Stock-Based Compensation - Summary of Share Based Compensation Expense (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2016 |
Jun. 30, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
|
| Stock-based compensation expense: | ||||
| Total stock-based compensation expense | $ 1,406 | $ 1,640 | $ 2,896 | $ 3,359 |
| Time-based Restricted Units [Member] | ||||
| Stock-based compensation expense: | ||||
| Total stock-based compensation expense | 597 | 571 | 1,216 | 1,208 |
| Performance-based Restricted Units [Member] | ||||
| Stock-based compensation expense: | ||||
| Total stock-based compensation expense | $ 809 | $ 1,069 | $ 1,680 | $ 2,151 |