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Share-based Compensation (Details 1) (USD $)	9 Months Ended
Share-based Compensation (Details 1) (USD $)	Sep. 30, 2012	Sep. 30, 2011
Computation of fair values of employee stock options for option grants issued under Black-Scholes option model
Dividend yield	1.60%	1.10%
Volatility	61.80%	66.10%
Risk-free interest rate	0.60%	1.40%
Weighted average expected option term (in years)	5 years 6 months	4 years 9 months 18 days
Weighted average fair value per share of options granted	$ 2.91	$ 3.57

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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