Note 11 - Stockholders' Equity (Deficit) - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Granted, shares (in shares)	582,353	640,748
Forfeited, shares (in shares)		(186,339)
Nonvested, shares (in shares)	799,376	835,297	899,672
The 2011 and 2017 Plans [Member]
Balance, shares (in shares)	4,595,247	5,009,342
Balance, weighted average exercise price (in dollars per share)	$ 62.43	$ 71.42
Outstanding, weighted average remaining contractual term (Year)	5 years 1 month 6 days	4 years 6 months	5 years 1 month 6 days
Outstanding, aggregate intrinsic value	$ 1,046	$ 0	$ 3,458
Granted, shares (in shares)	582,353	640,748
Granted, weighted average exercise price (in dollars per share)	$ 2.43	$ 11.12
Granted, weighted average remaining contractual term (Year)	9 years 2 months 12 days	8 years 2 months 12 days
Forfeited, shares (in shares)		(186,339)
Forfeited, weighted average exercise price (in dollars per share)		$ 10.60
Expired, shares (in shares)	(965,119)	(868,504)
Expired, weighted average exercise price (in dollars per share)	$ 38.63	$ 87.55
Balance, shares (in shares)	4,212,481	4,595,247	5,009,342
Balance, weighted average exercise price (in dollars per share)	$ 59.59	$ 62.43	$ 71.42
Nonvested, shares (in shares)	799,376
Nonvested, weighted average exercise price (in dollars per share)	$ 5.95
Nonvested, weighted average remaining contractual term (Year)	8 years 9 months 18 days
Nonvested, aggregate intrinsic value	$ 817
Exercisable, shares (in shares)	3,413,105
Exercisable, weighted average exercise price (in dollars per share)	$ 72.15
Exercisable, weighted average remaining contractual term (Year)	4 years 3 months 18 days
Exercisable, aggregate intrinsic value	$ 229