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Stock-Based Compensation (Details 8) (Stock Appreciation Rights [Member])	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Appreciation Rights [Member]
Summary of fair value of stock appreciation rights
Expected dividend yield	1.75%	2.39%	1.46%
Risk-free interest rate	0.48%	0.62%	1.46%
Expected volatility	40.42%	41.94%	39.93%
Expected life (in years)	4 years 1 month 21 days	4 years 0 months 24 days	4 years 0 months 14 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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