Reportable Segments Supplemental Product Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2023	Jul. 02, 2022	Jul. 01, 2023	Jul. 02, 2022
Segment Reporting Information [Line Items]
Net sales	$ 4,041	$ 3,864	$ 8,094	$ 7,536
Snacks
Segment Reporting Information [Line Items]
Net sales	2,052	1,917	4,074	3,692
Cereal
Segment Reporting Information [Line Items]
Net sales	1,397	1,342	2,787	2,623
Frozen
Segment Reporting Information [Line Items]
Net sales	265	257	557	548
Noodles and other
Segment Reporting Information [Line Items]
Net sales	$ 327	$ 348	$ 676	$ 673