v3.26.1
Fair Value Measurements (Schedule of Recurring Fair Value Measures of Assets and Liabilities) (Details) - Fair Value, Recurring - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Derivative Financial Instruments:    
Derivative Asset Netting Adjustment [1] $ (15,704) $ (47,095)
Derivative Asset, Statement of Financial Position [Extensible Enumeration] Fair Value of Derivative Financial Instruments Fair Value of Derivative Financial Instruments
Total Assets [1] $ 1,384,032 $ 93,807
Derivative Financial Instruments:    
Derivative Liability Netting Adjustments [1] $ (15,704) $ (47,095)
Derivative Liability, Statement of Financial Position [Extensible Enumeration] Fair Value of Derivative Financial Instruments Fair Value of Derivative Financial Instruments
Total Liabilities [1] $ 292 $ 6,003
Total Net Assets/(Liabilities) Netting Adjustments [1] 0 0
Total Net Assets/(Liabilities) [1] 1,383,740 87,804
Balanced Equity Mutual Fund    
Derivative Financial Instruments:    
Other Investments [1] 15,093 13,786
Fixed Income Mutual Fund    
Derivative Financial Instruments:    
Other Investments [1] 10,292 10,082
Over the Counter Swaps – Gas    
Derivative Financial Instruments:    
Derivative Asset Netting Adjustment [1] (14,890) (33,615)
Derivative asset [1] 100,658 28,575
Derivative Financial Instruments:    
Derivative Liability Netting Adjustments [1] (14,890) (33,615)
Derivative liability [1] 0 554
Over the Counter No Cost Collars – Gas    
Derivative Financial Instruments:    
Derivative Asset Netting Adjustment [1] 0 (12,805)
Derivative asset [1] 27,756 11,344
Derivative Financial Instruments:    
Derivative Liability Netting Adjustments [1] 0 (12,805)
Derivative liability [1] 0 5,231
Foreign Currency Contracts    
Derivative Financial Instruments:    
Derivative Asset Netting Adjustment [1] (814) (675)
Derivative asset [1] (784) (531)
Derivative Financial Instruments:    
Derivative Liability Netting Adjustments [1] (814) (675)
Derivative liability [1] 292 218
Money Market Funds    
Assets:    
Cash Equivalents – Money Market Mutual Funds [1] 1,231,017 30,551
Level 1    
Derivative Financial Instruments:    
Total Assets 1,256,402 54,419
Derivative Financial Instruments:    
Total Liabilities 0 0
Total Net Assets/(Liabilities) 1,256,402 54,419
Level 1 | Balanced Equity Mutual Fund    
Derivative Financial Instruments:    
Other Investments 15,093 13,786
Level 1 | Fixed Income Mutual Fund    
Derivative Financial Instruments:    
Other Investments 10,292 10,082
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 | Foreign Currency Contracts    
Derivative Financial Instruments:    
Derivative Asset 0 0
Derivative Financial Instruments:    
Derivative Liability 0 0
Level 1 | Money Market Funds    
Assets:    
Cash Equivalents – Money Market Mutual Funds 1,231,017 30,551
Level 2    
Derivative Financial Instruments:    
Total Assets 143,334 86,483
Derivative Financial Instruments:    
Total Liabilities 15,996 53,098
Total Net Assets/(Liabilities) 127,338 33,385
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 2 | Over the Counter Swaps – Gas    
Derivative Financial Instruments:    
Derivative Asset 115,548 62,190
Derivative Financial Instruments:    
Derivative Liability 14,890 34,169
Level 2 | Over the Counter No Cost Collars – Gas    
Derivative Financial Instruments:    
Derivative Asset 27,756 24,149
Derivative Financial Instruments:    
Derivative Liability 0 18,036
Level 2 | Foreign Currency Contracts    
Derivative Financial Instruments:    
Derivative Asset 30 144
Derivative Financial Instruments:    
Derivative Liability 1,106 893
Level 2 | Money Market Funds    
Assets:    
Cash Equivalents – Money Market Mutual Funds 0 0
Level 3    
Derivative Financial Instruments:    
Total Assets 0 0
Derivative Financial Instruments:    
Total Liabilities 0 0
Total Net Assets/(Liabilities) 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
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 | Foreign Currency Contracts    
Derivative Financial Instruments:    
Derivative Asset 0 0
Derivative Financial Instruments:    
Derivative Liability 0 0
Level 3 | Money Market Funds    
Assets:    
Cash Equivalents – Money Market Mutual Funds $ 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.