Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2013

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

The following table summarizes stock option activity for the three months ended March 31, 2013:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ⁽¹⁾
Outstanding at December 31, 2012		7,038,291		$	18.90
Granted		37,200		$	52.46
Exercised		(177,815	)	$	10.25
Forfeited		—			—

Outstanding at March 31, 2013		6,897,676		$	19.31		7.09	$	195.7

Vested and exercisable at March 31, 2013		3,908,361		$	11.12		5.86	$	139.3

⁽¹⁾

The aggregate intrinsic value is calculated as the pre-tax difference between the weighted average exercise price of the underlying awards and the closing price per share of $46.76 of the Company’s common stock on March 28, 2013. The calculation excludes any awards with an exercise price higher than the closing price of the Company’s common stock on March 28, 2013. The amounts are presented in millions.

Summary of Restricted Stock Units

The following table summarizes restricted stock unit activity for the three months ended March 31, 2013:


	Number of Shares		Weighted- Average Grant-Date Fair Value
Unvested at December 31, 2012		373,625	$	39.06
Granted		9,600	$	53.66
Vested		—		—
Forfeited		—		—

Unvested at March 31, 2013		383,225	$	39.43

Summary of Stock Appreciation Rights Activity

The following table summarizes stock appreciation rights activity for the three months ended March 31, 2013:


	Number of Rights			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ⁽¹⁾
Outstanding at December 31, 2012		883,600		$	23.91
Granted		—			—
Exercised		(9,508	)	$	23.20
Forfeited		—			—

Outstanding at March 31, 2013		874,092		$	23.92		8.73	$	20.0

Vested and exercisable at March 31, 2013		259,144		$	23.96		8.72	$	5.9

⁽¹⁾

Schedule of Black-Scholes Assumptions Used for Stock Options and Stock Appreciations Rights

The Company estimated the fair value of stock options and stock appreciation rights using the Black-Scholes valuation model, which requires the use of subjective assumptions related to the estimated stock price volatility, estimated term, estimated dividend yield and risk-free interest rate. The Black-Scholes assumptions used for stock options and stock appreciations rights granted and/or remeasured were as follows:


	Three Months Ended March 31,
	2013			2012
Risk-free interest rate		0.93-0.94	%		0.99-1.18	%
Estimated term (in years)		5.24			5.48
Estimated volatility		68	%		73	%
Estimated dividend yield		—			—

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense was as follows:


	Three Months Ended March 31,
	2013		2012
Stock-based compensation expense recognized as:
R&D	$	3,818	$	2,437
SG&A		4,478		1,899

Total	$	8,296	$	4,336