Note 11 - Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Options outstanding, number of options (in shares)	1,382,986
Options outstanding, weighted average exercise price (in dollars per share)	$ 9.10
Options outstanding, weighted average remaining contract term (Year)	5 years 14 days	5 years 164 days
Options outstanding, aggregate intrinsic value		$ 4,793
Granted, number of options (in shares)
Granted, weighted average exercise price (in dollars per share)
Exercised, number of options (in shares)	(15,544)
Exercised, weighted average exercise price (in dollars per share)	$ 10.15
Canceled or forfeited, number of options (in shares)	(4,274)
Canceled or forfeited, weighted average exercise price (in dollars per share)	$ 10.15
Options outstanding, number of options (in shares)	1,363,168	1,382,986
Options outstanding, weighted average exercise price (in dollars per share)	$ 9.08	$ 9.10
Options exercisable, number of options (in shares)	1,233,857
Options exercisable, weighted average exercise price (in dollars per share)	$ 8.54
Options exercisable, weighted average remaining contract term (Year)	4 years 292 days
Options exercisable, aggregate intrinsic value