Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Contract With Customer Asset [Line Items]
Total billed receivables	$ 322,119	$ 364,554
Current unbilled receivables (contract assets)	204,596	181,792
Total accounts receivable	526,715	546,346
Less: Allowance for uncollectible amounts	(3,664)	(8,359)
Total accounts receivable, net	523,051	537,987
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	298,951	307,914
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 23,168	$ 56,640