Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Types and Geography (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	$ 16,443	$ 698	$ 42,633	$ 1,925
Product
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	15,366	0	40,745	0
Service
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	958	579	1,650	1,687
Distribution Rights
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	119	119	238	238
U.S.
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	6,555	312	20,486	1,191
U.S. | Product
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	6,053	0	19,588	0
U.S. | Service
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	502	312	898	1,191
Outside of U.S. ("OUS")
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	9,888	386	22,147	734
Outside of U.S. ("OUS") | Product
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	9,313	0	21,157	0
Outside of U.S. ("OUS") | Service
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	456	267	752	496
Outside of U.S. ("OUS") | Distribution Rights
Disaggregation Of Revenue [Line Items]
Product, service and distribution rights revenue	$ 119	$ 119	$ 238	$ 238