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v3.22.4

Summary Of Significant Accounting Policies (Narrative) (Details) $ in Millions | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Sep. 30, 2022 USD ($) | Jun. 30, 2022 USD ($) | Dec. 31, 2024 MWd | Dec. 31, 2023 | Dec. 31, 2022 USD ($) customer MW | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Current Expected Credit Losses Estimates: |  |  |  |  |  |  |  |
New accounting standard, cumulative effect adjustment to retained earnings, after-tax |  |  |  |  | $ (3,509) | $ (3,250) |  |
Variable Interest Entities |  |  |  |  |  |  |  |
Distributions to noncontrolling interest |  |  |  |  | $ 29 | 0 | $ 0 |
Non-utility wind farm in Oklahoma [Member] |  |  |  |  |  |  |  |
General: |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  | 50.00% |  |  |
Cumulative Effect, Period of Adoption, Adjustment [Member] |  |  |  |  |  |  |  |
Current Expected Credit Losses Estimates: |  |  |  |  |  |  |  |
New accounting standard, cumulative effect adjustment to retained earnings, pre-tax |  |  |  |  |  |  | 12 |
New accounting standard, cumulative effect adjustment to retained earnings, after-tax |  |  |  |  |  |  | 9 | $ 9
IPL [Member] |  |  |  |  |  |  |  |
General: |  |  |  |  |  |  |  |
Generation and distribution of steam, number of customers served (in customers) | customer |  |  |  |  | 2 |  |  |
Electric capacity of wind farm (in megawatts) | MW |  |  |  |  | 1,000 |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
AFUDC accrual recorded, percentage of estimated CWIP |  |  |  |  | 100.00% |  |  |
Current Expected Credit Losses Estimates: |  |  |  |  |  |  |  |
New accounting standard, cumulative effect adjustment to retained earnings, after-tax |  |  |  |  | $ (968) | (929) |  |
WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
AFUDC accrual recorded, percentage of estimated CWIP |  |  |  |  | 50.00% |  |  |
AFUDC accrual recorded, percentage earning a return as part of rate base |  |  |  |  | 50.00% |  |  |
AFUDC rates, projects with approval |  |  |  |  | 100.00% |  |  |
Current Expected Credit Losses Estimates: |  |  |  |  |  |  |  |
New accounting standard, cumulative effect adjustment to retained earnings, after-tax |  |  |  |  | $ (1,192) | (1,053) |  |
Variable Interest Entities |  |  |  |  |  |  |  |
WPL's cash contribution |  | $ 62 |  |  |  |  |  |
Tax equity partner's cash contribution |  | 29 |  |  |  |  |  |
Contributed funds paid to WPL for equity interests |  | $ 88 |  |  |  |  |  |
Distributions to noncontrolling interest | $ 29 |  |  |  | $ 29 | $ 0 | $ 0 |
Alliant Energy Finance, LLC [Member] |  |  |  |  |  |  |  |
General: |  |  |  |  |  |  |  |
Electric capacity of wind farm (in megawatts) | MW |  |  |  |  | 225 |  |  |
Alliant Energy Finance, LLC [Member] | Non-utility wind farm in Oklahoma [Member] |  |  |  |  |  |  |  |
General: |  |  |  |  |  |  |  |
Ownership interest |  |  |  |  | 50.00% |  |  |
Sheboygan Falls Energy Facility [Member] |  |  |  |  |  |  |  |
General: |  |  |  |  |  |  |  |
Fossil-fueled EGU capacity (in megawatts) | MW |  |  |  |  | 347 |  |  |
Finance lease, lease term |  |  |  |  | 20 years |  |  |
Electric Generation Equipment [Member] | IPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  |  | 3.40% | 3.40% | 3.50% |
Electric Generation Equipment [Member] | WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  |  | 3.40% | 3.50% | 3.50% |
Distribution [Member] | IPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  |  | 2.80% | 2.90% | 2.80% |
Distribution [Member] | WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  |  | 2.50% | 2.60% | 2.60% |
Gas [Member] | IPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  |  | 3.30% | 3.30% | 3.30% |
Gas [Member] | WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  |  | 2.40% | 2.40% | 2.40% |
Forecast [Member] | Solar [Member] | WPL [Member] |  |  |  |  |  |  |  |
Variable Interest Entities |  |  |  |  |  |  |  |
Nameplate capacity (in MWs) | MWd |  |  | 1,100 |  |  |  |  |
Forecast [Member] | Electric Generation Equipment [Member] | WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  | 3.60% |  |  |  |
Forecast [Member] | Distribution [Member] | WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  | 2.70% |  |  |  |
Forecast [Member] | Gas [Member] | WPL [Member] |  |  |  |  |  |  |  |
Property, Plant and Equipment: |  |  |  |  |  |  |  |
Average rate of depreciation |  |  |  | 2.90% |  |  |  |

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