Consolidated Statement of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Income Statement [Abstract]
Net sales	$ 3,360	$ 3,175	$ 6,761	$ 6,423
Cost of goods sold	2,151	1,950	4,300	4,038
Selling, general and administrative expense	735	840	1,477	1,720
Operating profit	474	385	984	665
Interest expense	72	63	141	124
Other income (expense), net	69	63	139	151
Income before income taxes	471	385	982	692
Income taxes	70	102	137	145
Earnings (loss) from unconsolidated entities	198	0	198	2
Net income	599	283	1,043	549
Net income (loss) attributable to noncontrolling interests	3	0	3	0
Net income attributable to Kellogg Company	$ 596	$ 283	$ 1,040	$ 549
Per share amounts:
Basic earnings (in dollars per share)	$ 1.72	$ 0.81	$ 3.00	$ 1.57
Diluted earnings (in dollars per share)	1.71	0.80	2.99	1.56
Dividends per share (in dollars per share)	$ 0.54	$ 0.52	$ 1.08	$ 1.04
Average shares outstanding:
Basic (in shares)	347	349	346	350
Diluted (in shares)	348	352	348	353
Actual shares outstanding at period end (in shares)	346	346	346	346