Consolidated Statement of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 3,469	$ 3,246	$ 10,230	$ 9,669
Cost of goods sold	2,293	2,074	6,593	6,112
Selling, general and administrative expense	780	839	2,257	2,559
Operating profit	396	333	1,380	998
Interest expense	72	64	213	188
Other income (expense), net	130	117	269	268
Income before income taxes	454	386	1,436	1,078
Income taxes	69	101	206	246
Earnings (loss) from unconsolidated entities	(2)	3	196	5
Net income	383	288	1,426	837
Net income (loss) attributable to noncontrolling interests	3	0	6	0
Net income attributable to Kellogg Company	$ 380	$ 288	$ 1,420	$ 837
Per share amounts:
Basic earnings (in dollars per share)	$ 1.10	$ 0.83	$ 4.10	$ 2.40
Diluted earnings (in dollars per share)	1.09	0.83	4.07	2.38
Dividends per share (in dollars per share)	$ 0.56	$ 0.54	$ 1.64	$ 1.58
Average shares outstanding:
Basic (in shares)	347	345	346	348
Diluted (in shares)	349	348	349	351
Actual shares outstanding at period end (in shares)	347	345	347	345