Note 12 - Stock-based Compensation (Details) - Summary of Outstanding Stock Options - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Summary of Outstanding Stock Options [Abstract]
Number of Shares - Options Outstanding	954,678	1,074,552
Weighted Average Exercise Price - Options Outstanding	$ 46.92	$ 46.44
Options exercisable at June 30, 2015	187,263
Options exercisable at June 30, 2015	$ 51.36
Options exercisable at June 30, 2015	$ 2,553,000
Number of Shares - Options Granted	56,904	57,716
Weighted Average Exercise Price - Options Granted	$ 61.48	$ 53.10
Number of Shares - Options Exercised	(123,001)	(157,590)
Weighted Average Exercise Price - Options Exercised	$ 46.67	$ 45.97
Options cancelled		(20,000)
Options cancelled		$ 46.69
Number of Shares - Options Outstanding	888,581	954,678
Weighted Average Exercise Price - Options Outstanding	$ 47.88	$ 46.92
Aggregate Intrinsic Value - Options Outstanding	$ 15,202,000