Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 286	$ 477
Accumulated depreciation and amortization	$ 75,408	$ 74,311
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	15,000,000	15,000,000
Common stock, shares issued (in shares)	9,735,055	9,619,755
Common stock, shares outstanding (in shares)	9,735,055	9,619,755