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Stockholders' Equity (Details) (USD $)	12 Months Ended
Stockholders' Equity (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Weighted-average fair value of options granted and assumptions
Weighted average fair value of options on grant date	$ 4.87	$ 6.84
Expected life (years)	6 years	6 years
Risk-free interest rate	2.30%	2.50%
Expected dividend yield
Expected volatility	76.20%	71.10%

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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