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Fair Value Measurements - Recurring Fair Value Measures of Assets and Liabilities (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Sep. 30, 2023
--- | --- | ---
Assets: |  |  |
Cash Equivalents — Money Market Mutual Funds | [1] | $ 29,238 | $ 39,332
Derivative Financial Instruments: |  |  |
Derivative Asset, Statement of Financial Position [Extensible Enumeration] |  | Fair Value of Derivative Financial Instruments | Fair Value of Derivative Financial Instruments
Total Assets | [1] | $ 154,040 | $ 121,553
Derivative Financial Instruments: |  |  |
Derivative Liability, Statement of Financial Position [Extensible Enumeration] |  | Fair Value of Derivative Financial Instruments | Fair Value of Derivative Financial Instruments
Total Liabilities | [1] | $ 4,735 | $ 31,009
Total Net Assets/(Liabilities) | [1] | 149,305 | 90,544
Over the Counter Swaps — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | 58,811 | 28,292
Derivative Financial Instruments: |  |  |
Derivative Liability | [1] | 5,008 | 30,803
Over the Counter No Cost Collars — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | 28,810 | 16,221
Derivative Financial Instruments: |  |  |
Derivative Liability | [1] | (273) | 205
Contingent Consideration for Asset Sale |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | 729 | 7,277
Foreign Currency Contracts |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | (445) | (1,303)
Derivative Financial Instruments: |  |  |
Derivative Liability | [1] | 0 | 1
Balanced Equity Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments | [1] | 19,523 | 15,837
Fixed Income Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments | [1] | 17,374 | 15,897
Level 1 |  |  |
Assets: |  |  |
Cash Equivalents — Money Market Mutual Funds |  | 29,238 | 39,332
Derivative Financial Instruments: |  |  |
Total Assets |  | 66,135 | 71,066
Derivative Financial Instruments: |  |  |
Total Liabilities |  | 0 | 0
Total Net Assets/(Liabilities) |  | 66,135 | 71,066
Level 1 | Over the Counter Swaps — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 0 | 0
Level 1 | Over the Counter No Cost Collars — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 0 | 0
Level 1 | Contingent Consideration for Asset Sale |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Level 1 | Foreign Currency Contracts |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 0 | 0
Level 1 | Balanced Equity Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments |  | 19,523 | 15,837
Level 1 | Fixed Income Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments |  | 17,374 | 15,897
Level 2 |  |  |
Assets: |  |  |
Cash Equivalents — Money Market Mutual Funds |  | 0 | 0
Derivative Financial Instruments: |  |  |
Total Assets |  | 109,603 | 104,193
Derivative Financial Instruments: |  |  |
Total Liabilities |  | 26,433 | 84,715
Total Net Assets/(Liabilities) |  | 83,170 | 19,478
Level 2 | Over the Counter Swaps — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 76,009 | 65,800
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 22,206 | 68,311
Level 2 | Over the Counter No Cost Collars — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 32,584 | 30,966
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 3,501 | 14,950
Level 2 | Contingent Consideration for Asset Sale |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 729 | 7,277
Level 2 | Foreign Currency Contracts |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 281 | 150
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 726 | 1,454
Level 2 | Balanced Equity Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments |  | 0 | 0
Level 2 | Fixed Income Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments |  | 0 | 0
Level 3 |  |  |
Assets: |  |  |
Cash Equivalents — Money Market Mutual Funds |  | 0 | 0
Derivative Financial Instruments: |  |  |
Total Assets |  | 0 | 0
Derivative Financial Instruments: |  |  |
Total Liabilities |  | 0 | 0
Total Net Assets/(Liabilities) |  | 0 | 0
Level 3 | Over the Counter Swaps — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 0 | 0
Level 3 | Over the Counter No Cost Collars — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 0 | 0
Level 3 | Contingent Consideration for Asset Sale |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Level 3 | Foreign Currency Contracts |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset |  | 0 | 0
Derivative Financial Instruments: |  |  |
Derivative Liability |  | 0 | 0
Level 3 | Balanced Equity Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments |  | 0 | 0
Level 3 | Fixed Income Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments |  | 0 | 0
Netting Adjustments |  |  |
Assets: |  |  |
Cash Equivalents — Money Market Mutual Funds | [1] | 0 | 0
Derivative Financial Instruments: |  |  |
Total Assets | [1] | (21,698) | (53,706)
Derivative Financial Instruments: |  |  |
Total Liabilities | [1] | (21,698) | (53,706)
Total Net Assets/(Liabilities) | [1] | 0 | 0
Netting Adjustments | Over the Counter Swaps — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | (17,198) | (37,508)
Derivative Financial Instruments: |  |  |
Derivative Liability | [1] | (17,198) | (37,508)
Netting Adjustments | Over the Counter No Cost Collars — Gas |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | (3,774) | (14,745)
Derivative Financial Instruments: |  |  |
Derivative Liability | [1] | (3,774) | (14,745)
Netting Adjustments | Contingent Consideration for Asset Sale |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | 0 | 0
Netting Adjustments | Foreign Currency Contracts |  |  |
Derivative Financial Instruments: |  |  |
Derivative Asset | [1] | (726) | (1,453)
Derivative Financial Instruments: |  |  |
Derivative Liability | [1] | (726) | (1,453)
Netting Adjustments | Balanced Equity Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments | [1] | 0 | 0
Netting Adjustments | Fixed Income Mutual Fund |  |  |
Derivative Financial Instruments: |  |  |
Other Investments | [1] | $ 0 | $ 0
[1] | Netting Adjustments represent the impact of legally-enforceable master netting arrangements that allow the Company to net gain and loss positions held with the same counterparties. The net asset or net liability for each counterparty is recorded as an asset or liability on the Company’s balance sheet.

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