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Regulatory Assets and Liabilities (Tables) | 6 Months Ended
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Mar. 31, 2018
Regulatory Assets and Liabilities Disclosure [Abstract] |
Regulatory Assets and Liabilities | Components of regulatory assets and regulatory liabilities are summarized in the table below:
Regulatory Assets and Liabilities
| At March 31, 2018 |  | At September 30, 2017
Current regulatory assets |  |  |
Deferred nuclear generating units | $ | 237 |  |  | $ | 237 |
Unrealized losses on interest rate derivatives | 80 |  |  | 93 |
Unrealized losses on commodity derivatives | 44 |  |  | 68 |
Fuel cost adjustment receivable | 39 |  |  | 1 |
Environmental agreements | 3 |  |  | 2 |
Environmental cleanup costs - Kingston ash spill | 44 |  |  | 44 |
Gallatin coal combustion residual facilities | 21 |  |  | — |
Other current regulatory assets | 3 |  |  | 2 |
Total current regulatory assets | 471 |  |  | 447 |
Non-current regulatory assets |  |  |  |  |
Deferred pension costs and other post-retirement benefits costs | 3,881 |  |  | 4,009 |
Unrealized losses on interest rate derivatives | 824 |  |  | 982 |
Gallatin coal combustion residual facilities | 878 |  |  | 899 |
Nuclear decommissioning costs | 821 |  |  | 823 |
Deferred nuclear generating units | 645 |  |  | 759 |
Non-nuclear decommissioning costs | 701 |  |  | 703 |
Environmental cleanup costs - Kingston ash spill | 242 |  |  | 263 |
Unrealized losses on commodity derivatives | 36 |  |  | 9 |
Environmental agreements | 11 |  |  | 13 |
Other non-current regulatory assets | 201 |  |  | 238 |
Total non-current regulatory assets | 8,240 |  |  | 8,698 |
Total regulatory assets | $ | 8,711 |  |  | $ | 9,145 |
Current regulatory liabilities |  |  |  |  |
Fuel cost adjustment tax equivalents | $ | 147 |  |  | $ | 153 |
Fuel cost adjustment | — |  |  | 2 |
Unrealized gains on commodity derivatives | 12 |  |  | 8 |
Total current regulatory liabilities | 159 |  |  | 163 |
Non-current regulatory liabilities |  |  |  |  |
Deferred other post-retirement benefits cost | 16 |  |  | 23 |
Unrealized gains on commodity derivatives | 3 |  |  | 2 |
Total non-current regulatory liabilities | 19 |  |  | 25 |
Total regulatory liabilities | $ | 178 |  |  | $ | 188 |

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- Definition Tabular disclosure of assets and liabilities that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet or that result from rate actions of a regulator. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. Regulatory liabilities can result from obligations to make refunds to customers or deferral of gains that will be credited to customers in future periods + References No definition available. + Details
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