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Share-Based Compensation Share-Based Compensation (Average Fair Value of Stock Options Granted, Assumptions) (Details)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Dividend yield	1.33%	1.33%
Volatility	43.60%	34.81%
Risk-free rate of return	0.92%	2.45%
Expected life, in years	5 years 1 month 0 days	5 years 3 months 18 days

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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