Accounts Receivable and Reserves for Product Sales - Summary of Total Reserves Included in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Receivables Net Current [Abstract]
Reduction to accounts receivable	$ 105	$ 1
Component of accrued expenses	875	305
Total reserves	$ 980	$ 306