Description of Business and Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 26, 2015 |
Jun. 28, 2014 |
Jun. 26, 2015 |
Jun. 28, 2014 |
|
| Concentration Risk [Line Items] | ||||
| Revenue | $ 309,509 | $ 312,902 | $ 570,429 | $ 616,853 |
| Sales Revenue, Net | U.S. Army | Government Contracts Concentration Risk | ||||
| Concentration Risk [Line Items] | ||||
| Concentration risk, percentage | 90.90% | 86.10% | ||
| Four Largest Contracts | Sales Revenue, Net | U.S. Army | Government Contracts Concentration Risk | ||||
| Concentration Risk [Line Items] | ||||
| Concentration risk, percentage | 66.00% | 66.30% | ||
| Revenue | $ 377,700 | $ 409,300 | ||