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Stock-Based Compensation (Details 7)	6 Months Ended	12 Months Ended
Stock-Based Compensation (Details 7)	Jun. 30, 2012	Dec. 31, 2011
Calculation of fair value of each employee stock purchase grant using the Black-Scholes option-pricing model
Dividend yield	1.80%
Risk-free interest rate	0.20%	0.30%
Expected volatility	51.00%	52.00%
Expected life (in years)	6 months	6 months

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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