Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Allowance for doubtful accounts	$ 4,117	$ 4,627
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	145,000,000	145,000,000
Common stock, shares issued (in shares)	54,822,000	54,085,000
Common stock, shares outstanding (in shares)	53,823,000	53,085,000
Treasury stock, shares (in shares)	1,000	1,000