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Stock Compensation (Assumptions used for Valuing Options) (Details) (Stock Options, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Per share fair value of options granted during the period (in dollars per share)	$ 13.17	$ 9.80
Risk-free interest rate (as a percentage)	0.85%	1.98%
Dividend yield (as a percentage)	1.77%	1.48%
Volatility factor (as a percentage)	49.70%	48.00%
Weighted-average expected life in years	5 years 3 months 18 days	2 years 3 months 18 days

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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