Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2012

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, 2011		8,410,765		$	6.76
Granted		2,488,574			11.06
Exercised		(805,827	)		2.08
Forfeited, cancelled or expired		(571,542	)		9.17
Balance at December 31, 2012		9,521,970		$	8.13		8.0	$	17,704
Options vested and exercisable at December 31, 2012		4,367,013		$	6.30		7.2	$	14,026
Options vested and expected to vest as of December 31, 2012		9,326,658		$	7.76			$	19,887

(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, 2012 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, 2012:

	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		1,381,244	$	0.58		4.7		1,272,281	$	0.54		4.6
$2.35		1,181,704		2.35		7.5		753,440		2.35		7.5
$6.79–8.92		2,703,723		7.87		8.2		1,249,747		7.83		8.1
$9.37–11.59		2,628,609		10.89		9.1		551,766		11.10		9.1
$11.61–27.03		1,626,690		14.75		8.9		539,779		16.93		8.6
Totals		9,521,970		8.13		8.0		4,367,013		6.30		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,
	2012		2011		2010
Research and development	$	3,924	$	2,278	$	509
Sales, general and administrative		11,478		8,645		1,443
Total	$	15,402	$	10,923	$	1,952

Summary of Restricted Stock Award Activity

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, 2011		36,167			14.89
Granted		—			—
Vested		(23,497	)		14.46
Forfeited or cancelled		—			—
Unvested at December 31, 2012		12,670		$	15.68

Employee Stock Option

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,
	2012	2011	2010
Expected term (in years)	5.3–6.0	5.0–6.1	3.3–6.5
Volatility	62.8%–68.0%	49.6%–68.2%	42.4%–62.7%
Risk-free interest rate	0.6%–1.3%	1.0%–2.5%	1.4%–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,
	2012	2011	2010
Expected term (in years)	8.5–8.9	6.2–10.0	6.0–10.0
Volatility	60.3%–64.8%	46.2%–66.7%	44.8%–55.4%
Risk-free interest rate	1.3%–1.9%	1.2%–3.5%	1.6%–3.8%
Dividend yield	0%	0%	0%