Share-Based Compensation Expense Recognized in Accompanying Statements of Operations (Detail) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Share-based compensation expense | $ 9,203 | $ 12,406 | $ 29,744 | $ 29,458 |
| Research and development | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Share-based compensation expense | 7,039 | 9,039 | 20,962 | 19,798 |
| General and administrative | ||||
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | ||||
| Share-based compensation expense | $ 2,164 | $ 3,367 | $ 8,782 | $ 9,660 |