Consolidated Cases Number Of Lawsuits

No definition available.

Name:	ldos_ConsolidatedCasesNumberOfLawsuits
Namespace Prefix:	ldos_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	duration

- Definition

Legal Proceedings [Line Items]

+ References

No definition available.

+ Details

Name:	ldos_LegalProceedingsLineItems
Namespace Prefix:	ldos_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Litigation Settlement, Amount Awarded from Other Party, Pre Interest

+ References

No definition available.

+ Details

Name:	ldos_LitigationSettlementAmountAwardedfromOtherPartyPreInterest
Namespace Prefix:	ldos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Litigation Settlement, Amount Awarded from Other Party, Royalty Rate, Per Device

+ References

No definition available.

+ Details

Name:	ldos_LitigationSettlementAmountAwardedfromOtherPartyRoyaltyRatePerDevice
Namespace Prefix:	ldos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Litigation Settlement, Amount, Percentage of Total

+ References

No definition available.

+ Details

Name:	ldos_LitigationSettlementAmountPercentageofTotal
Namespace Prefix:	ldos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Litigation Settlement, Awarded from the Other Party, Interest and Legal Fees

+ References

No definition available.

+ Details

Name:	ldos_LitigationSettlementAwardedfromtheOtherPartyInterestandLegalFees
Namespace Prefix:	ldos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loss Contingency Claims Resolved

+ References

No definition available.

+ Details

Name:	ldos_LossContingencyClaimsResolved
Namespace Prefix:	ldos_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Loss Contingency, Estimate of Possible Loss, Amount Deferred

+ References

No definition available.

+ Details

Name:	ldos_LossContingencyEstimateofPossibleLossAmountDeferred
Namespace Prefix:	ldos_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, Percentage of Damages Covered, Between Thirty Eight Million and Sixty Four Million Settlement Amount

+ References

No definition available.

+ Details

Name:	ldos_LossContingencyPercentageofDamagesCoveredBetweenThirtyEightMillionandSixtyFourMillionSettlementAmount
Namespace Prefix:	ldos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Loss Contingency, Percentage of Damages Covered, Excess of Sixty Four Million Settlement Amount

+ References

No definition available.

+ Details

Name:	ldos_LossContingencyPercentageofDamagesCoveredExcessofSixtyFourMillionSettlementAmount
Namespace Prefix:	ldos_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Lawsuits

+ References

No definition available.

+ Details

Name:	ldos_NumberOfLawsuits
Namespace Prefix:	ldos_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of indemnification assets (amounts to be reimbursed if and when certain assumed liabilities are paid) recognized at the acquisition date of a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

+ Details

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

- Definition

The amount or range of possible amounts of gain that could be realized upon the resolution of a contingency.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

+ Details

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

- Definition

Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

+ Details

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

- Definition

Amount of increase (decrease) in loss contingency liability.

+ References

+ Details

Name:	us-gaap_LossContingencyAccrualCarryingValuePeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=115931803&loc=d3e12021-110248

+ Details

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

- Details

Name:	ldos_LegalProceedingsAndRelatedMattersAxis=ldos_SecuritiesClassActionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ldos_ContractsByThirdPartyAxis=ldos_GreekGovernmentContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_LitigationCaseAxis=ldos_MSAVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_LitigationCaseAxis=ldos_LockheedMartinMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ldos_LockheedMartinMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ldos_VirnetXIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ldos_LeidosMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ldos_InformationSystemsGlobalSolutionsBusinessofLockheedMartinMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Contingencies - Additional Information (Detail) € in Millions				3 Months Ended	12 Months Ended
	Aug. 30, 2018 USD ($)	Apr. 10, 2018 USD ($)	Sep. 29, 2017 USD ($)	Apr. 30, 2012 LegalMatter	Dec. 28, 2018 USD ($)	Dec. 29, 2017 USD ($)	Nov. 10, 2015 USD ($)	Jan. 03, 2014 EUR (€)
Legal Proceedings [Line Items]
Loss contingency accrual, period increase (decrease)					$ (19,000,000)
Securities Class Actions
Legal Proceedings [Line Items]
Number of lawsuits \| LegalMatter				3
Number of lawsuits, withdrawn \| LegalMatter				1
Number of lawsuits, consolidated \| LegalMatter				2
Greek Government Contract
Legal Proceedings [Line Items]
Arbitral award \| €								€ 39
MSA Venture
Legal Proceedings [Line Items]
Estimate of loss					64,000,000		$ 64,000,000
Estimate of possible loss, amount deferred					32,000,000
Loss contingency accrual					39,000,000	$ 39,000,000
Lockheed Martin
Legal Proceedings [Line Items]
Estimate of loss					$ 56,000,000
Lockheed Martin \| MSA Venture
Legal Proceedings [Line Items]
Percentage of damages covered, between $38 million and $64 million settlement amount					100.00%
Percentage of damages covered, in excess of $64 million settlement amount					50.00%
Virnet X Inc
Legal Proceedings [Line Items]
Amount awarded to other party, pre interest			$ 343,000,000
Litigation settlement	$ 595,000,000	$ 502,000,000	439,000,000
Litigation settlement, amount awarded from other party, royalty rate, per device	1.20
Litigation settlement, awarded from the other party, interest and legal fees	$ 93,000,000		$ 96,000,000
Leidos
Legal Proceedings [Line Items]
Percentage of settlement					25.00%
Leidos \| MSA Venture
Legal Proceedings [Line Items]
Estimate of loss					$ 38,000,000
Information Systems & Global Solutions Business of Lockheed Martin \| MSA Venture
Legal Proceedings [Line Items]
Indemnification assets, amount as of acquisition date					$ 1,000,000	$ 1,000,000