Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Mar. 28, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less allowance for doubtful accounts	$ (3,763)	$ (3,827)
Accounts receivable, net	227,463	205,873
Contract changes, negotiated settlements and claims for unanticipated contract costs	189	1,021
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	139,096	125,092
U.S. Government [Member] | Billed Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	28,868	14,364
U.S. Government [Member] | Unbilled Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	7,011	6,340
Commercial and Other Government [Member] | Billed Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	50,348	63,051
Commercial and Other Government [Member] | Unbilled Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	$ 5,903	$ 853