Reportable Segments Supplemental Product Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Oct. 01, 2022	Sep. 30, 2023	Oct. 01, 2022
Segment Reporting Information [Line Items]
Net sales	$ 3,939	$ 3,946	$ 12,033	$ 11,482
Snacks
Segment Reporting Information [Line Items]
Net sales	2,040	1,943	6,114	5,635
Cereal
Segment Reporting Information [Line Items]
Net sales	1,368	1,355	4,155	3,978
Frozen
Segment Reporting Information [Line Items]
Net sales	281	281	838	829
Noodles and other
Segment Reporting Information [Line Items]
Net sales	$ 250	$ 367	$ 926	$ 1,040