Stock-based compensation - Schedule of Stock-Based Compensation Under Statements Of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 02, 2022	Jan. 03, 2021	Dec. 29, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 22.5	$ 8.6	$ 18.6
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	0.5	0.8	1.8
Selling, marketing and administrative expenses
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	21.5	7.5	16.4
Research and development expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 0.5	$ 0.2	$ 0.5