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Regulatory Matters (Narrative) (Details) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Aug. 31, 2020 customer | Dec. 31, 2022 USD ($) MW | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory assets |  | $ 2,046 | $ 1,940 |  |
Credits issued to customers |  | 22 | (66) | $ (113) |
Regulatory liabilities |  | 1,324 | 1,271 |  |
Electric transmission cost recovery [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory liabilities |  | 20 | 51 |  |
IPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory assets not earning a return |  | 66 |  |  |
Regulatory assets |  | 1,386 | 1,443 |  |
Credits issued to customers |  | $ 53 | 1 | (20) |
Electric capacity of wind farm (in megawatts) | MW |  | 1,000 |  |  |
Regulatory liabilities |  | $ 754 | 691 |  |
IPL [Member] | Electric transmission cost recovery [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Credits issued to customers |  |  |  | 42 |
Regulatory liabilities |  | 10 | 27 |  |
IPL [Member] | Derecho windstorm [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Number of customers without power, derecho windstorm (number of customers) | customer | 250,000 |  |  |  |
Derecho windstorm repair and rebuilding costs |  | 140 |  |  |
Net regulatory liability, derecho windstorm |  | 8 |  |  |
WPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory assets not earning a return |  | 28 |  |  |
Regulatory assets |  | 660 | 497 |  |
Credits issued to customers |  | (31) | (67) | (93) |
Regulatory liabilities |  | 570 | 580 |  |
WPL [Member] | Electric transmission cost recovery [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory liabilities |  | 10 | $ 24 |  |
2021 Test Period Fuel-related Costs [Member] | WPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory assets |  | 37 |  |  |
2022 Test Period Fuel-related Costs [Member] | WPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory assets |  | 117 |  |  |
2020 Test Period Retail Electric [Member] | IPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Interim rate increase (decrease), amount |  |  |  |  | $ 90
Authorized increase (decrease) in final rates, amount |  |  |  | 127 |
2020 Test Period Retail Electric [Member] | IPL [Member] | Tax-related [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory liabilities |  | 27 |  |  |
2020 Test Period Retail Electric [Member] | IPL [Member] | Revenue Subject to Refund [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Regulatory liabilities |  | 8 |  |  |
2020 Test Period Retail Gas [Member] | IPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Authorized increase (decrease) in final rates, amount |  |  |  | 12 |
2019 Test Period Retail Electric [Member] | WPL [Member] | Revenue Subject to Refund [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Credits issued to customers |  |  |  | 12 |
2022 Test Period Retail Electric [Member] | WPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Authorized increase (decrease) in final rates, amount |  | 114 |  |  |
2022 Test Period Retail Gas [Member] | WPL [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Authorized increase (decrease) in final rates, amount |  | $ 15 |  |  |
DAEC PPA [Member] |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |
Buyout payment |  |  |  | $ 110 |
PPA term amendment |  | 5 years |  |  |

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