Summary Of Significant Accounting Policies (Schedule Of Other Accruals And Current Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018
Summary Of Significant Accounting Policies [Line Items]
Regulatory Liabilities	$ 50,233	$ 57,425
Reserve for Gas Replacement	(17,075)	(37,813)
Liability for Royalty and Working Interests	19,846	12,062
Other Accruals and Current Liabilities	180,063	132,693
Accrued Capital Expenditures [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	60,082	38,354
Reserve For Gas Replacement [Member]
Summary Of Significant Accounting Policies [Line Items]
Reserve for Gas Replacement	16,251	0
Other Accruals [Member]
Summary Of Significant Accounting Policies [Line Items]
Other	$ 33,651	$ 24,852