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Summary Of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2018
Schedule of Average Rates of Depreciation | The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:
| IPL |  | WPL
| 2018 |  | 2017 |  | 2016 |  | 2018 |  | 2017 |  | 2016
Electric - generation | 3.6% |  | 3.5% |  | 3.5% |  | 3.6% |  | 3.5% |  | 3.1%
Electric - distribution | 2.8% |  | 2.4% |  | 2.4% |  | 2.6% |  | 2.6% |  | 2.6%
Electric - other | 4.7% |  | 4.5% |  | 4.2% |  | 5.7% |  | 6.9% |  | 4.7%
Gas | 3.2% |  | 3.4% |  | 3.3% |  | 2.5% |  | 2.5% |  | 2.5%
Other | 5.2% |  | 4.0% |  | 3.9% |  | 5.8% |  | 6.0% |  | 5.9%
Schedule of Allowance for Funds Used During Construction Rate | The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:
| 2018 |  | 2017 |  | 2016
IPL (Marshalltown CWIP) | N/A |  | 7.8% |  | 7.9%
IPL (Wind generation CWIP) | 7.5% |  | 7.6% |  | N/A
IPL (other CWIP) | 7.5% |  | 7.6% |  | 7.7%
WPL (retail jurisdiction) | 7.7% |  | 7.6% |  | 8.2%
WPL (wholesale jurisdiction) | 7.2% |  | 6.0% |  | 6.7%
IPL [Member] |
Schedule of Average Rates of Depreciation | The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:
| IPL |  | WPL
| 2018 |  | 2017 |  | 2016 |  | 2018 |  | 2017 |  | 2016
Electric - generation | 3.6% |  | 3.5% |  | 3.5% |  | 3.6% |  | 3.5% |  | 3.1%
Electric - distribution | 2.8% |  | 2.4% |  | 2.4% |  | 2.6% |  | 2.6% |  | 2.6%
Electric - other | 4.7% |  | 4.5% |  | 4.2% |  | 5.7% |  | 6.9% |  | 4.7%
Gas | 3.2% |  | 3.4% |  | 3.3% |  | 2.5% |  | 2.5% |  | 2.5%
Other | 5.2% |  | 4.0% |  | 3.9% |  | 5.8% |  | 6.0% |  | 5.9%
Schedule of Allowance for Funds Used During Construction Rate | The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:
| 2018 |  | 2017 |  | 2016
IPL (Marshalltown CWIP) | N/A |  | 7.8% |  | 7.9%
IPL (Wind generation CWIP) | 7.5% |  | 7.6% |  | N/A
IPL (other CWIP) | 7.5% |  | 7.6% |  | 7.7%
WPL (retail jurisdiction) | 7.7% |  | 7.6% |  | 8.2%
WPL (wholesale jurisdiction) | 7.2% |  | 6.0% |  | 6.7%
WPL [Member] |
Schedule of Average Rates of Depreciation | The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:
| IPL |  | WPL
| 2018 |  | 2017 |  | 2016 |  | 2018 |  | 2017 |  | 2016
Electric - generation | 3.6% |  | 3.5% |  | 3.5% |  | 3.6% |  | 3.5% |  | 3.1%
Electric - distribution | 2.8% |  | 2.4% |  | 2.4% |  | 2.6% |  | 2.6% |  | 2.6%
Electric - other | 4.7% |  | 4.5% |  | 4.2% |  | 5.7% |  | 6.9% |  | 4.7%
Gas | 3.2% |  | 3.4% |  | 3.3% |  | 2.5% |  | 2.5% |  | 2.5%
Other | 5.2% |  | 4.0% |  | 3.9% |  | 5.8% |  | 6.0% |  | 5.9%
Schedule of Allowance for Funds Used During Construction Rate | The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:
| 2018 |  | 2017 |  | 2016
IPL (Marshalltown CWIP) | N/A |  | 7.8% |  | 7.9%
IPL (Wind generation CWIP) | 7.5% |  | 7.6% |  | N/A
IPL (other CWIP) | 7.5% |  | 7.6% |  | 7.7%
WPL (retail jurisdiction) | 7.7% |  | 7.6% |  | 8.2%
WPL (wholesale jurisdiction) | 7.2% |  | 6.0% |  | 6.7%

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