Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2012

Fair Value of the Warrants

The fair value of the warrants at December 31, 2012 and 2011 consisted of the following (in thousands):

	December 31,
	2012		2011
2009 Warrants	$	2,009	$	3,010
2010 Warrants		3,894		4,969
Total warrant liability	$	5,903	$	7,979

Fair Value Assumptions of Warrants

The fair value of the Company’s warrants was based on using the Black-Scholes model and/or binomial-lattice option valuation model and using the following assumptions at December 31, 2012 and 2011:

	December 31,
	2012	2011
2009 Warrants:
Expected term (in years)	1.65	2.65
Estimated volatility	45%	74%
Risk-free interest rate	0.25%	0.36%
Expected dividend yield	0%	0%
2010 Warrants:
Expected term (in years)	2.86	3.86
Estimated volatility	51%	70%
Risk-free interest rate	0.36%	0.60%
Expected dividend yield	0%	0%