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Share-Based Payments (Schedule of Assumptions Used to Estimate Fair Value of Stock Options) (Details)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Share-Based Payments [Abstract]
Weighted-average expected stock-price volatility	40.00%	38.00%
Employee stock options, term	4 years 6 months	4 years 6 months
Weighted-average risk-free interest rate	0.84%	2.00%
Weighted-average dividend yield	1.70%	1.70%

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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