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Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
3 Months Ended 6 Months Ended 9 Months Ended 12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Mar. 31, 2013
Mar. 31, 2012
Jun. 30, 2012
Sep. 30, 2012
Sep. 30, 2011
Summary Of Significant Accounting Policies [Line Items]              
Revisions to increase operating cash flows and decrease investing cash flows       $ 17,700,000 $ 32,800,000    
Revisions to decrease operating cash flows and increase investing cash flows           1,800,000 6,600,000
Hedging collateral deposits 750,000   750,000     364,000  
Gas stored underground - current (14,443,000)   (14,443,000)     (49,795,000)  
Capitalized costs of unproved properties excluded from amortization     152,000,000     146,100,000  
Full cost ceiling test discount factor 10.00%   10.00%        
Amount full cost ceiling exceeds book value of oil and gas properties 61,000,000   61,000,000        
Antidilutive securities 208,819 879,847 362,681 297,081      
Reserve For Gas Replacement [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Gas stored underground - current 46,963,000   46,963,000     0  
Stock Options [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Stock options granted     0        
Restricted Shares [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Share based compensation other than options grants in period     0        
Stock Appreciation Right [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Share based compensation other than options grants in period     412,970        
Share based compensation arrangement by share based payment award other than options grants in period weighted average grant date excise price     $ 53.05        
Granted in fiscal year, weighted average grant date fair value     $ 10.66        
Non-performance Based Restricted Stock Units [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Share based compensation other than options grants in period     26,100        
Granted in fiscal year, weighted average grant date fair value     $ 47.20        
Performance Based Restriced Stock Units [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Share based compensation other than options grants in period     255,604        
Granted in fiscal year, weighted average grant date fair value     $ 49.51        
Exchange-Traded Futures Contracts [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Hedging collateral deposits           400,000  
Over-The-Counter Crude Oil And Gas Swap Agreements [Member]
             
Summary Of Significant Accounting Policies [Line Items]              
Hedging collateral deposits $ 800,000   $ 800,000