Note 14 - Stock Options Oustanding by Range of Exercise Prices (Details)	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Range01 [Member]
Range of exercise prices, minimum (in dollars per share)	$ 17.55
Range of exercise prices, maximum (in dollars per share)	$ 21.29
Options outstanding, number of shares (in shares) | shares	17,350
Options outstanding, weighted average remaining contractual life	4 years 332 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 19.78
Options exercisable, number of shares (in shares) | shares	11,500
Options exercisable, weighted average exercise price (in dollars per share)	$ 19.48
Range 02 [Member]
Range of exercise prices, minimum (in dollars per share)	21.51
Range of exercise prices, maximum (in dollars per share)	$ 21.51
Options outstanding, number of shares (in shares) | shares	2,050
Options outstanding, weighted average remaining contractual life	3 years 200 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 21.51
Options exercisable, number of shares (in shares) | shares	2,050
Options exercisable, weighted average exercise price (in dollars per share)	$ 21.51
Range 03 [Member]
Range of exercise prices, minimum (in dollars per share)	28.42
Range of exercise prices, maximum (in dollars per share)	$ 28.42
Options outstanding, number of shares (in shares) | shares	24,600
Options outstanding, weighted average remaining contractual life	292 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 28.42
Options exercisable, number of shares (in shares) | shares	24,600
Options exercisable, weighted average exercise price (in dollars per share)	$ 28.42
Range 04 [Member]
Range of exercise prices, minimum (in dollars per share)	30.31
Range of exercise prices, maximum (in dollars per share)	$ 30.31
Options outstanding, number of shares (in shares) | shares	28,090
Options outstanding, weighted average remaining contractual life	1 year 288 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 30.31
Options exercisable, number of shares (in shares) | shares	28,090
Options exercisable, weighted average exercise price (in dollars per share)	$ 30.31
Range 05 [Member]
Range of exercise prices, minimum (in dollars per share)	40.57
Range of exercise prices, maximum (in dollars per share)	$ 40.57
Options outstanding, number of shares (in shares) | shares	43,720
Options outstanding, weighted average remaining contractual life	7 years 332 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 40.57
Options exercisable, number of shares (in shares) | shares	43,720
Options exercisable, weighted average exercise price (in dollars per share)	$ 40.57
Range 06 [Member]
Range of exercise prices, minimum (in dollars per share)	40.72
Range of exercise prices, maximum (in dollars per share)	$ 40.72
Options outstanding, number of shares (in shares) | shares	1,500
Options outstanding, weighted average remaining contractual life	8 years 138 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 40.72
Options exercisable, number of shares (in shares) | shares	300
Options exercisable, weighted average exercise price (in dollars per share)	$ 40.72
Range 07 [Member]
Range of exercise prices, minimum (in dollars per share)	44.40
Range of exercise prices, maximum (in dollars per share)	$ 44.40
Options outstanding, number of shares (in shares) | shares	54,825
Options outstanding, weighted average remaining contractual life	8 years 127 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 44.40
Options exercisable, number of shares (in shares) | shares	26,877
Options exercisable, weighted average exercise price (in dollars per share)	$ 44.40
Range 08 [Member]
Range of exercise prices, minimum (in dollars per share)	45.50
Range of exercise prices, maximum (in dollars per share)	$ 45.50
Options outstanding, number of shares (in shares) | shares	258,255
Options outstanding, weighted average remaining contractual life	9 years 40 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 45.50
Options exercisable, number of shares (in shares) | shares	77,161
Options exercisable, weighted average exercise price (in dollars per share)	$ 45.50
Range 09 [Member]
Range of exercise prices, minimum (in dollars per share)	47.02
Range of exercise prices, maximum (in dollars per share)	$ 47.02
Options outstanding, number of shares (in shares) | shares	58,090
Options outstanding, weighted average remaining contractual life	9 years 204 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 47.02
Options exercisable, number of shares (in shares) | shares
Options exercisable, weighted average exercise price (in dollars per share)
Range 10 [Member]
Range of exercise prices, minimum (in dollars per share)	48.13
Range of exercise prices, maximum (in dollars per share)	$ 48.13
Options outstanding, number of shares (in shares) | shares	3,305
Options outstanding, weighted average remaining contractual life	9 years 76 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 48.13
Options exercisable, number of shares (in shares) | shares	1,258
Options exercisable, weighted average exercise price (in dollars per share)	$ 48.13
Range of exercise prices, minimum (in dollars per share)	17.55
Range of exercise prices, maximum (in dollars per share)	$ 48.13
Options outstanding, number of shares (in shares) | shares	491,785
Options outstanding, weighted average remaining contractual life	7 years 350 days
Options outstanding, weighted average exercise price (in dollars per share)	$ 42.39
Options exercisable, number of shares (in shares) | shares	215,556
Options exercisable, weighted average exercise price (in dollars per share)	$ 38.83