Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Contract With Customer Asset [Line Items]
Total billed receivables	$ 367,060	$ 457,234
Current unbilled receivables (contract assets)	333,332	320,570
Total accounts receivable	700,392	777,804
Less: Allowance for uncollectible amounts	(7,793)	(7,738)	$ (7,793)	$ (7,738)
Total accounts receivable, net	692,599	770,066
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	365,322	455,831
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 1,738	$ 1,403