Income Taxes - Income Taxes Computed Using Federal Income Tax Rate (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Amount computed using statutory rate													$ (1,977)	$ 841	$ 2,122
Net change in valuation allowance for net deferred tax assets													221	(459)	(367)
Other													0	0	(191)
Foreign rate differential													86	664	22
Non-deductible items													(178)	(151)	(276)
State income tax													(205)	(370)	50
Impact of tax reform on deferred taxes													0	0	(4,901)
Research and development credits													897	1,694	475
Foreign income tax													10	(494)	0
Stock compensation, net													(449)	1,539	0
Income tax benefit (provision)	$ (1,135)	$ (231)	$ (188)	$ (41)	$ (1,597)	$ 2,712	$ 794	$ 1,355	$ (783)	$ 1,430	$ (99)	$ (3,614)	$ (1,595)	$ 3,264	$ (3,066)