Revenue - Revenue by Contract Relationship (Details) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 29, 2019 |
Mar. 30, 2018 |
|
| Disaggregation of Revenue [Line Items] | ||
| Total revenue | $ 325,928 | $ 320,516 |
| Prime contractor | ||
| Disaggregation of Revenue [Line Items] | ||
| Total revenue | 307,058 | 301,028 |
| Subcontractor | ||
| Disaggregation of Revenue [Line Items] | ||
| Total revenue | $ 18,870 | $ 19,488 |