Description of Business	12 Months Ended
Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	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. In the third quarter of 2018, the Company completed a realignment of its business segments to maximize growth and improve its integration and collaboration across the enterprise. As a result of the realignment, 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. Financial information with respect to each of its segments is included in Note 22. 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 ISR Systems, Airborne Sensor Systems, Warrior Sensor Systems, Space & Sensor Systems, Aircraft Systems, MAS, Intelligence & Mission Systems and Advanced 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 Broadband Communication Systems, Naval Power Systems, Advanced Communications, Space & Power Systems and Maritime Sensor Systems. 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, Link Training & Simulation and Security & Detection Systems. 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 divestiture of the Vertex Aerospace business represents a strategic shift by the Company to exit the logistics solution and maintenance services business for military aircraft where the Company does not provide complex ISR systems integration and modification. The Vertex Aerospace business generated sales of $0.6 billion in 2018, $1.4 billion in 2017 and $1.3 billion in 2016. The assets and liabilities and results of operations of the Vertex Aerospace business are reported as discontinued operations for all periods presented. See Note 3 for additional information. All references made to financial data in this Annual Report on Form 10-K 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. The merger is expected to close in the middle of 2019, subject to customary closing conditions, including the receipt of regulatory approvals and approval by the shareholders of both L3 and Harris.

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.

In the third quarter of 2018, the Company completed a realignment of its business segments to maximize growth and improve its integration and collaboration across the enterprise. As a result of the realignment, 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. Financial information with respect to each of its segments is included in Note 22.

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 ISR Systems, Airborne Sensor Systems, Warrior Sensor Systems, Space & Sensor Systems, Aircraft Systems, MAS, Intelligence & Mission Systems and Advanced 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 Broadband Communication Systems, Naval Power Systems, Advanced Communications, Space & Power Systems and Maritime Sensor Systems.

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, Link Training & Simulation and Security & Detection Systems.

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 divestiture of the Vertex Aerospace business represents a strategic shift by the Company to exit the logistics solution and maintenance services business for military aircraft where the Company does not provide complex ISR systems integration and modification. The Vertex Aerospace business generated sales of $0.6 billion in 2018, $1.4 billion in 2017 and $1.3 billion in 2016. The assets and liabilities and results of operations of the Vertex Aerospace business are reported as discontinued operations for all periods presented. See Note 3 for additional information.

All references made to financial data in this Annual Report on Form 10-K 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. The merger is expected to close in the middle of 2019, subject to customary closing conditions, including the receipt of regulatory approvals and approval by the shareholders of both L3 and Harris.