Note 9 - Stock-Based Compensation (Details) - Stock Option Activity (USD $)	6 Months Ended
	Jun. 30, 2014
Stock Option Activity [Abstract]
Options outstanding at December 31, 2013	1,143,250
Options outstanding at December 31, 2013	$ 19.03
Granted	108,860
Granted	$ 72.70
Exercised	(103,648)
Exercised	$ 10.56
Forfeited	(3,604)
Forfeited	$ 22.41
Options outstanding at June 30, 2014	1,144,858
Options outstanding at June 30, 2014	$ 24.89
Exercisable at June 30, 2014	535,033
Exercisable at June 30, 2014	$ 15.36