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Income Taxes (Schedule Of Effective Income Tax Rates) (Details) | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Effective Tax Rate [Line Items] |  |  |
Statutory federal income tax rate | 21.00% | 21.00% | 21.00%
State income taxes, net of federal benefits | 2.00% | 3.00% | 2.00%
Production tax credits | (17.00%) | (18.00%) | (17.00%)
Amortization of excess deferred taxes | (2.00%) | (2.00%) | (18.00%)
Effect of rate-making on property-related differences | (4.00%) | (1.00%) | (1.00%)
Adjustment for prior period taxes | 0.00% | 1.00% | 1.00%
Other items, net | 1.00% | (1.00%) | 0.00%
Overall income tax rate | 1.00% | 3.00% | (12.00%)
IPL [Member] |  |  |
Effective Tax Rate [Line Items] |  |  |
Statutory federal income tax rate | 21.00% | 21.00% | 21.00%
State income taxes, net of federal benefits | (2.00%) | (2.00%) | (1.00%)
Production tax credits | (31.00%) | (34.00%) | (27.00%)
Amortization of excess deferred taxes | (2.00%) | (2.00%) | (4.00%)
Effect of rate-making on property-related differences | (5.00%) | (1.00%) | (2.00%)
Adjustment for prior period taxes | 0.00% | 1.00% | 2.00%
Other items, net | 0.00% | 1.00% | 0.00%
Overall income tax rate | (19.00%) | (16.00%) | (11.00%)
WPL [Member] |  |  |
Effective Tax Rate [Line Items] |  |  |
Statutory federal income tax rate | 21.00% | 21.00% | 21.00%
State income taxes, net of federal benefits | 5.00% | 6.00% | 6.00%
Production tax credits | (7.00%) | (5.00%) | (6.00%)
Amortization of excess deferred taxes | (2.00%) | (3.00%) | (43.00%)
Effect of rate-making on property-related differences | (3.00%) | (2.00%) | (1.00%)
Adjustment for prior period taxes | 0.00% | 0.00% | 0.00%
Other items, net | 1.00% | 0.00% | (1.00%)
Overall income tax rate | 15.00% | 17.00% | (24.00%)

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