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Stock-Based Compensation (Summary Of Weighted Average Fair Value Assumptions of Awards) (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		2.40%	2.60%
Expected life (years)		6 years 9 months 18 days	6 years
Expected stock price volatility		31.70%	33.20%
Expected dividend yield		0.00%	0.00%
Performance-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate	27.80%
Risk-free interest rate	0.40%	1.00%	1.40%
Expected life (years)	3 years	3 years	3 years
Expected stock price volatility		37.90%	38.80%

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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