Accounts Receivable, Net - Schedule of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Mar. 29, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less allowance for doubtful accounts	$ (3,433)	$ (4,114)
Accounts receivable, net	260,461	301,094
Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	181,210	164,752
U.S. Government contracts | Billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	13,587	38,173
U.S. Government contracts | Not billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	653	780
Commercial and other government contracts | Billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	67,518	100,603
Commercial and other government contracts | Not billed | Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable	$ 926	$ 900