Quarterly Financial Data (Unaudited) - Summarized Quarterly Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 7,352	$ 6,525	$ 6,945	$ 5,463	$ 5,732	$ 5,804	$ 5,862	$ 5,576	$ 26,285	$ 22,974
Gross profit	6,424	5,546	5,829	4,154	4,377	4,645	4,577	4,293	21,952	17,892
Operating income (loss)	679	55	74	(2,021)	(535)	(942)	(1,619)	(2,578)	(1,214)	(5,674)
Net income (loss)	$ 2,801	$ (983)	$ (2,177)	$ (2,381)	$ (160)	$ (1,670)	$ (1,952)	$ (2,880)	$ (2,740)	$ (6,661)
Net earnings (loss) per share - basic	$ 0.10	$ (0.04)	$ (0.10)	$ (0.16)	$ (0.01)	$ (0.12)	$ (0.15)	$ (0.24)	$ (0.14)	$ (0.49)
Weighted average shares outstanding - basic	26,925	25,020	21,888	15,299	14,281	14,297	13,179	12,163	22,322	13,489
Net earnings (loss) per share - diluted	$ 0.10	$ (0.04)	$ (0.10)	$ (0.16)	$ (0.01)	$ (0.12)	$ (0.15)	$ (0.24)	$ (0.14)	$ (0.49)
Weighted average shares outstanding - diluted	27,395	25,020	21,888	15,299	14,281	14,297	13,179	12,163	22,322	13,489