Accounting policies - Allocation of Expenses from Parent (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 28, 2024	Sep. 30, 2023	Sep. 28, 2024	Sep. 30, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of goods sold	$ 495	$ 496	$ 1,475	$ 1,544
Selling, general and administrative expense	$ 162	179	$ 468	497
Kellanova
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of goods sold		39		128
Selling, general and administrative expense		59		233
Other (income) expense, net		(32)		(43)
Total		$ 66		$ 318

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 808
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
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-Paragraph 1
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