Quarterly Financial Data - Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 9,381	$ 7,857	$ 7,329	$ 6,773	$ 6,954	$ 6,192	$ 6,162	$ 6,313	$ 31,340	$ 25,621	$ 28,102
Gross profit	7,165	6,054	5,726	5,282	5,410	4,738	4,784	4,498	24,227	19,430	18,176
Net loss	$ (3,348)	$ (2,956)	$ (3,530)	$ (3,717)	$ (3,344)	$ (1,365)	$ (1,027)	$ (3,281)	$ (13,551)	$ (9,017)	$ (14,256)
Income (loss) per share	$ (0.17)	$ (0.15)	$ (0.20)	$ (0.22)	$ (0.20)	$ (0.08)	$ (0.06)	$ (0.20)
Weighted average number of shares outstanding	19,320	19,284	17,640	17,200	16,774	16,700	16,664	16,583