Revenue - Revenue by Contract Type (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 29, 2019 |
Mar. 30, 2018 |
|
| Disaggregation of Revenue [Line Items] | ||
| Total revenue | $ 325,928 | $ 320,516 |
| Cost-plus and cost-reimbursable | ||
| Disaggregation of Revenue [Line Items] | ||
| Total revenue | 251,478 | 230,208 |
| Firm-fixed-price | ||
| Disaggregation of Revenue [Line Items] | ||
| Total revenue | $ 74,450 | $ 90,308 |