Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2015

The following table summarizes stock option activity for the nine months ended September 30, 2015:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ⁽¹⁾
Outstanding at December 31, 2014		10,135,914		$	16.76
Granted		1,631,634		$	53.86
Exercised		(1,278,016	)	$	11.22
Forfeited/expired		(230,274	)	$	41.34

Outstanding at September 30, 2015		10,259,258		$	22.80		6.24	$	221.5

Vested and exercisable at September 30, 2015		6,893,054		$	13.05		5.02	$	203.1

⁽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 $42.50 of the Company’s common stock on September 30, 2015. The calculation excludes any awards with an exercise price higher than the closing price of the Company’s common stock on September 30, 2015. The amounts are presented in millions.

Summary of Restricted Stock Units

The following table summarizes restricted stock unit activity for the nine months ended September 30, 2015:


	Number of Shares			Weighted- Average Grant-Date Fair Value
Unvested at December 31, 2014		967,160		$	38.10
Granted		574,695		$	53.93
Vested		(247,572	)	$	38.04
Forfeited		(98,926	)	$	44.84

Unvested at September 30, 2015		1,195,357		$	45.16

Summary of Stock Appreciation Rights Activity

The following table summarizes stock appreciation rights activity for the nine months ended September 30, 2015:


	Number of Rights			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ⁽¹⁾
Outstanding at December 31, 2014		1,376,456		$	12.03
Granted		—			—
Exercised		(55,048	)	$	11.60
Forfeited		(17,156	)	$	11.60

Outstanding at September 30, 2015		1,304,252		$	12.05		6.19	$	39.7

Vested and exercisable at September 30, 2015		1,213,404		$	12.05		6.18	$	36.9

(1)

Schedule of Black-Scholes Assumptions Used for Stock Options

The Black-Scholes assumptions used to estimate the fair value of stock options granted were as follows:


	Three Months Ended September 30,		Nine Months Ended September 30,
	2015	2014	2015	2014
Risk-free interest rate	1.37-1.77%	1.56-1.79%	1.33-1.78%	1.56-1.79%
Estimated term (in years)	5.01-7.17	5.06	4.99-7.17	5.06-5.50
Estimated volatility	57-64%	63%	50-64%	60-64%
Estimated dividend yield	—	—	—	—

Schedule of Black-Scholes Assumptions Used to Estimate Fair Value of Shares Issued under ESPP

The Black-Scholes assumptions used to estimate the fair value of shares issued under the ESPP on the commencement date of the offering period were as follows:


	Nine Months Ended September 30,
	2015			2014
Risk-free interest rate		0.12	%		0.06	%
Estimated term (in years)		0.50			0.50
Estimated volatility		37	%		53	%
Estimated dividend yield		—			—

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense was as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Stock-based compensation expense recognized as:
R&D expense	$	5,673	$	4,611	$	17,593	$	13,236
SG&A expense		7,719		7,346		23,249		19,563

Total	$	13,392	$	11,957	$	40,842	$	32,799