Stock Incentive Plans and Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2012

Stock Option Activity

The following table summarizes all stock option activity for the year ended December 31, 2012:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
	(in thousands, except for per share amounts)
Outstanding January 1, 2012		11,871		$	5.33
Granted		2,705			10.49
Cancelled/Expired		(304	)		13.09
Exercised		(3,380	)		2.44
Outstanding, December 31, 2012		10,892		$	7.29		8.3 years	$	26,337
Exercisable, December 31, 2012		3,857		$	5.23		7.8 years	$	15,234
Vested and Expected to Vest, December 31, 2012		10,632		$	7.26		8.2 years	$	25,927
Available for future grant at December 31, 2012		7,864

Assumptions Used to Estimate Fair Value of Share-Based Payment Awards

For 2012, 2011 and 2010, the Company used the following assumptions to estimate the fair value of share-based payment awards:

	2012	2011	2010
Risk free interest rate	0.81% - 1.39%	2.03% - 2.56%	1.5% - 3.1%
Expected dividend yield	0.00%	0.00%	0.00%
Expected option life (years)	6.25	6.25	5.75 - 6.25
Expected volatility	109% - 111%	105% - 112%	105% - 110%

Restricted stock unit activity

The following table presents the restricted stock unit activity for the year ended December 31, 2012.

	Shares			Weighted Average Grant Date Fair Value
	(in thousands)
Outstanding January 1, 2012:
Granted		584		$	8.86
Vested		(97	)		8.86
Forfeited		(22	)		8.86
Outstanding—as of December 31, 2012		465			8.86

Stock-Based Compensation Expense Related to Option Awards

The following table presents the stock-based compensation expense related to stock based awards for the period ended December 31:

	2012		2011		2010
	(in thousands)
Research and development	$	3,700	$	1,464	$	1,534
General and administrative		14,375		7,830		3,673
Stock-based compensation expense	$	18,075	$	9,294	$	5,207