Note 7 - Share-based Compensation - Stock-settled Stock Appreciation Rights Transactions (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2021	Dec. 31, 2020
Outstanding SARS (in shares)		317,128
Outstanding SARS, weighted average exercise price (in dollars per share)		$ 13.47
Outstanding SARS, weighted average remaining life (Year)		3 years 1 month 20 days	3 years 4 months 9 days
Outstanding SARS, aggregate intrinsic value		$ 3,146	$ 2,031
Granted SARs (in shares)	[1]	31,687
Granted SARS, weighted average exercise price (in dollars per share)	[1]	$ 25.75
Exercised SARs (in shares)		(21,438)
Exercised SARS, weighted average exercise price (in dollars per share)		$ 16.19
Outstanding SARS (in shares)		327,377	317,128
Outstanding SARS, weighted average exercise price (in dollars per share)		$ 14.48	$ 13.47
Exercisable (in shares)		165,586
Exercisable, weighted average exercise price (in dollars per share)		$ 15.08
Exercisable, weighted average remaining life (Year)		2 years 6 months
Exercisable, aggregate intrinsic value		$ 1,462

[1] The weighted average grant date fair value of SARs granted was $10.09 per share.