Note 11 - Equity Incentive Plan - Stock Options (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares
Outstanding, shares (in shares) | shares	896,819
Outstanding, Weighted Average Exercise (in dollars per share) | $ / shares	$ 41.50
Granted, shares (in shares) | shares	493,628
Granted, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 37.67
Exercised, shares (in shares) | shares	(27,851)
Exercised, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 34.62
Exercised, Aggregate Intrinsic Value | $	$ 234
Forfeited and canceled, shares (in shares) | shares	(177,604)
Forfeited and canceled, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 44.32
Outstanding, shares (in shares) | shares	1,184,992
Outstanding, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 39.65
Outstanding, Weighted Average Remaining Contractual Term (Year)	8 years 6 months
Outstanding, Aggregate Intrinsic Value | $	$ 4,654
Vested, shares (in shares) | shares	304,172
Vested, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 44.01
Vested, Weighted Average Remaining Contractual Term (Year)	7 years 3 months 18 days
Vested, Aggregate Intrinsic Value | $	$ 812
Vested and expected to vest, shares (in shares) | shares	1,184,992
Vested and expected to vest, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 39.65
Vested and expected to vest, Weighted Average Remaining Contractual Term (Year)	8 years 6 months
Vested and expected to vest, Aggregate Intrinsic Value | $	$ 4,654