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Summary Of Significant Accounting Policies (Components Of Other Current Assets) (Details) - USD ($)
$ in Thousands
Jun. 30, 2017
Sep. 30, 2016
Summary Of Significant Accounting Policies [Line Items]    
Prepayments $ 11,396 $ 10,919
Prepaid Property and Other Taxes 11,180 13,138
Fair Values of Firm Commitments 1,473 3,962
Regulatory Assets 17,145 15,616
Other Current Assets 50,852 59,354
Federal [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Income Taxes Receivable 0 11,758
State [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Income Taxes Receivable $ 9,658 $ 3,961