Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 260	$ 510
Preferred stock, authorized	4,000,000	4,000,000
Preferred stock, issued	0	0
Common stock, par value	$ 1	$ 1
Common stock, authorized	100,000,000	100,000,000
Common stock, issued	40,611,991	40,519,351