Note 13 - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Outstanding-Number of options (in shares)	82,875	88,375	115,800
Exercised-Number of options (in shares)	(22,700)	(13,750)	(20,050)
Forfeited-Number of options (in shares)	(9,725)	(12,750)	(27,375)
Granted-Number of options (in shares)	23,500	21,000	20,000
Outstanding ending-Number of options (in shares)	73,950	82,875	88,375
Exercisable-Number of options (in shares)	18,825
Outstanding-Weighted average exercise price (in dollars per share)	$ 24.33	$ 23.27	$ 23.51
Exercised-Weighted average exercise price (in dollars per share)	20.90	18.11	17.82
Forfeited-Weighted average exercise price (in dollars per share)	25.60	31.80	29.66
Granted-Weighted average exercise price (in dollars per share)	30.40	29.25	25.16
Outstanding ending-Weighted average exercise price (in dollars per share)	27.14	$ 24.33	$ 23.27
Exercisable-Weighted average exercise price (in dollars per share)	$ 22.52
Outstanding ending-Weighted average remaining contractual term	2 years 7 months 13 days
Exercisable-Weighted average remaining contractual term	8 months 9 days
Outstanding ending-Aggregate intrinsic value	$ 640
Exercisable-Aggregate intrinsic value	$ 250