Revenue - Revenue by Contract Type (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 28, 2019 |
Jun. 29, 2018 |
Jun. 28, 2019 |
Jun. 29, 2018 |
|
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 331,589 | $ 321,132 | $ 657,517 | $ 641,649 |
| Cost-plus and cost-reimbursable | ||||
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | 256,737 | 242,742 | 508,215 | 472,951 |
| Firm-fixed-price | ||||
| Disaggregation of Revenue [Line Items] | ||||
| Total revenue | $ 74,852 | $ 78,390 | $ 149,302 | $ 168,698 |