.8) | (39.9)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (46.8) | (39.9)
Customer Advances [Member] | WPL [Member] |  |
Deferred tax assets, gross | (9.6) | (11.6)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (9.6) | (11.6)
Federal Credit Carryforward [Member] |  |
Deferred tax assets, gross | (133.8) | (107.4)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (133.8) | (107.4)
Federal Credit Carryforward [Member] | IPL [Member] |  |
Deferred tax assets, gross | (37.4) | (25.0)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (37.4) | (25.0)
Federal Credit Carryforward [Member] | WPL [Member] |  |
Deferred tax assets, gross | (39.4) | (26.1)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (39.4) | (26.1)
Regulatory Liability, IPL's Tax Benefit Rider [Member] |  |
Deferred tax assets, gross | (144.6) | (140.6)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (144.6) | (140.6)
Regulatory Liability, IPL's Tax Benefit Rider [Member] | IPL [Member] |  |
Deferred tax assets, gross | (144.6) | (140.6)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (144.6) | (140.6)
Net Operating Losses Carryforward - Federal [Member] |  |
Deferred tax assets, gross | (306.0) | (336.1)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (306.0) | (336.1)
Net Operating Losses Carryforward - Federal [Member] | IPL [Member] |  |
Deferred tax assets, gross | (131.0) | (154.4)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (131.0) | (154.4)
Net Operating Losses Carryforward - Federal [Member] | WPL [Member] |  |
Deferred tax assets, gross | (142.2) | (141.1)
Deferred tax liabilities, gross | 0 | 0
Deferred tax assets and liabilities, net | (142.2) | (141.1)
Other [Member] |  |
Deferred tax assets, gross | (113.7) | (128.2)
Deferred tax liabilities, gross | 208.2 | 224.7
Deferred tax assets and liabilities, net | 94.5 | 96.5
Other [Member] | IPL [Member] |  |
Deferred tax assets, gross | (70.4) | (76.5)
Deferred tax liabilities, gross | 31.9 | 42.7
Deferred tax assets and liabilities, net | (38.5) | (33.8)
Other [Member] | WPL [Member] |  |
Deferred tax assets, gross | (31.6) | (29.3)
Deferred tax liabilities, gross | 37.3 | 34.1
Deferred tax assets and liabilities, net | 5.7 | 4.8
Subtotal [Member] |  |
Deferred tax assets, gross | (744.9) | (752.2)
Deferred tax liabilities, gross | 2,507.0 | 2,320.4
Deferred tax assets and liabilities, net | $ 1,762.1 | $ 1,568.2

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