Note 2 - Earnings Per Share - Securities Potentially Dilute Calculation of Diluted Earnings Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive securities (in shares)	4,835,752	8,592,698
Warrants to Purchase Common Stock - Liability Classified [Member]
Antidilutive securities (in shares)	7,126	52,032
Warrants to Purchase Common Stock - Equity Classified [Member]
Antidilutive securities (in shares)	90,608	2,682,166
Convertible 2020/21 Notes [Member]
Antidilutive securities (in shares)	0	5,789,209
Share-based Payment Arrangement, Option [Member]
Antidilutive securities (in shares)	4,670,279	1,552
Stock Appreciation Rights (SARs) [Member]
Antidilutive securities (in shares)	67,739	67,739