Accrued Severance Benefits - Future Benefits Payments to Employees (Detail) $ in Thousands |
Jun. 30, 2018
USD ($)
|
|---|---|
| Retirement Benefits [Abstract] | |
| Remainder of 2018 | $ 0 |
| 2019 | 589 |
| 2020 | 1,093 |
| 2021 | 1,565 |
| 2022 | 1,329 |
| 2023 | 1,791 |
| 2024 - 2028 | $ 27,725 |