Amount of cash proceeds that can be collected under transfer agreement

No definition available.

Name:	k_TransfersOfAccountsReceivableAgreements
Namespace Prefix:	k_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of gain (loss) on sale of accounts receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121570589&loc=d3e107425-111719

+ Details

Name:	us-gaap_GainLossOnSaleOfAccountsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of derecognized financial assets from transactions which comprise an initial transfer and an agreement entered into in contemplation of the initial transfer resulting in retention of substantially all of the exposure to the economic return throughout the term of the transaction, at the date of derecognition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121570589&loc=SL51823488-111719

+ Details

Name:	us-gaap_TransferOfFinancialAssetsAccountedForAsSalesAmountDerecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_TransferOfFinancialAssetsAccountedForAsSalesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	k_TransferOfAccountsReceivableProgramsAxis=k_MonetizationProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis=k_AccountsReceivableSoldAndOutstandingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	k_TransferOfAccountsReceivableProgramsAxis=k_KelloggForeignSubsidiariesOtherProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Sale of Accounts Receivable (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 02, 2021	Dec. 28, 2019	Dec. 29, 2018
Monetization Program
Transfer of Financial Assets Accounted for as Sales [Line Items]
Gain (Loss) on Sale of Accounts Receivable	$ (14)	$ (25)	$ (26)
Monetization Program \| Maximum
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfers Of Accounts Receivable Agreements	1,033
Monetization Program \| Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Accounts Receivable Agreements	783	774
Kellogg Foreign Subsidiaries Program \| Sold And Outstanding
Transfer of Financial Assets Accounted for as Sales [Line Items]
Transfer of Accounts Receivable Agreements	$ 55	$ 89