Selected Quarterly Results (Unaudited) (Detail) - USD ($) $ / shares in Units, $ 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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Revenue	$ 31,637	$ 30,306	$ 29,677	$ 19,769	$ 18,028	$ 14,156	$ 12,175	$ 11,281	$ 12,510	$ 11,253	$ 8,744	$ 29,478	$ 111,389	$ 55,640	$ 61,985
Gross profit	24,372	24,956	24,754	15,717	14,005	10,377	7,609	7,866	7,275	6,808	4,573	23,833
Income (loss) from operations	613	1,596	2,799	(1,272)	(4,448)	(3,811)	(7,266)	(8,123)	(14,291)	(10,045)	(12,987)	7,903	3,736	(23,648)	(29,420)
Net income (loss)	$ (696)	$ 354	$ (11,130)	$ (3,833)	$ (7,008)	$ (18,880)	$ (9,770)	$ (10,709)	$ (16,210)	$ (11,951)	$ (14,879)	$ 48,325	$ (15,305)	$ (46,367)	$ 5,285
Basic (loss) earnings per share (in usd per share)	$ 0	$ 0	$ (0.13)	$ (0.05)	$ (0.13)	$ (0.29)	$ (0.16)	$ (0.18)	$ (0.31)	$ (0.21)	$ (0.27)	$ 0.89	$ (0.18)	$ (0.73)	$ 0.10
Diluted (loss) earnings per share (in usd per share)	$ 0	$ 0	$ (0.13)	$ (0.05)	$ (0.13)	$ (0.29)	$ (0.16)	$ (0.18)	$ (0.30)	$ (0.21)	$ (0.27)	$ 0.87	$ (0.18)	$ (0.73)	$ 0.09