Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Stock-Based Compensation Expense

We issue stock-based awards from our equity incentive plans, which are more fully described in Note 9. Stock-based compensation expense was recognized as follows (in thousands):

	Year Ended December 31,
	2015		2014		2013
Cost of goods sold	$	1,142	$	1,161	$	1,297
Research and development		9,207		7,528		7,910
General and administrative		9,320		8,328		8,501
Total stock-based compensation	$	19,669	$	17,017	$	17,708

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

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

	Year Ended December 31,
	2015			2014			2013
Average risk-free interest rate		1.6	%		1.6	%		0.9	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		50.8	%		51.6	%		61.2	%
Average weighted average expected life	5.3 years			5.2 years			5.2 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, 2014		21,995		$	10.50
Options granted		1,746			14.00
Options exercised		(3,937	)		7.89
Options forfeited & canceled		(1,022	)		13.42
Outstanding at December 31, 2015		18,782		$	11.22		4.67	$	105,830
Vested and expected to vest at December 31, 2015		18,360		$	11.14		4.62	$	104,749
Exercisable at December 31, 2015		12,222		$	9.89		3.60	$	85,074

(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, 2015.

Restricted Stock Units (RSU) [Member]

Restricted Stock Unit Award Activity

A summary of RSU award activity is as follows (in thousands except for per share amounts):

	Units Issued		Weighted- Average Grant Date Fair Value		Aggregate Intrinsic Value(1)
Balance at December 31, 2014		—
Granted		1,306	$	15.30
Vested		—
Forfeited and canceled		—
Balance at December 31, 2015		1,306			$	22,012

(1) Aggregate intrinsic value represents the difference between the grant price of the award and the closing market price of our common stock on December 31, 2015.