DISCONTINUED OPERATIONS (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 29, 2023	Dec. 28, 2024	Dec. 30, 2023	Dec. 31, 2022
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Net Sales			$ 2,085	$ 2,662
Disposal Group, Including Discontinued Operation, Costs of Goods Sold			1,387	1,858
Disposal Group, Including Discontinued Operation, General and Administrative Expense			479	381
Disposal Group, Including Discontinued Operation, Operating Profit			219	423
Disposal Group, Including Discontinued Operation, Interest Expense			26	17
Disposal Group, Including Discontinued Operation, Other Income			54
Disposal Group, Including Discontinued Operation, Other Expense				(111)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax			247	295
Discontinued Operation, Tax Effect of Discontinued Operation			71	64
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent			176	231
Disposal Group, Including Discontinued Operation, Depreciation and Amortization			52	74
Capital Expenditure, Discontinued Operations			107	87
Disposal Group, Including Discontinued Operation, Postretirement benefit plan expense (benefit)			(53)	123
Disposal Group, Including Discontinued Operation, Transition Services Agreement Cost		$ 157	52
Net sales from continuing operations		12,749	13,122	12,653
Cost of goods sold		8,204	8,839	$ 8,842
WK Kellogg Co
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales from continuing operations		45	18
Cost of goods sold		$ 39	16
WK Kellogg Co | Supply Agreement | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operation, Period of Continuing Involvement after Disposal		3 years
SGA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Transition Services Agreement Cost		$ 56	15
Cost of Goods and Service, Product and Service Benchmark
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Transition Services Agreement Cost		$ 101	$ 37
2.65% U.S. Dollar Notes Due 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt instrument, stated interest rate	2.65%
Long-term Debt, Gross	$ 550
Revolving Credit Facility | Line of Credit | WK Kellogg Co
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Debt, Long-Term and Short-Term, Combined Amount	664
Payments of Dividends	$ 663