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Summary Of Significant Accounting Policies (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Mar. 31, 2023
Mar. 31, 2022
Sep. 30, 2022
Sep. 30, 2023
Summary Of Significant Accounting Policies [Line Items]            
Gas Stored Underground $ 6,554   $ 6,554   $ 32,364  
Capitalized Costs Oil and Gas Producing Activities Net $ 2,200,000   2,200,000   1,900,000  
Capitalized costs of unproved properties excluded from amortization     $ 73,000   66,000  
Full cost ceiling test discount factor 10.00%   10.00%      
Amount Full Cost Ceiling Exceeds Book Value Of Oil And Gas Properties $ 2,700,000   $ 2,700,000      
Decrease estimated future net cash flows (936,800)          
Other Post-Retirement Adjustment for Regulatory Proceeding $ 0 $ (7,351) $ 0 $ (7,351)    
Other Post-Retirement Adjustment for Regulatory Proceeding After Tax   $ (5,807)   $ (5,807)    
Antidilutive securities 9,909 13,815 4,094 11,883    
Reserve For Gas Replacement [Member]            
Summary Of Significant Accounting Policies [Line Items]            
Gas Stored Underground $ 106,835   $ 106,835   $ 0  
Restricted Stock Units [Member]            
Summary Of Significant Accounting Policies [Line Items]            
Share based compensation other than options grants in period     115,073      
Granted in fiscal year, weighted average grant date fair value     $ 59.69      
Performance Shares [Member]            
Summary Of Significant Accounting Policies [Line Items]            
Share based compensation other than options grants in period     202,259      
Granted in fiscal year, weighted average grant date fair value     $ 64.28      
Subsequent Event [Member] | Reserve For Gas Replacement [Member]            
Summary Of Significant Accounting Policies [Line Items]            
Gas Stored Underground           $ 0