Note 8 - Stock Based Awards - Activity Under Stock Option Plan (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares
Balances, number of shares (in shares) | shares	4,570,432
Balances, weighted average exercise price (in dollars per share) | $ / shares	$ 2.50
Options granted, number of shares (in shares) | shares	2,707,654
Options granted, weighted average exercise price (in dollars per share) | $ / shares	$ 1.67
Options expired, number of shares (in shares) | shares	(43,838)
Options expired, weighted average exercise price (in dollars per share) | $ / shares	$ 6.18
Balances, number of shares (in shares) | shares	7,234,248
Balances, weighted average exercise price (in dollars per share) | $ / shares	$ 2.17
Balances, weighted average remaining contractual life (Year)	8 years 1 month 6 days
Balances, aggregate intrinsic value | $	$ 3,677
Outstanding and expected to vest, number of shares (in shares) | shares	6,286,788
Outstanding and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 2.22
Outstanding and expected to vest, weighted average remaining contractual life (Year)	7 years 10 months 24 days
Outstanding and expected to vest, aggregate intrinsic value | $	$ 3,328
Exercisable, number of shares (in shares) | shares	2,619,503
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 2.74
Exercisable, weighted average remaining contractual life (Year)	5 years 7 months 6 days
Exercisable, aggregate intrinsic value | $	$ 1,814