Nature of Operations and Summary of Significant Accounting Policies - Calculation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Net income	$ 2,167	$ 560
Weighted-average shares outstanding - basic (in shares)	42,476	40,615
Common stock equivalents (in shares)	1,421	1,213
Weighted-average shares outstanding - diluted (in shares)	43,897	41,828
Net income per share:
Basic (in dollars per share)	$ 0.05	$ 0.01
Diluted (in dollars per share)	$ 0.05	$ 0.01