Note 11 - Summary of Outstanding Stock Options (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Options outstanding (in shares)	954,678	1,074,552
Options outstanding (in dollars per share)	$ 46.92	$ 46.44
Options outstanding	$ 0	$ 0
Number of Shares - Options Granted (in shares)	56,792	57,716
Weighted Average Exercise Price - Options Granted (in dollars per share)	$ 61.47	$ 53.10
Number of Shares - Options Exercised (in shares)	(176,184)	(157,590)
Weighted Average Exercise Price - Options Exercised (in dollars per share)	$ 46.68	$ 45.97
Options cancelled (in shares)		(20,000)
Options cancelled (in dollars per share)		$ 46.69
Options outstanding (in shares)	835,286	954,678
Options outstanding (in dollars per share)	$ 47.95	$ 46.92
Options outstanding	$ 10,839,000	$ 0
Options exercisable at September 30, 2015 (in shares)	187,263
Options exercisable at September 30, 2015 (in dollars per share)	$ 51.36
Options exercisable at September 30, 2015	$ 1,802,000