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Commitments and Contingencies, Fuel Contracts (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Coal |  |  |
Fuel Contracts [Abstract] |  |  |
2019 | $ 461 |  |
2020 | 260 |  |
2021 | 149 |  |
2022 | 109 |  |
2023 | 61 |  |
Thereafter | 108 |  |
Total | 1,148 |  |
Nuclear Fuel |  |  |
Fuel Contracts [Abstract] |  |  |
2019 | 127 |  |
2020 | 51 |  |
2021 | 99 |  |
2022 | 79 |  |
2023 | 99 |  |
Thereafter | 337 |  |
Total | 792 |  |
Natural Gas Supply |  |  |
Fuel Contracts [Abstract] |  |  |
2019 | 416 |  |
2020 | 263 |  |
2021 | 254 |  |
2022 | 114 |  |
2023 | 60 |  |
Thereafter | 0 |  |
Total | 1,107 |  |
Natural Gas Storage and Transportation |  |  |
Fuel Contracts [Abstract] |  |  |
2019 | 268 |  |
2020 | 255 |  |
2021 | 245 |  |
2022 | 234 |  |
2023 | 170 |  |
Thereafter | 923 |  |
Total | $ 2,095 |  |
Minimum |  |  |
Unrecorded Unconditional Purchase Obligation [Line Items] |  |  |
Fuel Contract Expiration Date | 2019 |  |
Maximum |  |  |
Unrecorded Unconditional Purchase Obligation [Line Items] |  |  |
Fuel Contract Expiration Date | 2060 |  |
Capacity |  |  |
Unrecorded Unconditional Purchase Obligation [Line Items] |  |  |
Utilities Operating Expense, Purchased Power under Long-term Contracts | $ 131 | $ 168 | $ 191
Fuel Contracts [Abstract] |  |  |
2019 | 86 |  |
2020 | 70 |  |
2021 | 78 |  |
2022 | 77 |  |
2023 | 79 |  |
Thereafter | 125 |  |
Total | $ 515 |  |

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