Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Assumptions Used to Determine Fair Value of Stock Options Granted During Period

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model. The following assumptions apply to the options to purchase 2,518,500 and 3,130,083 shares of common stock granted to employees and directors during the nine months ended September 30, 2014 and 2013, respectively:

	Nine Months Ended September 30,
	2014			2013
Average risk free interest rate		1.6	%		1.3	%
Expected dividend yield		—			—
Expected lives (years)		4.8			5.2
Expected volatility		83.0	%		62.0	%
Weighted average grant date fair value of options granted during the period (per share)	$	2.47		$	0.49
Weighted average exercise price of options granted during the period (per share)	$	3.80		$	0.92