Note 13 - Summary of Stock Options - Summary of Option Activity Under All Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options outstanding (in shares)	1,008,833	4,098
Options outstanding, weighted average exercise price (in dollars per share)	$ 22.47	$ 4,567.36
Options outstanding, weighted average remaining contractual term (Year)	8 years 328 days	9 years 328 days	7 years 146 days
Options outstanding, aggregate intrinsic value	$ 675,000	$ 3,928,715,000
Options granted (in shares)	146,700	1,006,602
Options granted, weighted average exercise price (in dollars per share)	$ 6.36	$ 11.42
Options exercised (in shares)
Options exercised, weighted average exercise price (in dollars per share)
Options canceled (in shares)	(169,134)	(1,867)
Options canceled, weighted average exercise price (in dollars per share)	$ 28.45	$ 4,040.64
Options outstanding (in shares)	986,399	1,008,833	4,098
Options outstanding, weighted average exercise price (in dollars per share)	$ 19.10	$ 22.47	$ 4,567.36
Vested and exercisable and expected to vest (in shares)	923,646
Vested and exercisable and expected to vest, end of period, weighted average exercise price (in dollars per share)	$ 19.77
Vested and exercisable and expected to vest, end of period, weighted average remaining contractual term (Year)	8 years 328 days
Vested and exercisable and expected to vest, end of period, aggregate intrinsic value	$ 598
Vested and exercisable (in shares)	245,445
Vested and exercisable, end of period, weighted average exercise price (in dollars per share)	$ 45.09
Vested and exercisable, end of period, weighted average remaining contractual term (Year)	8 years 219 days
Vested and exercisable, end of period, aggregate intrinsic value