Fair Value Measurements - Recurring Fair Value Measures Of Assets And Liabilities (Details) - USD ($) $ in Thousands		Mar. 31, 2025	Sep. 30, 2024
Assets:
Cash Equivalents – Money Market Mutual Funds	[1]	$ 29,300	$ 29,238
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]	$ 58,147	$ 154,040
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]	$ 201,464	$ 4,735
Total Net Assets/(Liabilities)	[1]	(143,317)	149,305
Over the Counter Swaps – Gas
Derivative Financial Instruments:
Derivative Asset	[1]	0	58,811
Derivative Financial Instruments:
Derivative Liability	[1]	126,862	5,008
Over the Counter No Cost Collars – Gas
Derivative Financial Instruments:
Derivative Asset	[1]	0	28,810
Derivative Financial Instruments:
Derivative Liability	[1]	72,884	(273)
Contingent Consideration for Asset Sale
Derivative Financial Instruments:
Derivative Asset	[1]	45	729
Foreign Currency Contracts
Derivative Financial Instruments:
Derivative Asset	[1]	0	(445)
Derivative Financial Instruments:
Derivative Liability	[1]	1,718	0
Balanced Equity Mutual Fund
Derivative Financial Instruments:
Other Investments	[1]	12,210	19,523
Fixed Income Mutual Fund
Derivative Financial Instruments:
Other Investments	[1]	16,592	17,374
Level 1
Assets:
Cash Equivalents – Money Market Mutual Funds		29,300	29,238
Derivative Financial Instruments:
Total Assets		58,102	66,135
Derivative Financial Instruments:
Total Liabilities		0	0
Total Net Assets/(Liabilities)		58,102	66,135
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		12,210	19,523
Level 1 | Fixed Income Mutual Fund
Derivative Financial Instruments:
Other Investments		16,592	17,374
Level 2
Assets:
Cash Equivalents – Money Market Mutual Funds		0	0
Derivative Financial Instruments:
Total Assets		17,477	109,603
Derivative Financial Instruments:
Total Liabilities		218,896	26,433
Total Net Assets/(Liabilities)		(201,419)	83,170
Level 2 | Over the Counter Swaps – Gas
Derivative Financial Instruments:
Derivative Asset		16,763	76,009
Derivative Financial Instruments:
Derivative Liability		143,625	22,206
Level 2 | Over the Counter No Cost Collars – Gas
Derivative Financial Instruments:
Derivative Asset		626	32,584
Derivative Financial Instruments:
Derivative Liability		73,510	3,501
Level 2 | Contingent Consideration for Asset Sale
Derivative Financial Instruments:
Derivative Asset		45	729
Level 2 | Foreign Currency Contracts
Derivative Financial Instruments:
Derivative Asset		43	281
Derivative Financial Instruments:
Derivative Liability		1,761	726
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]	(17,432)	(21,698)
Derivative Financial Instruments:
Total Liabilities	[1]	(17,432)	(21,698)
Total Net Assets/(Liabilities)	[1]	0	0
Netting Adjustments | Over the Counter Swaps – Gas
Derivative Financial Instruments:
Derivative Asset	[1]	(16,763)	(17,198)
Derivative Financial Instruments:
Derivative Liability	[1]	(16,763)	(17,198)
Netting Adjustments | Over the Counter No Cost Collars – Gas
Derivative Financial Instruments:
Derivative Asset	[1]	(626)	(3,774)
Derivative Financial Instruments:
Derivative Liability	[1]	(626)	(3,774)
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]	(43)	(726)
Derivative Financial Instruments:
Derivative Liability	[1]	(43)	(726)
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.