Income Taxes (Unrecognized Tax Benefits, Additional Information) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	$ 2,400
Unrecognized tax benefits	2,600	$ 1,713	$ 1,561	$ 1,335
Accrued income tax penalties and interest for unrecognized tax benefits	100	$ 100
Noncurrent income taxes payable
Income Tax Contingency [Line Items]
Unrecognized tax benefits	1,900
Noncurrent deferred tax assets
Income Tax Contingency [Line Items]
Unrecognized tax benefits	700
Maximum
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits that is reasonably possible	$ 100