Document and Entity Information Document - USD ($) $ in Billions	12 Months Ended
	Dec. 29, 2018	Jan. 26, 2019	Jun. 30, 2018
Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 29, 2018
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2018
Trading Symbol	K
Entity Registrant Name	KELLOGG CO
Entity Central Index Key	0000055067
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-29
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		343,894,654
Entity Public Float			$ 19.1