Condensed Quarterly Financial Data (unaudited) - Schedule of Condensed Quarterly Financial Data (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, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 36,931	$ 30,604	$ 30,345	$ 27,688	$ 30,032	$ 28,616	$ 24,999	$ 23,085	$ 125,568	$ 106,732	$ 114,905
Product and service gross profit	18,845	15,424	12,765	12,641	12,848	12,162	11,832	10,350
Net loss	$ 23,987	$ (22,748)	$ (20,037)	$ (21,898)	$ (21,111)	$ (16,486)	$ (20,601)	$ (19,202)	$ (40,696)	$ (77,400)	$ (43,562)
Earnings Per Share, Basic	$ 0.67	$ (0.64)	$ (0.57)	$ (0.69)
Net loss per share - basic and diluted (in dollars per share)					$ (0.68)	$ (0.56)	$ (0.80)	$ (0.75)	$ (1.18)	$ (2.78)	$ (1.84)
Earnings Per Share, Diluted	$ 0.61	$ (0.64)	$ (0.57)	$ (0.69)