Supporting Financial Information - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 12,843	$ 11,911
Less: Allowance for doubtful accounts	0	0
Accounts receivable, net	12,843	11,911
Billed Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	12,843	11,862
Unbilled Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 0	$ 49