Reportable Segments Supplemental Product Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 02, 2022	Jul. 03, 2021	Jul. 02, 2022	Jul. 03, 2021
Segment Reporting Information [Line Items]
Net sales	$ 3,864	$ 3,555	$ 7,536	$ 7,139
Snacks
Segment Reporting Information [Line Items]
Net sales	1,917	1,656	3,692	3,303
Cereal
Segment Reporting Information [Line Items]
Net sales	1,342	1,336	2,623	2,710
Frozen
Segment Reporting Information [Line Items]
Net sales	257	267	548	564
Noodles and other
Segment Reporting Information [Line Items]
Net sales	$ 348	$ 296	$ 673	$ 562