Stock-based compensation - Assumptions Used to Estimated Grant Fair Value (Details) - $ / shares	12 Months Ended
Jan. 02, 2022	Jan. 03, 2021	Dec. 29, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Range of expected volatility minimum	45.00%
Range of expected volatility maximum	50.00%
Weighted-average dividend rate	0.00%	0.00%	0.00%
Range of risk-free rates minimum	1.07%
Range of risk-free rates maximum	1.10%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Price	$ 19.06	$ 12.56	$ 11.92
Range of expected term	5 years 6 months	3 months 18 days	1 year
Range of expected volatility minimum		55.00%	45.00%
Range of risk-free rates minimum		0.11%	1.50%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Price	$ 19.97	$ 14.13	$ 12.55
Range of expected term	6 years 3 months	4 years 9 months 18 days	6 years 1 month 20 days
Range of expected volatility maximum		80.00%	55.00%
Range of risk-free rates maximum		0.30%	2.56%

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 maximum 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.

+ References

No definition available.

+ Details

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- Definition

The estimated measure of the minimum 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.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

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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.

+ References

No definition available.

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- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

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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)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=122041274&loc=d3e301413-122809

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