Note 8 - Stock-based Compensation - Stock Option Activity (Details) - Jun. 30, 2015 - $ / shares	Total
Options outstanding (in shares)	998,987
Options outstanding (in dollars per share)	$ 26.49
Granted (in shares)	110,335
Granted (in dollars per share)	$ 67.36
Exercised (in shares)	(86,656)
Exercised (in dollars per share)	$ 15.72
Forfeited (in shares)	(25,713)
Forfeited (in dollars per share)	$ 52.39
Options outstanding (in shares)	996,953
Options outstanding (in dollars per share)	$ 31.28
Exercisable at June 30, 2015 (in shares)	515,568
Exercisable at June 30, 2015 (in dollars per share)	$ 19.12