Composition of Certain Financial Statement Captions - Schedule of Other Accrued Liabilities (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Other Accrued Liabilities | ||
| Workers' compensation, auto and general liability reserve | $ 4,615 | $ 6,123 |
| Contract related reserves | 7,426 | 6,054 |
| Other accrued liabilities | 7,168 | 5,516 |
| Total | $ 19,209 | $ 17,693 |