Income Taxes - Summary of Activity Related to Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Income Tax Disclosure [Abstract] | |||
| Beginning balance | $ 4,340 | $ 582 | $ 0 |
| Increases related to prior year tax positions | 12,332 | 3,758 | 0 |
| Increases related to current year tax positions | 873 | 0 | 582 |
| Ending balance | $ 17,545 | $ 4,340 | $ 582 |