Revenue - Revenue by Contract Type (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Oct. 02, 2020 |
Sep. 27, 2019 |
Oct. 02, 2020 |
Sep. 27, 2019 |
|
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 352,415 | $ 359,873 | $ 1,040,212 | $ 1,017,368 |
| Cost-plus and cost-reimbursable | ||||
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 249,484 | 272,810 | $ 748,543 | 781,024 |
| Revenue, percent change | (8.60%) | (4.20%) | ||
| Firm-fixed-price | ||||
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 102,931 | $ 87,063 | $ 291,669 | $ 236,344 |
| Revenue, percent change | 18.20% | 23.40% | ||