Schedule of Assumptions Used in Determining Fair Value of Options (Detail)	1 Months Ended
Jul. 19, 2012 Year	Mar. 14, 2012 Year	Jul. 20, 2011 Year	Apr. 28, 2011 Year
Stockholders' Equity
Expected volatility	46.00%	46.00%	45.00%	45.00%
Expected life of grant, years	6	6	6	6
Risk-free interest rate	1.80%	2.30%	2.20%	3.10%
Expected dividend rate	1.80%	1.20%	0.90%	0.90%

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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