Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits at the beginning of the year	$ 1,607	$ 1,321	$ 1,181
Additions from tax positions taken in the current year	203	213	140
Additions from tax positions taken in prior years	0	73	0
Reductions from tax positions taken in prior years	0	0	0
Tax settlements	0	0	0
Gross unrecognized tax benefits at end of the year	$ 1,810	$ 1,607	$ 1,321