Share-Based Payments (Details)	6 Months Ended
Feb. 11, 2012 Y	Feb. 12, 2011 Y
Weighted average fair value of the stock option awards granted, weighted average key assumptions
Expected price volatility	31.00%	31.00%
Risk-free interest rate	0.70%	1.00%
Weighted average expected lives (in years)	5.3	4.3
Forfeiture rate	10.00%	10.00%
Dividend yield	0.00%	0.00%

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

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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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