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Assumptions Used to Determine Fair Value of Stock Appreciation Rights Granted to Employees (Detail) (SARs)	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
SARs
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	56.00%	56.00%
Average expected life of SAR (in years)	6 years 3 months	6 years 3 months
Risk-free interest rate	0.92%	0.92%
Dividend yield	0.00%	0.00%

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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