Performance Period [Domain] Performance Period [Domain] Performance Period [Domain] Finite-lived intangible assets, accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Revision of Prior Period [Axis] Revision of Prior Period [Axis] Number of government procurements Litigation Settlement, Number Of Government Procurements Litigation Settlement, Number Of Government Procurements Statistical Measurement [Domain] Statistical Measurement [Domain] Decrease in deferred tax assets Increase (Decrease) In Deferred Tax Assets Increase (Decrease) In Deferred Tax Assets Debt instrument, extension term (in years) Debt Instrument, Term, Extension Debt Instrument, Term, Extension Award Timing Predetermined Award Timing Predetermined [Flag] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Total intangible assets, gross carrying value Intangible Assets, Gross (Excluding Goodwill) Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-Lived Intangible Assets [Axis] Entity File Number Entity File Number Additional paid-in capital Additional Paid-in Capital [Member] $750 million notes, due March 2033 Term Loan Due March Two Thousand Thirty Three [Member] Term Loan Due March Two Thousand Thirty Three Interest rate swaps Interest Rate Swap [Member] Revenue recognized for performance obligation satisfied in the previous periods Contract with Customer, Performance Obligation Satisfied in Previous Period Equity earnings of non-consolidated subsidiaries Income (Loss) from Equity Method Investments Tabular List, Table Tabular List [Table Text Block] Standby Letters of Credit and Surety Bonds Standby Letters of Credit and Surety Bonds [Member] Standby Letters of Credit and Surety Bonds [Member] Intangible Asset, Acquired, Finite-Lived [Line Items] Intangible Asset, Acquired, Finite-Lived [Line Items] Accounting Standards Updates Issued But Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Contract assets - current: Contract with Customer, Asset, after Allowance for Credit Loss, Current Schedule of Changes in Estimates on Contracts Schedule of Change in Accounting Estimate [Table Text Block] Interest expense, net Total interest expense, net presented in the condensed consolidated statements of operations in which the effects of cash flow hedges are recorded Interest Income (Expense), Nonoperating Leidos, Inc. Leidos, Inc. [Member] Leidos, Inc. Goodwill [Line Items] Goodwill [Line Items] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] 2027 Other Commitment, to be Paid, Year Two Measurement Basis [Axis] Measurement Basis [Axis] Basic (in dollars per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Commercial Paper Commercial Paper [Member] Other U.S. government agencies Other Government Agencies [Member] Other Government Agencies [Member] Revenues Revenue from Contract with Customer [Text Block] Total other comprehensive income (loss), net of taxes Other comprehensive income (loss), net of taxes Other Comprehensive Income (Loss), Net of Tax Schedule of Segment Reporting Information by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] $300 million notes, due July 2033 Notes Which Mature On July Two Thousand Thirty Three [Member] Notes Which Mature On July Two Thousand Thirty Three [Member] Remaining performance obligations, which are expected to be recognized as revenue Revenue, Remaining Performance Obligation, Amount Adjustment to Compensation, Amount Adjustment to Compensation Amount Less: unamortized debt discounts and deferred debt issuance costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Remaining performance obligations, which are expected to be recognized as revenue (as percent) Revenue, Remaining Performance Obligation, Percentage Other current assets and other long-term assets Increase (Decrease) in Other Operating Assets Consolidation Consolidation, Policy [Policy Text Block] Stock-based compensation Share-Based Payment Arrangement, Noncash Expense Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Net proceeds from sale of assets Proceeds from Sale of Productive Assets Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Total Leidos stockholders’ equity Equity, Attributable to Parent $750 million notes, due May 2030 Notes Which Mature On May Two Thousand Thirty [Member] Notes Which Mature On May Two Thousand Thirty Insider Trading Policies and Procedures [Line Items] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Hedging Designation [Domain] Hedging Designation [Domain] Goodwill and Intangible Assets Disclosure [Abstract] Goodwill and Intangible Assets Disclosure [Abstract] Issuances of stock (in shares) Stock Issued During Period, Shares, New Issues Total liabilities and stockholders' equity Liabilities and Equity Pension adjustments Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Liabilities: Liabilities and Equity [Abstract] Cover page. 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share repurchases, initial delivery (in shares) Accelerated Share Repurchases, Initial Shares Delivered Accelerated Share Repurchases, Initial Shares Delivered Company Selected Measure Name Company Selected Measure Name Savanna Industries, Inc. 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employee benefits Employee-related Liabilities, Current Property, plant and equipment, net Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Net capital distributions to non-controlling interest Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Trade names Trade Names [Member] Net income attributable to Leidos common stockholders Net Income (Loss) Net Income (Loss) Attributable to Parent Expiration Date Trading Arrangement Expiration Date $500 million notes, due March 2032 Notes Which Mature On March Two Thousand Thirty Two [Member] Notes Which Mature On March Two Thousand Thirty Two Other Commitments [Domain] Other Commitments [Domain] Changes in Estimates on Contracts Changes In Estimates On Contracts [Policy Text Block] Changes In Estimates On Contracts [Policy Text Block] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Revenue recognized 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Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Statement [Table] Statement [Table] Other income (expense), net Corporate expense Other Nonoperating Income (Expense) Deferred income taxes Deferred Income Tax Expense (Benefit) Adjustments to reconcile net income to net cash provided by operations: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Impact on diluted EPS attributable to Leidos common stockholders (in dollars per share) Increase (Decrease) In Income From Change In Contract Estimates Per Diluted Share Increase (Decrease) In Income From Change In Contract Estimates Per Diluted Share Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Receivables, net Receivables, Net, Current Schedule of Financial Assets Measured on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Anti-dilutive shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount All Adjustments to Compensation All Adjustments to Compensation [Member] Revenue, Initial Application Period Cumulative Effect Transition [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Accounts payable and accrued liabilities Accounts Payable and Accrued Liabilities, Current Amendment Flag Amendment Flag Time-and-materials and fixed-price-level-of-effort Time-And-Materials And Fixed-Price-Level-Of-Effort [Member] Time-and-materials and Fixed-price-level-of-effort [Member] Other Commitments And Contingencies [Table] Other Commitments [Table] Termination Date Trading Arrangement Termination Date Net cash used in financing activities Cash 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