Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 148,504	$ 135,588	$ 123,737	$ 109,351	$ 134,897	$ 122,130	$ 101,505	$ 90,184	$ 517,180	$ 448,716
Gross profit	28,555	23,715	20,075	14,631	24,005	18,375	12,421	10,554	86,976	65,355	$ 50,769
Net income (loss)	$ 6,538	$ 5,089	$ 958	$ (2,695)	$ 1,539	$ 301	$ (3,330)	$ (5,662)	$ 9,890	$ (7,152)	$ (9,486)
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.56	$ 0.44	$ 0.08	$ (0.23)	$ 0.13	$ 0.03	$ (0.29)	$ (0.49)	$ 0.85	$ (0.62)	$ (0.83)
Diluted (in dollars per share)	$ 0.56	$ 0.44	$ 0.08	$ (0.23)	$ 0.13	$ 0.03	$ (0.29)	$ (0.49)	$ 0.85	$ (0.62)	$ (0.83)