Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 19	$ 260
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	48,503	45,671
Preferred stock, shares outstanding (in shares)	48,503	45,671
Preferred stock, liquidation value	$ 48,325	$ 44,718
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	10,364,663	3,492,200
Common stock, shares outstanding (in shares)	10,364,663	3,492,200