EMPLOYEE STOCK PLANS - Valuation Assumptions (Details) - $ / shares	3 Months Ended	12 Months Ended
Dec. 28, 2018	Dec. 29, 2017	Sep. 27, 2019
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	4 years 9 months 18 days	4 years 2 months 12 days	4 years 7 months 6 days
Risk-free interest rate	2.60%	1.60%	2.50%
Expected volatility	31.80%	23.60%	33.90%
Expected dividend	0.00%	0.00%	0.00%
Weighted average fair value at grant date (in USD per share)	$ 11.57	$ 8.08	$ 10.19
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months
Risk-free interest rate	2.00%	1.00%	2.50%
Expected volatility	34.10%	28.00%	43.90%
Expected dividend	0.00%	0.00%	0.00%
Weighted average fair value at grant date (in USD per share)	$ 8.92	$ 7.81	$ 7.81

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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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.

+ References

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
-Topic 718
-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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