Accounting policies -Components of net parent investment (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jul. 01, 2023	Jun. 29, 2024	Jul. 01, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock compensation		$ 6	$ 2
Pension and postretirement plan benefit		$ 18	13
Net transfer (to)/from Kellanova	$ (52)		(94)
Kellanova
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net transfers (to) from Kellanova			(82)
Stock compensation			2
Pension and postretirement plan benefit			(14)
Net transfer (to)/from Kellanova			$ (94)

Transfers (To) From Parent, Net

No definition available.

Name:	klg_TransfersToFromParentNet
Namespace Prefix:	klg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 808
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479402/808-10-50-1

+ Details

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

- Definition

Amount of noncash expense (reversal of expense) for pension and other postretirement benefits.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

+ Details

Name:	us-gaap_PensionAndOtherPostretirementBenefitsExpenseReversalOfExpenseNoncash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of noncash expense for share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (a)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

+ Details

Name:	us-gaap_ShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The change in equity as a result of a spin-off transaction (a regular or reverse spin-off) which is based on the recorded amounts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 505
-SubTopic 60
-Section 25
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481423/505-60-25-2

+ Details

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

- Details

Name:	srt_CounterpartyNameAxis=klg_KellanovaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: