Note 9 - Equity Incentive Plans - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Options Outstanding (in shares) | shares	826,769
Options Outstanding, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 32.72
Options Outstanding, Weighted Average Remaining Contractual Life (Year)	6 years 9 months	6 years 5 months 26 days
Options Outstanding, Aggregate Intrinsic Value | $	$ 0	$ 1,541
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares) | shares	59,818
Options Granted, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 17.72
Options Exercised (in shares) | shares	0
Options Exercised, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 0
Options Forfeited, expired or cancelled (in shares) | shares	(84,132)
Options Forfeited, expired or cancelled, Weighted Average Exercise Price (in dollars per share) | $ / shares
Options Outstanding (in shares) | shares	802,455	826,769
Options Outstanding, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 33.11	$ 32.72
Options Vested and expected to vest (in shares) | shares	802,455
Options Vested and expected to vest, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 33.11
Options Vested and expected to vest, Weighted Average Remaining Contractual Life (Year)	6 years 9 months
Options Vested and expected to vest, Aggregate Intrinsic Value | $	$ 0
Options Exercisable (in shares) | shares	759,743
Options Exercisable, Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 33.19
Options Exercisable, Weighted Average Remaining Contractual Life (Year)	6 years 7 months 28 days
Options Exercisable, Aggregate Intrinsic Value | $	$ 0