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Stock Options (Details 2)	6 Months Ended
Stock Options (Details 2)	Jun. 30, 2012	Jun. 30, 2011
Stock Options Details 2
Expected life (in years) Minimum		2 years 6 months
Expected life (in years) Maximum	6 years 6 months	6 years 6 months
Average risk-free interest rate	1.66%	2.00%
Expected volatility Minimum	1.80%	1.70%
Expected volatilty Maximum		1.32%
Expected dividend yield	0.00%	0.00%
Forfeiture rate	3.00%	3.00%

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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