XML 38 R81.htm IDEA: XBRL DOCUMENT

Share Based Compensation (Details 3) (Performance Shares [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Expected volatility	67.63%	77.84%	73.34%
Risk-free rate	0.36%	1.20%	1.24%
Expected term (in years)	2 years 10 months 21 days	2 years 10 months 21 days	2 years 10 months 21 days
Expected dividends	$ 0	$ 0	$ 0

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