Nature of Operations and Summary of Significant Accounting Policies - Calculation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accounting Policies [Abstract]
Net income (loss)	$ (2,784)	$ 616	$ (9,680)	$ 1,226
Weighted-average shares outstanding - basic (in shares)	36,190	33,024	35,122	32,732
Common stock equivalents (in shares)	0	2,586	0	2,301
Weighted-average shares outstanding - diluted (in shares)	36,190	35,610	35,122	35,033
Net income (loss) per share:
Basic (in dollars per share)	$ (0.08)	$ 0.02	$ (0.28)	$ 0.04
Diluted (in dollars per share)	$ (0.08)	$ 0.02	$ (0.28)	$ 0.03