Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Trade receivables, allowance for doubtful accounts	$ 1,061	$ 341
Common stock par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	34,270,975	33,927,595
Treasury stock, at cost (in shares)	1,424,153	1,583,909