XML 81 R47.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Commitments And Contingencies (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2024
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2024, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):
Alliant Energy | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $268 |  | $177 |  | $130 |  | $102 |  | $84 |  | $120 |  | $881
Coal | 75 |  | 33 |  | 22 |  | 5 |  | — |  | — |  | 135
Other (a) | 51 |  | 20 |  | 7 |  | 7 |  | 2 |  | 22 |  | 109
| $394 |  | $230 |  | $159 |  | $114 |  | $86 |  | $142 |  | $1,125
IPL | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $160 |  | $104 |  | $85 |  | $64 |  | $49 |  | $20 |  | $482
Coal | 34 |  | 19 |  | 10 |  | 5 |  | — |  | — |  | 68
Other (a) | 18 |  | 2 |  | 2 |  | 2 |  | 2 |  | 21 |  | 47
| $212 |  | $125 |  | $97 |  | $71 |  | $51 |  | $41 |  | $597
WPL | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $108 |  | $73 |  | $45 |  | $38 |  | $35 |  | $100 |  | $399
Coal | 41 |  | 14 |  | 12 |  | — |  | — |  | — |  | 67
Other (a) | 22 |  | 1 |  | — |  | — |  | — |  | — |  | 23
| $171 |  | $88 |  | $57 |  | $38 |  | $35 |  | $100 |  | $489
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2024.
Schedule of Environmental Liabilities | At December 31, 2024, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Range of estimated future costs | $7 |  | - | $28 |  | $5 |  | - | $17 |  | $2 |  | - | $11
Current and non-current environmental liabilities | $12 |  | $7 |  | $5
IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2024, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):
Alliant Energy | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $268 |  | $177 |  | $130 |  | $102 |  | $84 |  | $120 |  | $881
Coal | 75 |  | 33 |  | 22 |  | 5 |  | — |  | — |  | 135
Other (a) | 51 |  | 20 |  | 7 |  | 7 |  | 2 |  | 22 |  | 109
| $394 |  | $230 |  | $159 |  | $114 |  | $86 |  | $142 |  | $1,125
IPL | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $160 |  | $104 |  | $85 |  | $64 |  | $49 |  | $20 |  | $482
Coal | 34 |  | 19 |  | 10 |  | 5 |  | — |  | — |  | 68
Other (a) | 18 |  | 2 |  | 2 |  | 2 |  | 2 |  | 21 |  | 47
| $212 |  | $125 |  | $97 |  | $71 |  | $51 |  | $41 |  | $597
WPL | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $108 |  | $73 |  | $45 |  | $38 |  | $35 |  | $100 |  | $399
Coal | 41 |  | 14 |  | 12 |  | — |  | — |  | — |  | 67
Other (a) | 22 |  | 1 |  | — |  | — |  | — |  | — |  | 23
| $171 |  | $88 |  | $57 |  | $38 |  | $35 |  | $100 |  | $489
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2024.
Schedule of Environmental Liabilities | At December 31, 2024, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Range of estimated future costs | $7 |  | - | $28 |  | $5 |  | - | $17 |  | $2 |  | - | $11
Current and non-current environmental liabilities | $12 |  | $7 |  | $5
WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2024, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):
Alliant Energy | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $268 |  | $177 |  | $130 |  | $102 |  | $84 |  | $120 |  | $881
Coal | 75 |  | 33 |  | 22 |  | 5 |  | — |  | — |  | 135
Other (a) | 51 |  | 20 |  | 7 |  | 7 |  | 2 |  | 22 |  | 109
| $394 |  | $230 |  | $159 |  | $114 |  | $86 |  | $142 |  | $1,125
IPL | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $160 |  | $104 |  | $85 |  | $64 |  | $49 |  | $20 |  | $482
Coal | 34 |  | 19 |  | 10 |  | 5 |  | — |  | — |  | 68
Other (a) | 18 |  | 2 |  | 2 |  | 2 |  | 2 |  | 21 |  | 47
| $212 |  | $125 |  | $97 |  | $71 |  | $51 |  | $41 |  | $597
WPL | 2025 |  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | Thereafter |  | Total
Natural gas | $108 |  | $73 |  | $45 |  | $38 |  | $35 |  | $100 |  | $399
Coal | 41 |  | 14 |  | 12 |  | — |  | — |  | — |  | 67
Other (a) | 22 |  | 1 |  | — |  | — |  | — |  | — |  | 23
| $171 |  | $88 |  | $57 |  | $38 |  | $35 |  | $100 |  | $489
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2024.
Schedule of Environmental Liabilities | At December 31, 2024, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Range of estimated future costs | $7 |  | - | $28 |  | $5 |  | - | $17 |  | $2 |  | - | $11
Current and non-current environmental liabilities | $12 |  | $7 |  | $5

X
- Definition Tabular disclosure of material liabilities for remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal or abandonment of a property as a result of unanticipated contamination of the assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.Y.Q4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480102/450-20-S99-1 + Details
Name: | us-gaap_EnvironmentalExitCostsByCostTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_LongTermPurchaseCommitmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of unconditional purchase obligation not recognized as liability. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 440 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482648/440-10-50-4 + Details
Name: | us-gaap_UnrecordedUnconditionalPurchaseObligationsDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=lnt_IplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=lnt_WplMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |