Note 8 - Stock-based Compensation - Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2022 USD ($) $ / shares shares
Balance at January 1, 2021 (in shares) | shares	72,454
Balance at January 1, 2021 (in dollars per share) | $ / shares	$ 265.85
Granted (in shares) | shares	56,300
Granted, weighted-average exercise price (in dollars per share) | $ / shares	$ 11.40
Forfeited (in shares) | shares	(5,612)
Forfeited (in dollars per share) | $ / shares	$ 188.18
Expired (in shares) | shares	(260)
Expired (in dollars per share) | $ / shares	$ 1,575
Options outstanding, number (in shares) | shares	122,882
Options outstanding, weighted-average exercise price (in dollars per share) | $ / shares	$ 149.96
Options outstanding, weighted-average remaining contractual life (Year)	8 years 9 months 18 days
Options outstanding, aggregate intrinsic value | $	$ 0
Exercisable (in shares) | shares	60,688
Exercisable, weighted-average exercise price (in dollars per share) | $ / shares	$ 283.73
Exercisable, weighted-average remaining contractual life (Year)	8 years 1 month 6 days
Exercisable, aggregate intrinsic value | $	$ 0
Vested and expected to vest (in shares) | shares	122,882
Vested and expected to vest, weighted-average exercise price (in dollars per share) | $ / shares	$ 149.96
Vested and expected to vest, weighted-average remaining contractual life (Year)	8 years 9 months 18 days
Vested and expected to vest, aggregate intrinsic value | $	$ 0