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Asset Retirement Obligations (Tables) | 9 Months Ended
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Sep. 30, 2024
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation of Changes in Asset Retirement Obligations | A reconciliation of the changes in AROs associated with long-lived assets for the nine months ended September 30, 2024 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Balance, January 1 | $246 |  | $148 |  | $98
Revisions in estimated cash flows | (2) |  | — |  | (2)
Liabilities settled | (4) |  | (2) |  | (2)
Liabilities incurred (a) | 356 |  | 103 |  | 253
Accretion expense | 12 |  | 6 |  | 6
Balance, September 30 | $608 |  | $255 |  | $353
(a)In the second quarter of 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024 for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts recorded in the second quarter of 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.
IPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation of Changes in Asset Retirement Obligations | A reconciliation of the changes in AROs associated with long-lived assets for the nine months ended September 30, 2024 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Balance, January 1 | $246 |  | $148 |  | $98
Revisions in estimated cash flows | (2) |  | — |  | (2)
Liabilities settled | (4) |  | (2) |  | (2)
Liabilities incurred (a) | 356 |  | 103 |  | 253
Accretion expense | 12 |  | 6 |  | 6
Balance, September 30 | $608 |  | $255 |  | $353
(a)In the second quarter of 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024 for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts recorded in the second quarter of 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.
WPL [Member] |
Schedule of Asset Retirement Obligations [Line Items] |
Reconciliation of Changes in Asset Retirement Obligations | A reconciliation of the changes in AROs associated with long-lived assets for the nine months ended September 30, 2024 is as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Balance, January 1 | $246 |  | $148 |  | $98
Revisions in estimated cash flows | (2) |  | — |  | (2)
Liabilities settled | (4) |  | (2) |  | (2)
Liabilities incurred (a) | 356 |  | 103 |  | 253
Accretion expense | 12 |  | 6 |  | 6
Balance, September 30 | $608 |  | $255 |  | $353
(a)In the second quarter of 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024 for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews. The amounts recorded in the second quarter of 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.

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- Definition [Line Items] for Schedule of Asset Retirement Obligations [Table] + References No definition available. + Details
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- Definition Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481850/410-20-50-1 + Details
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