Note 10 - Equity Incentive Plans and Equity - Nonvested Stock Options Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 68.93	$ 24.24	$ 14.27
Service Period Stock Options [Member]
Balance (in shares)	347,796
Balance, weighted average grant date fair value (in dollars per share)	$ 8.11
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)	382,910
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 64.75
Vested (in shares)	(277,458)
Vested, weighted average grant date fair value (in dollars per share)	$ 6.17
Forfeited (in shares)	(357)
Forfeited, weighted average grant date fair value (in dollars per share)	$ 5.61
Balance (in shares)	452,891	347,796
Balance, weighted average grant date fair value (in dollars per share)	$ 57.19	$ 8.11