Accounting policies - Disaggregated net sales (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 30, 2024	Apr. 01, 2023
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 707	$ 720
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	623	637
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	75	74
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 9	$ 9