Accounting policies - Disaggregated net sales (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 28, 2024	Sep. 30, 2023	Sep. 28, 2024	Sep. 30, 2023
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 689	$ 692	$ 2,068	$ 2,112
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	601	605	1,813	1,859
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	78	78	229	225
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 10	$ 9	$ 26	$ 28