Note 8 - Share-based Compensation - Stock Option Activity (Details) - USD ($)		3 Months Ended	12 Months Ended
	Jan. 29, 2020	Mar. 31, 2021	Dec. 31, 2020
Stock options outstanding, beginning of period (in shares)		1,114,306
Balance, weighted average exercise price, beginning of period (in dollars per share)		$ 5.89
Stock options outstanding, weighted average remaining contractual term (Year)		6 years 328 days	7 years 182 days
Stock options outstanding, aggregate intrinsic value		$ 423,800	$ 177,100
Stock options granted (in shares)	515,036	18,850
Stock options granted, weighted average exercise price (in dollars per share)	$ 5.32	$ 4.63
Stock options exercised (in shares)		(1,580)
Stock options exercised, weighted average exercise price (in dollars per share)		$ 2.49
Stock options forfeited (in shares)		(44,643)
Stock options forfeited, weighted average exercise price (in dollars per share)		$ 4.30
Stock options expired (in shares)		(125)
Stock options expired, weighted average exercise price (in dollars per share)		$ 5.32
Stock options outstanding, end of period (in shares)		1,086,808	1,114,306
Balance, weighted average exercise price, end of period (in dollars per share)		$ 5.94	$ 5.89
Exercisable, March 31, 2021 (in shares)		661,430
Options exercisable, weighted average exercise price (in dollars per share)		$ 7.29
Options exercisable, weighted average remaining contractual term (Year)		5 years 219 days
Options exercisable, aggregate intrinsic value		$ 73,000