Reportable Segments Supplemental product information (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 01, 2022	Jan. 02, 2021	Dec. 28, 2019
Segment Reporting Information [Line Items]
Net sales	$ 14,181	$ 13,770	$ 13,578
Snacks
Segment Reporting Information [Line Items]
Net sales	6,807	6,281	6,663
Retail Channel Cereal
Segment Reporting Information [Line Items]
Net sales	5,123	5,433	5,029
Frozen
Segment Reporting Information [Line Items]
Net sales	1,106	1,139	1,037
Noodles and other
Segment Reporting Information [Line Items]
Net sales	$ 1,145	$ 917	$ 849