Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Types and Geography (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	$ 80,962	$ 34,042	$ 22,237
Product
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	76,626	30,458	20,555
Service
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	3,861	3,109	1,504
Distribution Rights
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	475	475	178
U.S.
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	34,231	11,506	1,106
U.S. | Product
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	32,265	9,529	0
U.S. | Service
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	1,966	1,977	1,066
U.S. | Distribution Rights
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	0	0	40
Outside of U.S. ("OUS")
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	46,731	22,536	21,131
Outside of U.S. ("OUS") | Product
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	44,361	20,929	20,555
Outside of U.S. ("OUS") | Service
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	1,895	1,132	438
Outside of U.S. ("OUS") | Distribution Rights
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	$ 475	$ 475	$ 138