Fair Value Measurements (Recurring Fair Value Measures Of Assets And Liabilities) (Details) - USD ($) $ in Thousands		Jun. 30, 2022		Sep. 30, 2021		Jun. 30, 2021	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	[1]	$ 406,961		$ 22,269
Hedging Collateral Deposits		154,470	[1]	88,610	[1]	$ 1,710	$ 0
Total Assets	[1]	628,638		215,951
Total Liabilities	[1]	703,788		616,410
Total Net Assets/(Liabilities)	[1]	(75,150)		(400,459)
Over The Counter Swaps - Gas and Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset	[1]			0
Derivative Liability	[1]			599,749
Over the Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liability	[1]	537,456
Over the Counter No Cost Collars - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset	[1]	0
Derivative Liability		166,349	[1]	17,385
Contingent Consideration for Asset Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		12,571
Foreign Currency Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset	[1]	0		0
Derivative Liability	[1]	(17)		(724)
Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments	[1]	20,700		34,433
Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments	[1]	33,936		70,639
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds		406,961		22,269
Hedging Collateral Deposits	[1]	154,470		88,610
Total Assets		616,067		215,951
Total Liabilities		0		0
Total Net Assets/(Liabilities)		616,067		215,951
Fair Value, Inputs, Level 1 [Member] | Over The Counter Swaps - Gas and Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset				0
Derivative Liability				0
Fair Value, Inputs, Level 1 [Member] | Over the Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liability		0
Fair Value, Inputs, Level 1 [Member] | Over the Counter No Cost Collars - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0
Derivative Liability		0		0
Fair Value, Inputs, Level 1 [Member] | Contingent Consideration for Asset Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0
Fair Value, Inputs, Level 1 [Member] | Foreign Currency Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0		0
Derivative Liability		0		0
Fair Value, Inputs, Level 1 [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments		20,700		34,433
Fair Value, Inputs, Level 1 [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments		33,936		70,639
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds		0		0
Hedging Collateral Deposits	[1]	0		0
Total Assets		13,961		2,740
Total Liabilities		705,178		619,150
Total Net Assets/(Liabilities)		(691,217)		(616,410)
Fair Value, Inputs, Level 2 [Member] | Over The Counter Swaps - Gas and Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset				1,802
Derivative Liability				601,551
Fair Value, Inputs, Level 2 [Member] | Over the Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liability		537,456
Fair Value, Inputs, Level 2 [Member] | Over the Counter No Cost Collars - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		893
Derivative Liability		167,242		17,385
Fair Value, Inputs, Level 2 [Member] | Contingent Consideration for Asset Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		12,571
Fair Value, Inputs, Level 2 [Member] | Foreign Currency Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		497		938
Derivative Liability		480		214
Fair Value, Inputs, Level 2 [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments		0		0
Fair Value, Inputs, Level 2 [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments		0		0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds		0		0
Hedging Collateral Deposits	[1]	0		0
Total Assets		0		0
Total Liabilities		0		0
Total Net Assets/(Liabilities)		0		0
Fair Value, Inputs, Level 3 [Member] | Over The Counter Swaps - Gas and Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset				0
Derivative Liability				0
Fair Value, Inputs, Level 3 [Member] | Over the Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liability		0
Fair Value, Inputs, Level 3 [Member] | Over the Counter No Cost Collars - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0
Derivative Liability		0		0
Fair Value, Inputs, Level 3 [Member] | Contingent Consideration for Asset Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0
Fair Value, Inputs, Level 3 [Member] | Foreign Currency Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0		0
Derivative Liability		0		0
Fair Value, Inputs, Level 3 [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments		0		0
Fair Value, Inputs, Level 3 [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments		0		0
Netting Adjustments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash Equivalents - Money Market Mutual Funds	[1]	0		0
Hedging Collateral Deposits	[1]	0		0
Total Assets	[1]	(1,390)		(2,740)
Total Liabilities	[1]	(1,390)		(2,740)
Total Net Assets/(Liabilities)	[1]	0		0
Netting Adjustments [Member] | Over The Counter Swaps - Gas and Oil [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset	[1]			(1,802)
Derivative Liability	[1]			(1,802)
Netting Adjustments [Member] | Over the Counter Swaps - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liability	[1]	0
Netting Adjustments [Member] | Over the Counter No Cost Collars - Gas [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset	[1]	(893)
Derivative Liability		(893)	[1]	0
Netting Adjustments [Member] | Contingent Consideration for Asset Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset		0
Netting Adjustments [Member] | Foreign Currency Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Asset	[1]	(497)		(938)
Derivative Liability	[1]	(497)		(938)
Netting Adjustments [Member] | Balanced Equity Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Other Investments	[1]	0		0
Netting Adjustments [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
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.