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Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions | Mar. 31, 2019 | Sep. 30, 2018
--- | --- | ---
Regulatory Assets and Liabilities |  |
Current regulatory assets | $ 241 | $ 414
Non-current regulatory assets | 6,822 | 6,612
Regulatory assets | 7,063 | 7,026
Current regulatory liabilities | 195 | 187
Non-current regulatory liabilities | 73 | 104
Regulatory liabilities | 268 | 291
Deferred other post-retirement benefits cost |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory liabilities | 63 | 73
Fuel cost adjustment tax equivalents |  |
Regulatory Assets and Liabilities |  |
Current regulatory liabilities | 144 | 146
Fuel cost adjustment receivable/liability |  |
Regulatory Assets and Liabilities |  |
Current regulatory liabilities | 19 | 0
Unrealized gains/losses on commodity derivatives |  |
Regulatory Assets and Liabilities |  |
Current regulatory liabilities | 32 | 41
Non-current regulatory liabilities | 10 | 31
Gallatin coal combustion residual facilities |  |
Regulatory Assets and Liabilities |  |
Gallatin coal combustion residual facilities estimated cost to cap and close | 26 | 38
Non-nuclear decommissioning costs |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 78 | 73
Non-current regulatory assets | 897 | 692
Unrealized gains/losses on commodity derivatives |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 7 | 4
Non-current regulatory assets | 7 | 8
Fuel cost adjustment receivable/liability |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 0 | 30
Deferred nuclear generating units |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 0 | 3
Non-current regulatory assets | 12 | 11
Environmental cleanup costs – Kingston ash spill |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 130 | 266
Nuclear decommissioning costs |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 864 | 861
Deferred pension costs and other post-retirement benefits costs |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 3,000 | 3,119
Gallatin coal combustion residual facilities |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 856 | 784
Environmental agreements |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 1,054 | 1,019
Other non-current regulatory assets |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | $ 132 | $ 118

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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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