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Fair Value of Each Market Based Option Award Estimated Using Monte Carlo Simulation Model (Detail) (Market Based Option Award, USD $)	3 Months Ended	6 Months Ended
	Jul. 30, 2011	Jul. 30, 2011
Market Based Option Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value	$ 5.08	$ 5.08
Expected volatility	42.00%	42.00%
Risk-free interest rate, minimum	0.90%	0.90%
Risk-free interest rate, maximum	3.60%	3.60%

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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