Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Time-based Option Activity (Details) - Time-based Options [Member] - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Options balances, number of shares (in shares)	4,730,394
Options balances, weighted average exercise price (in dollars per share)	$ 12.95
Options balances, weighted average remaining life (Year)	6 years 4 months 2 days	6 years 1 month 28 days
Options granted, number of shares (in shares)	25,000
Options granted, weighted average exercise price (in dollars per share)	$ 2.52
Options exercised, number of shares (in shares)	0
Options exercised, weighted average exercise price (in dollars per share)	$ 0
Options canceled, number of shares (in shares)	(68,894)
Options canceled, weighted average exercise price (in dollars per share)	$ 11.24
Options expired, number of shares (in shares)	(302,720)
Options expired, weighted average exercise price (in dollars per share)	$ 13.13
Options balances, number of shares (in shares)	4,383,780	4,730,394
Options balances, weighted average exercise price (in dollars per share)	$ 12.91	$ 12.95
Options exercisable, number of shares (in shares)	3,226,526
Options exercisable, weighted average exercise price (in dollars per share)	$ 14.98
Options exercisable, weighted average remaining life (Year)	5 years 7 months 2 days