Note 16 - Stock-Based Compensation - Stock Option Plans (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Outstanding, shares (in shares)	469,572	513,554	587,961
Outstanding, Weighted average exercise price (in dollars per share)	$ 18.52	$ 17.13	$ 14.83
Granted, shares (in shares)	20,200	16,315	43,250
Granted, Weighted average exercise price (in dollars per share)	$ 36.00	$ 44.02	$ 43.86
Exercised, shares (in shares)	(59,393)	(60,127)	(114,100)
Exercised, Weighted average exercise price (in dollars per share)	$ 12.11	$ 13.56	$ 15.12
Forfeited, shares (in shares)	(3,466)	(170)	(3,557)
Forfeited, Weighted average exercise price (in dollars per share)	$ 31.59	$ 16.81	$ 26.74
Outstanding, shares (in shares)	426,913	469,572	513,554
Outstanding, Weighted average exercise price (in dollars per share)	$ 20.14	$ 18.52	$ 17.13
Exercisable, , shares (in shares)	365,084	358,270	354,269
Weighted-average grant date fair value (in dollars per share)	$ 11.29	$ 14.68	$ 14.75