Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Trade accounts receivable, allowance	$ 273	$ 167
Inventory allowance	2,652	2,495
Accumulated depreciation	4,130	4,234
Accumulated amortization	$ 13,789	$ 13,191
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	325,000,000	325,000,000
Common stock, issued (in shares)	28,581,953	28,552,886
Common stock, outstanding (in shares)	28,581,953	28,552,886