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Regulatory Assets and Liabilities Regulatory Assets and Liabilities (Tables) | 12 Months Ended
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Sep. 30, 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 September 30
| 2018 |  | 2017
Current regulatory assets |  |  |
Gallatin coal combustion residual facilities | $ | 38 |  |  | $ | — |
Unrealized losses on interest rate derivatives | 73 |  |  | 93 |
Environmental agreements | 3 |  |  | 2 |
Unrealized losses on commodity contracts | 4 |  |  | 68 |
Deferred nuclear generating units | — |  |  | 237 |
Environmental cleanup costs – Kingston ash spill | 266 |  |  | 44 |
Fuel cost adjustment receivable | 30 |  |  | 1 |
Other current regulatory assets | — |  |  | 2 |
Total current regulatory assets | 414 |  |  | 447 |
Non-current regulatory assets |  |  |  |  |
Deferred pension costs and other post-retirement benefits costs | 3,119 |  |  | 4,009 |
Non-nuclear decommissioning costs | 1,019 |  |  | 703 |
Gallatin CCR facilities | 861 |  |  | 899 |
Nuclear decommissioning costs | 784 |  |  | 823 |
Unrealized losses on interest rate derivatives | 692 |  |  | 982 |
Environmental agreements | 11 |  |  | 13 |
Unrealized losses on commodity contracts | 8 |  |  | 9 |
Deferred nuclear generating units | — |  |  | 759 |
Environmental cleanup costs - Kingston ash spill | — |  |  | 263 |
Other non-current regulatory assets | 118 |  |  | 238 |
Total non-current regulatory assets | 6,612 |  |  | 8,698 |
Total regulatory assets | $ | 7,026 |  |  | $ | 9,145 |
Current regulatory liabilities |  |  |  |  |
Fuel cost adjustment tax equivalents | $ | 146 |  |  | $ | 153 |
Fuel cost adjustment | — |  |  | 2 |
Unrealized gains on commodity derivatives | 41 |  |  | 8 |
Total current regulatory liabilities | 187 |  |  | 163 |
Non-current regulatory liabilities |  |  |  |  |
Deferred other post-retirement benefits cost | 73 |  |  | 23 |
Unrealized gains on commodity derivatives | 31 |  |  | 2 |
Total non-current regulatory liabilities | 104 |  |  | 25 |
Total regulatory liabilities | $ | 291 |  |  | $ | 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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