Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Types and Geography (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Product	$ 25,379	$ 0
Service	692	1,108
Distribution rights	119	119
Total revenue	26,190	1,227
U.S.
Disaggregation Of Revenue [Line Items]
Product	13,535	0
Service	396	879
Total revenue	13,931	879
Outside of U.S. ("OUS")
Disaggregation Of Revenue [Line Items]
Product	11,844	0
Service	296	229
Distribution rights	119	119
Total revenue	$ 12,259	$ 348