Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Contract With Customer Asset [Line Items]
Total billed receivables	$ 483,696	$ 485,227
Current unbilled receivables (contract assets)	300,146	270,479
Total accounts receivable	783,842	755,706
Less: Allowance for uncollectible amounts	(5,777)	(5,847)
Total accounts receivable, net	778,065	749,859
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	426,598	434,287
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 57,098	$ 50,940