Note 16 - Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	2017			2016			2015
Expected volatility	37.73%	-	45.91%	42.09%	-	46.49%	41.84%	-	58.25%
Expected term (in years)	0.97	-	6.80	0.99	-	6.80	1.25	-	6.83
Risk-free interest rate	1.06%	-	2.22%	0.54%	-	1.63%	0.24%	-	1.93%

Share-based Compensation, Stock Options, Activity [Table Text Block]

				Weighted Average
	Number of Shares			Exercise Price		Options Exercisable
Outstanding at December 31, 2016		1,519,338		$	25.22		701,797
Granted		317,331			47.53
Exercised		(343,380	)		13.92
Forfeited or expired		(8,375	)		38.13
Outstanding at December 31, 2017		1,484,914			32.53
Exercisable at December 31, 2017		727,645		$	24.91

Schedule of Nonvested Share Activity [Table Text Block]

	Nonvested Stock Options					Nonvested Restricted Stock					Nonvested Performance Shares
	Number of Shares			Weighted- Average Grant- Date Fair Value		Number of Shares			Weighted- Average Grant- Date Fair Value		Number of Shares			Weighted- Average Grant-Date  Fair Value
Nonvested at December 31, 2016		817,540		$	12.50		260		$	41.05		316,750		$	30.08
Granted		317,331			17.71		9,761			58.57		115,250			43.43
Vested during period		(371,102	)		11.40		(9,756	)		58.50		(150,000	)		17.81
Forfeited		(6,500	)		14.64		-			-		(5,750	)		41.36
Nonvested at December 31, 2017		757,269		$	15.20		265		$	44.23		276,250		$	42.08