Stock Incentive Plans and Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

The following table summarizes all stock option activity for the year ended December 31, 2017

In thousands (except per share amounts and years)	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding as of January 1, 2017		21,188		$	3.37
Granted		3,827			3.09
Forfeited		(219	)		2.52
Expired		(331	)		10.17
Exercised		(357	)		1.79
Outstanding as of December 31, 2017		24,108			3.26	6.8 years	$	34,659
Exercisable as of December 31, 2017		16,115			3.68	6.0 years		21,976
Vested and expected to vest as of December 31, 2017		23,709		$	3.27	6.7 years	$	34,025
Available for future grant as of December 31, 2017		16,994

For 2017, 2016 and 2015, the Company used the following assumptions to estimate the fair value of share-based payment awards:

The following table presents the restricted stock unit activity for the years ended December 31, 2017 and 2016:

In thousands (except per share amounts)	Shares			Weighted Average Grant Date Fair Value
Outstanding as of January 1, 2016		10,887		$	2.12
Granted		1,756			1.47
Vested		(1,853	)		1.62
Forfeited		(647	)		1.74
Outstanding as of December 31, 2016		10,143			2.09
Granted		4,197			3.04
Vested		(2,179	)		1.62
Forfeited		(155	)		2.91
Outstanding as of December 31, 2017		12,006		$	2.50

The following table presents the stock-based compensation expense related to stock-based awards for the years ended December 31, 2017, 2016 and 2015:

In thousands	2017		2016		2015
Research and development	$	2,122	$	2,252	$	3,280
Selling, general and administrative		11,838		11,361		10,609
Stock-based compensation expense	$	13,960	$	13,613	$	13,889