Fair Value Measurements (Recurring Fair Value Measures Of Assets And Liabilities) (Details) - USD ($) $ in Thousands		Mar. 31, 2024		Sep. 30, 2023
Assets:
Cash Equivalents – Money Market Mutual Funds	[1]	$ 27,965		$ 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]	$ 259,138		$ 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]	$ 0		$ 31,009
Total Net Assets/(Liabilities)	[1]	259,138		90,544
Over the Counter Swaps – Gas
Derivative Financial Instruments:
Derivative Asset	[1]	137,525		28,292
Derivative Financial Instruments:
Derivative Liability	[1]	0		30,803
Over the Counter No Cost Collars – Gas
Derivative Financial Instruments:
Derivative Asset		55,909	[1]	16,221
Derivative Financial Instruments:
Derivative Liability	[1]			205
Contingent Consideration for Asset Sale
Derivative Financial Instruments:
Derivative Asset	[1]	3,615		7,277
Foreign Currency Contracts
Derivative Financial Instruments:
Derivative Asset	[1]	(758)		(1,303)
Derivative Financial Instruments:
Derivative Liability	[1]	0		1
Balanced Equity Mutual Fund
Derivative Financial Instruments:
Other Investments	[1]	18,291		15,837
Fixed Income Mutual Fund
Derivative Financial Instruments:
Other Investments	[1]	16,591		15,897
Level 1
Assets:
Cash Equivalents – Money Market Mutual Funds		27,965		39,332
Derivative Financial Instruments:
Total Assets		62,847		71,066
Derivative Financial Instruments:
Total Liabilities		0		0
Total Net Assets/(Liabilities)		62,847		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
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		18,291		15,837
Level 1 | Fixed Income Mutual Fund
Derivative Financial Instruments:
Other Investments		16,591		15,897
Level 2
Assets:
Cash Equivalents – Money Market Mutual Funds		0		0
Derivative Financial Instruments:
Total Assets		214,642		104,193
Derivative Financial Instruments:
Total Liabilities		18,351		84,715
Total Net Assets/(Liabilities)		196,291		19,478
Level 2 | Over the Counter Swaps – Gas
Derivative Financial Instruments:
Derivative Asset		154,896		65,800
Derivative Financial Instruments:
Derivative Liability		17,371		68,311
Level 2 | Over the Counter No Cost Collars – Gas
Derivative Financial Instruments:
Derivative Asset		55,909		30,966
Derivative Financial Instruments:
Derivative Liability				14,950
Level 2 | Contingent Consideration for Asset Sale
Derivative Financial Instruments:
Derivative Asset		3,615		7,277
Level 2 | Foreign Currency Contracts
Derivative Financial Instruments:
Derivative Asset		222		150
Derivative Financial Instruments:
Derivative Liability		980		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
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]	(18,351)		(53,706)
Derivative Financial Instruments:
Total Liabilities	[1]	(18,351)		(53,706)
Total Net Assets/(Liabilities)	[1]	0		0
Netting Adjustments | Over the Counter Swaps – Gas
Derivative Financial Instruments:
Derivative Asset	[1]	(17,371)		(37,508)
Derivative Financial Instruments:
Derivative Liability	[1]	(17,371)		(37,508)
Netting Adjustments | Over the Counter No Cost Collars – Gas
Derivative Financial Instruments:
Derivative Asset		0	[1]	(14,745)
Derivative Financial Instruments:
Derivative Liability	[1]			(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]	(980)		(1,453)
Derivative Financial Instruments:
Derivative Liability	[1]	(980)		(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.