Stockholders' Equity - Stock Option Activity (Details) - $ / shares	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Number of Shares
Beginning balance (in shares)	2,806,364	2,845,866	3,015,374
Granted (in shares)	409,368	299,397	147,800
Exercised (in shares)	(1,384,647)	(250,823)	(235,514)
Canceled (in shares)	(144,183)	(88,076)	(81,794)
Ending balance (in shares)	1,686,902	2,806,364	2,845,866	3,015,374
Weighted- Average Exercise Price Per Share
Beginning balance (in dollars per share)	$ 4.75	$ 4.21	$ 3.95
Granted (in dollars per share)	9.59	8.60	7.06
Exercised (in dollars per share)	3.25	2.96	2.92
Cancelled (in dollars per share)	6.62	5.23	3.59
Ending balance (in dollars per share)	$ 7.00	$ 4.75	$ 4.21	$ 3.95
Additional Disclosures [Abstract]
Weighted- Average Remaining Contractual Term (in Years)	5 years 4 months 24 days	4 years 7 months 6 days	5 years 4 months 24 days	6 years 4 months 24 days