401(K) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Defined Benefit Plan Disclosure [Line Items] | |||
| Employer matching contribution expenses | $ 1.9 | $ 0.9 | $ 1.0 |
| First 3% of each Participant's Contributions | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Company's matching contributions to the 401(k)plan | 100.00% | ||
| Second 2% of each Participant's Contributions | |||
| Defined Benefit Plan Disclosure [Line Items] | |||
| Company's matching contributions to the 401(k)plan | 50.00% | ||