Description of Business	3 Months Ended
Mar. 29, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	L3 Technologies, Inc. (L3 Technologies, Inc. and, together with its subsidiaries, referred to herein as L3 or the Company) is a prime contractor in Intelligence, Surveillance and Reconnaissance (ISR) systems, aircraft sustainment (including modifications and fleet management of special mission aircraft), simulation and training, night vision and image intensification equipment, and security and detection systems. L3 is also a leading provider of a broad range of communication, electronic and sensor systems used on military, homeland security and commercial platforms. The Company’s customers include the United States (U.S.) Department of Defense (DoD) and its prime contractors, U.S. Government intelligence agencies, the U.S. Department of Homeland Security (DHS), foreign governments, and domestic and foreign commercial customers. L3's structure consists of the following three reportable segments: (1) ISR Systems (ISRS), (2) Communications and Networked Systems (C&NS) and (3) Electronic Systems. ISRS provides products and services for the global ISR and Command, Control and Communications (C³) markets, specializing in ISR mission solutions from seabed to space, signals intelligence (SIGINT) and multi-intelligence platforms, including engineering, modernization and sustainment solutions for military and various government aircraft, ground support equipment and other platforms. These strategic and tactical products and services provide warfighters with the ability to detect, collect, identify, analyze and disseminate information from command centers, communication nodes and air defense systems for real-time situational awareness and response. Other major capabilities and mission solutions include space avionics and imaging payloads, Counter Unmanned Aircraft Systems mission solutions, cyber and electronic warfare, special mission command & control, modeling & simulation and life cycle support. ISRS sells these products and services primarily to the DoD and select foreign governments. The ISRS sectors are Reconnaissance Mission Systems, Tactical Mission Systems, Integrated Land Systems, Space & Sensors, Surveillance & Strike Systems, Intelligence & Mission Systems, Advanced C²ISR Systems and Special Programs. C&NS provides network and communication systems, secure communications products, radio frequency (RF) components, satellite communication terminals and space, microwave and telemetry products. These products include secure data links that are used to connect a variety of space, airborne, ground and sea-based communication systems and are used in transmission, processing, recording, monitoring and dissemination functions of these communication systems. Other major capabilities include integrated maritime mission solutions, directed energy, lightweight unmanned undersea vehicles and naval power delivery on submarines and surface ships. C&NS sells these products and services primarily to the DoD and select foreign governments. The C&NS sectors are Communications & Microwave Products, Integrated Maritime Systems and Broadband Communications. Electronic Systems provides a broad range of products and services, including components, products, subsystems, systems and related services to military and commercial customers. These products and services serve markets, such as commercial and military aircraft simulation and training, cockpit avionics, airport security and precision weapons. Electronic Systems sells these products and services primarily to the DoD and select foreign governments. The Electronic Systems sectors are Commercial Aviation Solutions, Precision Engagement Systems and Defense Training Solutions. Financial information with respect to each of the Company's segments is included in Note 22 to the unaudited condensed consolidated financial statements and Note 22 to the audited consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2018. On June 29, 2018, the Company completed the sale of its Vertex Aerospace businesses for a sales price of $540 million subject to customary closing net working capital adjustments. In connection with the sale, the Company recognized: (1) a pre-tax gain from continuing operations of $42 million ($19 million after income taxes) related to the Crestview Aerospace and TCS businesses (the "Crestview & TCS Businesses") and (2) a pre-tax gain from discontinued operations of $234 million ($177 million after income taxes) related to the Vertex Aerospace business. The results of operations of the Vertex Aerospace business are reported as discontinued operations for all periods presented. During the first quarter of 2019, the Company finalized and paid a working capital adjustment of $20 million related to the sale. See Note 4 for additional information. All references to financial data in this Quarterly Report on Form 10-Q are to the Company’s continuing operations, unless specifically noted. Planned Merger with Harris Corporation On October 14, 2018, L3 and Harris Corporation (“Harris”) announced an agreement to combine in an all stock merger of equals. Under the terms of the Agreement and Plan of Merger (the “Merger Agreement”) governing the proposed transaction, which was unanimously approved by the boards of directors of both companies, L3 shareholders will receive a fixed exchange ratio of 1.30 shares of Harris common stock for each share of L3 common stock they hold. Upon completion of the merger, Harris shareholders will own approximately 54% and L3 shareholders will own approximately 46% of the combined company, which will be renamed L3 Harris Technologies, Inc. On April 4, 2019, Harris and L3 shareholders approved all shareholder proposals necessary to complete the merger of equals transaction to create L3 Harris Technologies, Inc. The merger is expected to close in the middle of 2019, subject to customary closing conditions, including the receipt of regulatory approvals.

L3 Technologies, Inc. (L3 Technologies, Inc. and, together with its subsidiaries, referred to herein as L3 or the Company) is a prime contractor in Intelligence, Surveillance and Reconnaissance (ISR) systems, aircraft sustainment (including modifications and fleet management of special mission aircraft), simulation and training, night vision and image intensification equipment, and security and detection systems. L3 is also a leading provider of a broad range of communication, electronic and sensor systems used on military, homeland security and commercial platforms. The Company’s customers include the United States (U.S.) Department of Defense (DoD) and its prime contractors, U.S. Government intelligence agencies, the U.S. Department of Homeland Security (DHS), foreign governments, and domestic and foreign commercial customers. L3's structure consists of the following three reportable segments: (1) ISR Systems (ISRS), (2) Communications and Networked Systems (C&NS) and (3) Electronic Systems.

ISRS provides products and services for the global ISR and Command, Control and Communications (C³) markets, specializing in ISR mission solutions from seabed to space, signals intelligence (SIGINT) and multi-intelligence platforms, including engineering, modernization and sustainment solutions for military and various government aircraft, ground support equipment and other platforms. These strategic and tactical products and services provide warfighters with the ability to detect, collect, identify, analyze and disseminate information from command centers, communication nodes and air defense systems for real-time situational awareness and response. Other major capabilities and mission solutions include space avionics and imaging payloads, Counter Unmanned Aircraft Systems mission solutions, cyber and electronic warfare, special mission command & control, modeling & simulation and life cycle support. ISRS sells these products and services primarily to the DoD and select foreign governments. The ISRS sectors are Reconnaissance Mission Systems, Tactical Mission Systems, Integrated Land Systems, Space & Sensors, Surveillance & Strike Systems, Intelligence & Mission Systems, Advanced C²ISR Systems and Special Programs.

C&NS provides network and communication systems, secure communications products, radio frequency (RF) components, satellite communication terminals and space, microwave and telemetry products. These products include secure data links that are used to connect a variety of space, airborne, ground and sea-based communication systems and are used in transmission, processing, recording, monitoring and dissemination functions of these communication systems. Other major capabilities include integrated maritime mission solutions, directed energy, lightweight unmanned undersea vehicles and naval power delivery on submarines and surface ships. C&NS sells these products and services primarily to the DoD and select foreign governments. The C&NS sectors are Communications & Microwave Products, Integrated Maritime Systems and Broadband Communications.

Electronic Systems provides a broad range of products and services, including components, products, subsystems, systems and related services to military and commercial customers. These products and services serve markets, such as commercial and military aircraft simulation and training, cockpit avionics, airport security and precision weapons. Electronic Systems sells these products and services primarily to the DoD and select foreign governments. The Electronic Systems sectors are Commercial Aviation Solutions, Precision Engagement Systems and Defense Training Solutions.

Financial information with respect to each of the Company's segments is included in Note 22 to the unaudited condensed consolidated financial statements and Note 22 to the audited consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2018.

On June 29, 2018, the Company completed the sale of its Vertex Aerospace businesses for a sales price of $540 million subject to customary closing net working capital adjustments. In connection with the sale, the Company recognized: (1) a pre-tax gain from continuing operations of $42 million ($19 million after income taxes) related to the Crestview Aerospace and TCS businesses (the "Crestview & TCS Businesses") and (2) a pre-tax gain from discontinued operations of $234 million ($177 million after income taxes) related to the Vertex Aerospace business. The results of operations of the Vertex Aerospace business are reported as discontinued operations for all periods presented. During the first quarter of 2019, the Company finalized and paid a working capital adjustment of $20 million related to the sale. See Note 4 for additional information.

All references to financial data in this Quarterly Report on Form 10-Q are to the Company’s continuing operations, unless specifically noted.

Planned Merger with Harris Corporation

On October 14, 2018, L3 and Harris Corporation (“Harris”) announced an agreement to combine in an all stock merger of equals. Under the terms of the Agreement and Plan of Merger (the “Merger Agreement”) governing the proposed transaction, which was unanimously approved by the boards of directors of both companies, L3 shareholders will receive a fixed exchange ratio of 1.30 shares of Harris common stock for each share of L3 common stock they hold. Upon completion of the merger, Harris shareholders will own approximately 54% and L3 shareholders will own approximately 46% of the combined company, which will be renamed L3 Harris Technologies, Inc. On April 4, 2019, Harris and L3 shareholders approved all shareholder proposals necessary to complete the merger of equals transaction to create L3 Harris Technologies, Inc. The merger is expected to close in the middle of 2019, subject to customary closing conditions, including the receipt of regulatory approvals.