Accounting policies - Narrative (Details) - USD ($) $ in Millions	Mar. 29, 2025	Dec. 28, 2024
Supplier Finance Program [Line Items]
Supplier finance program, obligation	$ 132	$ 132
Minimum
Supplier Finance Program [Line Items]
Supplier finance program general payment timing, period	0 days
Maximum
Supplier Finance Program [Line Items]
Supplier finance program general payment timing, period	135 days

Amount of obligation for supplier finance program.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 55
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477128/405-50-55-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Name:	us-gaap_SupplierFinanceProgramObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant