Summary of Disaggregation of Product Revenues from Contracts with Customers by Major Product Line (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Product revenue	$ 44,799	$ 30,569
Royalty and other revenue	31	21
Total revenue	44,830	$ 30,590
Product revenue, percentage change amount	14,230
Royalty and other revenue, percentage change amount	10
Total revenue, percentage change amount	$ 14,240
Product revenue, percentage change	47.00%
Royalty and other revenue, percentage change	48.00%
Total revenue, percentage change	47.00%