Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Contract With Customer Asset [Line Items]
Total billed receivables	$ 265,311	$ 322,119
Current unbilled receivables (contract assets)	244,214	204,596
Total accounts receivable	509,525	526,715
Less: Allowance for uncollectible amounts	(3,309)	(3,664)
Total accounts receivable, net	506,216	523,051
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	258,270	298,951
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 7,041	$ 23,168