Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2013

The following table summarizes stock option activity for the six months ended June 30, 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		337,606		$	49.75
Exercised		(308,914	)	$	11.82
Forfeited		(18,104	)	$	35.56

Outstanding at June 30, 2013		7,048,879		$	20.65		6.95	$	205.8

Vested and exercisable at June 30, 2013		4,093,583		$	11.67		5.72	$	153.6

⁽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 $49.20 of the Company’s common stock on June 28, 2013. The calculation excludes any awards with an exercise price higher than the closing price of the Company’s common stock on June 28, 2013. The amounts are presented in millions.

Summary of Restricted Stock Units

The following table summarizes restricted stock unit activity for the six months ended June 30, 2013:


	Number of Shares			Weighted- Average Grant-Date Fair Value
Unvested at December 31, 2012		373,625		$	39.06
Granted		73,993		$	50.94
Vested		—			—
Forfeited		(1,856	)	$	52.92

Unvested at June 30, 2013		445,762		$	40.98

Summary of Stock Appreciation Rights Activity

The following table summarizes stock appreciation rights activity for the six months ended June 30, 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		(22,410	)	$	23.20
Forfeited		—			—

Outstanding at June 30, 2013		861,190		$	23.93		8.48	$	21.8

Vested and exercisable at June 30, 2013		294,790		$	23.97		8.47	$	7.4

⁽¹⁾

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

The Company estimates 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 appreciation rights granted were as follows:


	Three Months Ended June 30,		Six Months Ended June 30,
	2013	2012	2013	2012
Risk-free interest rate	0.73-1.55%	0.83%	0.73-1.55%	0.83-1.01%
Estimated term (in years)	5.25-5.50	5.42	5.24-5.50	5.42-5.48
Estimated volatility	73-75%	71%	68-75%	71-73%
Estimated dividend yield	—	—	—	—

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense was as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
Stock-based compensation expense recognized as:
R&D expense	$	3,619	$	3,048	$	7,437	$	5,485
SG&A expense		4,512		2,533		8,990		4,432

Total	$	8,131	$	5,581	$	16,427	$	9,917