Stock Compensation Plans and Stock Based Compensation (Details 8) - Purchase rights granted [Member] - $ / shares	12 Months Ended
Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Weighted-average grant date fair value of purchase rights granted under ESPP and weighted-average assumptions used in model
Expected volatility	27.90%	21.10%	20.40%
Risk-free interest rate	2.23%	2.05%	0.92%
Expected term (in years)	15 days	15 days	15 days
Weighted-average fair value of options granted	$ 14.37	$ 9.24	$ 6.64

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- Definition

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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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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