Note 4 - Summary of Restricted Stock Unit Activity (Details) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2016 $ / shares shares
Unvested balance (in shares) | shares	643,506
Unvested balance (in dollars per share) | $ / shares	$ 23.38
Granted (in shares) | shares	719,250
Granted (in dollars per share) | $ / shares	$ 16.87
Vested (in shares) | shares	(72,785)
Vested (in dollars per share) | $ / shares	$ 28.10
Forfeited (in shares) | shares	(17,925)
Forfeited (in dollars per share) | $ / shares	$ 18.91
Unvested balance (in shares) | shares	1,272,046
Unvested balance (in dollars per share) | $ / shares	$ 22.62