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Stock-Based Compensation (Details 7) (Employee Stock Purchase Plan ("ESPP") [Member])	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Employee Stock Purchase Plan ("ESPP") [Member]
Calculation of fair value of each employee stock purchase grant using the Black-Scholes option-pricing model
Dividend yield	1.90%	1.80%
Risk-free interest rate	0.20%	0.20%
Expected volatility	52.00%	51.00%
Expected life (in years)	6 months 0 days	6 months 0 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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