STOCK COMPENSATION - Summary of restricted stock activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		12 Months Ended
		Dec. 28, 2024	Dec. 30, 2023		Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental expense for modification of restricted stock units			$ 11
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period, years		3 years
Non-vested, beginning of year - shares	[1]	3,183	1,661		1,786
Granted - shares		668	572		709
Vested - shares		(1,172)	(491)		(619)
Forfeited - shares		(202)	(359)		(215)
Performance share conversion			1,486		0
Awards transferred to WK Kellogg Co			(529)		0
Adjustment for spin-off			843	[2]	0
Non-vested, end of year - shares		2,477	3,183	[1]	1,661	[1]
Non-vested, beginning of year - weighted-average grant-date fair value	[1]	$ 58	$ 64		$ 60
Granted - weighted average grant-date fair value		56	68		67
Vested - weighted-average grant-date fair value		56	65		57
Forfeited - weighted-average grant-date fair value		59	65		62
Performance share conversion			63		0
Awards transferred to WK Kellogg Co			65		0
Non-vested, end of year - weighted-average grant-date fair value		$ 59	$ 58	[1]	$ 64	[1]
Total fair value of restricted stock and restricted stock units vested during period		$ 64	$ 33		$ 41

[1] Activities prior to the spin-off remain unadjusted to ensure consistency with historical reporting.

[2] In connection with the spin-off of WK Kellogg Co, the modification of restricted stock units resulted in incremental expense totaling approximately $11 million to be amortized over the remaining vesting period of the award.