Note 3 - Stock-based Awards - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020
Outstanding (in shares)		604
Outstanding, weighted average exercise price (in dollars per share)		$ 14.31
Outstanding, weighted average remaining contractual life (Year)		6 years 3 months 18 days	7 years
Forfeited (in shares)		(29)
Forfeited, weighted average exercise price (in dollars per share)		$ 3.47
Outstanding (in shares)		575	604
Outstanding, weighted average exercise price (in dollars per share)		$ 14.23	$ 14.31
Outstanding, aggregate intrinsic value	[1]	$ 147
Exercisable (in shares)		464
Exercisable, weighted average exercise price (in dollars per share)		$ 15.12
Exercisable, weighted average remaining contractual life (Year)		6 years

[1] Intrinsic value is calculated based on the amount by which the closing market value of the Company’s stock exceeded the exercise price of the underlying options, multiplied by the number of shares.