Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | $ 6,747 | $ 4,595 | $ 3,598 |
Cost of product revenue | |||
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | 704 | 341 | 213 |
Research and development | |||
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | 481 | 537 | 336 |
Selling, general and administrative | |||
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | $ 5,562 | $ 3,717 | $ 3,049 |