Derivative Instruments and Fair Value Measurements - Effect of Derivative Instruments on the Consolidated Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income	$ (4)	$ 2	$ 1	$ (24)
Not Designated as Hedging Instrument \| Foreign currency exchange contracts \| COGS
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income	4	(4)	7	(13)
Not Designated as Hedging Instrument \| Foreign currency exchange contracts \| Selling, General and Administrative Expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income	0	(1)	1	(1)
Not Designated as Hedging Instrument \| Foreign currency exchange contracts \| Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income	0	(3)	(4)	(8)
Not Designated as Hedging Instrument \| Commodity contracts \| COGS
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income	(8)	10	(3)	(3)
Not Designated as Hedging Instrument \| Commodity contracts \| Selling, General and Administrative Expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income			0	1
Net Investment Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in AOCI	181	(157)	100	(182)
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	3	0	6	0
Net Investment Hedging \| Foreign currency denominated long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in AOCI	146	(157)	73	(182)
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	0	0	0	0
Net Investment Hedging \| Cross Currency Interest Rate Contract [Member] \| Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in AOCI	35	0	27	0
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net	$ 3	$ 0	$ 6	$ 0

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.

No definition available.

+ Details

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

- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1),(2)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

+ Details

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

- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

+ Details

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

- Definition

Net gain (loss) relating to components of the gain (loss) on the fair value hedging instrument excluded from the assessment of fair value hedge effectiveness. Recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

+ Details

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

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_CostOfSalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_SellingGeneralAndAdministrativeExpensesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=k_OtherIncomeExpenseNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_NetInvestmentHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=k_ForeignCurrencyDenominatedLongTermDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CrossCurrencyInterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: