Note 10 - Equity Incentive Plans and Equity - Restricted Stock Units Award Activity (Details)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Restricted Stock Units (RSUs) [Member]
Balance (in shares) | shares	240,229
Balance, weighted average grant date fair value (in dollars per share) | $ / shares	$ 29.07
Granted (in shares) | shares	55,134
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 63.68
Vested (in shares) | shares	(123,744)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 24.33
Forfeited (in shares) | shares	(1,328)
Forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 45.32
Balance (in shares) | shares	170,291
Balance, weighted average grant date fair value (in dollars per share) | $ / shares	$ 43.60
Performance Based Restricted Stock Units [Member]
Balance (in shares) | shares	0
Balance, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0
Granted (in shares) | shares	22,894
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 55.54
Balance (in shares) | shares	22,894
Balance, weighted average grant date fair value (in dollars per share) | $ / shares	$ 55.54