Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ 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, 2020	Sep. 30, 2019	Sep. 30, 2018
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 73,169	$ 70,338	$ 73,447	$ 62,317		$ 64,960	$ 61,166	$ 65,764	$ 62,313	$ 279,271	$ 254,203	$ 226,893
Gross profit	37,518	37,349	38,641	30,464		30,595	28,328	30,329	29,783	143,972	119,035	109,054
Net (loss) income	$ 4,433	$ 1,766	$ 2,004	$ 208	[1]	$ 2,286	$ 1,648	$ 1,342	$ 4,682	$ 8,411	$ 9,958	$ 1,631
Net (loss) income per common share, basic (USD per share)	$ 0.15	$ 0.06	$ 0.07	$ 0.01		$ 0.08	$ 0.06	$ 0.05	$ 0.17	$ 0.29	$ 0.36	$ 0.06
Net (loss) income per common share, diluted (USD per share)	$ 0.15	$ 0.06	$ 0.07	$ 0.01		$ 0.08	$ 0.06	$ 0.05	$ 0.17	$ 0.28	$ 0.35	$ 0.06

[1] During fiscal 2020, we recorded a discrete tax benefit of $1.0 million in the first quarter of fiscal 2020 resulting from excess tax benefits recognized on stock compensation and an adjustment of our state deferred tax rate due to the Opengear acquisition.