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Commitments And Contingencies (Tables) | 12 Months Ended
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Dec. 31, 2020
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2020, the related minimum future commitments were as follows (in millions):
Alliant Energy | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 252 |  | 174 |  | 137 |  | 105 |  | 68 |  | 185 |  | 921
Coal | 70 |  | 27 |  | 17 |  | — |  | — |  | — |  | 114
Other (a) | 61 |  | 17 |  | 11 |  | 8 |  | 3 |  | 29 |  | 129
| $383 |  | $218 |  | $165 |  | $113 |  | $71 |  | $214 |  | $1,164
IPL | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 130 |  | 88 |  | 79 |  | 68 |  | 38 |  | 71 |  | 474
Coal | 32 |  | 16 |  | 13 |  | — |  | — |  | — |  | 61
Other (a) | 25 |  | 5 |  | 4 |  | 2 |  | 2 |  | 27 |  | 65
| $187 |  | $109 |  | $96 |  | $70 |  | $40 |  | $98 |  | $600
WPL | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 122 |  | 86 |  | 58 |  | 37 |  | 30 |  | 114 |  | 447
Coal | 38 |  | 11 |  | 4 |  | — |  | — |  | — |  | 53
Other (a) | 26 |  | 2 |  | 1 |  | 1 |  | 1 |  | 1 |  | 32
| $186 |  | $99 |  | $63 |  | $38 |  | $31 |  | $115 |  | $532
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2020.
Schedule of Environmental Liabilities | At December 31, 2020, 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). At December 31, 2020, such amounts for WPL were not material.
| Alliant Energy |  | IPL
Range of estimated future costs | $11 |  | - | $28 |  | $8 |  | - | $22
Current and non-current environmental liabilities | 15 |  | 12
IPL [Member] |
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2020, the related minimum future commitments were as follows (in millions):
Alliant Energy | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 252 |  | 174 |  | 137 |  | 105 |  | 68 |  | 185 |  | 921
Coal | 70 |  | 27 |  | 17 |  | — |  | — |  | — |  | 114
Other (a) | 61 |  | 17 |  | 11 |  | 8 |  | 3 |  | 29 |  | 129
| $383 |  | $218 |  | $165 |  | $113 |  | $71 |  | $214 |  | $1,164
IPL | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 130 |  | 88 |  | 79 |  | 68 |  | 38 |  | 71 |  | 474
Coal | 32 |  | 16 |  | 13 |  | — |  | — |  | — |  | 61
Other (a) | 25 |  | 5 |  | 4 |  | 2 |  | 2 |  | 27 |  | 65
| $187 |  | $109 |  | $96 |  | $70 |  | $40 |  | $98 |  | $600
WPL | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 122 |  | 86 |  | 58 |  | 37 |  | 30 |  | 114 |  | 447
Coal | 38 |  | 11 |  | 4 |  | — |  | — |  | — |  | 53
Other (a) | 26 |  | 2 |  | 1 |  | 1 |  | 1 |  | 1 |  | 32
| $186 |  | $99 |  | $63 |  | $38 |  | $31 |  | $115 |  | $532
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2020.
Schedule of Environmental Liabilities | At December 31, 2020, 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). At December 31, 2020, such amounts for WPL were not material.
| Alliant Energy |  | IPL
Range of estimated future costs | $11 |  | - | $28 |  | $8 |  | - | $22
Current and non-current environmental liabilities | 15 |  | 12
WPL [Member] |
Long-term Purchase Commitment [Line Items] |
Other Purchase Commitments | At December 31, 2020, the related minimum future commitments were as follows (in millions):
Alliant Energy | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 252 |  | 174 |  | 137 |  | 105 |  | 68 |  | 185 |  | 921
Coal | 70 |  | 27 |  | 17 |  | — |  | — |  | — |  | 114
Other (a) | 61 |  | 17 |  | 11 |  | 8 |  | 3 |  | 29 |  | 129
| $383 |  | $218 |  | $165 |  | $113 |  | $71 |  | $214 |  | $1,164
IPL | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 130 |  | 88 |  | 79 |  | 68 |  | 38 |  | 71 |  | 474
Coal | 32 |  | 16 |  | 13 |  | — |  | — |  | — |  | 61
Other (a) | 25 |  | 5 |  | 4 |  | 2 |  | 2 |  | 27 |  | 65
| $187 |  | $109 |  | $96 |  | $70 |  | $40 |  | $98 |  | $600
WPL | 2021 |  | 2022 |  | 2023 |  | 2024 |  | 2025 |  | Thereafter |  | Total
Natural gas | 122 |  | 86 |  | 58 |  | 37 |  | 30 |  | 114 |  | 447
Coal | 38 |  | 11 |  | 4 |  | — |  | — |  | — |  | 53
Other (a) | 26 |  | 2 |  | 1 |  | 1 |  | 1 |  | 1 |  | 32
| $186 |  | $99 |  | $63 |  | $38 |  | $31 |  | $115 |  | $532
(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2020.

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