Receivables - Schedule of Receivables (Details) - USD ($) $ in Thousands |
Sep. 28, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Receivables [Abstract] | ||
| Billed receivables | $ 28,467 | $ 50,595 |
| Unbilled receivables (contract assets) | 188,396 | 121,601 |
| Other | 6,526 | 2,799 |
| Total receivables | 223,389 | $ 174,995 |
| Estimate of unbilled contract receivables | $ 1,700 |