Consolidated Statement of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Income Statement [Abstract]
Net sales	$ 3,372	$ 3,469	$ 10,355	$ 10,230
Cost of goods sold	2,372	2,293	7,062	6,593
Selling, general and administrative expense	737	780	2,252	2,257
Operating profit	263	396	1,041	1,380
Interest expense	72	72	221	213
Other income (expense), net	150	130	247	269
Income before income taxes	341	454	1,067	1,436
Income taxes	91	69	237	206
Earnings (loss) from unconsolidated entities	(2)	(2)	(5)	196
Net income	248	383	825	1,426
Net income attributable to noncontrolling interests	1	3	10	6
Net income attributable to Kellogg Company	$ 247	$ 380	$ 815	$ 1,420
Per share amounts:
Basic earnings (in dollars per share)	$ 0.73	$ 1.10	$ 2.39	$ 4.10
Diluted earnings (in dollars per share)	$ 0.72	$ 1.09	$ 2.38	$ 4.07
Average shares outstanding:
Basic (in shares)	341	347	341	346
Diluted (in shares)	342	349	342	349
Actual shares outstanding at period end (in shares)	341	347	341	347