Note 8 - Stock-based Compensation - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2021 USD ($) $ / shares shares
Balance at January 1, 2022 (in shares) | shares	72,454
Balance at January 1, 2022 (in dollars per share) | $ / shares	$ 265.85
Granted (in shares) | shares	48,300
Granted, weighted-average exercise price (in dollars per share) | $ / shares	$ 12.00
Cancelled/forfeited (in shares) | shares	(4,190)
Cancelled/forfeited, weighted-average exercise price (in dollars per share) | $ / shares	$ 75.33
Options outstanding, number (in shares) | shares	116,564
Options outstanding, weighted-average exercise price (in dollars per share) | $ / shares	$ 164.31
Options outstanding, weighted-average remaining contractual life (Year)	8 years 10 months 20 days
Options outstanding, aggregate intrinsic value | $	$ 23,163
Exercisable (in shares) | shares	52,849
Exercisable, weighted-average exercise price (in dollars per share) | $ / shares	$ 346.79
Exercisable, weighted-average remaining contractual life (Year)	8 years 1 month 17 days
Exercisable, aggregate intrinsic value | $	$ 1,956
Vested and expected to vest (in shares) | shares	116,564
Vested and expected to vest, weighted-average exercise price (in dollars per share) | $ / shares	$ 164.31
Vested and expected to vest, weighted-average remaining contractual life (Year)	8 years 10 months 20 days
Vested and expected to vest, aggregate intrinsic value | $	$ 23,163