Consolidated Statement of Income (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Income Statement [Abstract]
Net sales	$ 3,429	$ 3,372	$ 10,306	$ 10,355
Cost of goods sold	2,228	2,372	6,764	7,062
Selling, general and administrative expense	790	737	2,166	2,252
Operating profit	411	263	1,376	1,041
Interest expense	63	72	196	221
Other income (expense), net	70	150	151	247
Income before income taxes	418	341	1,331	1,067
Income taxes	65	91	268	237
Earnings (loss) from unconsolidated entities	(1)	(2)	(7)	(5)
Net income	352	248	1,056	825
Net income attributable to noncontrolling interests	4	1	10	10
Net income attributable to Kellogg Company	$ 348	$ 247	$ 1,046	$ 815
Per share amounts:
Basic earnings (in dollars per share)	$ 1.02	$ 0.73	$ 3.05	$ 2.39
Diluted earnings (in dollars per share)	$ 1.01	$ 0.72	$ 3.03	$ 2.38
Average shares outstanding:
Basic (in shares)	343,000	341,000	343,000	341,000
Diluted (in shares)	346,000	342,000	345,000	342,000
Actual shares outstanding at period end (in shares)	344,000	341,000	344,000	341,000