Summary Of Significant Accounting Policies (Consolidated Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	Jun. 30, 2019		Sep. 30, 2018		Jun. 30, 2018	Sep. 30, 2017
Cash and Cash Equivalents [Line Items]
Cash and Temporary Cash Investments	$ 87,515		$ 229,606		$ 313,307	$ 555,530
Hedging Collateral Deposits	6,835	[1]	3,441	[1]	2,283	1,741
Cash, Cash Equivalents and Restricted Cash	$ 94,350		$ 233,047		$ 315,590	$ 557,271

[1] Netting Adjustments represent the impact of legally-enforceable master netting arrangements that allow the Company to net gain and loss positions held with the same counterparties. The net asset or net liability for each counterparty is recorded as an asset or liability on the Company’s balance sheet.