Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Contract With Customer Asset [Line Items]
Less: Allowance for uncollectible amounts	$ (4,053)	$ (7,908)
Net billed receivables	399,638	416,205
Current unbilled receivables (contract assets), net	201,586	175,324
Total accounts receivable, net	601,224	591,529
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	363,661	381,942
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 40,030	$ 42,171