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Revenue Recognition - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Product Revenue Allowance and Revenue Categories [Line Items]    
Concentration risk, percentage 66.00% 86.00%
Remaining reserves balances recorded as accrued liabilities $ 1.8  
Chargebacks and Discounts    
Product Revenue Allowance and Revenue Categories [Line Items]    
Reserves recorded as reduction of accounts receivable $ 2.3  
Product | Revenue | Credit Concentration Risk    
Product Revenue Allowance and Revenue Categories [Line Items]    
Concentration risk, customer three largest Customers