Letters of credit outstanding relate to joint venture operations.

No definition available.

Name:	kbr_LettersOfCreditOutstandingRelateToJointVentureOperations
Namespace Prefix:	kbr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=kbr_LettersOfCreditSuretyBondsAndBankGuaranteesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=kbr_CommittedLineOfCreditMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=kbr_UncommittedLineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt and Other Credit Facilities (Letters of Credit, Surety Bonds and Guarantees) (Details) - USD ($)	Jun. 30, 2021	Jul. 02, 2020
Debt Instrument [Line Items]
Long-term line of credit		$ 1,795,000,000
Letters Of Credit Surety Bonds And Bank Guarantees
Debt Instrument [Line Items]
Letters of credit outstanding relate to joint venture operations	$ 168,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Letters of credit outstanding, amount		$ 1,000,000,000
Performance Letter of Credit Fee \| Letter of Credit
Debt Instrument [Line Items]
Long-term line of credit	781,000,000
Performance Letter of Credit Fee \| Letter of Credit \| Committed Line Of Credit
Debt Instrument [Line Items]
Aggregate principal amount	1,000,000,000
Performance Letter of Credit Fee \| Letter of Credit \| Uncommitted Line Of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	365,000,000
Letters of credit outstanding, amount	210,000,000
Performance Letter of Credit Fee \| Revolving Credit Facility
Debt Instrument [Line Items]
Long-term line of credit	260,000,000
Letters of credit outstanding, amount	$ 114,000,000