Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2015

Employee Benefit Plans

Assumptions made for the purpose of estimating fair value

	2015	2014	2013
Expected term of options (years)	6	6	6
Risk free interest rate	1.52% - 1.87%	1.77% - 1.94%	0.93% - 1.70%
Volatility	104.03% - 105.29%	107.17% - 113.92%	92.46% - 107.01%

Schedule of Share-based Compensation, Stock Options, Activity

        A summary of stock option activity for the year December 31, 2015 is as follows (in thousands except share amounts):

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Terms		Aggregate Instrinsic Value
Options outstanding at December 31, 2014		8,367,271		$	3.94		8.7
Granted		3,960,000			2.46
Exercised		(173,334	)		0.96
Forfeited		(406,975	)		3.18
Expired		(46,176	)		59.35
Options outstanding at December 31, 2015		11,700,786		$	3.29		8.3	$	3,397
Options exercisable at December 31, 2015		4,273,425			3.66		7.2		3,159
Options unvested at December 31, 2015		7,427,361		$	3.08		9.0		815

Nonvested Restricted Stock Shares Activity

        A summary of restricted stock activity for the year ended December 31, 2015 is as follows (in thousands except share amounts):

	Shares			Aggregate Instrinsic Value
Unvested restricted stock at December 31, 2014		473,336
Granted		—
Vested		(191,114	)
Forfeited		(77,778	)
Unvested restricted stock at December 31, 2015		204,444		$	431