| Cover Page Cover Page | Oct. 29, 2020 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 29, 2020 |
| Entity Registrant Name | Kellogg Company |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-4171 |
| Entity Tax Identification Number | 38-0710690 |
| Entity Address, Address Line One | One Kellogg Square |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000055067 |
| Amendment Flag | false |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| Entity Information [Line Items] | |
| Title of 12(b) Security | 1.250% Senior Notes due 2025 |
| Trading Symbol | K 25 |
| Security Exchange Name | NYSE |
