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Stock-Based Compensation - Schedule of Share Based Payment Award Stock Options Valuation Assumptions (Detail) (Stock Options [Member], USD $)	3 Months Ended
	Nov. 30, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	67.00%
Expected life (years)	5 years
Interest rate, Minimum	0.60%
Interest rate, Maximum	1.00%
Weighted-average fair values (in USD per share)	$ 4.20

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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