Note 7 - Share-based Compensation - Stock Option Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2021	Dec. 31, 2020
Outstanding, options (in shares)		970,022
Outstanding, weighted average exercise price (in dollars per share)		$ 12.92
Outstanding, weighted average remaining life (Year)		3 years 7 months 6 days	3 years 8 months 26 days
Outstanding, aggregate intrinsic value		$ 7,268	$ 11,128
Granted (in shares)	[1]	114,263
Granted, weighted average exercise price (in dollars per share)	[1]	$ 25.80
Exercised (in shares)		(234,092)
Exercised, weighted average exercise price (in dollars per share)		$ 9.96
Lapsed or cancelled (in shares)		(12,740)
Lapsed or cancelled, weighted average exercise price (in dollars per share)		$ 14.09
Outstanding, options (in shares)		837,453	970,022
Outstanding, weighted average exercise price (in dollars per share)		$ 15.49	$ 12.92
Exercisable, options (in shares)		484,635
Exercisable, weighted average exercise price, options (in dollars per share)		$ 14.38
Exercisable, weighted average remaining life, options (Year)		3 years 25 days
Exercisable, aggregate intrinsic value, options		$ 4,624

[1] The weighted average grant date fair value of stock options granted was $10.28 per share.