Note 11 - Stock Option and Equity Incentive Plans - Summary of Stock Option Activity (Details) - Employee and Nonemployee Stock Option [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Outstanding (in shares) | shares	270,205
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 15.40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross | shares	17,184
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 22.02
Exercised (in shares) | shares	(54,811)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 24.57
Outstanding (in shares) | shares	232,578
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 16.53
Outstanding, weighted average remaining contractual life (Year)	3 years 240 days
Outstanding, aggregate intrinsic value | $	$ 2,074
Exercisable (in shares) | shares	210,078
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 16.02
Exercisable, weighted average remaining contractual life (Year)	3 years 313 days
Exercisable, aggregate intrinsic value | $	$ 1,981
Vested and expected to vest (in shares) | shares	232,578
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 16.53
Vested and expected to vest, weighted average remaining contractual life (Year)	3 years 240 days
Vested and expected to vest, aggregate intrinsic value | $	$ 2,074