Segment, Customer and Geographic Information - Revenue by Geographical Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Major Customer [Line Items]
Revenue	$ 114,249	$ 93,774	$ 76,051
Product
Revenue, Major Customer [Line Items]
Revenue	91,920	74,649	60,908
Product | UNITED STATES
Revenue, Major Customer [Line Items]
Revenue	31,517	20,611	12,563
Product | FRANCE
Revenue, Major Customer [Line Items]
Revenue	19,404	20,075	23,043
Product | BELGIUM
Revenue, Major Customer [Line Items]
Revenue	6,921	7,272	6,788
Product | Other Countries
Revenue, Major Customer [Line Items]
Revenue	34,078	26,691	18,514
Government Contract
Revenue, Major Customer [Line Items]
Revenue	22,329	19,125	15,143
Government Contract | UNITED STATES
Revenue, Major Customer [Line Items]
Revenue	$ 22,329	$ 19,125	$ 15,143