Quarterly Financial Information (Unaudited) - Summary of Selected Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 11,790	$ 12,986	$ 13,956	$ 11,247	$ 20,930	$ 11,556	$ 11,610	$ 10,477	$ 49,979	$ 54,573	$ 38,287
Gross profit	4,754	5,267	6,306	4,691	15,159	5,851	5,143	4,127	21,018	30,280	16,873
Operating expenses	5,271	6,802	6,662	6,146	6,042	5,674	7,420	5,865	24,881	25,001	18,746
(Loss) income from operations	(517)	(1,535)	(356)	(1,455)	9,117	177	(2,277)	(1,738)	(3,863)	5,279	(1,873)
Net (loss) income	$ 1,167	$ (1,410)	$ (376)	$ (1,441)	$ 9,614	$ 248	$ (2,268)	$ (1,643)	$ (2,060)	$ 5,951	$ (1,496)
(Loss) income per common share:
Basic	$ 0.11	$ (0.13)	$ 0.01	$ (0.13)	$ 0.89	$ 0.02	$ (0.21)	$ (0.15)	$ (0.15)	$ 0.55	$ (0.14)
Diluted	$ 0.11	$ (0.13)	$ (0.03)	$ (0.13)	$ 0.88	$ 0.02	$ (0.21)	$ (0.15)	$ (0.15)	$ 0.55	$ (0.14)