Supplemental financial statement data (Details) - USD ($) $ in Millions	Sep. 28, 2024	Dec. 30, 2023
Condensed Financial Statements, Captions [Line Items]
Trade receivables	$ 169	$ 225
Allowance for expected credit losses	(1)	0
Other receivables	31	19
Accounts receivable, net	199	244
Raw materials	54	49
Manufacturing supplies	55	53
Materials in process	21	15
Finished goods	209	228
Inventories	339	345
Property, cost	2,745	2,676
Accumulated depreciation	(1,976)	(1,937)
Accumulated impairment	(5)	0
Property, net	764	739
Accounts payable	508	541
Obligations under Transition Services Agreement	12	52
Operating lease obligations	18	6
Income taxes payable	13	7
Other	58	40
Other current liabilities	101	105
Other third party
Condensed Financial Statements, Captions [Line Items]
Accounts payable	500	502
Kellanova
Condensed Financial Statements, Captions [Line Items]
Accounts payable	$ 8	$ 39