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Stockholders' Equity Assumptions used to Value Options Grants (Details) (Stock Options)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Options
Share based Compensation Arrangement Assumptions Used to Estimate Fair Values of Share Options Granted [Line Items]
Expected term	4 years 8 months 12 days	4 years 8 months 12 days	4 years 8 months 12 days
Expected volatility	94.00%	96.00%	94.00%
Risk free interest rate	1.42%	0.74%	1.19%

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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