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Shareholders' Equity (Details 2)	12 Months Ended
Shareholders' Equity (Details 2)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options, Valuation Assumptions
Expected dividend yield	1.80%	1.90%	2.20%
Expected volatility	39.00%	38.00%	39.00%
Expected term (in years)	7 years 3 months 18 days	7 years 3 months 18 days	7 years 6 months
Risk-free rate	1.40%	3.00%	3.20%

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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