Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2013

Summary of Stock Options Activity under Plans and Related Information

A summary of the Company’s stock option activity under the Plans and related information is as follows:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value⁽¹⁾
								(in thousands)
Balance at December 31, 2012		9,521,970		$	8.13
Granted		2,342,729			9.08
Exercised		(1,114,819	)		3.30
Forfeited, cancelled or expired		(792,513	)		10.36

Balance at December 31, 2013		9,957,367		$	8.72		7.7	$	28,262

Options vested and exercisable at December 31, 2013		5,639,981		$	7.95		7.2	$	21,101

Options vested and expected to vest as of December 31, 2013		9,358,952		$	8.65			$	27,280

(1)

The aggregate intrinsic value represents the value by which the Company’s closing stock price on the last trading day of the year ended December 31, 2013 exceeds the exercise price of the stock multiplied by the number of options outstanding or exercisable, excluding any that have a negative intrinsic value.

Summary of Stock Options Outstanding by Exercise Price Range

The following table presents the composition of options outstanding and vested and exercisable as of December 31, 2013:


	Options Outstanding						Options Vested and Exercisable
Range of Exercise Prices	Number of Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Number of Vested and Exercisable Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)
$ 0.001-1.01		763,155	$	0.65		4.5		748,363	$	0.64		4.5
$ 2.35		1,011,650		2.35		6.6		888,997		2.35		6.5
$ 6.79-8.92		3,669,357		7.95		8.0		1,837,104		7.89		7.5
$ 9.03-11.59		2,771,210		10.84		8.2		1,190,164		10.97		8.2
$11.61-27.03		1,741,995		14.20		8.2		975,353		15.11		7.9

Totals		9,957,367		8.72		7.7		5,639,981		7.95		7.2

Stock-Based Compensation Expense Allocation

Stock-based compensation expense related to stock-based awards granted to employees and nonemployees were allocated to research and development and sales, general and administrative expense as follows (in thousands):


	Year ended December 31,
	2013		2012		2011
Research and development	$	5,917	$	3,924	$	2,278
Sales, general and administrative		12,736		11,478		8,645

Total	$	18,653	$	15,402	$	10,923

Summary of Restricted Stock Award Activity

Restricted Stock Awards—A summary of the Company’s restricted stock award activity is summarized as follows:


	Number of Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2012		12,670			15.68
Granted		—			—
Vested		(11,502	)		14.88
Forfeited or cancelled		—			—

Unvested at December 31, 2013		1,168		$	23.47

Options to purchase common stock

Weighted-Average Assumptions Used to Estimate Grant Date Fair Value of Stock-Based Awards

The grant date fair value of employee stock-based awards was estimated using the following weighted-average assumptions:


	Year ended December 31,
	2013	2012	2011
Expected term (in years)	5.1-6.0	5.3-6.0	5.0-6.1
Volatility	60.1%-61.5%	62.8%-68.0%	49.6%-68.2%
Risk-free interest rate	0.8%-2.1%	0.6%-1.3%	1.0%-2.5%
Dividend yield	0%	0%	0%

Non Employee Stock Awards

Weighted-Average Assumptions Used to Estimate Grant Date Fair Value of Stock-Based Awards

The fair value of non-employee stock-based awards was estimated using the following weighted-average assumptions:


	Year ended December 31,
	2013	2012	2011
Expected term (in years)	7.8-8.9	8.5-8.9	6.2-10.0
Volatility	60.4%-60.9%	60.3%-64.8%	46.2%-66.7%
Risk-free interest rate	1.6%-2.8%	1.3%-1.9%	1.2%-3.5%
Dividend yield	0%	0%	0%