Note 9 - Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

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

	Stock Options			Weighted- Average Exercise Price
Options outstanding at December 31, 2013		1,143,250		$	19.03
Granted		108,860			72.70
Exercised		(103,648	)		10.56
Forfeited		(3,604	)		22.41
Options outstanding at June 30, 2014		1,144,858		$	24.89
Exercisable at June 30, 2014		535,033		$	15.36

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

	Six Months Ended June 30,
	2014				2013
Risk-free interest rate		0.43	-	2.14%		1.03	-	1.30%
Expected life (years)		2.00	-	6.50		5.50	-	6.50
Expected volatility		48.87	-	49.30%		53.32	-	53.54%
Expected dividend yield			0%				0%

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Restricted Stock Awards		Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted stock at December 31, 2013		-	$	-
Granted		74,137		69.42
Vested		-		-
Forfeited		-		-
Nonvested restricted stock at June 30, 2014		74,137	$	69.42

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

	Six Months Ended June 30,
	2014				2013
Risk-free interest rate		0.01%	-	0.11%		0.11	-	0.13%
Expected life (months)			6.00				6.00
Expected volatility		39.16%	-	39.80%		53.14%	-	53.32%
Expected dividend yield			0%				0%