Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2024
Summary Of Significant Accounting Policies [Line Items]
Gas Stored Underground	$ 14,186		$ 14,186		$ 32,509
Capitalized Costs Exploration and Production Activities Net	$ 2,600,000		2,600,000		2,400,000
Capitalized costs of unproved properties excluded from amortization			$ 202,200		$ 161,100
Full cost ceiling test discount factor (as a percent)	10.00%		10.00%
Impairment of Exploration and Production Properties	$ 200,696	$ 0	$ 200,696	$ 0
Increase estimated future net cash flows	$ 375,800
Antidilutive securities (in shares)	567,681	8,322	335	4,526
Number of shares available for future grant (in shares)	3,890,301		3,890,301
Impairment of Exploration and Production Properties
Summary Of Significant Accounting Policies [Line Items]
Deferred income tax benefit	$ 55,700
Reserve For Gas Replacement
Summary Of Significant Accounting Policies [Line Items]
Gas Stored Underground	$ 6,700		$ 6,700
Restricted Stock Units
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period (in shares)			220,778
Granted in fiscal year, weighted average grant date fair value (in USD per share)			$ 42.44
Performance Shares
Summary Of Significant Accounting Policies [Line Items]
Share based compensation other than options grants in period (in shares)			361,729
Granted in fiscal year, weighted average grant date fair value (in USD per share)			$ 44.23
Greenhouse gas emissions reductions, performance cycle			3 years
Performance Shares | Minimum
Summary Of Significant Accounting Policies [Line Items]
Return on capital, performance cycle (in years)			3 years
Relative shareholder return, performance cycle			3 years
Performance Shares | Maximum
Summary Of Significant Accounting Policies [Line Items]
Return on capital, performance cycle (in years)			5 years
Relative shareholder return, performance cycle			5 years
Subsequent Event | Reserve For Gas Replacement | Forecast
Summary Of Significant Accounting Policies [Line Items]
Gas Stored Underground						$ 0