CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 21	$ 28
Patents and licenses, accumulated amortization	$ 12,181	$ 12,062
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	1,567	1,568