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Income Taxes (Schedule Of Effective Income Tax Rates) (Details) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Effective Tax Rate [Line Items] |  |  |
Statutory federal income tax rate | 21.00% | 35.00% | 35.00%
State income taxes, net of federal benefits | 7.00% | 5.50% | 5.40%
Effect of rate-making on property-related differences | (7.60%) | (8.50%) | (8.50%)
Production tax credits | (5.20%) | (6.10%) | (7.20%)
Adjustment for prior period taxes | (2.30%) | (1.50%) | (0.80%)
Federal Tax Reform Adjustments | (1.00%) | (3.40%) | (0.00%)
Other items, net | (1.20%) | (0.90%) | (0.50%)
Overall income tax rate | 8.40% | 12.50% | 13.40%
IPL [Member] |  |  |
Effective Tax Rate [Line Items] |  |  |
Statutory federal income tax rate | 21.00% | 35.00% | 35.00%
State income taxes, net of federal benefits | 7.70% | 6.50% | 6.40%
Effect of rate-making on property-related differences | (14.00%) | (19.10%) | (16.20%)
Production tax credits | (5.20%) | (6.70%) | (6.30%)
Adjustment for prior period taxes | (4.80%) | (3.40%) | (1.20%)
Federal Tax Reform Adjustments | (0.40%) | 1.70% | (0.00%)
Other items, net | (0.60%) | (0.30%) | (0.30%)
Overall income tax rate | (1.20%) | (5.00%) | (2.70%)
WPL [Member] |  |  |
Effective Tax Rate [Line Items] |  |  |
Statutory federal income tax rate | 21.00% | 35.00% | 35.00%
State income taxes, net of federal benefits | 6.20% | 5.10% | 5.10%
Effect of rate-making on property-related differences | (2.30%) | (1.70%) | (0.70%)
Production tax credits | (6.40%) | (7.10%) | (6.20%)
Adjustment for prior period taxes | (0.20%) | (0.00%) | (0.10%)
Federal Tax Reform Adjustments | (2.30%) | (5.80%) | (0.00%)
Other items, net | (1.20%) | (0.60%) | (0.50%)
Overall income tax rate | 14.80% | 24.90% | 32.60%
IPL's tax benefit riders [Member] |  |  |
Effective Tax Rate [Line Items] |  |  |
IPL’s tax benefit riders | (2.30%) | (7.60%) | (10.00%)
IPL's tax benefit riders [Member] | IPL [Member] |  |  |
Effective Tax Rate [Line Items] |  |  |
IPL’s tax benefit riders | (4.90%) | (18.70%) | (20.10%)

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