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Commitments And Contingencies (Tables) | 12 Months Ended
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Dec. 31, 2023
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2023, 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 | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $301 |  | $187 |  | $123 |  | $78 |  | $49 |  | $142 |  | $880
Coal | 94 |  | 49 |  | 8 |  | 8 |  | 6 |  | — |  | 165
Other (a) | 61 |  | 17 |  | 14 |  | 9 |  | 2 |  | 22 |  | 125
| $456 |  | $253 |  | $145 |  | $95 |  | $57 |  | $164 |  | $1,170
IPL | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $165 |  | $86 |  | $47 |  | $35 |  | $14 |  | $25 |  | $372
Coal | 49 |  | 35 |  | 8 |  | 8 |  | 6 |  | — |  | 106
Other (a) | 23 |  | 2 |  | 2 |  | 2 |  | 2 |  | 22 |  | 53
| $237 |  | $123 |  | $57 |  | $45 |  | $22 |  | $47 |  | $531
WPL | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $136 |  | $101 |  | $76 |  | $43 |  | $35 |  | $117 |  | $508
Coal | 45 |  | 14 |  | — |  | — |  | — |  | — |  | 59
Other (a) | 23 |  | 1 |  | 1 |  | — |  | — |  | — |  | 25
| $204 |  | $116 |  | $77 |  | $43 |  | $35 |  | $117 |  | $592
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.
Schedule of Environmental Liabilities | At December 31, 2023, 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 | $9 |  | - | $36 |  | $5 |  | - | $11 |  | $4 |  | - | $25
Current and non-current environmental liabilities | $18 |  | $8 |  | $10
IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2023, 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 | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $301 |  | $187 |  | $123 |  | $78 |  | $49 |  | $142 |  | $880
Coal | 94 |  | 49 |  | 8 |  | 8 |  | 6 |  | — |  | 165
Other (a) | 61 |  | 17 |  | 14 |  | 9 |  | 2 |  | 22 |  | 125
| $456 |  | $253 |  | $145 |  | $95 |  | $57 |  | $164 |  | $1,170
IPL | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $165 |  | $86 |  | $47 |  | $35 |  | $14 |  | $25 |  | $372
Coal | 49 |  | 35 |  | 8 |  | 8 |  | 6 |  | — |  | 106
Other (a) | 23 |  | 2 |  | 2 |  | 2 |  | 2 |  | 22 |  | 53
| $237 |  | $123 |  | $57 |  | $45 |  | $22 |  | $47 |  | $531
WPL | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $136 |  | $101 |  | $76 |  | $43 |  | $35 |  | $117 |  | $508
Coal | 45 |  | 14 |  | — |  | — |  | — |  | — |  | 59
Other (a) | 23 |  | 1 |  | 1 |  | — |  | — |  | — |  | 25
| $204 |  | $116 |  | $77 |  | $43 |  | $35 |  | $117 |  | $592
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.
Schedule of Environmental Liabilities | At December 31, 2023, 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 | $9 |  | - | $36 |  | $5 |  | - | $11 |  | $4 |  | - | $25
Current and non-current environmental liabilities | $18 |  | $8 |  | $10
WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2023, 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 | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $301 |  | $187 |  | $123 |  | $78 |  | $49 |  | $142 |  | $880
Coal | 94 |  | 49 |  | 8 |  | 8 |  | 6 |  | — |  | 165
Other (a) | 61 |  | 17 |  | 14 |  | 9 |  | 2 |  | 22 |  | 125
| $456 |  | $253 |  | $145 |  | $95 |  | $57 |  | $164 |  | $1,170
IPL | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $165 |  | $86 |  | $47 |  | $35 |  | $14 |  | $25 |  | $372
Coal | 49 |  | 35 |  | 8 |  | 8 |  | 6 |  | — |  | 106
Other (a) | 23 |  | 2 |  | 2 |  | 2 |  | 2 |  | 22 |  | 53
| $237 |  | $123 |  | $57 |  | $45 |  | $22 |  | $47 |  | $531
WPL | 2024 |  | 2025 |  | 2026 |  | 2027 |  | 2028 |  | Thereafter |  | Total
Natural gas | $136 |  | $101 |  | $76 |  | $43 |  | $35 |  | $117 |  | $508
Coal | 45 |  | 14 |  | — |  | — |  | — |  | — |  | 59
Other (a) | 23 |  | 1 |  | 1 |  | — |  | — |  | — |  | 25
| $204 |  | $116 |  | $77 |  | $43 |  | $35 |  | $117 |  | $592
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.

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- 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
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