Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2013

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

Stock-based compensation is included in the following financial statement captions:



	Year Ended December 31,
	2013			2012			2011
Cost of sales	$	3,187		$	2,184		$	1,731
Sales and marketing	1,195			1,052			1,503
Research and development	1,929			1,327			1,036
General and administrative	5,409			4,002			3,778
Total stock-based compensation	11,720			8,565			8,048
Tax benefit recognized	(3,784		)	(2,629		)	(2,551		)
Net stock-based compensation	$	7,936		$	5,936		$	5,497

Weighted Average Assumptions

The Company calculates the fair value of stock option grants using the Black-Scholes option pricing model. Determining the appropriate fair value model and calculating the fair value of stock-based payment awards require the use of highly subjective assumptions, including the expected life of the stock-based payment awards and stock price volatility. The assumptions used in calculating the fair value of stock-based payment awards represent management’s best estimates, but the estimates involve inherent uncertainties and the application of management judgment. As a result, if factors change and the Company uses different assumptions, its stock-based compensation expense could be materially different in the future. The weighted average assumptions used in the Black-Scholes model or the calculation of compensation were as follows for the years ended December 31.



	2013	2012	2011
Expected term	4.4-6.3 years	4.0-6.6 years	3.4-6.9 years
Volatility	51%-54%	49%-56%	46%-56%
Risk-free rate of return	0.74%-1.32%	0.59%-1.23%	0.48%-2.82%
Dividend yield	0.25%	—%	—%
Forfeiture rate	0%-5.97%	0%-6.1%	0%-6.26%

Summary Of Option Activity

A summary of option activity, including the employee stock purchase plan, is presented below (see Note 11 for further information):



	Number of Options		Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life	Aggregate Intrinsic Value
					(In years)	(In thousands)
Outstanding — January 1, 2013	2,789,752		$	29.50
Granted	511,881		60.33
Exercised	(540,232	)	10.89
Forfeited	(61,504	)	48.13
Outstanding — December 31, 2013	2,699,897		$	38.00	6.79	$	113,234
Vested or expected to vest — December 31, 2013	2,554,470		$	37.01	6.70	$	109,308
Exercisable — December 31, 2013	951,180		$	20.93	4.98	$	53,916