Revenue (Schedule of Accounts Receivable) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Contract With Customer Asset [Line Items]
Less: Allowance for uncollectible amounts	$ (3,813)	$ (7,908)
Net billed receivables	366,974	416,205
Current unbilled receivables (contract assets), net	205,469	175,324
Total accounts receivable, net	572,443	591,529
Trade Accounts Receivable [Member]
Contract With Customer Asset [Line Items]
Billed receivables	354,152	381,942
Other (Chinese Financial Institutions) [Member]
Contract With Customer Asset [Line Items]
Billed receivables	$ 16,635	$ 42,171