Cover Page	6 Months Ended
	Jun. 27, 2020 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Entity Registrant Name	KELLOGG COMPANY
Document Period End Date	Jun. 27, 2020
Document Transition Report	false
Entity File Number	1-4171
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	38-0710690
Entity Address, Address Line One	One Kellogg Square
Entity Address, Address Line Two	P.O. Box 3599
Entity Address, City or Town	Battle Creek
Entity Address, State or Province	MI
Entity Address, Postal Zip Code	49016-3599
City Area Code	269
Local Phone Number	961-2000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	342,919,265
Amendment Flag	false
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2020
Entity Central Index Key	0000055067
Current Fiscal Year End Date	--01-02
Common stock
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $.25 par value per share
Trading Symbol	K
Security Exchange Name	NYSE
1.750% Senior Notes Due 2021 [Member]
Entity Information [Line Items]
Title of 12(b) Security	1.750% Senior Notes due 2021
Trading Symbol	K 21
Security Exchange Name	NYSE
0.800% Senior Notes Due 2022 [Member]
Entity Information [Line Items]
Title of 12(b) Security	0.800% Senior Notes due 2022
Trading Symbol	K 22A
Security Exchange Name	NYSE
1.000% Senior Notes Due 2024 [Member]
Entity Information [Line Items]
Title of 12(b) Security	1.000% Senior Notes due 2024
Trading Symbol	K 24
Security Exchange Name	NYSE
1.250% Senior Notes Due 2025 [Member]
Entity Information [Line Items]
Title of 12(b) Security	1.250% Senior Notes due 2025
Trading Symbol	K 25
Security Exchange Name	NYSE