Note 10 - Stockholders' Equity - Warrants (Details)	12 Months Ended
	Dec. 31, 2020 shares
Warrants outstanding at January 1 (in shares)	0
Prefunded warrants issued in May 2020 (in shares)	515,000
Exercises and conversions (in shares)	0
Warrants outstanding at December 31 (in shares)	515,000