Note 11 - Share Based Compensation and Employee Benefit Plans - Stock Option (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Balance (in shares) | shares	3,489,826
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 21.42
Granted (in shares) | shares	472,463
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 33.89
Exercised (in shares) | shares	(1,205,281)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 18.56
Forfeited (in shares) | shares	(32,700)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 27.05
Balance (in shares) | shares	2,724,308
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 24.78
Balance, weighted average remaining contractual life (Year)	6 years 156 days
Aggregate intrinsic value | $	$ 70,910,167
Expected to vest (in shares) | shares	1,784,417
Expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 26.74
Expected to vest, weighted average remaining contractual life (Year)	7 years 248 days
Expected to vest, aggregate intrinsic value | $	$ 42,945,946
Vested and exercisable (in shares) | shares	888,246
Vested and exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 20.75
Vested and exercisable, weighted average remaining contractual life (Year)	3 years 310 days
Vested and exercisable, aggregate intrinsic value | $	$ 26,701,699