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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Sep. 30, 2025
Accounting Policies [Abstract] |
Schedule of Allowance for Uncollectible Accounts | Activity in the allowance for uncollectible accounts are as follows:
| Year Ended September 30
| 2025 |  | 2024 |  | 2023
| (Thousands)
Balance at Beginning of Year | $ | 26,194 |  |  | $ | 36,295 |  |  | $ | 40,228 |
Additions Charged to Costs and Expenses | 19,195 |  |  | 13,180 |  |  | 14,482 |
Add: Discounts on Purchased Receivables | 863 |  |  | 753 |  |  | 1,380 |
Deduct: Net Accounts Receivable Written-Off | 29,153 |  |  | 24,034 |  |  | 19,795 |
Balance at End of Year | $ | 17,099 |  |  | $ | 26,194 |  |  | $ | 36,295 |
Schedule of Depreciable Plant By Segment | The following is a summary of depreciable plant by segment:
| As of September 30
| 2025 |  | 2024
| (Thousands)
Integrated Upstream and Gathering | $ | 9,151,025 |  |  | $ | 8,417,495 |
Pipeline and Storage | 3,003,944 |  |  | 2,919,506 |
Utility | 2,801,821 |  |  | 2,645,981 |
All Other and Corporate | 16,650 |  |  | 15,915 |
| $ | 14,973,440 |  |  | $ | 13,998,897 |
Schedule of Average Depreciation, Depletion and Amortization Rates | Average depreciation, depletion and amortization rates are as follows:
| Year Ended September 30
| 2025 |  | 2024 |  | 2023
Integrated Upstream and Gathering: |  |  |  |  |
Exploration and Production Operations, per Mcfe(1) | $ | 0.61 |  |  | $ | 0.69 |  |  | $ | 0.63 |
Integrated Upstream and Gathering Other Operations | 3.6 | % |  | 3.6 | % |  | 3.5 | %
Pipeline and Storage | 2.6 | % |  | 2.7 | % |  | 2.6 | %
Utility | 2.8 | % |  | 2.8 | % |  | 2.7 | %
All Other and Corporate | 3.7 | % |  | 3.0 | % |  | 2.9 | %
(1)Amounts represents depletion of exploration and production properties.
Schedule of Components of Accumulated Other Comprehensive Income (Loss) | The components of Accumulated Other Comprehensive Loss and changes for the years ended September 30, 2025 and 2024, net of related tax effects, 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
Year Ended September 30, 2025 |  |  |  |  |  |  |
Balance at October 1, 2024 | $ | 55,799 |  |  |  |  | $ | (71,275) |  |  | $ | (15,476) |
Other Comprehensive Gains and Losses Before Reclassifications | (2,308) |  |  |  |  | (11,148) |  |  | (13,456) |
Amounts Reclassified From Other Comprehensive Loss | (33,541) |  |  |  |  | 3,251 |  |  | (30,290) |
Balance at September 30, 2025 | $ | 19,950 |  |  |  |  | $ | (79,172) |  |  | $ | (59,222) |
Year Ended September 30, 2024 |  |  |  |  |  |  |
Balance at October 1, 2023 | $ | 4,623 |  |  |  |  | $ | (59,683) |  |  | $ | (55,060) |
Other Comprehensive Gains and Losses Before Reclassifications | 205,697 |  |  |  |  | (13,515) |  |  | 192,182 |
Amounts Reclassified From Other Comprehensive Loss | (154,521) |  |  |  |  | 1,923 |  |  | (152,598) |
Balance at September 30, 2024 | $ | 55,799 |  |  |  |  | $ | (71,275) |  |  | $ | (15,476) |
Schedule of Reclassifications Out of Accumulated Other Comprehensive Income (Loss) | The details about the reclassification adjustments out of accumulated other comprehensive loss for the years ended September 30, 2025 and 2024 are as follows (amounts in parentheses indicate debits to the income statement) (in thousands):
Details About Accumulated Other Comprehensive Loss Components |  | Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Loss for the Year Ended September 30, |  | Affected Line Item in the Statement Where Net Income is Presented
|  | 2025 |  | 2024 |  |
Gains (Losses) on Derivative Financial Instrument Cash Flow Hedges: |  |  |  |  |  |
Commodity Contracts |  | $ | 46,957 |  |  | $ | 217,012 |  |  | Operating Revenues
Foreign Currency Contracts |  | (1,066) |  |  | (357) |  |  | Operating Revenues
Amortization of Prior Year Funded Status of the Pension and Other Post-Retirement Benefit Plans: |  |  |  |  |  |
Prior Service Cost |  | (42) |  |  | (56) |  |  | (1)
Net Actuarial Loss |  | (4,210) |  |  | (2,451) |  |  | (1)
|  | 41,639 |  |  | 214,148 |  |  | Total Before Income Tax
|  | (11,349) |  |  | (61,550) |  |  | Income Tax Expense
|  | $ | 30,290 |  |  | $ | 152,598 |  |  | Net of Tax
(1)These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. Refer to Note K — Retirement Plan and Other Post-Retirement Benefits for additional details.
Schedule of Cash, Cash Equivalents and Restricted Cash | The components, as reported on the Company’s Consolidated Balance Sheets, of the total cash, cash equivalents, and restricted cash presented on the Statement of Cash Flows are as follows (in thousands):
| Year Ended September 30
| 2025 |  | 2024 |  | 2023 |  | 2022
Cash and Temporary Cash Investments | $ | 43,166 |  |  | $ | 38,222 |  |  | $ | 55,447 |  |  | $ | 46,048 |
Hedging Collateral Deposits | — |  |  | — |  |  | — |  |  | 91,670 |
Cash, Cash Equivalents, and Restricted Cash | $ | 43,166 |  |  | $ | 38,222 |  |  | $ | 55,447 |  |  | $ | 137,718 |
Schedule of Other Current Assets | The components of the Company’s Other Current Assets are as follows:
| Year Ended September 30
| 2025 |  | 2024
| (Thousands)
Prepayments | $ | 16,477 |  |  | $ | 18,463 |
Prepaid Property and Other Taxes | 13,920 |  |  | 14,187 |
Federal Income Taxes Receivable | 14,511 |  |  | 8,154 |
State Income Taxes Receivable | 489 |  |  | 13,161 |
Regulatory Assets | 35,362 |  |  | 38,264 |
| $ | 80,759 |  |  | $ | 92,229 |
Schedule of Other Accruals And Current Liabilities | The components of the Company’s Other Accruals and Current Liabilities are as follows:
| Year Ended September 30
| 2025 |  | 2024
| (Thousands)
Accrued Capital Expenditures | $ | 45,932 |  |  | $ | 47,344 |
Regulatory Liabilities | 20,624 |  |  | 29,352 |
Liability for Royalty and Working Interests | 28,076 |  |  | 15,007 |
Pennsylvania Impact Fee | 14,923 |  |  | 9,972 |
Non-Qualified Benefit Plan Liability | 11,567 |  |  | 14,135 |
Other | 53,567 |  |  | 47,093 |
| $ | 174,689 |  |  | $ | 162,903 |

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