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Inventory (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Inventory Disclosure [Abstract] |  |  |
Fuel oil | $ 8 | $ 37 |
Coal | 83 | 73 |
Natural gas | 206 | 22 |
Spare parts and finished goods | 201 | 195 |
Total Inventory | 498 | 327 |
Inventory [Line Items] |  |  |
Inventory lower of cost or market adjustment | $ 0 | 29 | $ 0
Fuel Oil |  |  |
Inventory [Line Items] |  |  |
Inventory lower of cost or market adjustment |  | $ 29 |

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