Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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,
	2016		2015		2014
Cost of goods sold	$	1,620	$	1,142	$	1,161
Research and development		13,093		9,207		7,528
General and administrative		11,137		9,320		8,328
Total stock-based compensation	$	25,850	$	19,669	$	17,017

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,
	2016			2015			2014
Average risk-free interest rate		1.4	%		1.6	%		1.6	%
Dividend yield		0.0	%		0.0	%		0.0	%
Average volatility factor		51.7	%		50.8	%		51.6	%
Average weighted average expected life	5.3 years			5.3 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, 2015		18,782		$	11.22
Options granted		3,368			13.92
Options exercised		(2,337	)		8.03
Options forfeited & canceled		(400	)		13.97
Outstanding at December 31, 2016		19,413		$	12.01		4.61	$	26,513
Vested and expected to vest at December 31, 2016		18,970		$	11.97		4.55	$	26,485
Exercisable at December 31, 2016		12,783		$	10.94		3.49	$	25,684

(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, 2016.

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, 2015		1,306		$	15.30
Granted		1,493			12.50
Vested and released		(491	)		14.96
Forfeited and canceled		(60	)		14.87
Balance at December 31, 2016		2,248		$	13.53	$	27,593

(1) Aggregate intrinsic value represents the difference between the grant price of the award, which is zero, and the closing market price of our common stock on December 31, 2016.