Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts receivable, allowance for doubtful accounts	$ 9	$ 21
Convertible preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock, authorized (in shares)	5,000,000	5,000,000
Convertible preferred stock, issued (in shares)	0	0
Convertible preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	50,000,000	50,000,000
Common stock, issued (in shares)	13,477,973	13,773,389
Common stock, outstanding (in shares)	13,477,973	13,773,389