Contingencies	12 Months Ended
Dec. 28, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Note 25—Contingencies Legal Proceedings MSA Joint Venture On November 10, 2015, MSA received a final decision by the Department of Energy ("DoE") contracting officer for the Mission Support Contract concluding that certain payments to MSA by DoE for the performance of IT services by Lockheed Martin Services, Inc. (“LMSI”) under a subcontract to MSA constituted alleged affiliate fees in violation of the FAR. Lockheed Martin Integrated Technology LLC (now known as Leidos Integrated Technology LLC) is a member entity of MSA. Subsequent to the contracting officer's final decision, MSA, LMSI and Lockheed Martin Corporation received notice from the U.S. Attorney's Office for the Eastern District of Washington that the U.S. government had initiated a False Claims Act investigation into the facts surrounding this dispute, and each of MSA, LMSI and Lockheed Martin Corporation have produced information in response to Civil Investigative Demands from the U.S. Attorney's Office. On February 8, 2019, the U.S. Attorney's office filed a complaint in the United States District Court for the Eastern District of Washington against MSA, Lockheed Martin Corporation, Lockheed Martin Services, Inc. and a Lockheed Martin employee. The complain alleges violations of the False Claims Act, the Anti-Kickback Act, breach of contract with DoE, among other things. The U.S. Attorney's office had previously advised that a parallel criminal investigation was open, although no subjects or targets of the investigation had been identified. The U.S. Attorney's office has informed MSA that it has closed the criminal investigation. Since this issue first was raised by the DoE, MSA has asserted that the IT services performed by LMSI under a fixed-price/fixed-unit rate subcontract approved by the DoE meet the definition of a "commercial item" under the FAR and any profits earned on that subcontract are permissible. MSA filed an appeal of the contracting officer's decision with the Civilian Board of Contract Appeals and that appeal is pending, but has been stayed pending resolution of the False Claims Act investigation. Subsequent to the filing of MSA's appeal, the contracting officer demanded that MSA reimburse the DoE in the amount of $64 million, which was his estimate of the profits earned during the period from 2010 to 2014 by LMSI. The DoE has deferred collection of $32 million of that demand, pending resolution of the appeal and without prejudice to MSA's position that it is not liable for any of the DOE's $64 million reimbursement claim. The Company has agreed to indemnify Jacobs Group and Centerra Group, LLC for any liability MSA incurs in this matter. Under the terms of the Separation Agreement, Lockheed Martin agreed to indemnify the Company for 100% of any damages in excess of $38 million up to $64 million, and 50% of any damages in excess of $64 million, with respect to claims asserted against MSA related to this matter. At December 28, 2018, and December 29, 2017, the Company has a liability of $39 million and an indemnification asset of $1 million recorded in the consolidated balance sheets. Securities Litigation Between February and April 2012, alleged stockholders filed three putative securities class actions against the Company and several former executives relating to the Company's contract to develop and implement an automated time and attendance and workforce management system for certain agencies of the City of New York ("CityTime"). One case was withdrawn and two cases were consolidated in the U.S. District Court for the Southern District of New York in In Re: SAIC, Inc. Securities Litigation. The consolidated securities complaint asserted claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 based on allegations that the Company and individual defendants made misleading statements or omissions about the Company's revenues, operating income and internal controls in connection with disclosures relating to the CityTime project. The plaintiffs sought to recover from the Company and the individual defendants an unspecified amount of damages class members allegedly incurred by buying Leidos' stock at an inflated price. The District Court dismissed the plaintiffs' claims with prejudice and without leave to replead. The plaintiffs then appealed to the United States Court of Appeals for the Second Circuit, which issued an opinion affirming in part, and vacating in part, the District Court's ruling. The Company filed a petition for a writ of certiorari in the U.S. Supreme Court, which was granted on March 27, 2017. The District Court granted the Company's request to stay all proceedings, including discovery, pending the outcome at the Supreme Court. In September 2017, the parties engaged in mediation resulting in an agreement to settle all remaining claims for an immaterial amount to be paid by the Company. The amounts payable by the Company are covered by an insurance policy. The terms of the proposed settlement remain subject to court approval. Greek Government Contract In 2003, the Company entered into an FFP contract with the Hellenic Republic of Greece to provide a Command, Control, Communications, Coordination and Integration System. The Greek government disputed the contract balance owed to the Company and has not paid the Company's final invoice. In 2013, the Company received an arbitral award by the International Chamber of Commerce for €39 million, which has not been satisfied. In January 2017, the U.S. District Court granted an order to enforce the arbitration award and entered judgment in the Company's favor. The Company has commenced enforcement proceedings against the Greek government in several jurisdictions. Separately, the Greek government has sought to annul the award through separate litigation in the Greek courts, and such a challenge is currently pending. Based on the complex nature of this contractual situation and the difficulties encountered to date, significant uncertainties exist and the Company is unable to reliably estimate the ultimate outcome. Arbitration Proceeding The Company is a party to an arbitration proceeding involving a claim by Lockheed Martin for indemnification for $56 million in taxes attributable to deferred revenue recognized as a result of the Transactions. Based on the arguments advanced to date, the Company believes that the claim appears to be without merit and intends to vigorously defend itself in arbitration. The Company does not believe that a material loss is probable, and has therefore not recorded any liability for this matter. We expect a final decision by the arbitration panel to be issued during the first half of fiscal 2019. Other The Company is also involved in various claims and lawsuits arising in the normal conduct of its business, none of which, in the opinion of the Company's management, based upon current information, will likely have a material adverse effect on the Company's consolidated financial position, results of operations or cash flows. Other Contingencies VirnetX, Inc. On September 29, 2017, the federal trial court in the Eastern District of Texas entered a final judgment in the VirnetX v. Apple case referred to as the Apple I case. The court found that Apple willfully infringed the VirnetX patents at issue in the Apple I case and awarded enhanced damages, bringing the total award against Apple to over $343 million in pre-interest damages. The court subsequently awarded an additional sum of over $96 million for costs, attorneys' fees and interest, bringing the total award to VirnetX in the Apple I case to over $439 million. Apple appealed the judgment in the Apple I case with the U.S. Court of Appeals for the Federal Circuit and on January 15, 2019, the court affirmed the $439 million judgment. It is expected that Apple will appeal this decision. On April 10, 2018, a jury trial concluded in an additional patent infringement case brought by VirnetX against Apple, referred to as the Apple II case, in which the jury returned a verdict against Apple for infringement and awarded VirnetX damages in the amount of over $502 million. On April 11, 2018, in a second phase of the Apple II trial, the jury found Apple's infringement to be willful. On August 30, 2018, the federal trial court in the Eastern District of Texas entered a final judgment and rulings on post-trial motions in the Apple II case. The court affirmed the jury’s verdict of over $502 million and granted VirnetX’s motions for supplemental damages, a sunset royalty and royalty rate of $1.20 per infringing device, along with pre-judgment and post-judgment interest and costs. The court denied VirnetX’s motions for enhanced damages, attorneys’ fees and an injunction. The court also denied Apple’s motions for judgment as a matter of law and for a new trial. An additional sum of over $93 million for costs and pre-judgment interest was subsequently agreed upon pursuant to a court order, bringing the total award to VirnetX in the Apple II case to over $595 million. Apple has filed an appeal of the judgment in the Apple II case with the U.S. Court of Appeals for the Federal Circuit. Under its agreements with VirnetX, the Company would receive 25% of the proceeds obtained by VirnetX after reduction for attorneys' fees and costs. However, the verdicts in these cases remain subject to appeal. In addition, the patents at issue in these cases are subject to U.S. Patent and Trademark Office post-grant inter partes review and/or reexamination proceedings and related appeals, which may result in all or part of these patents being invalidated or the claims of the patents being limited. Thus, no assurances can be given when or if the Company will receive any proceeds in connection with these jury awards. In addition, if the Company receives any proceeds, the Company is required to pay a royalty to the customer who paid for the development of the technology. The Company does not have any assets or liabilities recorded in connection with this matter as of December 28, 2018. Government Investigations and Reviews The Company is routinely subject to investigations and reviews relating to compliance with various laws and regulations with respect to its role as a contractor to federal, state and local government customers and in connection with performing services in countries outside of the United States. Adverse findings could have a material effect on the Company's business, financial position, results of operations and cash flows due to its reliance on government contracts. During fiscal 2018, pursuant to the resolution of certain government accounting matters, including audits by the DCAA, the Company recorded a net reduction of $19 million to its accrued liabilities. As of December 28, 2018, indirect cost audits by the DCAA remain open for fiscal 2013 and subsequent fiscal years. Although the Company has recorded contract revenues based upon an estimate of costs that the Company believes will be approved upon final audit or review, the Company cannot predict the outcome of any ongoing or future audits or reviews and adjustments and, if future adjustments exceed the Company's estimates, its profitability would be adversely affected. As of December 28, 2018, the Company believes it has adequately reserved for potential adjustments from audits or reviews of contract costs.

Note 25—Contingencies

Legal Proceedings

MSA Joint Venture

On November 10, 2015, MSA received a final decision by the Department of Energy ("DoE") contracting officer for the Mission Support Contract concluding that certain payments to MSA by DoE for the performance of IT services by Lockheed Martin Services, Inc. (“LMSI”) under a subcontract to MSA constituted alleged affiliate fees in violation of the FAR. Lockheed Martin Integrated Technology LLC (now known as Leidos Integrated Technology LLC) is a member entity of MSA. Subsequent to the contracting officer's final decision, MSA, LMSI and Lockheed Martin Corporation received notice from the U.S. Attorney's Office for the Eastern District of Washington that the U.S. government had initiated a False Claims Act investigation into the facts surrounding this dispute, and each of MSA, LMSI and Lockheed Martin Corporation have produced information in response to Civil Investigative Demands from the U.S. Attorney's Office. On February 8, 2019, the U.S. Attorney's office filed a complaint in the United States District Court for the Eastern District of Washington against MSA, Lockheed Martin Corporation, Lockheed Martin Services, Inc. and a Lockheed Martin employee. The complain alleges violations of the False Claims Act, the Anti-Kickback Act, breach of contract with DoE, among other things. The U.S. Attorney's office had previously advised that a parallel criminal investigation was open, although no subjects or targets of the investigation had been identified. The U.S. Attorney's office has informed MSA that it has closed the criminal investigation.

Since this issue first was raised by the DoE, MSA has asserted that the IT services performed by LMSI under a fixed-price/fixed-unit rate subcontract approved by the DoE meet the definition of a "commercial item" under the FAR and any profits earned on that subcontract are permissible. MSA filed an appeal of the contracting officer's decision with the Civilian Board of Contract Appeals and that appeal is pending, but has been stayed pending resolution of the False Claims Act investigation. Subsequent to the filing of MSA's appeal, the contracting officer demanded that MSA reimburse the DoE in the amount of $64 million, which was his estimate of the profits earned during the period from 2010 to 2014 by LMSI. The DoE has deferred collection of $32 million of that demand, pending resolution of the appeal and without prejudice to MSA's position that it is not liable for any of the DOE's $64 million reimbursement claim. The Company has agreed to indemnify Jacobs Group and Centerra Group, LLC for any liability MSA incurs in this matter. Under the terms of the Separation Agreement, Lockheed Martin agreed to indemnify the Company for 100% of any damages in excess of $38 million up to $64 million, and 50% of any damages in excess of $64 million, with respect to claims asserted against MSA related to this matter. At December 28, 2018, and December 29, 2017, the Company has a liability of $39 million and an indemnification asset of $1 million recorded in the consolidated balance sheets.

Securities Litigation

Between February and April 2012, alleged stockholders filed three putative securities class actions against the Company and several former executives relating to the Company's contract to develop and implement an automated time and attendance and workforce management system for certain agencies of the City of New York ("CityTime"). One case was withdrawn and two cases were consolidated in the U.S. District Court for the Southern District of New York in In Re: SAIC, Inc. Securities Litigation. The consolidated securities complaint asserted claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 based on allegations that the Company and individual defendants made misleading statements or omissions about the Company's revenues, operating income and internal controls in connection with disclosures relating to the CityTime project. The plaintiffs sought to recover from the Company and the individual defendants an unspecified amount of damages class members allegedly incurred by buying Leidos' stock at an inflated price. The District Court dismissed the plaintiffs' claims with prejudice and without leave to replead. The plaintiffs then appealed to the United States Court of Appeals for the Second Circuit, which issued an opinion affirming in part, and vacating in part, the District Court's ruling. The Company filed a petition for a writ of certiorari in the U.S. Supreme Court, which was granted on March 27, 2017. The District Court granted the Company's request to stay all proceedings, including discovery, pending the outcome at the Supreme Court. In September 2017, the parties engaged in mediation resulting in an agreement to settle all remaining claims for an immaterial amount to be paid by the Company. The amounts payable by the Company are covered by an insurance policy. The terms of the proposed settlement remain subject to court approval.

Greek Government Contract

In 2003, the Company entered into an FFP contract with the Hellenic Republic of Greece to provide a Command, Control, Communications, Coordination and Integration System. The Greek government disputed the contract balance owed to the Company and has not paid the Company's final invoice. In 2013, the Company received an arbitral award by the International Chamber of Commerce for €39 million, which has not been satisfied. In January 2017, the U.S. District Court granted an order to enforce the arbitration award and entered judgment in the Company's favor. The Company has commenced enforcement proceedings against the Greek government in several jurisdictions. Separately, the Greek government has sought to annul the award through separate litigation in the Greek courts, and such a challenge is currently pending. Based on the complex nature of this contractual situation and the difficulties encountered to date, significant uncertainties exist and the Company is unable to reliably estimate the ultimate outcome.

Arbitration Proceeding

The Company is a party to an arbitration proceeding involving a claim by Lockheed Martin for indemnification for $56 million in taxes attributable to deferred revenue recognized as a result of the Transactions. Based on the arguments advanced to date, the Company believes that the claim appears to be without merit and intends to vigorously defend itself in arbitration. The Company does not believe that a material loss is probable, and has therefore not recorded any liability for this matter. We expect a final decision by the arbitration panel to be issued during the first half of fiscal 2019.

Other

The Company is also involved in various claims and lawsuits arising in the normal conduct of its business, none of which, in the opinion of the Company's management, based upon current information, will likely have a material adverse effect on the Company's consolidated financial position, results of operations or cash flows.

Other Contingencies

VirnetX, Inc.

On September 29, 2017, the federal trial court in the Eastern District of Texas entered a final judgment in the VirnetX v. Apple case referred to as the Apple I case. The court found that Apple willfully infringed the VirnetX patents at issue in the Apple I case and awarded enhanced damages, bringing the total award against Apple to over $343 million in pre-interest damages. The court subsequently awarded an additional sum of over $96 million for costs, attorneys' fees and interest, bringing the total award to VirnetX in the Apple I case to over $439 million. Apple appealed the judgment in the Apple I case with the U.S. Court of Appeals for the Federal Circuit and on January 15, 2019, the court affirmed the $439 million judgment. It is expected that Apple will appeal this decision.

On April 10, 2018, a jury trial concluded in an additional patent infringement case brought by VirnetX against Apple, referred to as the Apple II case, in which the jury returned a verdict against Apple for infringement and awarded VirnetX damages in the amount of over $502 million. On April 11, 2018, in a second phase of the Apple II trial, the jury found Apple's infringement to be willful. On August 30, 2018, the federal trial court in the Eastern District of Texas entered a final judgment and rulings on post-trial motions in the Apple II case. The court affirmed the jury’s verdict of over $502 million and granted VirnetX’s motions for supplemental damages, a sunset royalty and royalty rate of $1.20 per infringing device, along with pre-judgment and post-judgment interest and costs. The court denied VirnetX’s motions for enhanced damages, attorneys’ fees and an injunction. The court also denied Apple’s motions for judgment as a matter of law and for a new trial. An additional sum of over $93 million for costs and pre-judgment interest was subsequently agreed upon pursuant to a court order, bringing the total award to VirnetX in the Apple II case to over $595 million. Apple has filed an appeal of the judgment in the Apple II case with the U.S. Court of Appeals for the Federal Circuit.

Under its agreements with VirnetX, the Company would receive 25% of the proceeds obtained by VirnetX after reduction for attorneys' fees and costs. However, the verdicts in these cases remain subject to appeal. In addition, the patents at issue in these cases are subject to U.S. Patent and Trademark Office post-grant inter partes review and/or reexamination proceedings and related appeals, which may result in all or part of these patents being invalidated or the claims of the patents being limited. Thus, no assurances can be given when or if the Company will receive any proceeds in connection with these jury awards. In addition, if the Company receives any proceeds, the Company is required to pay a royalty to the customer who paid for the development of the technology.

The Company does not have any assets or liabilities recorded in connection with this matter as of December 28, 2018.

Government Investigations and Reviews

The Company is routinely subject to investigations and reviews relating to compliance with various laws and regulations with respect to its role as a contractor to federal, state and local government customers and in connection with performing services in countries outside of the United States. Adverse findings could have a material effect on the Company's business, financial position, results of operations and cash flows due to its reliance on government contracts.

During fiscal 2018, pursuant to the resolution of certain government accounting matters, including audits by the DCAA, the Company recorded a net reduction of $19 million to its accrued liabilities.

As of December 28, 2018, indirect cost audits by the DCAA remain open for fiscal 2013 and subsequent fiscal years. Although the Company has recorded contract revenues based upon an estimate of costs that the Company believes will be approved upon final audit or review, the Company cannot predict the outcome of any ongoing or future audits or reviews and adjustments and, if future adjustments exceed the Company's estimates, its profitability would be adversely affected.

As of December 28, 2018, the Company believes it has adequately reserved for potential adjustments from audits or reviews of contract costs.