Income Taxes (Unrecognized Tax Benefits, Additional Information) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	$ 1,400
Unrecognized tax benefits	1,561	$ 1,335	$ 1,708	$ 1,618
Accrued income tax penalties and interest for unrecognized tax benefits	100	$ 100
Noncurrent income taxes payable
Income Tax Contingency [Line Items]
Unrecognized tax benefits	800
Noncurrent deferred tax assets
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 800