Note 10 - Stock Based Compensation - Summary of Stock Option Activity (Details) - Employee Stock Option [Member] - $ / shares	3 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Outstanding, beginning balance (in shares)	1,437,438	1,582,384	1,631,913
Outstanding, beginning balance (in dollars per share)	$ 20.98	$ 19.45	$ 19.17
Exercised (in shares)	(6,420)	(165,210)	(44,279)
Exercised (in dollars per share)	$ 24.84	$ 9.30	$ 9.47
Forfeited or expired (in shares)			(5,250)
Forfeited or expired (in dollars per share)			$ 16.45
Outstanding, ending balance (in shares)	1,431,018	1,437,438	1,582,384
Outstanding, ending balance (in dollars per share)	$ 20.96	$ 20.98	$ 19.45
Granted (in shares)		20,264
Granted (in dollars per share)		$ 45.12
Exercisable at September 30, 2016 (in shares)	520,904
Exercisable at September 30, 2016 (in dollars per share)	$ 13.64