Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable, allowance for doubtful accounts	$ 395	$ 284
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	46,435,802	46,363,945
Common stock, shares outstanding (in shares)	46,435,802	46,363,945