Note 10 - Equity, Share-based Compensation, Warrants and Securities Offerings - Exercisable and Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Weighted Average Exercise Price (in dollars per share)	$ 1.76	$ 9.76	$ 9.82
Nonvested, weighted average expense period (Year)	2 years 10 months 24 days	1 year 4 months 24 days	1 year 1 month 6 days
Warrants [Member]
Shares under warrants (in shares)	2,298,769
Weighted Average Exercise Price (in dollars per share)	$ 1.76
Nonvested, weighted average expense period (Year)	2 years 10 months 24 days
Shares under warrants, exercisable (in shares)	235,769
Weighted average exercise price, exercisable (in dollars per share)	$ 3.09
Weighted average remaining contractual term, exercisable (Year)	3 years 7 months 6 days
Warrants [Member] | Exercise Range One [Member]
Shares under warrants (in shares)	2,000,000
Weighted Average Exercise Price (in dollars per share)	$ 1.60
Nonvested, weighted average expense period (Year)	2 years 9 months 18 days
Shares under warrants, exercisable (in shares)	0
Weighted average exercise price, exercisable (in dollars per share)	$ 0
Warrants [Member] | Exercise Price Range Two [Member]
Shares under warrants (in shares)	63,000
Weighted Average Exercise Price (in dollars per share)	$ 1.88
Nonvested, weighted average expense period (Year)	4 years 9 months 18 days
Shares under warrants, exercisable (in shares)	0
Weighted average exercise price, exercisable (in dollars per share)	$ 0
Warrants [Member] | Exercise Price Range Three [Member]
Shares under warrants (in shares)	230,769
Weighted Average Exercise Price (in dollars per share)	$ 2.72
Nonvested, weighted average expense period (Year)	3 years 8 months 12 days
Shares under warrants, exercisable (in shares)	230,769
Weighted average exercise price, exercisable (in dollars per share)	$ 2.72
Weighted average remaining contractual term, exercisable (Year)	3 years 8 months 12 days
Warrants [Member] | Exercise Price Range Four [Member]
Shares under warrants (in shares)	5,000
Weighted Average Exercise Price (in dollars per share)	$ 20.00
Nonvested, weighted average expense period (Year)	1 month 6 days
Shares under warrants, exercisable (in shares)	5,000
Weighted average exercise price, exercisable (in dollars per share)	$ 20.00
Weighted average remaining contractual term, exercisable (Year)	1 month 6 days