Equity Method Investment, Foreign Currency Translation Adjustment

No definition available.

Name:	kbr_EquityMethodInvestmentForeignCurrencyTranslationAdjustment
Namespace Prefix:	kbr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Equity Method Investment, Other

+ References

No definition available.

+ Details

Name:	kbr_EquityMethodInvestmentOther
Namespace Prefix:	kbr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

+ References

+ Details

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

- Definition

Amount of income (loss) for proportionate share of equity method investee's income (loss).

+ 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

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481664/323-10-45-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(12))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(13)(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

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

- Definition

Amount of investment in equity method investee and investment in and advance to affiliate.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(18))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

The net cash outflow or inflow associated with the acquisition or sale of a business segment during the period.

+ References

No definition available.

+ Details

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

- Definition

Amount of distribution received from equity method investee for return of investment, classified as investing activities. Excludes distribution for return on investment, classified as operating activities.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 21D
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-21D

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=kbr_SustainableTechnologySolutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_EquityMethodInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=kbr_BRISMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=kbr_SubcontractorSettlementAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Equity Method Investments and Variable Interest Entities (Schedule of Equity in Earnings of Unconsolidated Affiliates) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jan. 02, 2026	Jan. 02, 2026	Jan. 03, 2025	Dec. 29, 2023
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at beginning of fiscal year		$ 192
Equity in earnings of unconsolidated affiliates		210	$ 107	$ 114
Distributions of earnings of unconsolidated affiliates		(170)	(163)	(74)
Return of equity method investments, net		(82)	(36)	(60)
Balance at end of fiscal year	$ 107	107	192
STS
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Equity in earnings of unconsolidated affiliates		177	75	81
Equity Method Investments
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at beginning of fiscal year		192	206
Equity in earnings of unconsolidated affiliates		210	107
Distributions of earnings of unconsolidated affiliates		(165)	(202)
Payments from unconsolidated affiliates, net		(9)	(9)
Return of equity method investments, net		(82)	(36)
Foreign currency translation adjustments		4	(2)
Other		(43)	128
Balance at end of fiscal year	107	107	192	$ 206
Equity Method Investments \| BRIS
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Return of equity method investments, net		(79)
Equity Method Investments \| Subcontractor Settlement Agreement
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Return of equity method investments, net			(36)
Other		43	$ 128
Equity Method Investments \| STS
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Distributions of earnings of unconsolidated affiliates	$ (34)	$ (39)