Description of Business and Summary of Significant Accounting Policies - Summary of Cumulative Catch-Up Adjustments (Details) - Contracts accounted for under percentage of completion - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Concentration Risk [Line Items] | |||
| Favorable adjustments | $ 18,256 | $ 15,296 | $ 9,721 |
| Unfavorable adjustments | (6,704) | (7,837) | (11,641) |
| Net favorable (unfavorable) adjustments | $ 11,552 | $ 7,459 | $ (1,920) |