Summary Of Significant Accounting Policies (Consolidated Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	Jun. 30, 2020		Sep. 30, 2019		Jun. 30, 2019	Sep. 30, 2018
Cash and Cash Equivalents [Line Items]
Cash and Temporary Cash Investments	$ 556,264		$ 20,428		$ 87,515	$ 229,606
Hedging Collateral Deposits	7,699	[1]	6,832	[1]	6,835	3,441
Cash, Cash Equivalents and Restricted Cash	$ 563,963		$ 27,260		$ 94,350	$ 233,047

[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.