Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts receivable, allowance	$ 30	$ 30
Preferred stock, shares authorized (in shares)	5,000	5,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares authorized (in shares)	45,000	45,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares issued (in shares)	22,887	20,140
Common stock, shares outstanding (in shares)	22,887	20,140