Summary Of Significant Accounting Policies (Components Of Other Current Assets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items]
Prepayments	$ 6,208	$ 10,927
Prepaid Property and Other Taxes	22,482	13,974
Fair Values of Firm Commitments	1,608	1,031
Regulatory Assets	10,373	15,884
Other Current Assets	60,324	51,505
Federal [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Receivable	17,282	0
State [Member]
Summary Of Significant Accounting Policies [Line Items]
Income Taxes Receivable	$ 2,371	$ 9,689