CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 28	$ 71
Patents and licenses, accumulated amortization	$ 12,062	$ 11,911
Common stock, par value	$ 0.10	$ 0.10
Common stock, authorized	10,000	10,000
Common stock, issued	3,420	3,420
Treasury shares, shares	1,584	1,596