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Share-Based Compensation (Schedule Of Assumptions Used In Black-Scholes-Merton Model To Estimate Fair Values Of Options Granted) (Details) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Volatility	37.60%	37.09%
Expected dividend yield	4.00%	4.00%
Expected term (in years)	7 years	7 years
Risk-free interest rate	1.09%	2.97%
Fair value	$ 2.39	$ 2.61

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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