Note 15 - Stock-based Compensation - Stock Option Plans (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Outstanding, shares (in shares)	623,176	661,771	662,506
Outstanding, Weighted average exercise price (in dollars per share)	$ 13.88	$ 13.89	$ 13.82
Granted, shares (in shares)	76,749	73,403	82,609
Granted, Weighted average exercise price (in dollars per share)	$ 22.92	$ 17.63	$ 17.11
Exercised, shares (in shares)	(111,423)	(79,638)	(23,659)
Exercised, Weighted average exercise price (in dollars per share)	$ 14.97	$ 14.70	$ 10.22
Forfeited, shares (in shares)	(541)	(32,360)	(59,685)
Forfeited, Weighted average exercise price (in dollars per share)	$ 18.36	$ 20.69	$ 19.02
Outstanding, shares (in shares)	587,961	623,176	661,771
Outstanding, Weighted average exercise price (in dollars per share)	$ 14.83	$ 13.88	$ 13.89
Exercisable, , shares (in shares)	385,372	405,832	420,429
Weighted-average grant date fair value (in dollars per share)	$ 7.31	$ 5.11	$ 5.68