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Stock-Based Compensation (Details) (USD $)	9 Months Ended
Stock-Based Compensation (Details) (USD $)	Sep. 30, 2012	Sep. 30, 2011
Estimation of fair value of options granted
Dividend yield	0.00%	0.00%
Expected volatility	41.80%
Expected life of option	5 years	5 years
Risk-free interest rate	0.80%
Fair value of each option on grant date	$ 2.73
Maximum [Member]
Estimation of fair value of options granted
Expected volatility		41.30%
Risk-free interest rate		2.00%
Fair value of each option on grant date		2.83
Minimum [Member]
Estimation of fair value of options granted
Expected volatility		40.50%
Risk-free interest rate		1.00%
Fair value of each option on grant date		2.75

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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