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Summary Of Significant Accounting Policies (Components Of Other Current Assets) (Details) - USD ($)
$ in Thousands
Jun. 30, 2018
Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items]    
Prepayments $ 10,594 $ 10,927
Prepaid Property and Other Taxes 11,177 13,974
Fair Values of Firm Commitments 1,350 1,031
Regulatory Assets 7,288 15,884
Other Current Assets 52,690 51,505
Federal [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Income Taxes Receivable 17,216 0
State [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Income Taxes Receivable $ 5,065 $ 9,689