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Regulatory Assets and Liabilities (Details) $ in Millions | Dec. 31, 2024 USD ($) | Sep. 30, 2024 USD ($)
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Regulatory Assets and Liabilities |  |
Current regulatory assets | $ 110 | $ 191
Non-current regulatory assets | 9,287 | 9,408
Environmental Remediation Costs Recognized [Abstract] | 215 | 215
Regulatory assets | 9,397 | 9,599
Current regulatory liabilities | 186 | 174
Regulatory Liability, Noncurrent | 78 | 83
Regulatory Liabilities | 264 | 257
Fair value | $ 32 | $ 64
Commodity Contract Derivatives |  |
Regulatory Assets and Liabilities |  |
Number of contracts | 51 | 45
Derivative, Nonmonetary Notional Amount | 508,000,000 | 321,000,000
Fair value | $ 6 | $ 2
Fuel cost adjustment tax equivalents |  |
Regulatory Assets and Liabilities |  |
Current regulatory liabilities | 169 | 169
Unrealized gains/losses on commodity derivatives |  |
Regulatory Assets and Liabilities |  |
Current regulatory liabilities | 17 | 5
Regulatory Liability, Noncurrent | 1 | 2
Postretirement Benefit Costs |  |
Regulatory Assets and Liabilities |  |
Regulatory Liability, Noncurrent | 77 | 81
Unrealized losses on interest rate derivatives [Member] |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 46 | 54
Non-current regulatory assets | 282 | 447
Unrealized gains/losses on commodity derivatives |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 55 | 102
Non-current regulatory assets | 32 | 64
Fuel cost adjustment receivable/liability |  |
Regulatory Assets and Liabilities |  |
Current regulatory assets | 9 | 35
Pension Costs [Member] |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 1,959 | 1,979
Nuclear desommissioning costs [Member] |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 440 | 362
Non-nuclear decommissioning [Member] |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | 6,202 | 6,187
Other non-current regulatory assets [Member] |  |
Regulatory Assets and Liabilities |  |
Non-current regulatory assets | $ 157 | $ 154

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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 -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 + Details
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