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Weighted-average assumptions used in determining the fair value of share based awards at the grant date by using the Black-Scholes option-pricing model (Detail)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Dividend Yield	0.00%	0.00%
Risk free interest rate	0.65%	1.00%
Expected volatility	73.00%	63.00%
Expected lives	5 years	5 years

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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