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Commitment, Contingencies And Guarantees: Power Sales Agreements (Details) - MW | 12 Months Ended |  |  |
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Dec. 31, 2021 | Jul. 01, 2020 | Jun. 26, 2019 | Sep. 03, 2014
City Of Gillette |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Megawatts Sold Under Long-Term Contract | 23 |  |  |
Purchase Power Contract, MEAN, for up to 20 Megawatts |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Megawatts Sold Under Long-Term Contract | 20 |  |  |
2020-2022 | 15 |  |  |
2022-2023 | 15 |  |  |
2023-2028 | 10 |  |  |
Purchase Power Contract, MEAN, for up to 20 Megawatts | Contingent Capacity Amounts on Wygen III |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
2020-2022 | 7 |  |  |
2022-2023 | 8 |  |  |
2023-2028 | 5 |  |  |
Purchase Power Contract, MEAN, for up to 20 Megawatts | Contingent Capacity Amounts on Neil Simpson II |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
2020-2022 | 8 |  |  |
2022-2023 | 7 |  |  |
2023-2028 | 5 |  |  |
Macquarie Energy, LLC Supply Agreement |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Megawatts Sold Under Long-Term Contract | 50 |  |  |
South Dakota Electric | M D U, Montana Dakota Utilities | Contingent Capacity Amounts on Wygen III |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Megawatts Sold Under Long-Term Contract | 25 |  |  |
South Dakota Electric | Maximum | M D U, Montana Dakota Utilities |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Megawatts Sold Under Long-Term Contract | 50 |  |  |
City of Colorado Springs | Colorado Electric |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Number of Megawatts Capacity Purchased |  | 60 |  |
Platte River Power Authority Wind Power Agreement |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Number of Megawatts Capacity Purchased |  |  | 60 |
Sharing Arrangement with the City of Gillette, Wyoming |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Long-term Purchase Commitment, Period | 20 years |  |  |
Sharing Arrangement with the City of Gillette, Wyoming | Black Hills Wyoming |  |  |  |
Long-term Purchase Commitment [Line Items] |  |  |  |
Number of Megawatts Capacity Sold |  |  |  | 40

X
- Definition Number of Megawatts Capacity Purchased + References No definition available. + Details
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- Definition Number of Megawatts Capacity Sold + References No definition available. + Details
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- Definition Number of Megawatts Sold Under Long-Term Contract + References No definition available. + Details
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- Definition Total Contract Capacity in Megawatts Due Per Year in Years Five Through Nine of the Contract + References No definition available. + Details
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- Definition Total Contract Capacity in Megawatts Due Per Year in Years Two and Three of the Contract + References No definition available. + Details
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