Consolidated Statement of Income (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Income Statement [Abstract]
Net sales	$ 3,465	$ 3,461	$ 6,877	$ 6,983
Cost of goods sold	2,268	2,275	4,536	4,690
Selling, general and administrative expense	691	789	1,375	1,515
Operating profit	506	397	966	778
Interest expense	69	75	133	149
Other income (expense), net	30	45	79	97
Income before income taxes	467	367	912	726
Income taxes	109	74	203	146
Earnings (loss) from unconsolidated entities	(4)	(1)	(5)	(3)
Net income	354	292	704	577
Net income attributable to noncontrolling interests	3	6	6	9
Net income attributable to Kellogg Company	$ 351	$ 286	$ 698	$ 568
Per share amounts:
Basic earnings (in dollars per share)	$ 1.02	$ 0.84	$ 2.04	$ 1.66
Diluted earnings (in dollars per share)	$ 1.02	$ 0.84	$ 2.02	$ 1.66
Average shares outstanding:
Basic (in shares)	343,000	340,000	342,000	341,000
Diluted (in shares)	345,000	341,000	345,000	342,000
Actual shares outstanding at period end (in shares)	343,000	341,000	343,000	341,000