Note 16 - Stock Based Compensation - Roll-forward of Non-vested Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Nonvested, beginning year, number of shares (in shares)	2,367,515	1,962,163
Nonvested, beginning of year, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 2.58
Granted, number of shares (in shares)	1,270,450	1,356,500	1,106,800
Granted, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 0.91	$ 2.15	$ 2.85
Vested, number of shares (in shares)	(918,790)
Vested, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 2.46
Forfeited, number of shares (in shares)	(204,375)
Forfeited, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 2.03
Nonvested, end of year, number of shares (in shares)	2,514,800	2,367,515	1,962,163
Nonvested, end of year, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 1.87	$ 2.58