Note 8 - Stock-based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares
Beginning balance, number of options outstanding (in shares) | shares	484,500
Beginning balance, option, weighted average exercise price (in dollars per share) | $ / shares	$ 3.57
Granted, options (in shares) | shares	0
Granted, option, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Exercised, options (in shares) | shares	0
Exercised, option, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Expired or forfeited, options (in shares) | shares	(50,000)
Expired or forfeited, option, weighted average exercise price (in dollars per share) | $ / shares	$ 8.16
Ending balance, number of options outstanding (in shares) | shares	434,500
Ending balance, option, weighted average exercise price (in dollars per share) | $ / shares	$ 3.05
Outstanding, weighted average remaining contractual term (Year)	3 years 4 months 2 days
Outstanding, aggregate intrinsic value | $	$ 73
Exercisable, options (in shares) | shares	434,500
Exercisable, option, weighted average exercise price (in dollars per share) | $ / shares	$ 3.05
Exercisable, weighted average remaining contractual term (Year)	3 years 4 months 2 days
Exercisable, aggregate intrinsic value | $	$ 73