Consolidated Statement of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 3,461	$ 3,360	$ 6,983	$ 6,761
Cost of goods sold	2,275	2,151	4,690	4,300
Selling, general and administrative expense	789	735	1,515	1,477
Operating profit	397	474	778	984
Interest expense	75	72	149	141
Other income (expense), net	45	69	97	139
Income before income taxes	367	471	726	982
Income taxes	74	70	146	137
Earnings (loss) from unconsolidated entities	(1)	198	(3)	198
Net income	292	599	577	1,043
Net income attributable to noncontrolling interests	6	3	9	3
Net income attributable to Kellogg Company	$ 286	$ 596	$ 568	$ 1,040
Per share amounts:
Basic earnings (in dollars per share)	$ 0.84	$ 1.72	$ 1.66	$ 3.00
Diluted earnings (in dollars per share)	$ 0.84	$ 1.71	$ 1.66	$ 2.99
Average shares outstanding:
Basic (in shares)	340	347	341	346
Diluted (in shares)	341	348	342	348
Actual shares outstanding at period end (in shares)	341	346	341	346