Note 11 - Equity Incentive Plan - Restricted Stock units (Details) - Restricted Stock Units (RSUs) [Member]	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Outstanding, shares (in shares) | shares	233,239
Outstanding, weighted average grant date fair value (in dollars per share) | $ / shares	$ 37.50
Granted, shares (in shares) | shares	308,243
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 35.42
Vested, shares (in shares) | shares	(90,013)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 37.63
Forfeited and cancelled, shares (in shares) | shares	(48,624)
Forfeited and cancelled, weighted average grant date fair value (in dollars per share) | $ / shares	$ 35.69
Outstanding, shares (in shares) | shares	402,845
Outstanding, weighted average grant date fair value (in dollars per share) | $ / shares	$ 36.10