Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Sep. 30, 2018
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 53,744	$ 57,425
Reserve for Gas Replacement	(6,848)	(37,813)
Liability for Royalty and Working Interests	21,438	12,062
Other Accruals and Current Liabilities	195,797	132,693
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	52,875	38,354
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	36,922	0
Other Accruals [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	$ 30,818	$ 24,852