Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounts receivable, allowance for doubtful accounts	$ 0	$ 6
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	1,000,000	1,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	18,547,406	14,021,422
Common stock, outstanding (in shares)	18,547,406	14,021,422
Series A Preferred Stock [Member]
Preferred stock, par value (in dollars per share)		$ 1,000
Preferred stock, designated (in shares)	4,250	4,250
Preferred stock, issued (in shares)	0	4,250
Preferred stock, outstanding (in shares)	0	4,250