Note 8 - Stock Based Awards - Activity Under Stock Option Plan (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($) $ / shares shares
Balances, number of shares (in shares) | shares	2,439,253
Balances, weighted average exercise price (in dollars per share) | $ / shares	$ 3.96
Options granted, number of shares (in shares) | shares	1,913,200
Options granted, weighted average exercise price (in dollars per share) | $ / shares	$ 1.97
Options cancelled, number of shares (in shares) | shares	(407,000)
Options cancelled, weighted average exercise price (in dollars per share) | $ / shares	$ 3.78
Options exercised, number of shares (in shares) | shares	0
Options exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Balances, number of shares (in shares) | shares	3,945,453
Balances, weighted average exercise price (in dollars per share) | $ / shares	$ 3.01
Balances, weighted average remaining contractual life (Year)	7 years 1 month 6 days
Balances, aggregate intrinsic value | $	$ 501
Outstanding and expected to vest, number of shares (in shares) | shares	3,568,032
Outstanding and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 3.05
Outstanding and expected to vest, weighted average remaining contractual life (Year)	7 years
Outstanding and expected to vest, aggregate intrinsic value | $	$ 501
Exercisable, number of shares (in shares) | shares	1,979,763
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 3.00
Exercisable, weighted average remaining contractual life (Year)	5 years 3 months 18 days
Exercisable, aggregate intrinsic value | $	$ 501