Summary of Significant Accounting Policies (Tables)
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9 Months Ended |
Jun. 30, 2026 |
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| Accounting Policies [Abstract] |
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| Schedule of Allowance for Uncollectible Accounts |
Activity in the allowance for uncollectible accounts for the nine months ended June 30, 2026 and 2025 are as follows (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Balance at Beginning of Period | | Additions Charged to Costs and Expenses | | Discounts on Purchased Receivables | | Net Accounts Receivable Written-Off | | Balance at End of Period | | Nine Months Ended June 30, 2026 | | | | | | | | | | | Allowance for Uncollectible Accounts | $ | 17,099 | | | $ | 14,903 | | | $ | 912 | | | $ | (9,303) | | | $ | 23,611 | | | Nine Months Ended June 30, 2025 | | | | | | | | | | | Allowance for Uncollectible Accounts | $ | 26,194 | | | $ | 17,758 | | | $ | 807 | | | $ | (21,027) | | | $ | 23,732 | |
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| Schedule of Components of Accumulated Other Comprehensive Income (Loss) |
The components of Accumulated Other Comprehensive Income (Loss) and changes for the nine months ended June 30, 2026 and 2025, net of related tax effect, are as follows (amounts in parentheses indicate debits) (in thousands): | | | | | | | | | | | | | | | | | | | | | | Gains and Losses on Derivative Financial Instruments | | | | Funded Status of the Pension and Other Post-Retirement Benefit Plans | | Total | | Three Months Ended June 30, 2026 | | | | | | | | | Balance at April 1, 2026 | $ | 80,283 | | | | | $ | (79,172) | | | $ | 1,111 | | Other Comprehensive Gains and Losses Before Reclassifications | 51,060 | | | | | — | | | 51,060 | | | Amounts Reclassified From Other Comprehensive Income | (42,595) | | | | | — | | | (42,595) | | | | | | | | | | | Balance at June 30, 2026 | $ | 88,748 | | | | | $ | (79,172) | | | $ | 9,576 | | | Nine Months Ended June 30, 2026 | | | | | | | | | Balance at October 1, 2025 | $ | 19,950 | | | | | $ | (79,172) | | | $ | (59,222) | | Other Comprehensive Gains and Losses Before Reclassifications | 85,408 | | | | | — | | | 85,408 | | | Amounts Reclassified From Other Comprehensive Income | (16,610) | | | | | — | | | (16,610) | | | | | | | | | | | | | | | | | | | Balance at June 30, 2026 | $ | 88,748 | | | | | $ | (79,172) | | | $ | 9,576 | | | Three Months Ended June 30, 2025 | | | | | | | | | Balance at April 1, 2025 | $ | (151,700) | | | | | $ | (71,275) | | | $ | (222,975) | | Other Comprehensive Gains and Losses Before Reclassifications | 108,818 | | | | | — | | | 108,818 | | | Amounts Reclassified From Other Comprehensive Loss | (1,650) | | | | | — | | | (1,650) | | | | | | | | | | | Balance at June 30, 2025 | $ | (44,532) | | | | | $ | (71,275) | | | $ | (115,807) | | | Nine Months Ended June 30, 2025 | | | | | | | | | Balance at October 1, 2024 | $ | 55,799 | | | | | $ | (71,275) | | | $ | (15,476) | | Other Comprehensive Gains and Losses Before Reclassifications | (83,082) | | | | | — | | | (83,082) | | | Amounts Reclassified From Other Comprehensive Loss | (17,249) | | | | | — | | | (17,249) | | | | | | | | | | | Balance at June 30, 2025 | $ | (44,532) | | | | | $ | (71,275) | | | $ | (115,807) | |
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| Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) |
The details about the reclassification adjustments out of accumulated other comprehensive income (loss) for the nine months ended June 30, 2026 and 2025 are as follows (amounts in parentheses indicate debits to the income statement) (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Details About Accumulated Other Comprehensive Income (Loss) Components | | Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income (Loss) | | Affected Line Item in the Statement Where Net Income is Presented | | Three Months Ended
June 30, | | Nine Months Ended
June 30, | | | 2026 | | 2025 | | 2026 | | 2025 | | Gains (Losses) on Derivative Financial Instrument Cash Flow Hedges: | | | | | | | | | | | | Commodity Contracts | | $58,258 | | | $2,515 | | | $22,959 | | | $24,409 | | | Operating Revenues | | | | | | | | | | | | | Foreign Currency Contracts | | (88) | | | (257) | | | (275) | | | (808) | | | Operating Revenues | | | | 58,170 | | | 2,258 | | | 22,684 | | | 23,601 | | | Total Before Income Tax | | | | (15,575) | | | (608) | | | (6,074) | | | (6,352) | | | Income Tax Expense | | | | $42,595 | | | $1,650 | | | $16,610 | | | $17,249 | | | Net of Tax |
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| Schedule of Other Current Assets |
The components of the Company’s Other Current Assets are as follows (in thousands): | | | | | | | | | | | | | | At June 30, 2026 | | At September 30, 2025 | | | | | | Prepayments | $ | 23,159 | | | $ | 16,477 | | | Prepaid Property and Other Taxes | 10,586 | | | 13,920 | | | Federal Income Taxes Receivable | — | | | 14,511 | | | State Income Taxes Receivable | — | | | 489 | | | | | | | Regulatory Assets | 33,915 | | | 35,362 | | | | $ | 67,660 | | | $ | 80,759 | |
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| Schedule of Other Accruals and Current Liabilities |
The components of the Company’s Other Accruals and Current Liabilities are as follows (in thousands): | | | | | | | | | | | | | | At June 30, 2026 | | At September 30, 2025 | | | | | | Accrued Capital Expenditures | $ | 63,908 | | | $ | 45,932 | | | Regulatory Liabilities | 17,737 | | | 20,624 | | | Reserve for Gas Replacement | 19,793 | | | — | | | Liability for Royalty and Working Interests | 27,038 | | | 28,076 | | | Federal Income Taxes Payable | 25,631 | | | — | | | State Income Taxes Payable | 9,628 | | | — | | | | | | | Pennsylvania Impact Fee | 7,479 | | | 14,923 | | | Non-Qualified Benefit Plan Liability | 11,567 | | | 11,567 | | | Other | 58,617 | | | 53,567 | | | | $ | 241,398 | | | $ | 174,689 | |
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