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Stock-Based Compensation Plans (Details 1)	12 Months Ended
Stock-Based Compensation Plans (Details 1)	Dec. 31, 2011
Incentive Stock Option Plan [Member]
Black-Scholes Option-Pricing Model weighted average assumptions:
Dividend yield	4.73%
Expected life	5 years
Expected volatility	23.51%
Risk-free interest rate	2.07%
Non-Qualified-Directors Plan [Member]
Black-Scholes Option-Pricing Model weighted average assumptions:
Dividend yield	4.73%
Expected life	5 years
Expected volatility	23.51%
Risk-free interest rate	1.85%

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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