Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Jun. 29, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less allowance for doubtful accounts	$ (3,043)	$ (3,294)
Accounts receivable, net	211,891	190,081
Contract changes, negotiated settlements and claims for unanticipated contract costs	119	119
Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	134,045	123,081
U.S. Government [Member] | Billed Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	24,350	18,726
U.S. Government [Member] | Unbilled Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	2,873	2,494
Commercial and Other Government [Member] | Billed Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	53,188	48,023
Commercial and Other Government [Member] | Unbilled Revenues [Member] | Trade Accounts Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable, Gross, Current	$ 478	$ 1,051