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Commitments and Contingencies Commitments and Contingencies - Table (Details) $ in Millions | Sep. 30, 2018 USD ($) megawatts | Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($)
--- | --- | --- | ---
Obligations |  |  |  |
Megawatts provided under transmission obligations | megawatts |  | 1,450 |  |
Accrual for Environmental Loss Contingencies, Gross |  | $ 12 | $ 7 |
Estimated future decommissioning cost | [1] | 4,779 | 4,304 | $ 4,052
2018 |  | 51 |  |
2019 |  | 51 |  |
2020 |  | 51 |  |
2021 |  | 51 |  |
2022 |  | 51 |  |
Thereafter |  | 468 |  |
Total |  | 723 |  |
2018 |  | 69 |  |
2019 |  | 64 |  |
2020 |  | 62 |  |
2021 |  | 47 |  |
2022 |  | 7 |  |
Thereafter |  | 1 |  |
Total |  | 250 |  |
CT and QTE outstanding leaseback obligation |  | 301 | $ 338 |
2018 |  | 49 |  |
2019 |  | 50 |  |
2020 |  | 207 |  |
2021 |  | 25 |  |
2022 |  | 0 |  |
Thereafter |  | 0 |  |
Total |  | $ 331 |  |
[1] | (1) The current portions of the ARO liability in the amounts of $115 million and $128 million as of September 30, 2018 and 2017, respectively, are included in Accounts payable and accrued liabilities.

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