Inventories - Summary of Inventories (Detail) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|---|---|---|---|
| Inventory Disclosure [Abstract] | ||||||
| Finished goods | $ 10,953 | $ 13,737 | ||||
| Semi-finished goods and work-in-process | 35,862 | 53,148 | ||||
| Raw materials | 14,502 | 12,445 | ||||
| Materials in-transit | 838 | 134 | ||||
| Less: inventory reserve | (4,699) | $ (4,672) | (6,391) | $ (5,297) | $ (7,966) | $ (7,177) |
| Inventories, net | $ 57,456 | $ 73,073 |