Stock-Based Compensation (Details)	3 Months Ended	6 Months Ended
Jun. 18, 2011	Jun. 19, 2010	Jun. 18, 2011	Jun. 19, 2010
Weighted-average assumptions to estimates the fair value of stock options granted
Expected market price volatility	38.50%	37.20%	38.60%	37.90%
Risk-free interest rate	1.60%	2.10%	1.80%	1.90%
Dividend yield	1.60%	1.70%	1.60%	1.90%
Expected term (in years)	4	4	4	4

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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