Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 30,638	$ 25,413	$ 23,192	$ 22,067	$ 25,018	$ 21,906	$ 19,983	$ 17,683	$ 21,037	$ 16,109	$ 14,277	$ 12,136	$ 101,310	$ 84,590	$ 63,559
Cost of revenue	3,577	3,496	3,186	2,933	3,229	3,168	2,991	2,878	2,674	2,678	1,717	1,617
Operating expenses	20,991	20,483	18,941	18,835	17,260	21,647	18,642	19,365	19,729	16,294	13,825	12,831
Operating income (loss)	6,070	1,434	1,065	299	4,529	(2,909)	(1,650)	(4,560)	(1,366)	(2,863)	(1,265)	(2,312)	8,868	(4,590)	(7,806)
Other income (expense), net	61	145	32	303	350	98	140	14	22	(1,351)	204	190	541	602	(935)
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)
Net income (loss)	$ 4,996	$ 1,348	$ 909	$ 561	$ 3,282	$ (99)	$ (716)	$ (3,191)	$ (2,127)	$ (2,784)	$ (1,160)	$ (5,736)	$ 7,814	$ (724)	$ (11,807)
Net income (loss) per share:
Net income (loss) per share—basic (in dollars per share)	$ 0.12	$ 0.03	$ 0.02	$ 0.01	$ 0.08	$ 0	$ (0.02)	$ (0.08)					$ 0.19	$ (0.02)	$ (0.33)
Net income (loss) per share—diluted (in dollars per share)	$ 0.12	$ 0.03	$ 0.02	$ 0.01	$ 0.08	$ 0	$ (0.02)	$ (0.08)					$ 0.18	$ (0.02)	$ (0.33)
Net income (loss) per share—basic and diluted (in dollars per share)									$ (0.06)	$ (0.08)	$ (0.03)	$ (0.17)
Shares used in calculating net income (loss) per share—basic (in shares)	41,770	41,483	41,022	40,615	40,252	39,936	38,926	38,247					41,410	39,341	35,811
Shares used in calculating net income (loss) per share—diluted (in shares)	43,101	42,428	42,028	41,828	41,635	39,936	38,926	38,247					42,533	39,341	35,811
Shares used in calculating net income (loss) per share—basic and diluted (in shares)									37,858	36,190	34,976	34,207