Fair Value Measurements (Narrative) (Details) - USD ($)	Sep. 30, 2022		Sep. 30, 2021		Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Hedging collateral deposits	$ 91,670,000	[1]	$ 88,610,000	[1]	$ 0	$ 6,832,000
Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Level 3 Fair Value	0		0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Hedging collateral deposits	$ 91,670,000		$ 88,610,000

[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.