Note 10 - Stock Incentive Plans Activity - Restricted Stock (Details) - Restricted Stock [Member]	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Balance (in shares) | shares	464,758
Balance (in dollars per share) | $ / shares	$ 36.33
Granted (in shares) | shares	171,185
Granted (in dollars per share) | $ / shares	$ 88.74
Vested (in shares) | shares	(216,833)
Vested (in dollars per share) | $ / shares	$ 62.74
Forfeited (in shares) | shares	(8,036)
Forfeited (in dollars per share) | $ / shares	$ 57.73
Balance (in shares) | shares	411,074
Balance (in dollars per share) | $ / shares	$ 59.13