Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less allowance for doubtful accounts	$ (4,134)	$ (4,123)
Total	313,451	230,864
Contract changes, negotiated settlements and claims for unanticipated contract costs	900	900
Trade receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	152,078	143,471
U.S. Government contracts | Billed | Contract receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	26,093	17,244
U.S. Government contracts | Costs and accrued profit – not billed | Contract receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	862	1,478
Commercial and other government contracts | Billed | Contract receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	107,962	50,560
Commercial and other government contracts | Costs and accrued profit – not billed | Contract receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 30,590	22,234
K-MAX® program
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled receivables and accrued profit, included in Other Assets		$ 3,700