Accounting policies - Narrative (Details) - USD ($) $ in Millions	Sep. 28, 2024	Dec. 30, 2023
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Supplier finance program, obligation	$ 133	$ 142
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Supplier finance program general payment timing, period	0 days
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Supplier finance program general payment timing, period	135 days