Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

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

Stock-Based Compensation Expense

Stock-based compensation expense was recognized as follows (in thousands):

	Year Ended December 31,
	2014		2013		2012
Cost of goods sold	$	1,161	$	1,297	$	1,496
Research and development		7,528		7,910		7,082
General and administrative		8,328		8,501		7,621
Total stock-based compensation	$	17,017	$	17,708	$	16,199

Black-Scholes Option-Pricing Model Assumptions Used to Calculate Fair Value of Employee Stock Options

The following tables list the Black-Scholes option-pricing model assumptions used to calculate the fair value of employee and director stock options.

	Year Ended December 31, 2014			Year Ended December 31, 2013			Year Ended December 31, 2012
Average risk-free interest rate		1.6	%		0.9	%		0.9	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		51.6	%		61.2	%		62.2	%
Average weighted average expected life		5.2 years			5.2 years			5.0 years

Stock Option Activity Under Equity Incentive Plans

The table below presents a summary of stock option activity under our equity incentive plans (in thousands, except for price per share and contractual life information):

	Number of Shares			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Life (in Years)		Aggregate Intrinsic Value(1)
Outstanding at December 31, 2013		20,655		$	9.06
Options granted		7,713			13.96
Options exercised		(4,852	)		9.43
Options forfeited & canceled		(1,521	)		11.89
Outstanding at December 31, 2014		21,995		$	10.50		4.96	$	112,549
Vested and expected to vest at December 31, 2014		21,338		$	10.41		4.89	$	111,071
Exercisable at December 31, 2014		13,007		$	8.90		3.47	$	85,839

(1) Aggregate intrinsic value represents the difference between the exercise price of the option and the closing market price of our common stock on December 31, 2014.