Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018		Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income (loss)	$ 1,342	$ (126)	[1]	$ 6,024	$ (4,613)	[1]
Denominator:
Denominator for basic net income (loss) per common share — weighted average shares outstanding	27,866,000	27,084,000	[1]	27,687,000	26,914,000	[1]
Effect of dilutive securities:
Stock options and restricted stock units	572,000	0	[1]	602,000	0	[1]
Denominator for diluted net income (loss) per common share — adjusted weighted average shares	28,438,000	27,084,000	[1]	28,289,000	26,914,000	[1]
Basic net income (loss) per common share:
Net income (loss), basic (USD per share)	$ 0.05	$ 0.00	[1]	$ 0.22	$ (0.17)	[1]
Diluted net income (loss) per common share
Net income (loss), diluted (USD per share)	$ 0.05	$ 0.00	[1]	$ 0.21	$ (0.17)	[1]
Potentially dilutive securities excluded from computation of earnings per share	633,752	1,458,297		683,752	1,988,673
Excluded incremental common shares related to common stock options and restricted stock units		275,522			333,801

[1] Prior period information has been restated for the adoption of ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” which we adopted on October 1, 2018.