Accounts Receivable, Net - Schedule of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less allowance for doubtful accounts	$ (4,225)		$ (4,134)
Accounts receivable, net	290,564	$ 284,209	313,451
Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	163,333		152,078
U.S. Government contracts | Billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	17,130		26,093
U.S. Government contracts | Not billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	1,580		862
Commercial and other government contracts | Billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	111,516		107,962
Commercial and other government contracts | Not billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 1,230		$ 30,590