Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value of Warrants

The fair value of the warrants at September 30, 2013, and December 31, 2012, consisted of the following (in thousands):

	September 30, 2013		December 31, 2012
2009 Warrants	$	9,203	$	2,009
2010 Warrants		13,503		3,894
Total warrant liability	$	22,706	$	5,903

Fair Value Assumptions of Warrants

The fair value of the Company’s warrants was based on using the binomial-lattice option valuation model and using the following assumptions at September 30, 2013, and December 31, 2012:

	September 30, 2013			December 31, 2012
2009 Warrants:
Expected term (in years)		0.90			1.65
Estimated volatility		43	%		45	%
Risk-free interest rate		0.10	%		0.25	%
Expected dividend yield		0	%		0	%
2010 Warrants:
Expected term (in years)		2.11			2.86
Estimated volatility		41	%		51	%
Risk-free interest rate		0.33	%		0.36	%
Expected dividend yield		0	%		0	%