Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Sep. 30, 2020
Contract With Customer Asset [Line Items]
Total billed receivables	$ 361,717	$ 364,554
Current unbilled receivables (contract assets)	214,057	181,792
Total accounts receivable	575,774	546,346
Less: Allowance for uncollectible amounts	(3,831)	(8,359)
Total accounts receivable, net	571,943	537,987
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	273,951	307,914
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 87,766	$ 56,640