Revenue - Revenue by Contract Type (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 28, 2018 |
Sep. 29, 2017 |
Sep. 28, 2018 |
Sep. 29, 2017 |
|
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 308,095 | $ 269,625 | $ 949,744 | $ 819,005 |
| Cost-plus and cost-reimbursable | ||||
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | 240,338 | 194,982 | 713,289 | 609,323 |
| Firm-fixed-price | ||||
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 67,757 | $ 74,643 | $ 236,455 | $ 209,682 |