Note 6 - Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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		69,350			78.59
Exercised		(47,255	)		14.06
Forfeited		(804	)		30.58
Options outstanding at March 31, 2014		1,164,541		$	22.77
Exercisable at March 31, 2014		434,412		$	10.99

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

	Three Months Ended March 31,
	2014			2013
Risk-free interest rate		2.14	%		1.27	%
Expected life (years)		6.50			6.50
Expected volatility		49.30	%		53.54	%
Expected dividend yield		0	%		0	%

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

	Stock Options		Weighted- Average Grant Date Fair Value Per Share
Restricted stock outstanding at December 31, 2013		-	$	-
Granted		31,693		78.59
Vested		-		-
Forfeited		-		-
Restricted stock outstanding at March 31, 2014		31,693	$	78.59

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

	Three Months Ended March 31,
	2014			2013
Risk-free interest rate		0.11	%		0.13	%
Expected life (months)		6.00			6.00
Expected volatility		39.80	%		53.14	%
Expected dividend yield		0	%		0	%