XML 22 R31.htm IDEA: XBRL DOCUMENT

Share-Based Compensation (Details 1) (USD $)	3 Months Ended	9 Months Ended
Share-Based Compensation (Details 1) (USD $)	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair value per share and Black-Scholes option pricing model
Weighted average fair value of options	$ 2.62	$ 7.54	$ 2.15
Risk-free interest rate	0.99%	0.87%	2.07%
Expected dividend yield	0.00%
Expected option term (in years)	5 years 2 months 12 days	5 years 3 months 26 days	5 years 2 months 12 days
Expected volatility	74.80%	79.30%	75.00%

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.

+ References+ Details