Stock-Based Awards - Schedule of Stock-Based Compensation Expense Related to Stock Options, Vesting of Restricted Common Stock and Grants of Common Stock (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | $ 4,640 | $ 2,644 | $ 476 |
| Research and Development Expense [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | 1,589 | 397 | 70 |
| Selling and Marketing Expense [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | 340 | 68 | 22 |
| General and Administrative Expense [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] | |||
| Stock-based compensation expense | $ 2,711 | $ 2,179 | $ 384 |