Share-Based Compensation Plans (Schedule Of Assumptions Of Weighted Average For ESPP Purchases Utilizing The Black-Scholes Model) (Details) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Dividend yield	0.80%	0.90%	0.90%
Risk-free interest rate	1.03%	1.29%	1.72%
Expected life in years	7.0	7.2	7.1
Expected volatility rate	23.00%	23.00%	24.00%
Fair value	$ 19.82	$ 21.34	$ 22.64
Employee Stock Purchase Plan [Member]
Dividend yield	0.80%	0.90%	0.80%
Risk-free interest rate	0.16%	0.20%	0.30%
Expected life in years	0.5	0.5	0.5
Expected volatility rate	17.00%	20.00%	32.00%
Fair value	$ 19.63	$ 15.70	$ 18.74

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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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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