Stock Compensation Plans (Estimated Fair Value Of Performance Shares Granted) (Details) (Performance Shares [Member], USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.30%	1.20%	1.40%
Expected life, in years	3 years	3 years	3 years
Expected volatility	22.70%	26.90%	27.80%
Dividend yield	4.50%	4.70%	4.60%
Weighted average fair value at grant date	$ 26.06	$ 20.79	$ 15.30

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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