L3 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	L3 TECHNOLOGIES, INC.
Entity Central Index Key	1,039,101
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 12.9
Entity Common Stock, Shares Outstanding		78,223,953
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 662	$ 363
Billed receivables, net of allowances of $18 in 2017 and $13 in 2016	723	700
Contracts in process	1,933	1,858
Inventories	389	330
Prepaid expenses and other current assets	300	175
Assets held for sale	135	0
Assets of discontinued operations	306	481
Total current assets	4,448	3,907
Property, plant and equipment, net	1,110	1,107
Goodwill	6,615	6,374
Identifiable intangible assets	292	229
Other assets	264	248
Total assets	12,729	11,865
Current liabilities:
Accounts payable, trade	531	419
Accrued employment costs	493	462
Accrued expenses	217	188
Advance payments and billings in excess of costs incurred	509	476
Income taxes payable	19	22
Other current liabilities	367	392
Liabilities held for sale	17	0
Liabilities of discontinued operations	226	235
Total current liabilities	2,379	2,194
Pension and postretirement benefits	1,313	1,177
Deferred income taxes	158	189
Other liabilities	398	356
Long-term debt	3,330	3,325
Total liabilities	7,578	7,241
Commitments and contingencies (see Note 18)
Shareholders' equity:
Common stock: $.01 par value; 300,000,000 shares authorized, 77,876,687 shares outstanding at December 31, 2017 and 77,232,204 shares outstanding at December 31, 2016	6,519	6,285
Treasury stock (at cost), 83,362,412 shares at December 31, 2017 and 82,385,075 shares at December 31, 2016	(7,404)	(7,224)
Retained earnings	6,659	6,218
Accumulated other comprehensive loss	(691)	(726)
Total shareholders' equity	5,083	4,553
Noncontrolling interests	68	71
Total equity	5,151	4,624
Total liabilities and equity	$ 12,729	$ 11,865

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Allowances for billed receivables	$ 18	$ 13
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares outstanding (in shares)	77,876,687	77,232,204
Treasury stock at cost (in shares)	83,362,412	82,385,075

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales:
Products		$ 6,733	$ 6,453	$ 6,600
Services		2,840	2,757	2,631
Total net sales		9,573	9,210	9,231
Cost of sales:
Products		(5,999)	(5,818)	(6,036)
Services		(2,554)	(2,435)	(2,333)
Total cost of sales		(8,553)	(8,253)	(8,369)
Goodwill impairment charge	[1]	0	0	(46)
Loss related to business divestitures	[2]	0	0	(31)
Operating income		1,020	957	785
Interest expense		(169)	(164)	(162)
Interest and other income, net		20	18	17
Debt retirement charges		0	(7)	(1)
Income from continuing operations before income taxes		871	804	639
Provision for income taxes		(102)	(171)	(132)
Income from continuing operations		769	633	507
(Loss) income from discontinued operations, net of income taxes		(76)	91	(732)
Net income (loss)		693	724	(225)
Net income from continuing operations attributable to noncontrolling interests		(16)	(14)	(15)
Net income (loss) attributable to L-3		$ 677	$ 710	$ (240)
Basic earnings (loss) per share attributable to common shareholders:
Continuing operations (in dollars per share)		$ 9.65	$ 7.99	$ 6.10
Discontinued operations (in dollars per share)		(0.97)	1.18	(9.07)
Basic earnings (loss) per share (in dollars per share)		8.68	9.17	(2.97)
Diluted earnings (loss) per share attributable to common shareholders:
Continuing operations (in dollars per share)		9.46	7.86	6.01
Discontinued operations (in dollars per share)		(0.95)	1.15	(8.94)
Diluted earnings (loss) per share (in dollars per share)		8.51	9.01	(2.93)
Cash dividends declared per common share (in dollars per share)		$ 3	$ 2.80	$ 2.60
Weighted average common shares outstanding:
Basic (in shares)		78	77.4	80.7
Diluted (in shares)		79.6	78.8	81.9
[1]	Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment.
[2]	See Note 3 for information regarding the Company's business divestitures.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Net income (loss)		$ 693	$ 724	$ (225)
Other comprehensive income (loss):
Foreign currency translation adjustments		124	(77)	(120)
Unrealized gains (losses) on hedging instruments	[1]	3	14	(3)
Pension and postretirement benefit plans:
Amortization of net loss and prior service cost previously recognized	[2]	45	30	43
Net (loss) gain arising during the period	[3]	(137)	(119)	90
Net change in pension and postretirement benefit plans		(92)	(89)	133
Total other comprehensive income (loss)		35	(152)	10
Comprehensive income (loss)		728	572	(215)
Comprehensive income attributable to noncontrolling interests		(16)	(14)	(15)
Comprehensive income (loss) attributable to L-3		$ 712	$ 558	$ (230)
[1]	Net of income taxes of $1 million in 2017, $5 million in 2016 and income tax benefits of $2 million in 2015.
[2]	Net of income taxes of $14 million in 2017, $18 million in 2016 and $24 million in 2015.
[3]	Net of income tax benefits of $42 million in 2017, $69 million in 2016 and income taxes of $49 million in 2015. The 2015 amount includes $9 million (net of income taxes of $5 million) for the reclassification of actuarial losses into net income related to the Marine Systems International business divestiture in accordance with Accounting Standards Codification 715, Defined Benefit Plans - Pension.

CONSOLIDATED STATEMENTS OF COM6

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Income tax expense (benefit) on unrealized gains (losses) on hedging instruments	$ (1)	$ (5)	$ (2)
Income tax (expense) on amortization of net loss and prior service cost previously recognized	(14)	(18)	(24)
Income tax expense (benefit) on net (loss) gain arising during the period	$ 42	$ 69	49
Amount includes in other comprehensive income (loss), net actuarial gain (loss), before tax			9
Other comprehensive income (loss), net actuarial gain (loss), tax			$ 5

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Millions, $ in Millions	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Noncontrolling Interests [Member]	Total
Beginning Balance at Dec. 31, 2014	$ 1	$ 5,798	$ (6,111)	$ 6,181	$ (584)	$ 75	$ 5,360
Beginning Balance (in shares) at Dec. 31, 2014	82
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income				(240)		15	(225)
Other comprehensive income (loss)					10		10
Distributions to noncontrolling interests						(16)	(16)
Cash dividends declared				(213)			(213)
Shares issued:
Employee savings plans		120					120
Employee savings plans (in shares)	1.1
Exercise of stock options		74					74
Exercise of stock options (in shares)	0.7
Employee stock purchase plan		34					34
Employee stock purchase plan (in shares)	0.3
Vesting of restricted stock and performance units (in shares)	0.7
Repurchases of common stock to satisfy tax withholding obligations		(33)					(33)
Repurchases of common stock to satisfy tax withholding obligations (in shares)	(0.3)
Stock-based compensation expense		49					49
Treasury stock purchased			(740)				(740)
Treasury stock purchased (in shares)	(6.4)
Retirement of Convertible Contingent Debt Securities		(161)					(161)
Other		9					9
Ending Balance at Dec. 31, 2015	$ 1	6,051	(6,851)	5,728	(574)	74	4,429
Ending Balance (in shares) at Dec. 31, 2015	78.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income				710		14	724
Other comprehensive income (loss)					(152)		(152)
Distributions to noncontrolling interests						(17)	(17)
Cash dividends declared				(220)			(220)
Shares issued:
Employee savings plans		115					115
Employee savings plans (in shares)	0.9
Exercise of stock options		53					53
Exercise of stock options (in shares)	0.6
Employee stock purchase plan		31					31
Employee stock purchase plan (in shares)	0.4
Vesting of restricted stock and performance units (in shares)	0.5
Repurchases of common stock to satisfy tax withholding obligations		(21)					(21)
Repurchases of common stock to satisfy tax withholding obligations (in shares)	(0.3)
Stock-based compensation expense		49					49
Treasury stock purchased			(373)				(373)
Treasury stock purchased (in shares)	(3)
Other		6					6
Ending Balance at Dec. 31, 2016	$ 1	6,284	(7,224)	6,218	(726)	71	4,624
Ending Balance (in shares) at Dec. 31, 2016	77.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income				677		16	693
Other comprehensive income (loss)					35		35
Distributions to noncontrolling interests						(19)	(19)
Cash dividends declared				(236)			(236)
Shares issued:
Employee savings plans		113					113
Employee savings plans (in shares)	0.8
Exercise of stock options		46					46
Exercise of stock options (in shares)	0.5
Employee stock purchase plan		32					32
Employee stock purchase plan (in shares)	0.2
Vesting of restricted stock and performance units (in shares)	0.3
Repurchases of common stock to satisfy tax withholding obligations		(18)					(18)
Repurchases of common stock to satisfy tax withholding obligations (in shares)	(0.1)
Stock-based compensation expense		53					53
Treasury stock purchased			(180)				(180)
Treasury stock purchased (in shares)	(1)
Other		8					8
Ending Balance at Dec. 31, 2017	$ 1	$ 6,518	$ (7,404)	$ 6,659	$ (691)	$ 68	$ 5,151
Ending Balance (in shares) at Dec. 31, 2017	77.9

CONSOLIDATED STATEMENTS OF EQU8

CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF EQUITY [Abstract]
Cash dividends declared per common share (in dollars per share)	$ 3	$ 2.80	$ 2.60

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income (loss)		$ 693	$ 724	$ (225)
Less: Loss (income) from discontinued operations, net of tax		76	(91)	732
Income from continuing operations		769	633	507
Depreciation of property, plant and equipment		172	156	161
Amortization of intangibles and other assets		53	42	42
Deferred income tax (benefit) provision		(8)	27	18
Stock-based employee compensation expense		53	49	46
Contributions to employee savings plans in L3's common stock		106	102	98
Goodwill impairment charges	[1]	0	0	46
Amortization of pension and postretirement benefit plans net loss and prior service cost		59	48	67
Amortization of bond discounts and deferred debt issue costs (included in interest expense)		6	8	8
Gain on sale of property, plant and equipment		(31)	(5)	0
Loss related to business divestitures	[2]	0	0	31
Other non-cash items		9	17	(3)
Changes in operating assets and liabilities, excluding amounts from acquisitions, divestitures, and discontinued operations:
Billed receivables		(18)	1	61
Contracts in process		(70)	26	6
Inventories		(69)	22	(38)
Other assets		(13)	29	(27)
Accounts payable, trade		99	(5)	(27)
Accrued employment costs		28	10	35
Accrued expenses		32	(6)	23
Advance payments and billings in excess of costs incurred		13	(73)	(7)
Income taxes		(39)	33	(9)
Other current liabilities		(42)	(20)	3
Pension and postretirement benefits		(48)	(57)	(8)
All other operating activities		(76)	(15)	2
Net cash from operating activities from continuing operations		985	1,022	1,035
Investing activities:
Business acquisitions, net of cash acquired		(316)	(388)	(320)
Proceeds from the sale of businesses, net of closing date cash balances		18	561	318
Capital expenditures		(224)	(210)	(195)
Dispositions of property, plant and equipment		74	21	3
Other investing activities		(5)	6	4
Net cash used in investing activities from continuing operations		(453)	(10)	(190)
Financing activities:
Proceeds from sale of senior notes		0	547	0
Repurchases, redemptions and maturities of senior notes		0	(856)	(297)
Borrowings under revolving credit facility		1,328	819	1,194
Repayments of borrowings under revolving credit facility		(1,328)	(819)	(1,194)
Common stock repurchased		(180)	(373)	(740)
Dividends paid		(236)	(220)	(214)
Proceeds from exercise of stock options		46	53	48
Proceeds from employee stock purchase plan		32	31	34
Debt issue costs		0	(10)	0
Repurchases of common stock to satisfy tax withholding obligations		(18)	(21)	(33)
Other financing activities		(10)	(7)	(3)
Net cash used in financing activities from continuing operations		(366)	(856)	(1,205)
Effect of foreign currency exchange rate changes on cash and cash equivalents		20	(13)	(19)
Net cash from (used in) discontinued operations:
Operating activities		117	19	90
Investing activities		(4)	(6)	(7)
Net cash from discontinued operations		113	13	83
Change in cash balance in assets held for sale		0	0	61
Net increase (decrease) in cash and cash equivalents		299	156	(235)
Cash and cash equivalents, beginning of the year		363	207	442
Cash and cash equivalents, end of the year		$ 662	$ 363	$ 207
[1]	Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment.
[2]	See Note 3 for information regarding the Company's business divestitures.

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2017
Description of Business [Abstract]
Description of Business	1. 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. The Company has the following four reportable segments: (1) Electronic Systems, (2) Aerospace Systems, (3) Communication Systems and (4) Sensor Systems. Financial information with respect to each of its segments is included in Note 21. 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 niche markets such as, aircraft simulation and training, power and distribution, cockpit avionics, airport security and precision weapons. The Electronic Systems business areas are Total Training Solutions, Power & Propulsion Systems, Aviation Products, Precision Engagement Systems and Security & Detection Systems. Aerospace Systems provide products and services for the global ISR and Command, Control and Communications (C 3 Communication Systems provide 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. Communication Systems sells these products and services primarily to the DoD and select foreign governments. The Communications Systems business areas are Broadband Communication Systems, Space & Power Systems and Advanced Communications. Sensor Systems provide a broad range of multi-domain ISR mission solutions from seabed to space for DoD, intelligence community, international, federal civil and commercial customers. Major capabilities and mission solutions include networked warfighter systems, integrated ISR and targeting systems, space avionics and imaging payloads, Counter Unmanned Aircraft Systems mission solutions, integrated maritime mission solutions, directed energy, cyber and electronic warfare, special mission command & control, lightweight unmanned undersea vehicles, modeling & simulation and life cycle support. Sensor Systems sells these products and services primarily to the DoD and select foreign governments. The Sensor Systems business areas are Space & Sensor Systems, Airborne Sensor Systems, Warrior Sensor Systems, Maritime Sensor Systems, Intelligence & Mission Systems and Advanced Programs. On October 16, 2017, the Company’s Board of Directors approved a plan to explore strategic alternatives to sell or otherwise divest the Vertex Aerospace business. The Company expects to complete a sale in 2018. 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 $1.4 billion in 2017, $1.3 billion in 2016 and $1.2 billion in 2015. The assets and liabilities and results of operations of the Vertex Aerospace business are reported as discontinued operations for all periods presented. On December 7, 2015, the Company entered into a definitive agreement to sell its National Security Solutions (NSS) segment to CACI International Inc. The transaction was completed on February 1, 2016. NSS provided cybersecurity solutions, high-performance computing, enterprise IT services, analytics and intelligence analysis to the DoD, U.S. Government intelligence agencies, federal civilian agencies and foreign governments. The results of operations of NSS are reported as discontinued operations for all periods presented. All references made to financial data in this Annual Report on Form 10-K are to the Company’s continuing operations, unless specifically noted. See Note 3 for additional information.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation: All references made to financial data noted in the footnotes are to L3’s continuing operations unless otherwise specifically noted. Accounting Estimates: Revisions or adjustments to estimates for a contract’s revenue, estimated costs at completion and estimated profit or loss are often required as work progresses under a contract, as experience is gained, as facts and circumstances change and as new information is obtained, even though the scope of work required under the contract may not change. Revisions or adjustments may also be required if contract modifications occur. The impact of revisions in profit (loss) estimates for all types of contracts subject to percentage-of-completion (POC) accounting are recognized on a cumulative catch-up basis in the period in which the revisions are made. The revisions in contract estimates, if significant, can materially affect the Company’s results of operations and cash flows, as well as reduce the valuations of receivables and inventories, and in some cases result in liabilities to complete contracts in a loss position. Aggregate net changes in contract estimates amounted to increases of $184 million, or 18%, of consolidated operating income ($1.48 per diluted share) for the year ended December 31, 2017, increases of $149 million, or 16%, of consolidated operating income ($1.23 per diluted share) for the year ended December 31, 2016, and increases of $52 million, or 7%, of consolidated operating income ($0.45 per diluted share) for the year ended December 31, 2015. Revenue Recognition: Sales and profits on fixed-price type contracts that are covered by contract accounting standards are substantially recognized using POC methods of accounting. Sales and profits on fixed-price production contracts under which units are produced and delivered in a continuous or sequential process are recorded as units are delivered based on their contractual selling prices (the “units-of-delivery” method). Sales and profits on each fixed-price production contract under which units are not produced and delivered in a continuous or sequential process, or under which a relatively few number of units are produced, are recorded based on the ratio of actual cumulative costs incurred to the total estimated costs at completion of the contract, multiplied by the total estimated contract revenue, less cumulative sales recognized in prior periods (the “cost-to-cost” method). Under both POC methods of accounting, a single estimated total profit margin is used to recognize profit for each contract over its entire period of performance, which can exceed one year. Losses on contracts are recognized in the period in which they become evident. Amounts representing contract change orders or claims are included in sales only when they can be reliably estimated and their realization is reasonably assured. The impact of revisions of contract estimates, which may result from contract modifications, performance or other reasons, are recognized on a cumulative catch-up basis in the period in which the revisions are made. Sales and profits on cost-plus type contracts that are covered by contract accounting standards are recognized as allowable costs are incurred on the contract, at an amount equal to the allowable costs plus the estimated profit on those costs. The estimated profit on a cost-plus type contract is fixed or variable based on the contractual fee arrangement types. Incentive and award fees are the primary variable fee contractual arrangement types for the Company. Incentive and award fees on cost-plus type contracts are included as an element of total estimated contract revenues and are recorded as sales when a basis exists for the reasonable prediction of performance in relation to established contractual targets and the Company is able to make reasonably dependable estimates for them. Sales and profits on time-and-material type contracts are recognized on the basis of direct labor hours expended multiplied by the contractual fixed rate per hour, plus the actual costs of materials and other direct non-labor costs. Sales on arrangements for (1) fixed-price type contracts that require the Company to perform services that are not related to the production of tangible assets (Fixed-Price Service Contracts) and (2) certain commercial customers are recognized in accordance with accounting standards for revenue arrangements with commercial customers. Sales for the Company’s businesses whose customers are primarily commercial business enterprises are substantially all generated from single element revenue arrangements. Sales are recognized when there is persuasive evidence of an arrangement, delivery has occurred or services have been performed, the selling price to the buyer is fixed or determinable and collectability is reasonably assured. Sales for Fixed-Price Service Contracts that do not contain measurable units of work performed are generally recognized on a straight-line basis over the contractual service period, unless evidence suggests that the revenue is earned, or obligations fulfilled, in a different manner. Sales for Fixed-Price Service Contracts that contain measurable units of work performed are generally recognized when the units of work are completed. Sales and profit on cost-plus and time-and-material type contracts within the scope of accounting standards for revenue arrangements with commercial customers are recognized in the same manner as those within the scope of contract accounting standards, except for incentive and award fees. Cost-based incentive fees are recognized when they are realizable in the amount that would be due under the contractual termination provisions as if the contract was terminated. Performance based incentive fees and award fees are recorded as sales when objective evidence exists that the fees have been earned. For contracts with multiple deliverables, the Company applies the separation and allocation guidance under the accounting standard for revenue arrangements with multiple deliverables, unless all the deliverables are covered by contract accounting standards, in which case the Company applies the separation and allocation guidance under contract accounting standards. Revenue arrangements with multiple deliverables are evaluated to determine if the deliverables should be separated into more than one unit of accounting. The Company recognizes revenue for each unit of accounting based on the revenue recognition policies discussed above. Sales and cost of sales in connection with contracts to provide services to the U.S. Government that contain collection risk because the contracts are incrementally funded and subject to the availability of funds appropriated, are deferred until a contract modification is obtained, indicating that adequate funds are available to the contract or task order. Research and Development: Customer-funded research and development costs are incurred pursuant to contracts (revenue arrangements) to perform research and development activities according to customer specifications. These costs are not accounted for as research and development expenses, and are also not indirect contract costs. Instead, these costs are direct contract costs and are expensed to cost of sales when the corresponding revenue is recognized, which is generally as the research and development services are performed. Customer-funded research and development costs are substantially all incurred under cost-plus type contracts with the U.S. Government. Product Warranties: The table below presents the changes in the Company’s accrued product warranty costs. Year Ended December 31, 2017 2016 (in millions) Accrued product warranty costs (1) : Balance at January 1 $ 109 $ 105 Acquisitions during this period 3 3 Accruals for product warranties issued during the period 52 51 Foreign currency translation adjustments 1 (1 ) Settlements made during the period (66 ) (49 ) Balance at December 31 $ 99 $ 109 (1) Warranty obligations incurred in connection with long-term production contracts that are accounted for under the POC cost-to-cost method are included within the contract estimates at completion and are excluded from the above amounts. The balances above include both the current and non-current amounts. Deferred Debt Issue Costs: Pension Plan and Postretirement Benefit Plan Obligations: The Company also provides postretirement medical and life insurance benefits for retired employees and dependents at certain locations. Participants are eligible for these benefits when they retire from active service and meet the eligibility requirements for the Company’s pension plans. These benefits are funded primarily on a pay-as-you-go basis with the retiree generally paying a portion of the cost through contributions, deductibles and coinsurance provisions. In accordance with accounting standards for employee pension and postretirement benefits, the Company recognizes on a plan-by-plan basis the unfunded status of its pension and postretirement benefit plans in the consolidated financial statements and measures its pension and postretirement benefit plan assets and benefit obligations at December 31. The obligation for the Company’s pension plans and postretirement benefit plans and the related annual costs of employee benefits are calculated based on several long-term assumptions, including discount rates and expected mortality for employee benefit liabilities, and rates of return on plan assets, and expected annual rates for salary increases for employee participants in the case of pension plans, and expected annual increases in the costs of medical and other health care benefits in the case of postretirement benefit obligations. See Note 19, Pensions and Other Employee Benefits Stock-Based Compensation: Compensation expense for restricted stock unit and stock option awards is generally recognized on a straight-line basis over the requisite service period for the entire award based on the grant date fair value. All of the stock options granted to employees by the Company are non-qualified stock options under U.S. income tax regulations. Compensation expense for performance units payable in L3 common stock is based on the fair value of the units at the grant date (measurement date), adjusted each reporting period for progress towards the target award, and recognized on a straight-line basis over the requisite service period. Stock-based compensation expense is recognized net of estimated forfeitures. Income Taxes: Income tax accounting standards prescribe: (1) a minimum recognition threshold that an income tax benefit arising from an uncertain income tax position taken, or expected to be taken, on an income tax return is required to meet before being recognized in the financial statements and (2) the measurement of the income tax benefits recognized from such positions. The Company’s accounting policy is to classify uncertain income tax positions that are not expected to be resolved in one year as non-current income tax liabilities and to classify potential interest and penalties on uncertain income tax positions as elements of the provision for income taxes in its financial statements. Cash and Cash Equivalents: Contracts in Process: The Company values its acquired contracts in process in connection with business acquisitions on the date of acquisition at contract value less the Company’s estimated costs to complete the contract and a reasonable profit allowance on the Company’s completion effort. Inventories: Property, Plant and Equipment: Goodwill and Indefinite-lived Intangible Assets: Simplifying the Test for Goodwill Impairment Identifiable Intangible Assets: Derivative Financial Instruments: The Company’s U.S. and foreign businesses enter into contracts with customers, subcontractors or vendors that are denominated in currencies other than their functional currencies. To protect the functional currency equivalent cash flows associated with certain of these contracts, the Company enters into foreign currency forward contracts. The Company’s activities involving foreign currency forward contracts are designed to hedge the changes in the functional currency equivalent cash flows due to movements in foreign exchange rates compared to the functional currency. The foreign currencies hedged are primarily the U.S. dollar, the Canadian dollar, the Euro and the British pound. The Company manages exposure to counterparty non-performance credit risk by entering into foreign currency forward contracts only with major financial institutions that are expected to fully perform under the terms of such contracts. Foreign currency forward contracts are recorded in the Company’s balance sheets at fair value and are generally designated and accounted for as cash flow hedges in accordance with the accounting standards for derivative instruments and hedging activities. Gains and losses on designated foreign currency forward contracts that are highly effective in offsetting the corresponding change in the cash flows of the hedged transactions are recorded net of income taxes in accumulated other comprehensive income (loss) (accumulated OCI) and then recognized in income when the underlying hedged transaction affects income. Gains and losses on foreign currency forward contracts that do not meet hedge accounting criteria are recognized in income immediately. Treasury Stock: Translation of Foreign Currency and Foreign Currency Transactions: Accounting Standards Issued and Not Yet Implemented: Targeted Improvements to Accounting for Hedging Activities In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cos In January 2017, the FASB issued ASU 2017-01, Clarifying the Definition of a Business In February 2016, the FASB issued ASU 2016-02, Leases In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, The Company will adopt the standard as of January 1, 2018, using the modified retrospective transition method, and has evaluated the impact of the adoption on its consolidated financial statements and related disclosures. Under the modified retrospective transition method, the Company will calculate and record the cumulative effect of adopting the new standard at January 1, 2018, in the Company’s Quarterly Report on Form 10-Q for the first quarter of 2018. The Company has evaluated the changes from adopting this new standard on its financial reporting, disclosures and its various revenue streams. The Company will recognize revenue over time on most of its (i) contracts that are covered by current contract accounting standards and (ii) fixed-price type contracts that require it to perform services that are not related to the production of tangible assets by using cost inputs to measure progress toward the completion of its performance obligations. This method is similar to the POC cost-to-cost method currently used on the majority of the Company’s contracts covered by current contract accounting standards. Accordingly, the adoption of this standard will primarily impact certain (i) contracts currently covered by contract accounting standards that currently recognize revenue using the POC units-of-delivery method and (ii) fixed-price type contracts for services that are not related to the production of tangible assets that currently recognize revenue on a straight-line basis over the contractual service period. Based on contracts in process at December 31, 2017, the Company expects to record, upon adoption of ASC 606, a net increase to shareholders’ equity ranging from $10 million to $20 million, which includes the acceleration of net sales ranging from $350 million to $400 million and the related cost of sales. The adjustment to retained earnings primarily relates to contracts currently accounted for under the POC units-of-delivery method, which would have been recognized under ASC 606 earlier in the performance period as costs were incurred, as opposed to when the units were delivered under ASC 605. The Company will make certain presentation changes on its consolidated balance sheets to comply with the new standard. The components of contracts in process will be presented separately as contract assets or inventories based on the amounts of unbilled revenue or the cost of inventories, respectively. Advance payments and billings in excess of costs and deferred revenue, which is currently classified in other current liabilities, will be combined and presented as contract liabilities. The Company expects that the adoption of ASC 606 will result in a decrease in inventories and an increase in contract assets (unbilled receivables) primarily to reflect the impact of converting contracts currently applying the units-of-delivery method to the cost input method for recognizing revenue and profit. Additionally, the Company will reclassify approximately $50 million of capitalized contract fulfillment costs from inventories to other assets upon adoption of ASC 606. The Company accounts for contract fulfillment costs as a contract cost under current accounting standards, and capitalizes them to inventoried contract costs if they relate to contracts that are accounted for under the POC units of delivery method of revenue recognition. The Company expects the net impact of these adjustments will decrease its current assets and current liabilities each by approximately 2%. Additionally, the Company has updated its accounting policies affected by this standard, redesigned its internal controls over financial reporting related to the standard, and determined the extent of the expanded disclosure requirements. The Company has substantially completed the evaluation of the impact of the accounting and disclosure changes on its business processes, controls and systems and has implemented the necessary changes to such business processes, controls and systems. Other accounting standard updates effective for interim and annual periods beginning after December 31, 2017 are not expected to have a material impact on the Company’s financial position, results of operations or cash flows.

Acquisitions, Divestitures and

Acquisitions, Divestitures and Discontinued Operations	12 Months Ended
	Dec. 31, 2017
Acquisitions, Divestitures and Discontinued Operations [Abstract]
Acquisitions, Divestitures and Discontinued Operations	3. Acquisitions, Divestitures and Discontinued Operations Business Acquisitions The Company continually evaluates potential acquisitions that either strategically fit within the Company’s existing portfolio or expand the Company’s portfolio into new product lines or adjacent markets. The Company has completed a number of acquisitions that have been accounted for as business combinations and have resulted in the recognition of goodwill in the Company's financial statements. This goodwill includes the know-how of the assembled workforce, the ability of the workforce to further improve technology and product offerings, and the expected cash flows resulting from these efforts. Goodwill may also include expected synergies resulting from the complementary strategic fit these businesses bring to existing operations. The business acquisitions discussed below are included in the Company’s results of operations from their respective dates of acquisition. 2017 Business Acquisitions Kigre, Inc. (Kigre) Escola De Aviacao Aerocondor, S.A. (G-Air) Doss Aviation, Inc. (Doss Aviation). Adaptive Methods, Inc. (Adaptive Methods). Open Water Power, Inc. (Open Water Power) The Company recorded a $14 million liability on the acquisition date for the fair value of the contingent consideration. The goodwill recognized for this business was $25 million, which was assigned to the Sensor Systems segment, and is not expected to be deductible for income tax purposes. The Company also recognized indefinite-lived intangible assets of $65 million for in-process research and development (IPR&D) costs. The purchase price and purchase price allocation of Open Water Power was finalized as of December 31, 2017, with no significant changes to preliminary amounts. OceanServer Technology, Inc. (OceanServer) Explosive Trace Detection business of Implant Sciences Net sales and income before income taxes for Kigre, G-Air, Doss Aviation, Adaptive Methods, Open Water Power, OceanServer and the ETD business, included in L3’s consolidated statement of operations for the year ended December 31, 2017, are presented in the table below. Year Ended December 31, 2017 (in millions) Net sales $ 80 Loss before income taxes $ (1 ) 2016 Business Acquisitions MacDonald Humfrey (Automation) Limited. Micreo Limited and Aerosim. Advanced Technical Materials, Inc. (ATM) Acquisition. 2015 Business Acquisitions ForceX, Inc. Acquisition. CTC Aviation Group Acquisition. MITEQ, Inc. Acquisition. Unaudited Pro Forma Statements of Operations Data The following unaudited pro forma Statements of Operations data present the combined results of the Company and its business acquisitions completed during the years ended December 31, 2017 and 2016 assuming that the business acquisitions completed during 2017 and 2016 had occurred on January 1, 2016 and January 1, 2015, respectively. The unaudited pro forma Statements of Operations data below include adjustments for additional amortization expense related to acquired intangible assets and depreciation assuming the 2017 and 2016 acquisitions had occurred on January 1, 2016 and January 1, 2015, respectively. Year Ended December 31, 2017 2016 (in millions, except per share data) Pro forma net sales $ 9,638 $ 9,493 Pro forma income from continuing operations attributable to L3 $ 753 $ 621 Pro forma net income attributable to L3 $ 677 $ 712 Pro forma diluted earnings per share from continuing operations $ 9.46 $ 7.88 Pro forma diluted earnings per share $ 8.51 $ 9.03 Business Divestitures 2017 Divestitures During the year ended December 31, 2017, the Company completed the sales of the CTC Aviation Jet Services Limited (Aviation Jet Services) business, the L3 Coleman Aerospace (Coleman) business and the Display Product Line. The table below presents pre-tax (loss) gain recognized, the proceeds received and net sales included in continuing operations from these divestitures. Year Ended December 31, 2017 Pre-Tax (Loss) gain Proceeds Received Net Sales (in millions) Aviation Jet Services divestiture $ (5 ) $ 1 $ 1 Coleman divestiture (3 ) 17 9 Display Product Line divestiture 4 7 — Total $ (4 ) $ 25 $ 10 Aviation Jet Services Divestiture. Coleman Divestiture. Display Product Line Divestiture. 201 6 Divestitures NSS 2015 Business Divestitures During the year ended December 31, 2015, the Company completed the sales of Marine Systems International (MSI), Broadcast Sports Inc. (BSI), the Tinsley Product Line and Klein Associates, Inc. (Klein). The table below presents pre-tax loss recognized, the proceeds received and net sales included in continuing operations from these business divestitures. Year Ended December 31, 2015 Pre-Tax Loss Proceeds Received Net Sales (in millions) MSI divestiture $ (17 ) $ 318 $ 185 BSI divestiture (4 ) 26 7 Tinsley Product Line divestiture (8 ) 4 9 Klein divestiture (2 ) 10 8 Total $ (31 ) $ 358 $ 209 MSI Divestiture. BSI Divestiture. Tinsley Product Line Divestiture. Klein Divestiture. Net sales and income before income taxes for Aviation Jet Services, Coleman, the Display Product Line, MSI, BSI, the Tinsley Product Line and Klein, included in L3’s consolidated statements of operations, are presented in the table below on an aggregate basis, and are included in income from continuing operations for all periods presented. Year Ended December 31, 2017 2016 2015 (in millions) Net sales $ 10 $ 59 $ 259 Income before income taxes $ 2 $ 8 $ 8 Discontinued Operations Vertex Aerospace. NSS The table below presents the statements of operations data for Vertex Aerospace and NSS. The amounts presented in discontinued operations include allocated interest expenses for debt not directly attributable or related to L3’s other operations. Interest expense was allocated in accordance with the accounting standards for discontinued operations and were based on the ratio of their net assets to the sum of: (1) total L3 consolidated net assets and (2) L3 consolidated total debt. Year Ended December 31, 2017 2016 2015 (in millions) Net sales $ 1,429 $ 1,402 $ 2,334 Cost of sales (1,342 ) (1,357 ) (2,259 ) (Loss) gain related to business divestiture (1) (1 ) 64 — Goodwill impairment charges (2) (187 ) — (909 ) Operating (loss) income from discontinued operations (101 ) 109 (834 ) Interest expense allocated to discontinued operations (2 ) (5 ) (26 ) (Loss) income from discontinued operations before income taxes (103 ) 104 (860 ) Income tax benefit (expense) 27 (13 ) 128 (Loss) income from discontinued operations net of income taxes $ (76 ) $ 91 $ (732 ) (1) For the year ended December 31, 2017, the Company recognized $1 million of trailing expenses related to the sale of NSS. The year ended December 31, 2016 included a gain of $64 million (before and after income taxes) on the sale of NSS. (2) Due to a decline in estimated fair value, the Company recorded goodwill impairment charges for the years ended December 31, 2017 and 2015. The impairment charge of $187 million recorded during 2017 relates to Vertex Aerospace. The impairment charge of $909 million recorded during 2015 consists of: (i) $571 million related to NSS and (ii) $338 million related to Vertex Aerospace. The major classes of assets and liabilities included in discontinued operations related to Vertex Aerospace are presented in the table below. As discussed above, since the sale of NSS was completed on February 1, 2016, the balances below do not reflect NSS. These balances have been classified as current as the sale is expected to be completed within one year and the proceeds are not expected to be used to pay down long-term debt. December 31, 2017 December 31, 2016 (in millions) Assets Current assets $ 284 $ 271 Property, plant and equipment, net 13 14 Goodwill — 187 Other Intangible Assets 7 9 Other assets 2 — Total assets of discontinued operations $ 306 $ 481 Liabilities Accounts payable, trade $ 63 $ 16 Other current liabilities 131 160 Current liabilities 194 176 Long-term liabilities 32 59 Total liabilities of discontinued operations $ 226 $ 235 Assets Held for Sale Aerostructures December 31, 2017 (in millions) Assets Billed receivables $ 14 Contracts in process 33 Total current assets 47 Property, plant and equipment, net 34 Goodwill 52 Indentifiable intangible assets 2 Total assets classified as held for sale $ 135 Liabilities Accounts payable, trade $ 3 Accrued employment costs 2 Accrued expenses 3 Other current liabilities 5 Total current liabilities 13 Deferred income taxes 4 Total liabilities classified as held for sale $ 17

Contracts in Process

Contracts in Process	12 Months Ended
	Dec. 31, 2017
Contracts in Process [Abstract]
Contracts in Process	4. Contracts in Process The components of contracts in process are presented in the table below. The unbilled contract receivables, inventoried contract costs and unliquidated progress payments principally relate to contracts with the U.S. Government and prime contractors or subcontractors of the U.S. Government. December 31, 2017 2016 (in millions) Unbilled contract receivables, gross $ 1,874 $ 1,890 Unliquidated progress payments (761 ) (827 ) Unbilled contract receivables, net 1,113 1,063 Inventoried contract costs, gross 891 998 Unliquidated progress payments (71 ) (203 ) Inventoried contract costs, net 820 795 Total contracts in process $ 1,933 $ 1,858 Unbilled Contract Receivables. Unliquidated Progress Payments. Inventoried Contract Costs. The table below presents a summary of G&A, IRAD and B&P costs included in inventoried contract costs and the changes to them, including amounts charged to cost of sales by the Company’s U.S. Government contractor businesses for the periods presented. Year Ended December 31, 2017 2016 2015 (in millions) Amounts included in inventoried contract costs at beginning of the year $ 173 $ 137 $ 114 Contract costs incurred: IRAD and B&P 333 304 280 Other G&A (1) 842 749 742 Total 1,175 1,053 1,022 Amounts charged to cost of sales (1,179 ) (1,017 ) (999 ) Amounts included in inventoried contract costs at end of the year $ 169 $ 173 $ 137 (1) Amounts include severance and restructuring-related costs of $91 million, $13 million and $14 million for the years ended December 31, 2017, 2016 and 2015, respectively. The table below presents a summary of selling, general and administrative expenses and research and development expenses for the Company’s commercial businesses, which are expensed as incurred and included in cost of sales on the consolidated statements of operations. Year Ended December 31, 2017 2016 2015 (in millions) Selling, general and administrative expenses $ 278 $ 223 $ 261 Research and development expenses 63 54 52 Total $ 341 $ 277 $ 313

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventories [Abstract]
Inventories	5. Inventories Inventories at Lower of Cost or Realizable Value. December 31, 2017 2016 (in millions) Raw materials, components and sub-assemblies $ 184 $ 165 Work in process 98 106 Finished goods 107 59 Total $ 389 $ 330

Goodwill and Identifiable Intan

Goodwill and Identifiable Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Identifiable Intangible Assets [Abstract]
Goodwill and Identifiable Intangible Assets	6. Goodwill and Identifiable Intangible Assets Goodwill. Generally, the largest intangible assets from the businesses that the Company acquires are the assembled workforces, which includes the human capital of the management, administrative, marketing and business development, scientific, engineering and technical employees of the acquired businesses. The success of the Company’s businesses, including their ability to retain existing business (revenue arrangements) and to successfully compete for and win new business (revenue arrangements), is primarily dependent on the management, marketing and business development, contracting, engineering and technical skills and knowledge of its employees, rather than on productive capital (plant and equipment, and technology and intellectual property). Additionally, for a significant portion of its businesses, the Company’s ability to attract and retain employees who have U.S. Government security clearances, particularly those of top-secret and above, is critical to its success, and is often a prerequisite for retaining existing revenue arrangements and pursuing new ones. Generally, patents, trademarks and licenses are not material for the Company’s acquired businesses. Furthermore, the Company’s U.S. Government contracts (revenue arrangements) generally permit other companies to use the Company’s patents in most domestic work performed by such other companies for the U.S. Government. Therefore, because intangible assets for assembled workforces are part of goodwill in accordance with the accounting standards for business combinations, the substantial majority of the intangible assets for the Company’s business acquisitions is recognized as goodwill. Additionally, the value assigned to goodwill for the Company’s business acquisitions also includes the value that the Company expects to realize from cost reduction measures that it implements for its acquired businesses. The table below presents the changes in goodwill allocated to the Company’s reporting units in each reportable segment. Electronic Systems Aerospace Systems Communication Systems Sensor Systems Consolidated Total (in millions) December 31, 2015 Goodwill $ 2,445 $ 1,167 $ 1,038 $ 1,549 $ 6,199 Accumulated impairment losses (43 ) — (35 ) (26 ) (104 ) 2,402 1,167 1,003 1,523 6,095 Business acquisitions (1) 287 — 20 28 335 Foreign currency translation adjustments (45 ) 7 — (18 ) (56 ) December 31, 2016 Goodwill 2,687 1,174 1,058 1,559 6,478 Accumulated impairment losses (43 ) — (35 ) (26 ) (104 ) 2,644 1,174 1,023 1,533 6,374 Business acquisitions (1) 131 — — 81 212 Business divestitures (2) (12 ) — — — (12 ) Foreign currency translation adjustments 60 14 — 19 93 Assets held for sale (3) (10 ) (42 ) — — (52 ) December 31, 2017 Goodwill 2,856 1,146 1,058 1,659 6,719 Accumulated impairment losses (43 ) — (35 ) (26 ) (104 ) $ 2,813 $ 1,146 $ 1,023 $ 1,633 $ 6,615 (1) For the year ended December 31, 2017, business acquisitions for the Electronic Systems segment included the acquisitions of the ETD, Doss Aviation and G-Air businesses and the purchase price allocation adjustments for the MacH and Aerosim business acquisitions. Business acquis i tions for the Sensor Systems segment included primarily the Adaptive Methods, Open Water Power, OceanServer and Kigre business acquisitions. For the year ended December 31, 2016, business acquis i tions for the Electronic Systems segment included the acquisitions of the MacH and Aerosim businesses and the final purchase price allocation for L3 CTC business acquisition. Business acquis i tion for the Communication Systems segment included the ATM business acquisition. Business acquis i tions for the Sensor Systems segment included the Micreo business acquisition and the final purchase price allocation for the L3 ForceX business acquisition. (2) The decrease for the Electronic Systems segment was due to the divestitures of Coleman and Aviation Jet Services during the quarterly period ended March 31, 2017. (3) The Aerostructures businesses from the Company’s Aerospace Systems segment are classified as held for sale as of December 31, 2017 . Identifiable Intangible Assets. The table below presents information for the Company’s identifiable intangible assets that are subject to amortization and indefinite-lived intangible assets. December 31, 2017 December 31, 2016 Weighed Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (in years) (in millions) Customer contractual relationships 14 $ 393 $ 257 $ 136 $ 360 $ 229 $ 131 Technology 10 189 114 75 191 102 89 Other 15 29 14 15 21 12 9 Total subject to amortization 611 385 226 572 343 229 IPR&D indefinite 66 — 66 — — — Total $ 677 $ 385 $ 292 $ 572 $ 343 $ 229 The table below presents amortization expense recorded by the Company for its identifiable intangible assets. Year Ended December 31, 2017 2016 2015 (in millions) Amortization expense $ 43 $ 33 $ 32 Based on gross carrying amounts at December 31, 2017, the Company’s estimate of amortization expense for identifiable intangible assets for the years ending December 31, 2018 through 2022 is presented in the table below. Year Ending December 31, 2018 2019 2020 2021 2022 (in millions) Estimated amortization expense $ 44 $ 39 $ 31 $ 25 $ 21

Other Current Liabilities and O

Other Current Liabilities and Other Liabilities	12 Months Ended
	Dec. 31, 2017
Other Current Liabilities and Other Liabilities [Abstract]
Other Current Liabilities and Other Liabilities	7. Other Current Liabilities and Other Liabilities The table below presents the components of other current liabilities. December 31, 2017 2016 (in millions) Other Current Liabilities: Accrued product warranty costs $ 69 $ 68 Estimated costs in excess of estimated contract value to complete contracts in process in a loss position 63 70 Accrued interest 43 43 Deferred revenues 38 34 Estimated contingent purchase price payable for acquired businesses (see Note 3) 11 — Accruals for pending and threatened litigation 3 14 Other 140 163 Total other current liabilities $ 367 $ 392 The table below presents the components of other liabilities. December 31, 2017 2016 (in millions) Other Liabilities: Non-current income taxes payable (see Note 16) $ 164 $ 121 Deferred compensation 49 47 Accrued product warranty costs 30 41 Accrued workers’ compensation 23 25 Estimated contingent purchase price payable for acquired businesses (see Note 3) 20 29 Notes payable and capital lease obligations 16 10 Other 96 83 Total other liabilities $ 398 $ 356

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	8. Property, Plant and Equipment The table below presents the components of property, plant and equipment. December 31, 2017 2016 (in millions) Land $ 34 $ 53 Buildings and improvements 404 437 Machinery, equipment, furniture and fixtures 1,959 1,857 Leasehold improvements 376 337 Gross property, plant and equipment 2,773 2,684 Accumulated depreciation and amortization (1,663 ) (1,577 ) Property, plant and equipment, net $ 1,110 $ 1,107

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt [Abstract]
Debt	9. Debt The components of debt and a reconciliation to the carrying amount of long-term debt is presented in the table below. December 31, 2017 2016 (in millions) Borrowings under Revolving Credit Facility (1) $ — $ — 5.20% Senior Notes due 2019 1,000 1,000 4.75% Senior Notes due 2020 800 800 4.95% Senior Notes due 2021 650 650 3.95% Senior Notes due 2024 350 350 3.85% Senior Notes due 2026 550 550 Principal amount of long-term debt 3,350 3,350 Unamortized discounts (7 ) (8 ) Deferred debt issue costs (13 ) (17 ) Carrying amount of long-term debt $ 3,330 $ 3,325 (1) During 2017, L3's aggregate borrowings and repayments under the Credit Facility were $1,328 million. L3 had the full availability of its $1 billion Credit Facility at December 31, 2017 and December 31, 2016. L3 Revolving Credit Facility On October 31, 2016, L3 entered into a new five year unsecured revolving credit facility (Credit Facility), which replaced its amended and restated revolving credit agreement dated February 3, 2012. The Credit Facility provides for total aggregate borrowings of $1 billion and any outstanding borrowings under the Credit Facility are due and payable on October 31, 2021. Borrowings under the Credit Facility may consist of: (1) base rate loans, which shall bear interest at a rate equal to the sum of the applicable rate (as defined in the Credit Facility), and the “base rate” (as defined in the Credit Facility) and/or (2) eurodollar loans, which shall bear interest at a rate equal to the sum of the applicable rate plus the “Eurodollar rate” (as defined in the Credit Facility). The applicable rate for base rate loans under the Credit Facility ranges from 0.125% to 1.000%, and the applicable rate for eurodollar loans ranges from 1.125% to 2.000%, in each case based on the long-term debt rating of L3. In addition, the Credit Facility provides for uncommitted incremental revolving facilities and additional term loan facilities in an aggregate principal amount of up to $600 million. L3 Senior Notes The Senior Notes are unsecured senior obligations of L3. The terms of each outstanding Senior Note are presented in the table below. Note Date of Issuance Amount Issued Discount (1) Net Cash Proceeds Effective Interest Rate Redemption at Treasury Rate (2)(3) (in millions) 5.20% Senior Notes due October 15, 2019 October 2, 2009 $ 1,000 $ 4 $ 987 5.25 % 30 bps 4.75% Senior Notes due May 21, 2010 $ 800 $ 3 $ 790 4.79 % 25 bps 4.95% Senior Notes due February 15, 2021 February 7, 2011 $ 650 $ 4 $ 639 5.02 % 25 bps 3.95% Senior Notes due May 28, 2014 $ 650 $ 3 $ 641 4.02 % 20 bps 3.85% Senior Notes due December 15, 2026 December 5, 2016 $ 550 $ 3 $ 542 3.91 % 25 bps (1) Bond discounts are recorded as a reduction to the principal amount of the notes and are amortized as interest expense over the term of the notes. (2) The Senior Notes maturing in 2019 and 2020 may be redeemed at any time prior to their maturity and the Senior Notes maturing in 2021, 2024 and 2026 may be redeemed at any time prior to November 15, 2020, February 28, 2024 and September 15, 2026, respectively, (three months prior to their maturity) at the option of L3, in whole or in part, at a redemption price equal to the greater of: (1) 100% of the principal amount, or (2) the present value of the remaining principal and interest payments discounted to the date of redemption, on a semi-annual basis, at the Treasury Rate (as defined in the indentures governing the Senior Notes), plus the spread indicated in the table above. In addition, if the Senior Notes maturing in 2021, 2024 and 2026 are redeemed at any time on or after November 15, 2020, February 28, 2024 and September 15, 2026, respectively, the redemption price would be equal to 100% of the principal amount. (3) Upon the occurrence of a change in control (as defined in the indentures governing the Senior Notes), each holder of the notes will have the right to require L3 to repurchase all or any part of such holder’s notes at an offer price in cash equal to 101% of the aggregate principal amount plus accrued and unpaid interest, if any, to the date of purchase. Repurchases, Redemptions and Maturities of Senior Notes The repurchases, redemptions and maturities of Senior Notes are presented in the table below. Note Settlement Type Date Settled Aggregate Amount Debt Retirement Charge Cash Payments (in millions) 1.50% Senior Notes due 2017 (1) Redemption December 30, 2016 $ 350 $ 2 $ 351 3.95% Senior Notes due 2016 Maturity November 15, 2016 $ 200 $ — $ 200 3.95% Senior Notes due 2016 (2) Redemption May 20, 2016 $ 300 $ 5 $ 305 3.95% Senior Notes due 2024 Tender Offer December 22, 2015 $ 300 $ 1 $ 297 (1) The 1.50% Senior Notes due 2017 were redeemed at a price equal to 100.323% of the principal amount thereof, plus accrued and unpaid interest to the redemption date. Interest ceased to accrue on and after the redemption date. (2) The 3.95% Senior Notes due 2016 were redeemed at a price equal to 101.475% of the principal amount thereof, plus accrued and unpaid interest. Interest ceased to accrue on and after May 20, 2016, and the only remaining right of holders of such Notes was to receive payment of the redemption price and accrued interest. Guarantees The borrowings under the Credit Facility are fully and unconditionally guaranteed by L3 and by substantially all of the material 100% owned domestic subsidiaries of L3 on an unsecured senior basis. The payment of principal and premium, if any, and interest on the Senior Notes is fully and unconditionally guaranteed, on an unsecured senior basis, jointly and severally, by L3’s material 100% owned domestic subsidiaries that guarantee any of its other indebtedness. See Note 24. Subordination The guarantees of the Credit Facility and the Senior Notes rank pari passu with each other. Covenants Financial and other restrictive covenants. The indentures governing the Senior Notes (Senior Indentures) contain covenants customary for investment grade notes, including covenants that restrict the ability of L3 and its 100% owned domestic subsidiaries to create, incur, assume or permit to exist any lien, except permitted liens (as defined in the Senior Indentures) and restrict the ability of L3 and its subsidiaries to enter into certain sale and leaseback transactions (as defined in the Senior Indentures). Cross default provisions.

Accumulated Other Comprehensive

Accumulated Other Comprehensive (Loss) Income (AOCI)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive (Loss) Income (AOCI) [Abstract]
Accumulated Other Comprehensive (Loss) Income (AOCI)	10. Accumulated Other Comprehensive (Loss) Income (AOCI) The changes in the AOCI balances, including amounts reclassified from AOCI into net income, are presented in the table below. Foreign currency translation Unrealized (losses) gains on hedging instruments Unrecognized (losses) gains and prior service cost, net Total accumulated other comprehensive loss (in millions) Balance at December 31, 2014 $ 19 $ (5 ) $ (598 ) $ (584 ) Other comprehensive (loss) income before reclassifications, net of tax (161 ) (15 ) 81 (95 ) Amounts reclassified from AOCI, net of tax 41 12 52 105 Net current period other comprehensive (loss) income (120 ) (3 ) 133 10 Balance at December 31, 2015 $ (101 ) $ (8 ) $ (465 ) $ (574 ) Other comprehensive (loss) income before reclassifications, net of tax (77 ) 3 (119 ) (193 ) Amounts reclassified from AOCI, net of tax — 11 30 41 Net current period other comprehensive (loss) income (77 ) 14 (89 ) (152 ) Balance at December 31, 2016 $ (178 ) $ 6 $ (554 ) $ (726 ) Other comprehensive income (loss) before reclassifications, net of tax 124 7 (137 ) (6 ) Amounts reclassified from AOCI, net of tax — (4 ) 45 41 Net current period other comprehensive income (loss) 124 3 (92 ) 35 Balance at December 31, 2017 $ (54 ) $ 9 $ (646 ) $ (691 ) Further details regarding the amounts reclassified from AOCI into net income are presented in the table below. Amount Reclassified from AOCI (a) Affected Line Item in the Audited Consolidated Statements of Operations Year Ended December 31, Details About AOCI Components 2017 2016 2015 (in millions) Foreign currency translation adjustments: MSI divestiture $ — $ — $ (41 ) Loss related to business divestitures — — (41 ) Income from continuing operations before income taxes $ — $ — $ (41 ) Income from continuing operations Gain (loss) on hedging instruments: MSI divestiture $ — $ — $ (2 ) Loss related to business divestitures Other 5 (13 ) (16 ) Cost of sales-products 5 (13 ) (18 ) Income from continuing operations before income taxes (1 ) 2 6 Provision for income taxes $ 4 $ (11 ) $ (12 ) Income from continuing operations Amortization of defined benefit pension and postretirement items: MSI divestiture $ — $ — $ (14 ) Loss related to business divestitures Net loss (59 ) (48 ) (67 ) (b) (59 ) (48 ) (81 ) Income from continuing operations before income taxes 14 18 29 Provision for income taxes $ (45 ) $ (30 ) $ (52 ) Income from continuing operations Total reclassification for the period $ (41 ) $ (41 ) $ (105 ) Income from continuing operations (a) Amounts in parentheses indicate charges to the consolidated statements of operations. (b) Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 19 for additional information).

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity	11. Equity On December 4, 2014, L3’s Board of Directors approved a share repurchase program that authorized L3 to repurchase up to $1.5 billion of its common stock which expired on June 30, 2017. On May 8, 2017, L3’s Board of Directors approved a new share repurchase program that authorizes L3 to repurchase up to an additional $1.5 billion of its common stock. The new program became effective on July 1, 2017 and has no set expiration date. Repurchases of L3’s common stock are made from time to time at management’s discretion in accordance with applicable U.S. Federal securities laws. The timing and actual number of shares to be repurchased in the future will depend on a variety of factors, including, but not limited to, the Company’s financial position, earnings, legal requirements, other investment opportunities (including acquisitions) and market conditions. L3 repurchased 1.0 million shares of its common stock at an average price of $183.67 per share for an aggregate amount of $180 million from January 1, 2017 through December 31, 2017. All share repurchases of L3’s common stock have been recorded as treasury shares. From January 1, 2018 through February 16, 2018, L3 repurchased 433,039 shares of its common stock at an average price of $203.33 per share for an aggregate amount of approximately $88 million. On February 12, 2018, L3’s Board of Directors declared a quarterly cash dividend of $0.80 per share, payable on March 15, 2018 to shareholders of record at the close of business on March 1, 2018. During the year ended December 31, 2017, the Company paid $236 million of cash dividends.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements [Abstract]
Fair Value Measurements	12. Fair Value Measurements Fair value is defined as the price that would be received for an asset or the exit price that would be paid to transfer a liability in the principal or most advantageous market in an orderly transaction between market participants. The standards establish a fair value hierarchy that gives the highest priority to observable inputs and the lowest priority to unobservable inputs. The following table presents the fair value hierarchy level for each of the Company’s assets and liabilities that are measured and recorded at fair value on a recurring basis. December 31, 2017 December 31, 2016 Description Level 1 (1) Level 2 (2) Level 3 (3) Level 1 (1) Level 2 (2) Level 3 (3) (in millions) Assets Cash equivalents $ 310 $ — $ — $ 104 $ — $ — Derivatives (foreign currency forward contracts) — 11 — — 12 — Total assets $ 310 $ 11 $ — $ 104 $ 12 $ — Liabilities Derivatives (foreign currency forward contracts) $ — $ 1 $ — $ — $ 6 $ — Contingent consideration (4) — — 31 — — 29 Total liabilities $ — $ 1 $ 31 $ — $ 6 $ 29 (1) Level 1 is based on quoted market prices available in active markets for identical assets or liabilities as of the reporting date. Cash equivalents are primarily held in registered money market funds, which are valued using quoted market prices. (2) Level 2 is based on pricing inputs other than quoted prices in active markets, which are either directly or indirectly observable. The fair value is determined using a valuation model based on observable market inputs, including quoted foreign currency forward exchange rates and consideration of non-performance risk. (3) Level 3 is based on pricing inputs that are not observable and not corroborated by market data. (4) The contingent consideration liability represents the future potential earn-out payments relating to the MacH and Open Water Power acquisitions. The fair value of the MacH contingent consideration liability is based on a Monte Carlo Simulation of the aggregate revenue of MacH for the three-year period ending December 31, 2019. The significant unobservable inputs used in calculating the fair value of the MacH contingent consideration include: (i) projected revenues of the MacH acquired business, (ii) company specific risk premium, which is a component of the discount rate applied to the revenue projections and (iii) volatility. The fair value of the Open Water Power contingent consideration liability is based on the Scenario-Based Method of the income approach using post-acquisition milestone achievements of Open Water Power through December 31, 2020. The significant unobservable inputs used in calculating the fair value of the Open Water Power contingent consideration include: (i) timing of achieving the milestones associated with the contingent consideration arrangement, (ii) probabilities of achieving each milestone and (iii) discount rate. The fair value of the contingent consideration for potential earn-out payments is reassessed quarterly, including an analysis of the significant inputs used in the evaluation, as well as the accretion of the present value discount. Changes are reflected within cost of sales in the consolidated statements of operations. The table below presents the changes to contingent consideration obligations during the year ended December 31, 2017. December 31, 2017 (in millions) Balance at beginning of period $ 29 Acquisitions 14 Changes in fair value of contingent consideration, net (12 ) Balance at end of period $ 31

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2017
Financial Instruments [Abstract]
Financial Instruments	13. Financial Instruments At December 31, 2017 and 2016, the Company’s financial instruments consisted primarily of cash and cash equivalents, billed receivables, trade accounts payable, Senior Notes and foreign currency forward contracts. The carrying amounts of cash and cash equivalents, billed receivables and trade accounts payable are representative of their respective fair values because of the short-term maturities or expected settlement dates of these instruments. The carrying amounts and estimated fair values of the Company’s other financial instruments are presented in the table below. December 31, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value (in millions) Senior Notes (1) $ 3,330 $ 3,502 $ 3,325 $ 3,526 Foreign currency forward contracts (2) $ 10 $ 10 $ 6 $ 6 (1) The Company measures the fair value of its Senior Notes using Level 2 inputs based primarily on current market yields for its existing debt traded in the secondary market. (2) The Company measures the fair values of foreign currency forward contracts based on forward exchange rates. See Note 14 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Financial Instruments [Abstract]
Derivative Financial Instruments	14. Derivative Financial Instruments Notional amounts are used to measure the volume of foreign currency forward contracts and do not represent exposure to foreign currency losses. The table below presents the notional amounts of the Company’s outstanding foreign currency forward contracts by currency at December 31, 2017. Currency Notional Amount (in millions) U.S. dollar $ 108 Canadian dollar 100 Euro 84 British pound 15 Total $ 307 At December 31, 2017, the Company’s foreign currency forward contracts had maturities through 2023. The table below presents the location of the Company’s derivative instruments recorded at fair value on the consolidated balance sheets. December 31, 2017 December 31, 2016 Other Current Assets Other Assets Other Current Liabilities Other Liabilities Other Current Assets Other Assets Other Current Liabilities Other Liabilities (in millions) Derivatives designated as hedging instruments: Foreign currency forward contracts (1) $ 11 $ — $ 1 $ — $ 10 $ 2 $ 6 $ — Total derivative instruments $ 11 $ — $ 1 $ — $ 10 $ 2 $ 6 $ — (1) See Note 12 for a description of the fair value hierarchy related to the Company's foreign currency forward contracts. The effects from foreign currency forward contracts on the consolidated statements of operations were a pre-tax gain of $5 million for the year ended December 31, 2017, a pre-tax loss of $13 million for the year ended December 31, 2016, and a pre-tax loss of $18 million for the year ended December 31, 2015. At December 31, 2017, the estimated net amount of existing gains that are expected to be reclassified into income within the next 12 months is $2 million.

L3's Earnings Per Share

L3's Earnings Per Share	12 Months Ended
	Dec. 31, 2017
L3's Earnings Per Share [Abstract]
L3's Earnings Per Share	15. L3’s Earnings Per Share A reconciliation of basic and diluted earnings per share (EPS) is presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions, except per share data) Reconciliation of net income (loss): Net income (loss) $ 693 $ 724 $ (225 ) Net income from continuing operations attributable to noncontrolling interests (16 ) (14 ) (15 ) Net income (loss) attributable to L3’s common shareholders $ 677 $ 710 $ (240 ) Earnings (loss) attributable to L3’s common shareholders: Continuing operations $ 753 $ 619 $ 492 Discontinued operations, net of income tax (76 ) 91 (732 ) Net income (loss) attributable to L3’s common shareholders $ 677 $ 710 $ (240 ) Earnings (loss) per share attributable to L3’s common shareholders: Basic: Weighted average common shares outstanding 78.0 77.4 80.7 Basic earnings (loss) per share: Continuing operations $ 9.65 $ 7.99 $ 6.10 Discontinued operations, net of income tax (0.97 ) 1.18 (9.07 ) Net income (loss) $ 8.68 $ 9.17 $ (2.97 ) Diluted: Common and potential common shares: Weighted average common shares outstanding 78.0 77.4 80.7 Effect of dilutive securities 1.6 1.4 1.2 Common and potential common shares 79.6 78.8 81.9 Diluted earnings (loss) per share: Continuing operations $ 9.46 $ 7.86 $ 6.01 Discontinued operations, net of income tax (0.95 ) 1.15 (8.94 ) Net income (loss) $ 8.51 $ 9.01 $ (2.93 ) The computation of diluted EPS excludes 0.3 million, 0.4 million and 0.6 million shares for the years ended December 31, 2017, 2016 and 2015, respectively, for share-based payment awards as they were anti-dilutive.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Taxes [Abstract]
Income Taxes	16. Income Taxes On December 22, 2017, the U.S. Government enacted the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform), which made significant changes to the U.S. tax system. Significant changes under U.S. Tax Reform include, among other things, the reduction of the U.S. corporate income tax rate from 35% to 21%, the implementation of a modified territorial tax system, and the imposition of a one-time repatriation tax on deemed repatriated earnings and profits of U.S. owned foreign subsidiaries (Toll Charge). The Company recognized the income tax effects of U.S. Tax Reform in accordance with the Securities and Exchange Commission Staff Accounting Bulletin No. 118, Income Tax Accounting Implication of the Tax Cuts and Job Act Income from continuing operations before income taxes is summarized in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Domestic $ 649 $ 608 $ 509 Foreign 222 196 130 Income from continuing operations before income taxes $ 871 $ 804 $ 639 The components of the Company’s current and deferred portions of the provision for income taxes on continuing operations are presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Current income tax provision: Federal $ 44 $ 88 $ 81 State and local 10 8 7 Foreign 56 48 26 Subtotal 110 144 114 Deferred income tax provision/(benefit): Federal (16 ) 25 9 State and local 6 2 7 Foreign 2 — 2 Subtotal (8 ) 27 18 Total provision for income taxes $ 102 $ 171 $ 132 A reconciliation of the statutory federal income tax rate to the effective income tax rate on continuing operations of the Company is presented in the table below. Year Ended December 31, 2017 2016 2015 Statutory federal income tax rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefit 2.0 2.0 2.0 Foreign income taxes (6.7 ) (3.0 ) (7.1 ) Manufacturing benefits (1.4 ) (2.2 ) (2.2 ) Research and experimentation and other tax credits (4.1 ) (4.6 ) (6.5 ) Resolution of tax contingencies (0.4 ) (3.1 ) (1.4 ) Tax deductible dividends (0.9 ) (1.0 ) (1.2 ) Equity compensation - excess income tax benefits (2.3 ) (2.1 ) — Goodwill impairment — — 1.9 Tax Reform (9.1 ) — — Other, net (0.4 ) 0.3 0.2 Effective income tax rate on continuing operations 11.7 % 21.3 % 20.7 % The significant components of the Company’s net deferred tax assets and liabilities are presented in the table below. December 31, 2017 2016 (in millions) Deferred tax assets: Inventoried costs $ 44 $ 53 Compensation and benefits 94 139 Pension and postretirement benefits 281 413 Loss carryforwards 12 19 Tax credit carryforwards 5 6 Other 57 87 Deferred tax assets 493 717 Less: valuation allowance (10 ) (12 ) Deferred tax assets, net of valuation allowance 483 705 Deferred tax liabilities: Goodwill and other intangible assets $ (514 ) $ (722 ) Income recognition on contracts in process (24 ) (22 ) Property, plant and equipment (59 ) (93 ) Other (41 ) (55 ) Deferred tax liabilities (638 ) (892 ) Total deferred tax liabilities, net of valuation allowance $ (155 ) $ (187 ) The classification of the Company’s deferred tax assets and liabilities are presented in the table below. December 31, 2017 2016 (in millions) Non-current deferred tax assets $ 3 $ 2 Non-current deferred tax liabilities (158 ) (189 ) Total net deferred tax liabilities $ (155 ) $ (187 ) Non-current deferred tax assets are presented in other assets on the consolidated balance sheets. The following table presents the Company’s loss and tax credit carryforwards at December 31, 2017 on a tax return basis. The Company has established a valuation allowance as indicated in those instances in which it does not believe that it is more likely than not it will generate sufficient taxable income, of the appropriate character and in the applicable subsidiary, to utilize the carryforwards. Year Ended December 31, 2017 Carryforwards Valuation Allowances Gross Tax Effected Gross Tax Effected Expiration Periods (in millions) Federal net operating loss carryforwards 29 6 (5 ) (1 ) 2026-2036 Foreign net operating loss carryforwards 12 3 (6 ) (2 ) Indefinite State net operating loss carryforwards 160 3 (135 ) (2 ) 2018-2037 Total loss carryforwards $ 12 $ (5 ) State tax credit carryforwards 6 5 (5 ) (4 ) 2018-2032 Total tax credit carryforwards $ 5 $ (4 ) At December 31, 2017, the total amount of unrecognized tax benefits was $178 million, $157 million of which would reduce the effective income tax rate, if recognized. A reconciliation of the change in unrecognized income tax benefits, excluding potential interest and penalties, is presented in the table below. 2017 2016 2015 (in millions) Balance at January 1 $ 110 $ 124 $ 150 Additions for tax positions related to the current year 14 16 14 Additions for tax positions related to prior years 66 2 2 Reductions for tax positions related to prior years (4 ) (24 ) (34 ) Reductions for tax positions related to settlements with taxing authorities — (1 ) (1 ) Reduction for tax positions related to prior years as a result of a lapse of statute of limitations (8 ) (7 ) (7 ) Balance at December 31 $ 178 $ 110 $ 124 The Company and its subsidiaries file income tax returns in the U.S. Federal jurisdiction, which is the Company’s primary tax jurisdiction, and various state and foreign jurisdictions. At December 31, 2017, the statutes of limitations for the Company’s U.S. Federal income tax returns for the years ended December 31, 2012 through 2016 were open. The U.S. Internal Revenue Service (IRS) commenced audits of the Company’s U.S. Federal income tax returns for the years ended 2012 and 2013. The Company cannot predict the outcome of the audits at this time. At December 31, 2017, the Company anticipates that unrecognized tax benefits will decrease by approximately $6 million over the next 12 months due to the potential resolution of unrecognized tax benefits involving several jurisdictions and tax periods. The actual amount of the decrease over the next 12 months could vary significantly depending on the ultimate timing and nature of any settlements. During the years ended December 31, 2017, 2016 and 2015, the Company effectively settled various Federal, state and local and foreign audits. As a result of these settlements, the Company reversed previously accrued income tax expense of $4 million, $25 million and $9 million, including interest and penalties. At December 31, 2017 and 2016, current and non-current income taxes payable include accrued potential interest of $15 million ($11 million after income taxes) and $11 million ($7 million after income taxes), respectively, and potential penalties of $8 million and $7 million, respectively. With respect to the interest related items, the Company’s income tax expense included an expense of $5 million for the year ended December 31, 2017 and a benefit of $3 million for the year ended December 31, 2016. Prior to 2015, the Company recorded a deferred tax liability related to the repatriation of earnings from certain subsidiaries. During 2015, the Company completed a legal restructuring of its significant foreign operations, and the earnings of these subsidiaries are now considered reinvested indefinitely. As a result, the Company recognized a $17 million deferred tax benefit in the year ended December 31, 2015. At December 31, 2017, the Company had not provided deferred income taxes and foreign withholding taxes for $844 million of undistributed earnings by its non-U.S. subsidiaries as such earnings are intended to be reinvested indefinitely. Quantification of additional taxes that may be payable on distribution is not practicable.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Stock-Based Compensation [Abstract]
Stock-Based Compensation	17. Stock-Based Compensation Stock-Based Compensation Plans. On May 3, 2016, the stockholders of L3 approved an amendment to the 2008 LTPP to increase the number of shares authorized for issuance by 6.8 million shares to approximately 26.0 million shares. Each share of L3’s common stock issued under a full value award (that is, awards other than stock options and stock appreciation rights) granted on or after February 23, 2016 is counted as 4.26 shares for purposes of this share limit. Each share issued under full value awards granted between February 26, 2013 and February 22, 2016 is counted as 3.69 shares for purposes of the share limit. At December 31, 2017, 7.9 million shares of L3’s common stock remained available for future awards under the 2008 LTPP. The Company’s stock-based compensation expense by form of award, including stock-based compensation recorded in discontinued operations related to Vertex Aerospace and NSS, is presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Stock options $ 7 $ 10 $ 9 Restricted stock units 43 35 38 Performance units 7 4 2 Total before income taxes 57 49 49 Income taxes (12 ) (18 ) (18 ) Total after income taxes 45 31 31 Less: Stock-based compensation recorded in discontinued operations, net of income taxes 1 1 1 Stock-based compensation recorded in continuing operations, net of income taxes $ 44 $ 30 $ 30 Stock Options. Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in thousands) (in years) (in millions) Number of shares under option: Outstanding at January 1, 2017 2,847.5 $ 99.54 6.1 $ 150 Options granted 470.5 174.53 Options exercised (521.3 ) 90.13 Options forfeited (97.8 ) 120.59 Outstanding at December 31, 2017 2,698.9 $ 113.67 5.7 $ 227 Vested and expected to vest at December 31, 2017 (1) 2,582.5 $ 110.21 5.5 $ 226 Exercisable at December 31, 2017 1,762.4 $ 95.80 4.5 $ 180 (1) Represents outstanding options reduced by expected forfeitures for options not fully vested. The weighted average grant date fair value of the stock options awarded during 2017, 2016 and 2015 was $28.35, $15.90 and $19.76, respectively. The aggregate intrinsic value, disclosed in the table above, represents the difference between L3’s closing stock price on the last trading day for the period, and the exercise price, multiplied by the number of in-the-money stock options. The total intrinsic value of stock options exercised, based on the difference between the L3’s stock price at the time of exercise and the related exercise price, was $44 million, $34 million and $35 million for the years ended December 31, 2017, 2016 and 2015, respectively. At December 31, 2017, unrecognized compensation cost related to stock options was $7 million ($6 million after income taxes), which is expected to be recognized over a weighted average remaining period of 1.3 years. The actual income tax benefit realized related to compensation deductions arising from the exercise of stock options by the Company’s employees totaled $16 million, $12 million and $13 million for the years ended December 31, 2017, 2016 and 2015, respectively. Stock Option Fair Value Estimation Assumptions. • Expected Holding Period. • Expected Volatility. • Expected Dividend Yield. • Risk-Free Interest Rates. Changes in assumptions can materially impact the estimated fair value of stock options. The weighted average assumptions used in the valuation model are presented in the table below. 2017 Grants 2016 Grants 2015 Grants Expected holding period (in years) 5.2 5.0 5.0 Expected volatility 19.9 % 21.3 % 21.4 % Expected dividend yield 2.0 % 2.8 % 2.4 % Risk-free interest rate 2.0 % 1.1 % 1.5 % Restricted Stock Units. The table below presents a summary of the Company’s nonvested restricted stock unit awards at December 31, 2017 and changes during the year then ended. Number of Shares Weighted Average Grant Date Fair Value (in thousands) Nonvested balance at January 1, 2017 977.9 $ 119.55 Granted 305.6 169.23 Vested (318.4 ) 114.46 Forfeited (62.4 ) 134.56 Nonvested balance at December 31, 2017 902.7 $ 137.12 At December 31, 2017, total unrecognized compensation costs related to nonvested restricted stock unit awards were $34 million ($26 million after income taxes) and are expected to be recognized over a weighted average remaining period of 1.1 years. The total fair value of restricted stock unit awards vested during the years ended December 31, 2017, 2016 and 2015 as of their vesting dates was $53 million, $57 million and $82 million, respectively. Performance Units. During the years ended December 31, 2017, 2016, and 2015, the Company granted performance unit awards with a weighted average grant date fair value per unit of $168.80, $116.20 and $129.03, respectively. All the awards granted in 2017, 2016, and 2015 have performance conditions based on L3’s diluted EPS. The performance periods for the awards began on January 1 of the applicable grant year and end on December 31 of the year corresponding to a three-year performance period. Units earned under the awards are convertible into shares of L3’s common stock. At December 31, 2017, total unrecognized compensation costs related to the awards were $5 million ($5 million after income taxes) and are expected to be recognized over a weighted average remaining period of 1.7 years. The table below presents a summary of the Company’s performance unit awards based on expected performance at December 31, 2017 and changes during the year then ended. Payable in Shares (EPS) Number of Units Weighted Average Grant Date Fair Value (in thousands) Outstanding at January 1, 2017 124.7 $ 120.83 Granted 33.9 168.80 Increase due to expected performance 29.7 146.89 Vested (48.4 ) 129.03 Forfeited (7.8 ) 121.06 Outstanding at December 31, 2017 132.1 $ 135.99 The performance period for awards granted in 2015 ended on December 31, 2017. Based on L3’s cumulative diluted EPS during the performance period, a total of 48,365 performance units having a fair market value of $10 million as of their vesting date were earned by the participants on December 31, 2017. Employee Stock Purchase Plan. common stock at the end of each six-month offering period at 95% of fair market value based on the average of the highest and lowest sales prices for the stock on the purchase date. Eligible employees generally include all employees of the Company and each subsidiary or affiliate of the Company that has been designated to participate in the 2009 ESPP. Offering periods begin on the first trading day in January and July of each calendar year and end on the last trading day in June and December of each calendar year. Share purchases are funded through payroll deductions of up to 10% of an employee’s eligible compensation for each payroll period, or $21,250 each calendar year. At December 31, 2017, 3.5 million shares were available for future issuance under the 2009 ESPP (i.e., excluding the effect of shares issued in January 2018 as described below). In July 2017, the Company issued 0.1 million shares under the 2009 ESPP at an average price of $158.59 per share, which covered employee contributions for the six months ended June 30, 2017. In January 2018, the Company issued 0.1 million shares under the 2009 ESPP at an average price of $188.72 per share, which covered employee contributions for the six months ended December 31, 2017. The 5% discount is not recognized as compensation expense in accordance with the accounting standard for share-based compensation expense.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies [Abstract]
Commitments and Contingencies	18. Commitments and Contingencies Non-Cancelable Operating Leases The Company leases certain facilities and equipment under agreements expiring at various dates through 2046. Certain leases contain renewal options or escalation clauses providing for increased rental payments based upon maintenance, utility and tax increases. No lease agreement imposes a restriction on the Company’s ability to pay dividends, engage in debt or equity financing transactions, or enter into further lease agreements. The following table presents future minimum payments under non-cancelable operating leases with initial or remaining terms in excess of one year at December 31, 2017. Real Estate Equipment Total (in millions) 2018 $ 101 $ 5 $ 106 2019 81 3 84 2020 106 2 108 2021 60 — 60 2022 57 — 57 Thereafter 236 — 236 Total minimum payments required 641 10 651 Sublease rentals under non-cancelable leases (9 ) — (9 ) Net minimum payments required $ 632 $ 10 $ 642 Rent expense was $103 million for 2017, $97 million for 2016, and $102 million for 2015. Sublease rental income was $1 million for 2017, and $2 million for each of 2016 and 2015, respectively. Letters of Credit The Company enters into standby letters of credit with financial institutions covering performance and financial guarantees pursuant to contractual arrangements with certain customers. The Company had total outstanding letters of credit aggregating to $416 million and $402 million at December 31, 2017 and 2016, respectively. The Company had the full availability of its $1 billion Credit Facility at December 31, 2017. These letters of credit may be drawn upon in the event of the Company’s nonperformance. Guarantees The Company, from time to time, enters into contractual guarantees that arise in connection with its business acquisitions, dispositions, and other contractual arrangements in the normal course of business. In connection with the spin-off of Engility in 2012, L3 entered into a Distribution Agreement and several other agreements that govern certain aspects of L3’s relationship with Engility, including employee matters, tax matters, transition services, and the future supplier/customer relationship between L3 and Engility. These agreements generally provide cross-indemnities that, except as otherwise provided, are principally designed to place the financial responsibility for the obligations and liabilities of each entity with that respective entity. Engility has joint and several liability with L3 to the U.S. IRS for the consolidated U.S. Federal income taxes of L3’s consolidated group for taxable periods in which Engility was a part of that group. However, the Tax Matters Agreement specifies the portion of this tax liability for which L3 and Engility will each bear responsibility, and L3 and Engility have agreed to indemnify each other against any amounts for which the other is not responsible. The Tax Matters Agreement also allocates responsibility between L3 and Engility for other taxes, including special rules for allocating tax liabilities in the event that the spin-off is determined not to be tax-free. Though valid as between the parties, the Tax Matters Agreement is not binding on the IRS. The Company has three existing real estate lease agreements, which include residual guarantee amounts, expiring on August 31, 2020 and are accounted for as operating leases. On or before the lease expiration date, the Company can exercise options under the lease agreements to renew the leases, purchase the properties for $45 million, or sell the properties on behalf of the lessor (the “Sale Option”). If the Company elects the Sale Option, the Company must pay the lessor a residual guarantee amount of $39 million for the properties, on or before the lease expiration date. In addition, at the time the properties are sold, the Company must pay the lessor a supplemental rent payment equal to the gross sales proceeds in excess of the residual guarantee, provided that such amount shall not exceed $6 million. For these real estate lease agreements, if the gross sales proceeds are less than the sum of the residual guarantee amount and the supplemental rent payment, the Company is required to pay a supplemental rent payment to the extent the reduction in the fair value of the properties is demonstrated by an independent appraisal to have been caused by the Company’s failure to properly maintain the properties. The aggregate residual guarantee amounts equal $39 million and are included in the future minimum payments under non-cancelable real estate operating lease payments relating to the expiration dates of such leases. The Company has a contract to provide and operate a full-service training facility for the USAF, including simulator systems adjacent to a USAF base in Oklahoma. The Company acted as the construction agent on behalf of the third-party owner-lessors for procurement and construction for the simulator systems, which were completed and delivered in August 2002. The Company, as lessee, entered into operating lease agreements for a term of 15 years for the simulator systems with the owner-lessors. During the first quarter of 2018, the Company expects to purchase the simulator systems at the end of their respective lease terms for approximately $15 million. Environmental Matters Management continually assesses the Company’s obligations with respect to applicable environmental protection laws, including those obligations assumed in connection with certain business acquisitions. While it is difficult to determine the timing and ultimate cost to be incurred by the Company in order to comply with these laws, based upon available internal and external assessments, with respect to those environmental loss contingencies of which management is aware, the Company believes that there are no environmental loss contingencies that, individually or in the aggregate, would be material to the Company’s consolidated results of operations. The Company accrues for these contingencies when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. Procurement Regulations A substantial majority of the Company’s revenues are generated from providing products and services under legally binding agreements or contracts with the U.S. Government, foreign government customers and state and local governments. U.S. Government contracts are subject to extensive legal and regulatory requirements, and, from time to time, agencies of the U.S. Government investigate whether such contracts were and are being conducted in accordance with these requirements. The Company is currently cooperating with the U.S. Government on several investigations from which civil, criminal or administrative proceedings have or could result and give rise to fines, penalties, compensatory and treble damages, restitution and/or forfeitures, including investigations into the pricing of certain contracts entered into by the Communication Systems segment. The Company does not currently anticipate that any of these investigations will have a material adverse effect, individually or in the aggregate, on its consolidated financial position, results of operations or cash flows. However, under U.S. Government regulations, an indictment of the Company by a federal grand jury, or an administrative finding against the Company as to its present responsibility to be a U.S. Government contractor or subcontractor, could result in the Company being suspended for a period of time from eligibility for awards of new government contracts or task orders or in a loss of export privileges. A conviction, or an administrative finding against the Company that satisfies the requisite level of seriousness, could result in debarment from contracting with the federal government for a specified term. In addition, all of the Company’s U.S. Government contracts: (1) are subject to audit and various pricing and cost controls, (2) include standard provisions for termination for the convenience of the U.S. Government or for default and (3) are subject to cancellation if funds for contracts become unavailable. Foreign government contracts generally include comparable provisions relating to terminations for convenience or default, as well as other procurement clauses relevant to the foreign government. Litigation Matters The Company is also subject to litigation, proceedings, claims or assessments and various contingent liabilities incidental to its businesses, including those specified below. Furthermore, in connection with certain business acquisitions, the Company has assumed some or all claims against, and liabilities of, such acquired businesses, including both asserted and unasserted claims and liabilities. In accordance with the accounting standard for contingencies, the Company records a liability when management believes that it is both probable that a liability has been incurred and the Company can reasonably estimate the amount of the loss. Generally, the loss is recorded at the amount the Company expects to resolve the liability. The estimated amounts of liabilities recorded for pending and threatened litigation are disclosed in Note 7. Amounts recoverable from insurance contracts or third parties are recorded as assets when recovery is deemed probable. At December 31, 2017, the Company did not record any amounts for recoveries from insurance contracts or third parties in connection with the amount of liabilities recorded for pending and threatened litigation. Legal defense costs are expensed as incurred. The Company believes it has recorded adequate provisions for its litigation matters. The Company reviews these provisions to reflect the impact of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular matter. While it is reasonably possible that an unfavorable outcome may occur in one or more of the following matters, unless otherwise stated below, the Company believes that it is not probable that a loss has been incurred in any of these matters. With respect to the litigation matters below for which it is reasonably possible that an unfavorable outcome may occur, an estimate of loss or range of loss is disclosed when such amount or amounts can be reasonably estimated. Although the Company believes that it has valid defenses with respect to legal matters and investigations pending against it, the results of litigation can be difficult to predict, particularly those involving jury trials. Therefore, it is possible that one or more of the following or other contingencies could have a material impact on the financial position, results of operations or cash flows of the Company in future periods. Derivative Action. HVC Alkmaar

Pension and Other Postretiremen

Pension and Other Postretirement Benefits	12 Months Ended
	Dec. 31, 2017
Pension and Other Postretirement Benefits [Abstract]
Pension and Other Postretirement Benefits	19. Pension and Other Postretirement Benefits The following table summarizes changes in the benefit obligations, the plan assets and funded status for all of the Company’s pension and postretirement benefit plans, as well as the aggregate balance sheet impact. Pension Plans Postretirement Benefit Plans 2017 2016 2017 2016 (in millions) Change in benefit obligation: Benefit obligation at the beginning of the year $ 3,758 $ 3,448 $ 177 $ 184 Service cost 112 108 2 2 Interest cost 142 135 5 6 Plan participants’ contributions 2 2 5 4 Amendments — 15 — (3 ) Actuarial loss (gain) 376 167 (13 ) (3 ) Foreign currency exchange rate changes 22 9 2 — Curtailments and special termination benefits 2 2 — — Benefits paid (186 ) (128 ) (13 ) (13 ) Benefit obligation at the end of the year $ 4,228 $ 3,758 $ 165 $ 177 Change in plan assets: Fair value of plan assets at the beginning of the year $ 2,721 $ 2,552 $ 60 $ 57 Actual return on plan assets 391 189 8 5 Employer contributions 97 97 7 7 Plan participants’ contributions 2 2 5 4 Foreign currency exchange rate changes 22 9 — — Benefits paid (186 ) (128 ) (13 ) (13 ) Fair value of plan assets at the end of the year $ 3,047 $ 2,721 $ 67 $ 60 Unfunded status at the end of the year $ (1,181 ) $ (1,037 ) $ (98 ) $ (117 ) Assets and (liabilities) recognized on the consolidated balance sheets consist of: Non-current assets $ 48 $ 37 $ — $ — Current liabilities (6 ) (6 ) (8 ) (8 ) Non-current liabilities (1,223 ) (1,068 ) (90 ) (109 ) $ (1,181 ) $ (1,037 ) $ (98 ) $ (117 ) The table below summarizes the net loss and prior service cost balances at December 31, in the accumulated other comprehensive loss account, before related tax effects, for all of the Company’s pension and postretirement benefit plans. Pension Plans Postretirement Benefit Plans 2017 2016 2017 2016 (in millions) Net loss (gain) $ 1,035 $ 896 $ (3 ) $ (12 ) Prior service cost (credit) 10 14 (27 ) (4 ) Total amount recognized $ 1,045 $ 910 $ (30 ) $ (16 ) The aggregate accumulated benefit obligation (ABO) for all of the Company’s pension plans was $3,831 million at December 31, 2017 and $3,413 million at December 31, 2016. The table below presents information for the pension plans with an ABO in excess of the fair value of plan assets at December 31, 2017 and 2016. Pension Plans 2017 2016 (in millions) Projected benefit obligation $ 3,875 $ 3,528 Accumulated benefit obligation $ 3,490 $ 3,192 Fair value of plan assets $ 2,651 $ 2,456 The table below summarizes the weighted average assumptions used to determine the benefit obligations for the Company’s pension and postretirement plans disclosed at December 31, 2017 and 2016. Pension Plans Postretirement Benefit Plans 2017 2016 2017 2016 Benefit obligations: Discount rate 3.78 % (1) 4.40 % (1) 3.59 % (2) 4.05 % (2) Rate of compensation increase 3.50 % (3) 3.50 % (3) (1) The weighted average discount rate assumptions used at December 31, 2017 and 2016 were comprised of separate assumptions determined by country of 3.81% and 4.45% for the U.S. based plans, respectively, and 3.39% and 3.79% for the Canadian based plans, respectively. (2) The weighted average discount rate assumptions used at December 31, 2017 and 2016 were comprised of separate assumptions determined by country of 3.63% and 4.11% for the U.S. based plans, respectively, and 3.33% and 3.64% for the Canadian based plans, respectively. (3) The weighted average rate of compensation increase assumptions were comprised of separate assumptions determined by country of 3.5% for both the U.S. based plans and Canadian based plans at December 31, 2017 and 2016. The following table summarizes the components of net periodic benefit cost for the Company’s pension and postretirement benefit plans for the years ended December 31, 2017, 2016 and 2015. Pension Plans Postretirement Benefit Plans 2017 2016 2015 2017 2016 2015 (in millions) Components of net periodic benefit cost: Service cost $ 112 $ 108 $ 123 $ 2 $ 2 $ 3 Interest cost 142 135 149 5 6 7 Expected return on plan assets (212 ) (200 ) (205 ) (4 ) (4 ) (5 ) Amortization of prior service cost (credits) 1 — 1 (1 ) (2 ) (2 ) Amortization of net loss (gains) 61 52 68 (2 ) (2 ) — Curtailment loss and special termination benefits (1) 6 2 3 — — — Net periodic benefit cost $ 110 $ 97 $ 139 $ — $ — $ 3 (1) During the year ended December 31, 2017, the curtailment loss and special termination benefits charge is primarily due to a pension curtailment charge in connection with the decision to discontinue future service accruals for substantially all salaried employee defined benefit plans effective January 1, 2019. In 2016, the Company changed the approach used to measure the service and interest components of expense for all of its pension and postretirement benefit plans. For fiscal 2015 and previous periods, the Company measured the service and interest cost components using a single weighted-average discount rate derived from the yield curve used to measure the benefit obligations at the beginning of the period. Beginning in fiscal 2016, the Company elected to use a spot rate approach for its plans in the measurement of the components of benefit cost by applying specific spot rates along that yield curve to the relevant projected cash flows, as the Company believes the new approach provides a more precise measurement of service and interest costs. This change does not affect the measurement of the Company’s total benefit obligation. The Company has accounted for this change prospectively as a change in accounting estimate. The following table summarizes the other changes in plan assets and benefit obligations recognized in other comprehensive income for the Company’s pension and postretirement benefit plans for the years ended December 31, 2017, 2016 and 2015. Pension Plans Postretirement Benefit Plans 2017 2016 2015 2017 2016 2015 (in millions) Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): Net loss (gain) $ 200 $ 179 $ (132 ) $ (17 ) $ (4 ) $ (7 ) Prior service (cost) credit (4 ) 15 — — (2 ) — Amortization of net (loss) gain (61 ) (52 ) (68 ) 2 2 — Amortization of prior service (cost) credit (1 ) — (1 ) 1 2 2 Total recognized in other comprehensive income (loss) 134 142 (201 ) (14 ) (2 ) (5 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 244 $ 239 $ (62 ) $ (14 ) $ (2 ) $ (2 ) The following table summarizes the amounts expected to be amortized from accumulated OCI and recognized as components of net periodic benefit costs during 2018. Pension Plans Postretirement Benefit Plans Total (in millions) Net loss (gain) $ 74 $ (3 ) $ 71 Prior service credit — (1 ) (1 ) $ 74 $ (4 ) $ 70 The table below summarizes the weighted average assumptions used to determine the net periodic benefit cost for the years ended December 31, 2017, 2016 and 2015. Pension Plans Postretirement Benefit Plans 2017 2016 2015 2017 2016 2015 Discount rates: Benefit obligation 4.40 % (1) 4.67 % (1) 4.14 % (1) 4.05 % (4) 4.22 % (4) 3.70 % (4) Service cost 4.55 % 4.83 % — (5) 4.21 % 4.37 % — (5) Interest cost 3.84 % 3.95 % — (5) 3.26 % 3.26 % — (5) Expected long-term return on plan assets 7.92 % (2) 7.92 % (2) 8.14 % (2) 7.43 % 7.42 % 7.65 % Rate of compensation increase 3.50 % (3) 3.50 % (3) 3.50 % (3) (1) The weighted average discount rate assumptions used for the years ended December 31, 2017, 2016, and 2015 were comprised of separate assumptions determined by country of 4.45%, 4.73% and 4.20% for the U.S. based plans and 3.79%, 3.93% and 3.90% for the Canadian based plans, respectively. (2) The weighted average expected long-term return on plan assets assumptions used were comprised of separate assumptions determined by country of 8.00% for each of the years ended December 31, 2017 and 2016 and 8.25% for the year ended December 31, 2015 for the U.S. based plans and 7.25% for the Canadian based plans for the years ended December 31, 2017, 2016 and 2015. (3) The weighted average rate of compensation increase assumptions used for the years ended December 31, 2017, 2016 and 2015 were comprised of separate assumptions determined by country of 3.50% for both the U.S and Canadian based plans. (4) The weighted average discount rate assumptions used for the years ended December 31, 2017, 2016 and 2015 were comprised of separate assumptions determined by country of 4.11%, 4.28% and 3.70% for the U.S. based plans and 3.64%, 3.74% and 3.70% for the Canadian based plans, respectively. (5) Not applicable as the Company changed to the spot rate approach beginning in 2016 as described above. The expected long-term return on plan assets assumption represents the average rate that the Company expects to earn over the long-term on the assets of the Company’s benefit plans, including those from dividends, interest income and capital appreciation. The Company utilizes a third-party consultant to assist in the development of the expected long-term return on plan assets, which is based on expectations regarding future long-term rates of return for the plans’ investment portfolio, with consideration given to the allocation of investments by asset class and historical rates of return for each individual asset class. The Company utilizes a building block methodology that utilizes historical and forward looking rates of return for each asset class and takes into account expected returns above inflation and risk premium. These long-term rates of return are then applied to the target portfolio allocations that are generally aligned with the actual asset allocations of the Company’s plans to develop the expected long-term rate of return. The annual increase in cost of benefits (health care cost trend rate) for the Company’s U.S. based plans covering retirees under 65 years of age is assumed to be an average of 6.5% in 2018 and is assumed to gradually decrease to a rate of 5.0% in 2021 and thereafter. The health care cost trend rate for the Company’s U.S. based plans covering retirees over 65 years of age is assumed to be an average of 8.0% in 2018 and is assumed to gradually decrease to a rate of 5.0% in 2024 and thereafter. The health care cost trend rate for the Company’s Canadian based plans is assumed to be an average of 6.25% in 2018 and is assumed to gradually decrease to a rate of 5.0% in 2023 and thereafter. Health care cost trend assumptions are based on (1) observed or expected short term rates of increase for different types of health models based on actual claims experience and benchmarking, and (2) a reasonable estimate of an appropriate, sustainable level of health care cost trend in the future, weighting the factors that primarily influence trends, which are price inflation and cost leveraging benefit plan features. Assumed health care cost trend rates can have a significant effect on amounts reported for postretirement medical benefit plans. A one percentage point change in the assumed health care cost trend rates would have the following effects: 1 percentage point Increase Decrease (in millions) Effect on total service and interest cost $ — $ — Effect on postretirement benefit obligations $ 5 $ (4 ) Plan Assets. The Committee retains a professional investment consultant to advise the Committee and help ensure that the above policies and strategies are met. The Committee does not actively manage the day to day operations and selection process of individual securities and investments, as it retains the professional services of qualified investment management organizations to fulfill those tasks. Qualified investment management organizations are evaluated on several criteria for selection, with a focus on the investment management organizations’ demonstrated capability to achieve results that will meet or exceed the investment objectives they have been assigned and conform to the policies established by the Committee. While the investment management organizations have investment discretion over the assets placed under their management, the Committee provides each investment manager with specific investment guidelines relevant to its asset class. The Committee has established the allowable range that the plans’ assets may be invested in for each major asset category. In addition, the Committee has established guidelines regarding diversification within asset categories to limit risk and exposure to a single or limited number of securities. The investments of the plans’ include a diversified portfolio of both equity and fixed income investments. Equity investments are further diversified across U.S. and non-U.S. stocks, small to large capitalization stocks, and growth and value stocks. Fixed income assets are diversified across U.S. and non-U.S. issuers, corporate and governmental issuers, and credit quality. The plan also invests in real estate through publicly traded real estate securities. Derivatives may be used only for hedging purposes or to create synthetic long positions. The plans are prohibited from directly owning commodities, unregistered securities, restricted stock, private placements, or interests in oil, gas, mineral exploration, or other development programs. Further, short selling or utilizing margin buying for investment purposes is prohibited. The table below presents the allowable range for each major category of the plans’ assets at December 31, 2017 as well as the Company’s pension plan and postretirement benefit plan weighted-average asset allocations at December 31, 2017 and 2016, by asset category. U.S. Canada Asset Category Range 2017 2016 Range 2017 2016 Domestic equity (1) 30%-60% 47 % 55 % — 15 % 15 % International equity (2) 10%-20% 11 10 — 47 62 Total equities 45%-75% 58 65 40%-80% 62 77 Fixed income securities 20%-40% 28 22 — 25 13 Other, primarily cash and cash equivalents 0%-15% 7 5 — 13 10 Total fixed income securities and cash and cash equivalents NA NA NA 20%-60% 38 23 Real estate securities 0%-15% 7 8 — — — Total 100 % 100 % 100 % 100 % (1) Domestic equities for Canadian plans refers to equities of Canadian companies. (2) International equities for Canadian plans includes equities of U.S. companies. NA - Not applicable. The Company’s Master Pension Trust Investment Policy does not provide an allocation percentage range to fixed income securities and cash and cash equivalents. The Committee regularly monitors the investment of the plans’ assets to ensure that the actual investment allocation remains within the established range. The Committee also regularly measures and monitors investment risk through ongoing performance reporting and investment manager reviews. Investment manager reviews include assessing the managers’ performance versus the appropriate benchmark index both in the short and long-term period, performance versus peers, and an examination of the risk the managers assumed in order to achieve rates of return. The table below presents the fair value of the Company’s pension plans’ assets by asset category segregated by level within the fair value hierarchy, as described below. U.S. Pension Plans’ Assets Canadian Pension Plans’ Assets Fair Value Measured at December 31, 2017 Fair Value Measured at December 31, 2017 Asset Category Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in millions) Equity securities (1) U.S. Equity $ 1,297 $ — $ — $ 1,297 $ 71 $ — $ — $ 71 International Equity 87 — — 87 105 — — 105 Fixed Income — Investment Grade (2) 329 205 — 534 — — — — Fixed Income — High Yield (3) — 219 — 219 — — — — Real Estate Investment Trusts (4) 196 — — 196 — — — — Other (5) — 198 — 198 8 37 — 45 Total assets at fair value $ 1,909 $ 622 $ — $ 2,531 $ 184 $ 37 $ — $ 221 Liabilities for unsettled trades, net (30 ) — Other investments measured at net asset value (6)(7) 203 122 Total $ 2,704 $ 343 U.S. Pension Plans’ Assets Canadian Pension Plans’ Assets Fair Value Measured at December 31, 2016 Fair Value Measured at December 31, 2016 Asset Category Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in millions) Equity securities (1) U.S. Equity $ 1,331 $ — $ — $ 1,331 $ 79 $ — $ — $ 79 International Equity 85 — — 85 104 — — 104 Fixed Income — Investment Grade (2) 255 159 — 414 — — — — Fixed Income — High Yield (3) — 136 — 136 — — — — Real Estate Investment Trusts (4) 193 — — 193 — — — — Other (5) — 114 — 114 5 27 — 32 Total assets at fair value $ 1,864 $ 409 $ — $ 2,273 $ 188 $ 27 $ — $ 215 Liabilities for unsettled trades, net (23 ) — Other investments measured at net asset value (6)(7) 171 85 Total $ 2,421 $ 300 (1) Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the New York Stock Exchange (NYSE), National Association of Securities Dealers Automated Quotations (NASDAQ), and various international exchanges. (2) Approximately 62% at December 31, 2017 and 2016 of U.S. plan assets that are invested in the Fixed Income — Investment Grade asset category consist of a mutual fund offered by a registered investment company (the Fund) and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy, as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 38% at December 31, 2017 and 2016 of U.S. plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2. (3) Fixed Income — High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs. (4) Real Estate Investment Trusts (REITs) consist of securities that trade on the major exchanges and invest directly in real estate, either through properties or mortgages. (5) Other consists primarily of: (1) money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit, and are classified as Level 2, and (2) cash, which is classified as Level 1. (6) In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value (NAV) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position. (7) All of the U.S. plans other investments measured using NAV at December 31, 2017 and 2016 and approximately 31% and 55% at December 31, 2017 and 2016, respectively, of the Canadian plans other investments measured using NAV consist of a regulated commingled equity trust fund, for which fair value is based on the NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund’s holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV. Approximately 69% and 45% at December 31, 2017 and 2016, respectively, of the Canadian plans other investments measured using NAV are invested in regulated commingled bond funds (the “Bond Funds”). As these Bond Funds do not trade in an active market, the fair value is based on NAVs calculated by fund managers based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs as a practical expedient to estimating fair value and classified as Level 2. Withdrawals are permitted monthly, with notice between 0 and 3 days of the transaction date, based on NAV. The table below presents the fair value of the Company’s postretirement benefit plans’ assets by asset category segregated by level within the fair value hierarchy, as described below. Postretirement Benefit Plans’ Assets Fair Value Measured at December 31, 2017 Fair Value Measured at December 31, 2016 Asset Category Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in millions) Equity securities (1) U.S. Equity $ 38 $ — $ — $ 38 $ 37 $ — $ — $ 37 International Equity 2 — — 2 1 — — 1 Fixed Income — Investment Grade (2) 10 3 — 13 8 3 — 11 Fixed Income — High Yield (3) — 3 — 3 — 2 — 2 Real Estate Investment Trusts (4) 3 — — 3 3 — — 3 Other (5) — 5 — 5 — 3 — 3 Total assets at fair value $ 53 $ 11 $ — $ 64 $ 49 $ 8 $ — $ 57 Other investments measured at net asset value (6)(7) 3 3 Total $ 67 $ 60 (1) Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the NYSE, NASDAQ, and various international exchanges. (2) Approximately 77 % and 73% at December 31, 2017 and 2016, respectively, of the postretirement benefit plan assets that are invested in the Fixed Income — Investment Grade asset category consist of the Fund and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 23 % and 27% at December 31, 2017 and 2016, respectively, of the postretirement benefit plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2. (3) Fixed Income — High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs. (4) REITs consist of securities that trade on the major exchanges and invest directly, either through properties or mortgages. (5) Other consists primarily of money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit. (6) In accordance with ASU 2015-07, certain investments that are measured at fair value using the NAV per share (or its equivalent)practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position. (7) All of the postretirement benefit plans other investments measured using NAV at December 31, 2017 and 2016 consist of a regulated commingled equity trust fund, which fair value is based on NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund’s holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV. Contributions. Estimated Future Benefit Payments. Postretirement Benefits Pension Benefits Benefit Payments Subsidy Receipts (in millions) 2018 $ 158 $ 12 $ — 2019 165 12 — 2020 175 13 — 2021 185 13 — 2022 194 12 — Years 2023 - 2027 1,128 55 1 Employee Savings Plans. Multiemployer Benefit Plans. Under these plans, the Company contributed cash and recorded expenses for each of its individually significant plans and all of its other plans in aggregate as noted in the table below. EIN/Pension Plan Number Pension Protection Act Zone Status (1) FIP/RP (2) Status Pending/ Implemented Contributions by L3 (7) Surcharge Imposed Expiration Date of Collective- Bargaining Agreement Pension Fund 2017 2016 2017 2016 2015 IAM National Pension Fund 51-6031295/002 Green Green No $ 27 (3) $ 26 (4) $ 23 (4) No 4/29/2018 to (5) Other Pension Funds (6) — — — Total contributions $ 27 $ 26 $ 23 (1) A zone status rating of green indicates the plan is at least 80% funded. (2) Funding improvement plan or rehabilitation plan. (3) At the date the audited financial statements for the Company were issued, the Form 5500 for the plan year ended December 31, 2017 was not available. (4) Represents 5% of total plan contributions for the years ended December 31, 2016 and 2015 based on Form 5500. (5) The Company is a party to multiple bargaining agreements for multiple projects that require contributions into the IAM National Pension Fund. The most significant of these agreements, expiring April 28, 2019, covers multiple programs in the Company’s Aerospace Systems reportable segment and represents 61% of 2017 contributions. (6) Consists of three pension funds in which the Company’s contributions are individually, and in the aggregate, insignificant. (7) These contributions include amounts attributable to discontinued operations of approximately $26 million for the years ended December 31, 2017 and 2016 and $22 million for the year ended December 31, 2015.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	20. Supplemental Cash Flow Information Year Ended December 31, 2017 2016 2015 (in millions) Interest paid $ 165 $ 162 $ 182 Income tax payments $ 163 $ 120 $ 130 Income tax refunds $ 16 $ 8 $ 8

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Information [Abstract]
Segment Information	21. Segment Information The Company has four reportable segments, which are described in Note 1. The Company evaluates the performance of its operating segments and reportable segments based on their sales, operating income and operating margin. Corporate expenses are allocated to the Company’s operating segments using an allocation methodology prescribed by U.S. Government regulations for government contractors. Accordingly, segment results include all costs and expenses, except for goodwill impairment charges, gains or losses related to business divestitures, and certain other items that are excluded by management for purposes of evaluating the operating performance of the Company’s business segments. Certain Corporate and segment expenses of $32 million for 2017 and $29 million for the years ended December 31, 2016 and 2015, that had previously been allocated to the Vertex Aerospace and NSS businesses were retained by the Company and were allocated to L3’s four reportable segments. The tables below present net sales, operating income, depreciation and amortization, capital expenditures and total assets by reportable segment. Year Ended December 31, 2017 2016 2015 (in millions) Net Sales Products Electronic Systems $ 2,234 $ 2,033 $ 2,102 Aerospace Systems 1,545 1,679 1,679 Communication Systems 1,745 1,586 1,649 Sensor Systems 1,292 1,266 1,298 Elimination of intercompany sales (83 ) (111 ) (128 ) Total products sales 6,733 6,453 6,600 Services Electronic Systems $ 848 $ 812 $ 810 Aerospace Systems 1,267 1,270 1,257 Communication Systems 510 488 441 Sensor Systems 273 235 193 Elimination of intercompany sales (58 ) (48 ) (70 ) Total services sales 2,840 2,757 2,631 Consolidated total $ 9,573 $ 9,210 $ 9,231 Year Ended December 31, 2017 2016 2015 (in millions) Operating income Electronic Systems $ 403 $ 360 $ 337 Aerospace Systems 210 255 193 Communication Systems 212 195 190 Sensor Systems 195 147 142 Segment total 1,020 957 862 Goodwill impairment charges (1) — — (46 ) Loss related to business divestitures (2) — — (31 ) Consolidated total $ 1,020 $ 957 $ 785 Depreciation and amortization Electronic Systems $ 79 $ 60 $ 59 Aerospace Systems 51 46 43 Communication Systems 49 47 50 Sensor Systems 46 45 51 Consolidated total $ 225 $ 198 $ 203 Capital Expenditures Electronic Systems $ 68 $ 76 $ 69 Aerospace Systems 43 50 53 Communication Systems 49 37 37 Sensor Systems 42 37 30 Corporate 22 10 6 Consolidated total $ 224 $ 210 $ 195 Total Assets Electronic Systems $ 4,796 $ 4,369 $ 3,968 Aerospace Systems 2,014 2,084 2,190 Communication Systems 2,063 2,031 1,984 Sensor Systems 2,706 2,433 2,458 Corporate 709 467 345 Assets held for sale 135 — — Assets of discontinued operations 306 481 1,124 Consolidated total $ 12,729 $ 11,865 $ 12,069 (1) Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment. (2) See Note 3 for information regarding the Company’s business divestitures. Corporate assets not allocated to the reportable segments primarily include cash and cash equivalents, corporate office fixed assets, and deferred income tax assets. The table below presents property, plant and equipment, net by geographic area. Year Ended December 31, 2017 2016 (in millions) United States $ 936 $ 960 All Other 174 147 Total $ 1,110 $ 1,107 The Company’s sales attributable to U.S. and international customers, based on location of the customer, are summarized in the table below. Year Ended December 31, 2017 2016 2015 (in millions) U.S. $ 7,344 $ 6,947 $ 6,734 International: United Kingdom 335 331 336 Canada 280 297 281 Australia 268 254 321 China 167 67 83 South Korea 134 127 207 Japan 125 81 95 France 84 75 62 Other 836 1,031 1,112 Total international 2,229 2,263 2,497 Consolidated $ 9,573 $ 9,210 $ 9,231 Net sales to principal customers are summarized in the table below. Year Ended December 31, 2017 2016 2015 (in millions) U.S. Government agencies (1) $ 6,697 $ 6,399 $ 6,120 Commercial 1,456 1,280 1,373 Foreign governments (1) 1,420 1,531 1,738 Consolidated $ 9,573 $ 9,210 $ 9,231 (1) Includes sales for which the Company is the prime contractor as well as sales based on the ultimate end customer for which the Company is a subcontractor.

Severance and Restructuring Rel

Severance and Restructuring Related Costs	12 Months Ended
	Dec. 31, 2017
Severance and Restructuring Related Costs [Abstract]
Severance and Restructuring Related Costs	22. Severance and Restructuring Related Costs Consistent with the Company’s strategy to continuously improve its cost structure and right-size its businesses, L3 is completing employment reduction actions across several of its businesses to reduce both direct and indirect costs, including overhead and general and administrative costs. As a result of these initiatives, the Company recorded employee severance and restructuring related costs of $101 million with respect to approximately 1,500 employees during the year ended December 31, 2017, $17 million with respect to approximately 700 employees during the year ended December 31, 2016 and $18 million with respect to approximately 800 employees during the year ended December 31, 2015. Severance and restructuring related costs are reported within cost of sales on the consolidated statements of operations. Severance and restructuring related costs incurred by reportable segment are presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Electronic Systems (1) $ 14 $ 5 $ 4 Aerospace Systems (1) 24 2 4 Communication Systems (2) 48 7 6 Sensor Systems (3) 15 3 4 Consolidated $ 101 $ 17 $ 18 (1) The severance and restructuring related costs incurred during the year ended December 31, 2017 include $1 million and $5 million of salaried employee pension plan curtailment losses for Electronic Systems and Aerospace Systems segments, respectively. See Note 19 for additional information. (2) The severance and restructuring related costs incurred during the year ended December 31, 2017 exclude a pre-tax gain of $42 million on the sale of the Company's property in San Carlos, California in the second quarter of 2017. (3) The severance and restructuring related costs incurred during the year ended December 31, 2017 include a $12 million loss on the sale of a building in Garland, Texas in the fourth quarter of 2017. The Company had severance and restructuring related liabilities of $23 million and $9 million included in other current liabilities on the Company’s balance sheets at December 31, 2017 and 2016, respectively. The remaining liability balance at December 31, 2017 is expected to be paid in 2018. The table below presents the change to the Company’s severance and restructuring related liability during the year ended December 31, 2017. December 31, 2017 (in millions) Balance at beginning of period $ 9 Additional provisions 101 Cash payments (87 ) Balance at end of period $ 23

Unaudited Quarterly Financial D

Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Unaudited Quarterly Financial Data [Abstract]
Unaudited Quarterly Financial Data	23. Unaudited Quarterly Financial Data Unaudited summarized financial data by quarter for the years ended December 31, 2017 and 2016 is presented in the table below. The Company’s unaudited quarterly results of operations are affected, significantly in some periods, by the Company’s business acquisitions and divestitures. See Note 3 for additional information. First Quarter Second Quarter Third Quarter (1) Fourth Quarter (2) (in millions, except per share data) 2017 Sales $ 2,321 $ 2,385 $ 2,293 $ 2,574 Operating income 236 292 229 263 Income from continuing operations 157 195 146 271 Net income 168 207 25 293 Net income attributable to L3 164 202 22 289 Basic EPS from continuing operations (3) 1.97 2.44 1.83 3.42 Basic EPS (3) 2.11 2.59 0.28 3.70 Diluted EPS from continuing operations (3) 1.93 2.39 1.79 3.34 Diluted EPS (3) 2.07 2.54 0.28 3.62 2016 Sales $ 2,065 $ 2,318 $ 2,184 $ 2,643 Operating income 244 220 211 282 Income from continuing operations 163 134 149 187 Net income 230 151 151 192 Net income attributable to L3 227 147 148 188 Basic EPS from continuing operations (3) 2.06 1.68 1.89 2.37 Basic EPS (3) 2.92 1.90 1.91 2.43 Diluted EPS from continuing operations (3) 2.02 1.66 1.85 2.32 Diluted EPS (3) 2.87 1.88 1.88 2.38 (1) The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017 , which is reported in discontinued operations . (2) Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017. (3) EPS in each quarter is computed using the weighted-average number of shares outstanding during that quarter, while EPS for the full year is computed using the weighted-average number of shares outstanding during the year. Therefore, the sum of the four quarters’ EPS may not equal the full year computed EPS.

Financial Information of L3 and

Financial Information of L3 and Its Subsidiaries	12 Months Ended
	Dec. 31, 2017
Financial Information of L3 and Its Subsidiaries [Abstract]
Financial Information of L3 and Its Subsidiaries	24. Financial Information of L3 and Its Subsidiaries The debt of L3, including the Senior Notes and borrowings under amounts drawn against the Credit Facility are guaranteed, on a joint and several, full and unconditional basis, by certain of its domestic subsidiaries (the Guarantor Subsidiaries). See Note 9 for additional information. The foreign subsidiaries and certain domestic subsidiaries of L3 (the Non-Guarantor Subsidiaries) do not guarantee the debt of L3. None of the debt of L3 has been issued by its subsidiaries. Under the terms of the indentures governing the Senior Notes, the guarantees of the Senior Notes will automatically and unconditionally be released and discharged: (1) upon the release of all guarantees of all other outstanding indebtedness of L3, or (2) upon the determination that such guarantor is no longer a “domestic subsidiary.” In addition, the guarantees of the Senior Notes will be automatically and unconditionally released and discharged in the event of a sale or other disposition of all of the assets of any guarantor, by way of merger, consolidation or otherwise, or a sale of all of the capital stock of such guarantor. There are no restrictions on the payment of dividends from the Guarantor Subsidiaries to L3. In lieu of providing separate audited financial statements for the Guarantor Subsidiaries, the Company has included the accompanying condensed combining financial statements based on Rule 3-10 of SEC Regulation S-X. The Company does not believe that separate financial statements of the Guarantor Subsidiaries are material to users of the financial statements. The following condensed combining financial information presents the results of operations, financial position and cash flows of: (1) L3 excluding its consolidated subsidiaries (the Parent), (2) the Guarantor Subsidiaries, (3) the Non-Guarantor Subsidiaries and (4) the eliminations to arrive at the information for L3 on a consolidated basis. L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) Condensed Combining Balance Sheets: At December 31, 2017: Current assets: Cash and cash equivalents $ 432 $ 14 $ 287 $ (71 ) $ 662 Billed receivables, net 266 232 225 — 723 Contracts in process 706 891 336 — 1,933 Prepaid expenses and other current assets 330 231 128 — 689 Assets held for sale — 118 17 — 135 Assets of discontinued operations — 306 — — 306 Total current assets 1,734 1,792 993 (71 ) 4,448 Goodwill 2,248 2,652 1,715 — 6,615 Other assets 658 556 452 — 1,666 Investment in and amounts due from consolidated subsidiaries 5,593 5,270 — (10,863 ) — Total assets $ 10,233 $ 10,270 $ 3,160 $ (10,934 ) $ 12,729 Current liabilities $ 811 $ 800 $ 596 $ (71 ) $ 2,136 Liabilities held for sale — 16 1 — 17 Liabilities of discontinued operations — 226 — — 226 Amounts due to consolidated subsidiaries — — 352 (352 ) — Other long-term liabilities 1,009 714 146 — 1,869 Long-term debt 3,330 — — — 3,330 Total liabilities 5,150 1,756 1,095 (423 ) 7,578 L3 shareholders’ equity 5,083 8,514 2,065 (10,579 ) 5,083 Noncontrolling interests — — — 68 68 Total equity 5,083 8,514 2,065 (10,511 ) 5,151 Total liabilities and equity $ 10,233 $ 10,270 $ 3,160 $ (10,934 ) $ 12,729 L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) At December 31, 2016: Current assets: Cash and cash equivalents $ 291 $ 1 $ 207 $ (136 ) $ 363 Billed receivables, net 261 254 185 — 700 Contracts in process 694 928 236 — 1,858 Prepaid expenses and other current assets 236 144 125 — 505 Assets of discontinued operations — 481 — — 481 Total current assets 1,482 1,808 753 (136 ) 3,907 Goodwill 2,258 2,613 1,503 — 6,374 Other assets 705 567 312 — 1,584 Investment in and amounts due from consolidated subsidiaries 5,721 5,272 — (10,993 ) — Total assets $ 10,166 $ 10,260 $ 2,568 $ (11,129 ) $ 11,865 Current liabilities $ 789 $ 846 $ 460 $ (136 ) $ 1,959 Liabilities of discontinued operations — 235 — — 235 Amounts due to consolidated subsidiaries — — 763 (763 ) — Other long-term liabilities 1,499 191 32 — 1,722 Long-term debt 3,325 — — — 3,325 Total liabilities 5,613 1,272 1,255 (899 ) 7,241 L3 shareholders’ equity 4,553 8,988 1,313 (10,301 ) 4,553 Noncontrolling interests — — — 71 71 Total equity 4,553 8,988 1,313 (10,230 ) 4,624 Total liabilities and equity $ 10,166 $ 10,260 $ 2,568 $ (11,129 ) $ 11,865 L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) Condensed Combining Statements of Operations: For the year ended December 31, 2017: Total net sales $ 3,519 $ 4,748 $ 1,690 $ (384 ) $ 9,573 Total cost of sales (3,179 ) (4,350 ) (1,408 ) 384 (8,553 ) Operating income 340 398 282 — 1,020 Interest expense (168 ) — (1 ) — (169 ) Interest and other income, net 17 — 3 — 20 Income from continuing operations before income taxes 189 398 284 — 871 Provision for income taxes (22 ) (47 ) (33 ) — (102 ) Equity in net income of consolidated subsidiaries 511 — — (511 ) — Income from continuing operations 678 351 251 (511 ) 769 Loss from discontinued operations, net of income tax (1 ) (75 ) — — (76 ) Net income 677 276 251 (511 ) 693 Net income attributable to noncontrolling interests — — — (16 ) (16 ) Net income attributable to L3 $ 677 $ 276 $ 251 $ (527 ) $ 677 Comprehensive income attributable to L3 $ 712 $ 278 $ 378 $ (656 ) $ 712 For the year ended December 31, 2016: Total net sales $ 3,350 $ 4,809 $ 1,381 $ (330 ) $ 9,210 Total cost of sales (3,069 ) (4,378 ) (1,136 ) 330 (8,253 ) Operating income 281 431 245 — 957 Interest expense (164 ) — — — (164 ) Interest and other income, net 15 — 3 — 18 Debt retirement charges (7 ) — — — (7 ) Income from continuing operations before income taxes 125 431 248 — 804 Provision for income taxes (26 ) (92 ) (53 ) — (171 ) Equity in net income of consolidated subsidiaries 611 — — (611 ) — Income from continuing operations 710 339 195 (611 ) 633 Income from discontinued operations, net of income tax — 91 — — 91 Net income 710 430 195 (611 ) 724 Net income attributable to noncontrolling interests — — — (14 ) (14 ) Net income attributable to L3 $ 710 $ 430 $ 195 $ (625 ) $ 710 Comprehensive income attributable to L3 $ 558 $ 440 $ 118 $ (558 ) $ 558 For the year ended December 31, 2015: Total net sales $ 3,267 $ 4,866 $ 1,449 $ (351 ) $ 9,231 Total cost of sales (3,031 ) (4,441 ) (1,248 ) 351 (8,369 ) Goodwill impairment charges — (26 ) (20 ) — (46 ) (Loss) gain related to business divestitures (13 ) (31 ) 13 — (31 ) Operating income 223 368 194 — 785 Interest expense (161 ) (1 ) — — (162 ) Interest and other income, net 17 — — — 17 Debt retirement charge (1 ) — — — (1 ) Income from continuing operations before income taxes 78 367 194 — 639 Provision for income taxes (16 ) (76 ) (40 ) — (132 ) Equity in net loss of consolidated subsidiaries (302 ) — — 302 — (Loss) income from continuing operations (240 ) 291 154 302 507 Loss from discontinued operations, net of income tax — (732 ) — — (732 ) Net (loss) income (240 ) (441 ) 154 302 (225 ) Net income attributable to noncontrolling interests — — — (15 ) (15 ) Net (loss) income attributable to L3 $ (240 ) $ (441 ) $ 154 $ 287 $ (240 ) Comprehensive (loss) income attributable to L3 $ (230 ) $ (445 ) $ 43 $ 402 $ (230 ) L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) Condensed Combining Statements of Cash Flows: For the year ended December 31, 2017: Operating activities: Net cash from operating activities from continuing operations $ 374 $ 438 $ 251 $ (78 ) $ 985 Investing activities: Business acquisitions, net of cash acquired (316 ) — — — (316 ) Proceeds from sale of businesses, net of closing date cash balances 17 — 1 — 18 Other investing activities (84 ) (41 ) (30 ) — (155 ) Net cash used in investing activities from continuing operations (383 ) (41 ) (29 ) — (453 ) Financing activities: Common stock repurchased (180 ) — — — (180 ) Dividends paid on L3’s common stock (236 ) — — — (236 ) Other financing activities 565 (496 ) (162 ) 143 50 Net cash from (used in) financing activities from continuing operations 149 (496 ) (162 ) 143 (366 ) Effect of foreign currency exchange rate changes on cash — — 20 — 20 Net increase in cash and cash equivalents of discontinued operations 1 112 — — 113 Net increase in cash 141 13 80 65 299 Cash and cash equivalents, beginning of the year 291 1 207 (136 ) 363 Cash and cash equivalents, end of the year $ 432 $ 14 $ 287 $ (71 ) $ 662 L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) For the year ended December 31, 2016: Operating activities: Net cash from operating activities from continuing operations $ 441 $ 509 $ 258 $ (186 ) $ 1,022 Investing activities: Business acquisitions, net of cash acquired (388 ) — — — (388 ) Proceeds from sale of businesses, net of closing date cash cash balances 563 — (2 ) — 561 Other investing activities (60 ) (80 ) (43 ) — (183 ) Net cash from (used in) investing activities from continuing operations 115 (80 ) (45 ) — (10 ) Financing activities: Proceeds from sale of senior notes 547 — — — 547 Redemption of senior notes (856 ) — — — (856 ) Common stock repurchased (373 ) — — — (373 ) Dividends paid on L3’s common stock (220 ) — — — (220 ) Other financing activities 496 (441 ) (158 ) 149 46 Net cash used in financing activities from continuing operations (406 ) (441 ) (158 ) 149 (856 ) Effect of foreign currency exchange rate changes on cash — — (13 ) — (13 ) Net increase in cash and cash equivalents of discontinued operations — 13 — — 13 Net increase in cash 150 1 42 (37 ) 156 Cash and cash equivalents, beginning of the year 141 — 165 (99 ) 207 Cash and cash equivalents, end of the year $ 291 $ 1 $ 207 $ (136 ) $ 363 For the year ended December 31, 2015: Operating activities: Net cash from operating activities from continuing operations $ 634 $ 425 $ 161 $ (185 ) $ 1,035 Investing activities: Business acquisitions, net of cash acquired (320 ) — — — (320 ) Proceeds from sale of businesses, net of closing date cash balances 14 28 276 — 318 Other investing activities (75 ) (78 ) (35 ) — (188 ) Net cash (used in) from investing activities from continuing operations (381 ) (50 ) 241 — (190 ) Financing activities: Repurchases of senior notes (297 ) — — — (297 ) Common stock repurchased (740 ) — — — (740 ) Dividends paid on L3's common stock (214 ) — — — (214 ) Other financing activities 781 (463 ) (420 ) 148 46 Net cash used in financing activities from continuing operations (470 ) (463 ) (420 ) 148 (1,205 ) Effect of foreign currency exchange rate changes on cash — — (19 ) — (19 ) Net increase in cash and cash equivalents of discontinued operations — 83 — — 83 Change in cash balance in assets held for sale — 1 60 — 61 Net (decrease) increase in cash (217 ) (4 ) 23 (37 ) (235 ) Cash and cash equivalents, beginning of the year 358 4 142 (62 ) 442 Cash and cash equivalents, end of the year $ 141 $ — $ 165 $ (99 ) $ 207

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation: All references made to financial data noted in the footnotes are to L3’s continuing operations unless otherwise specifically noted.
Accounting Estimates	Accounting Estimates: Revisions or adjustments to estimates for a contract’s revenue, estimated costs at completion and estimated profit or loss are often required as work progresses under a contract, as experience is gained, as facts and circumstances change and as new information is obtained, even though the scope of work required under the contract may not change. Revisions or adjustments may also be required if contract modifications occur. The impact of revisions in profit (loss) estimates for all types of contracts subject to percentage-of-completion (POC) accounting are recognized on a cumulative catch-up basis in the period in which the revisions are made. The revisions in contract estimates, if significant, can materially affect the Company’s results of operations and cash flows, as well as reduce the valuations of receivables and inventories, and in some cases result in liabilities to complete contracts in a loss position. Aggregate net changes in contract estimates amounted to increases of $184 million, or 18%, of consolidated operating income ($1.48 per diluted share) for the year ended December 31, 2017, increases of $149 million, or 16%, of consolidated operating income ($1.23 per diluted share) for the year ended December 31, 2016, and increases of $52 million, or 7%, of consolidated operating income ($0.45 per diluted share) for the year ended December 31, 2015.
Revenue Recognition	Revenue Recognition: Sales and profits on fixed-price type contracts that are covered by contract accounting standards are substantially recognized using POC methods of accounting. Sales and profits on fixed-price production contracts under which units are produced and delivered in a continuous or sequential process are recorded as units are delivered based on their contractual selling prices (the “units-of-delivery” method). Sales and profits on each fixed-price production contract under which units are not produced and delivered in a continuous or sequential process, or under which a relatively few number of units are produced, are recorded based on the ratio of actual cumulative costs incurred to the total estimated costs at completion of the contract, multiplied by the total estimated contract revenue, less cumulative sales recognized in prior periods (the “cost-to-cost” method). Under both POC methods of accounting, a single estimated total profit margin is used to recognize profit for each contract over its entire period of performance, which can exceed one year. Losses on contracts are recognized in the period in which they become evident. Amounts representing contract change orders or claims are included in sales only when they can be reliably estimated and their realization is reasonably assured. The impact of revisions of contract estimates, which may result from contract modifications, performance or other reasons, are recognized on a cumulative catch-up basis in the period in which the revisions are made. Sales and profits on cost-plus type contracts that are covered by contract accounting standards are recognized as allowable costs are incurred on the contract, at an amount equal to the allowable costs plus the estimated profit on those costs. The estimated profit on a cost-plus type contract is fixed or variable based on the contractual fee arrangement types. Incentive and award fees are the primary variable fee contractual arrangement types for the Company. Incentive and award fees on cost-plus type contracts are included as an element of total estimated contract revenues and are recorded as sales when a basis exists for the reasonable prediction of performance in relation to established contractual targets and the Company is able to make reasonably dependable estimates for them. Sales and profits on time-and-material type contracts are recognized on the basis of direct labor hours expended multiplied by the contractual fixed rate per hour, plus the actual costs of materials and other direct non-labor costs. Sales on arrangements for (1) fixed-price type contracts that require the Company to perform services that are not related to the production of tangible assets (Fixed-Price Service Contracts) and (2) certain commercial customers are recognized in accordance with accounting standards for revenue arrangements with commercial customers. Sales for the Company’s businesses whose customers are primarily commercial business enterprises are substantially all generated from single element revenue arrangements. Sales are recognized when there is persuasive evidence of an arrangement, delivery has occurred or services have been performed, the selling price to the buyer is fixed or determinable and collectability is reasonably assured. Sales for Fixed-Price Service Contracts that do not contain measurable units of work performed are generally recognized on a straight-line basis over the contractual service period, unless evidence suggests that the revenue is earned, or obligations fulfilled, in a different manner. Sales for Fixed-Price Service Contracts that contain measurable units of work performed are generally recognized when the units of work are completed. Sales and profit on cost-plus and time-and-material type contracts within the scope of accounting standards for revenue arrangements with commercial customers are recognized in the same manner as those within the scope of contract accounting standards, except for incentive and award fees. Cost-based incentive fees are recognized when they are realizable in the amount that would be due under the contractual termination provisions as if the contract was terminated. Performance based incentive fees and award fees are recorded as sales when objective evidence exists that the fees have been earned. For contracts with multiple deliverables, the Company applies the separation and allocation guidance under the accounting standard for revenue arrangements with multiple deliverables, unless all the deliverables are covered by contract accounting standards, in which case the Company applies the separation and allocation guidance under contract accounting standards. Revenue arrangements with multiple deliverables are evaluated to determine if the deliverables should be separated into more than one unit of accounting. The Company recognizes revenue for each unit of accounting based on the revenue recognition policies discussed above. Sales and cost of sales in connection with contracts to provide services to the U.S. Government that contain collection risk because the contracts are incrementally funded and subject to the availability of funds appropriated, are deferred until a contract modification is obtained, indicating that adequate funds are available to the contract or task order.
Research and Development	Research and Development: Customer-funded research and development costs are incurred pursuant to contracts (revenue arrangements) to perform research and development activities according to customer specifications. These costs are not accounted for as research and development expenses, and are also not indirect contract costs. Instead, these costs are direct contract costs and are expensed to cost of sales when the corresponding revenue is recognized, which is generally as the research and development services are performed. Customer-funded research and development costs are substantially all incurred under cost-plus type contracts with the U.S. Government.
Product Warranties	Product Warranties: The table below presents the changes in the Company’s accrued product warranty costs. Year Ended December 31, 2017 2016 (in millions) Accrued product warranty costs (1) : Balance at January 1 $ 109 $ 105 Acquisitions during this period 3 3 Accruals for product warranties issued during the period 52 51 Foreign currency translation adjustments 1 (1 ) Settlements made during the period (66 ) (49 ) Balance at December 31 $ 99 $ 109 (1) Warranty obligations incurred in connection with long-term production contracts that are accounted for under the POC cost-to-cost method are included within the contract estimates at completion and are excluded from the above amounts. The balances above include both the current and non-current amounts.
Deferred Debt Issue Costs	Deferred Debt Issue Costs:
Pension Plan and Postretirement Benefit Plan Obligations	Pension Plan and Postretirement Benefit Plan Obligations: The Company also provides postretirement medical and life insurance benefits for retired employees and dependents at certain locations. Participants are eligible for these benefits when they retire from active service and meet the eligibility requirements for the Company’s pension plans. These benefits are funded primarily on a pay-as-you-go basis with the retiree generally paying a portion of the cost through contributions, deductibles and coinsurance provisions. In accordance with accounting standards for employee pension and postretirement benefits, the Company recognizes on a plan-by-plan basis the unfunded status of its pension and postretirement benefit plans in the consolidated financial statements and measures its pension and postretirement benefit plan assets and benefit obligations at December 31. The obligation for the Company’s pension plans and postretirement benefit plans and the related annual costs of employee benefits are calculated based on several long-term assumptions, including discount rates and expected mortality for employee benefit liabilities, and rates of return on plan assets, and expected annual rates for salary increases for employee participants in the case of pension plans, and expected annual increases in the costs of medical and other health care benefits in the case of postretirement benefit obligations. See Note 19, Pensions and Other Employee Benefits
Stock-Based Compensation	Stock-Based Compensation: Compensation expense for restricted stock unit and stock option awards is generally recognized on a straight-line basis over the requisite service period for the entire award based on the grant date fair value. All of the stock options granted to employees by the Company are non-qualified stock options under U.S. income tax regulations. Compensation expense for performance units payable in L3 common stock is based on the fair value of the units at the grant date (measurement date), adjusted each reporting period for progress towards the target award, and recognized on a straight-line basis over the requisite service period. Stock-based compensation expense is recognized net of estimated forfeitures.
Income Taxes	Income Taxes: Income tax accounting standards prescribe: (1) a minimum recognition threshold that an income tax benefit arising from an uncertain income tax position taken, or expected to be taken, on an income tax return is required to meet before being recognized in the financial statements and (2) the measurement of the income tax benefits recognized from such positions. The Company’s accounting policy is to classify uncertain income tax positions that are not expected to be resolved in one year as non-current income tax liabilities and to classify potential interest and penalties on uncertain income tax positions as elements of the provision for income taxes in its financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents:
Contracts in Process	Contracts in Process: The Company values its acquired contracts in process in connection with business acquisitions on the date of acquisition at contract value less the Company’s estimated costs to complete the contract and a reasonable profit allowance on the Company’s completion effort.
Inventories	Inventories:
Property, Plant and Equipment	Property, Plant and Equipment:
Goodwill and Indefinite-lived Intangible Assets	Goodwill and Indefinite-lived Intangible Assets: Simplifying the Test for Goodwill Impairment
Identifiable Intangible Assets	Identifiable Intangible Assets:
Derivative Financial Instruments	Derivative Financial Instruments: The Company’s U.S. and foreign businesses enter into contracts with customers, subcontractors or vendors that are denominated in currencies other than their functional currencies. To protect the functional currency equivalent cash flows associated with certain of these contracts, the Company enters into foreign currency forward contracts. The Company’s activities involving foreign currency forward contracts are designed to hedge the changes in the functional currency equivalent cash flows due to movements in foreign exchange rates compared to the functional currency. The foreign currencies hedged are primarily the U.S. dollar, the Canadian dollar, the Euro and the British pound. The Company manages exposure to counterparty non-performance credit risk by entering into foreign currency forward contracts only with major financial institutions that are expected to fully perform under the terms of such contracts. Foreign currency forward contracts are recorded in the Company’s balance sheets at fair value and are generally designated and accounted for as cash flow hedges in accordance with the accounting standards for derivative instruments and hedging activities. Gains and losses on designated foreign currency forward contracts that are highly effective in offsetting the corresponding change in the cash flows of the hedged transactions are recorded net of income taxes in accumulated other comprehensive income (loss) (accumulated OCI) and then recognized in income when the underlying hedged transaction affects income. Gains and losses on foreign currency forward contracts that do not meet hedge accounting criteria are recognized in income immediately.
Treasury Stock	Treasury Stock:
Translation of Foreign Currency and Foreign Currency Transactions	Translation of Foreign Currency and Foreign Currency Transactions:
Accounting Standards Issued and Not Yet Implemented	Accounting Standards Issued and Not Yet Implemented: Targeted Improvements to Accounting for Hedging Activities In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cos In January 2017, the FASB issued ASU 2017-01, Clarifying the Definition of a Business In February 2016, the FASB issued ASU 2016-02, Leases In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, The Company will adopt the standard as of January 1, 2018, using the modified retrospective transition method, and has evaluated the impact of the adoption on its consolidated financial statements and related disclosures. Under the modified retrospective transition method, the Company will calculate and record the cumulative effect of adopting the new standard at January 1, 2018, in the Company’s Quarterly Report on Form 10-Q for the first quarter of 2018. The Company has evaluated the changes from adopting this new standard on its financial reporting, disclosures and its various revenue streams. The Company will recognize revenue over time on most of its (i) contracts that are covered by current contract accounting standards and (ii) fixed-price type contracts that require it to perform services that are not related to the production of tangible assets by using cost inputs to measure progress toward the completion of its performance obligations. This method is similar to the POC cost-to-cost method currently used on the majority of the Company’s contracts covered by current contract accounting standards. Accordingly, the adoption of this standard will primarily impact certain (i) contracts currently covered by contract accounting standards that currently recognize revenue using the POC units-of-delivery method and (ii) fixed-price type contracts for services that are not related to the production of tangible assets that currently recognize revenue on a straight-line basis over the contractual service period. Based on contracts in process at December 31, 2017, the Company expects to record, upon adoption of ASC 606, a net increase to shareholders’ equity ranging from $10 million to $20 million, which includes the acceleration of net sales ranging from $350 million to $400 million and the related cost of sales. The adjustment to retained earnings primarily relates to contracts currently accounted for under the POC units-of-delivery method, which would have been recognized under ASC 606 earlier in the performance period as costs were incurred, as opposed to when the units were delivered under ASC 605. The Company will make certain presentation changes on its consolidated balance sheets to comply with the new standard. The components of contracts in process will be presented separately as contract assets or inventories based on the amounts of unbilled revenue or the cost of inventories, respectively. Advance payments and billings in excess of costs and deferred revenue, which is currently classified in other current liabilities, will be combined and presented as contract liabilities. The Company expects that the adoption of ASC 606 will result in a decrease in inventories and an increase in contract assets (unbilled receivables) primarily to reflect the impact of converting contracts currently applying the units-of-delivery method to the cost input method for recognizing revenue and profit. Additionally, the Company will reclassify approximately $50 million of capitalized contract fulfillment costs from inventories to other assets upon adoption of ASC 606. The Company accounts for contract fulfillment costs as a contract cost under current accounting standards, and capitalizes them to inventoried contract costs if they relate to contracts that are accounted for under the POC units of delivery method of revenue recognition. The Company expects the net impact of these adjustments will decrease its current assets and current liabilities each by approximately 2%. Additionally, the Company has updated its accounting policies affected by this standard, redesigned its internal controls over financial reporting related to the standard, and determined the extent of the expanded disclosure requirements. The Company has substantially completed the evaluation of the impact of the accounting and disclosure changes on its business processes, controls and systems and has implemented the necessary changes to such business processes, controls and systems. Other accounting standard updates effective for interim and annual periods beginning after December 31, 2017 are not expected to have a material impact on the Company’s financial position, results of operations or cash flows.

Summary of Significant Accoun35

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Changes in Company's Accrued Product Warranty Costs	The table below presents the changes in the Company’s accrued product warranty costs. Year Ended December 31, 2017 2016 (in millions) Accrued product warranty costs (1) : Balance at January 1 $ 109 $ 105 Acquisitions during this period 3 3 Accruals for product warranties issued during the period 52 51 Foreign currency translation adjustments 1 (1 ) Settlements made during the period (66 ) (49 ) Balance at December 31 $ 99 $ 109 (1) Warranty obligations incurred in connection with long-term production contracts that are accounted for under the POC cost-to-cost method are included within the contract estimates at completion and are excluded from the above amounts. The balances above include both the current and non-current amounts.

Acquisitions, Divestitures an36

Acquisitions, Divestitures and Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Acquisitions, Divestitures and Discontinued Operations [Abstract]
Net Sales and Income Before Income Taxes for Kigre, G-Air, Doss Aviation, Adaptive Methods, Open Water Power, OceanServer and ETD Business	Net sales and income before income taxes for Kigre, G-Air, Doss Aviation, Adaptive Methods, Open Water Power, OceanServer and the ETD business, included in L3’s consolidated statement of operations for the year ended December 31, 2017, are presented in the table below. Year Ended December 31, 2017 (in millions) Net sales $ 80 Loss before income taxes $ (1 )
Unaudited Pro Forma Statements of Operations Data	The following unaudited pro forma Statements of Operations data present the combined results of the Company and its business acquisitions completed during the years ended December 31, 2017 and 2016 assuming that the business acquisitions completed during 2017 and 2016 had occurred on January 1, 2016 and January 1, 2015, respectively. The unaudited pro forma Statements of Operations data below include adjustments for additional amortization expense related to acquired intangible assets and depreciation assuming the 2017 and 2016 acquisitions had occurred on January 1, 2016 and January 1, 2015, respectively. Year Ended December 31, 2017 2016 (in millions, except per share data) Pro forma net sales $ 9,638 $ 9,493 Pro forma income from continuing operations attributable to L3 $ 753 $ 621 Pro forma net income attributable to L3 $ 677 $ 712 Pro forma diluted earnings per share from continuing operations $ 9.46 $ 7.88 Pro forma diluted earnings per share $ 8.51 $ 9.03
Components of Pre-tax (Loss) Gain Recognized, Proceeds Received and Net Sales Included in Continuing Operations From Business Divestitures	The table below presents pre-tax (loss) gain recognized, the proceeds received and net sales included in continuing operations from these divestitures. Year Ended December 31, 2017 Pre-Tax (Loss) gain Proceeds Received Net Sales (in millions) Aviation Jet Services divestiture $ (5 ) $ 1 $ 1 Coleman divestiture (3 ) 17 9 Display Product Line divestiture 4 7 — Total $ (4 ) $ 25 $ 10 The table below presents pre-tax loss recognized, the proceeds received and net sales included in continuing operations from these business divestitures. Year Ended December 31, 2015 Pre-Tax Loss Proceeds Received Net Sales (in millions) MSI divestiture $ (17 ) $ 318 $ 185 BSI divestiture (4 ) 26 7 Tinsley Product Line divestiture (8 ) 4 9 Klein divestiture (2 ) 10 8 Total $ (31 ) $ 358 $ 209
Net Sales and Income Before Income Taxes for Aviation Jet Services, Coleman, the Display Product Line, MSI, BSI, the Tinsley Product Line and Klein	Net sales and income before income taxes for Aviation Jet Services, Coleman, the Display Product Line, MSI, BSI, the Tinsley Product Line and Klein, included in L3’s consolidated statements of operations, are presented in the table below on an aggregate basis, and are included in income from continuing operations for all periods presented. Year Ended December 31, 2017 2016 2015 (in millions) Net sales $ 10 $ 59 $ 259 Income before income taxes $ 2 $ 8 $ 8
Assets Held for Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Major Classes of Assets and Liabilities Included as Discontinued Operations/Held For Sale	The major classes of assets and liabilities included as held for sale related to the Aerostructures businesses are presented in the table below. December 31, 2017 (in millions) Assets Billed receivables $ 14 Contracts in process 33 Total current assets 47 Property, plant and equipment, net 34 Goodwill 52 Indentifiable intangible assets 2 Total assets classified as held for sale $ 135 Liabilities Accounts payable, trade $ 3 Accrued employment costs 2 Accrued expenses 3 Other current liabilities 5 Total current liabilities 13 Deferred income taxes 4 Total liabilities classified as held for sale $ 17
Vertex Aerospace and NSS [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Statement of Operations Data Classified as Discontinued Operations	The table below presents the statements of operations data for Vertex Aerospace and NSS. The amounts presented in discontinued operations include allocated interest expenses for debt not directly attributable or related to L3’s other operations. Interest expense was allocated in accordance with the accounting standards for discontinued operations and were based on the ratio of their net assets to the sum of: (1) total L3 consolidated net assets and (2) L3 consolidated total debt. Year Ended December 31, 2017 2016 2015 (in millions) Net sales $ 1,429 $ 1,402 $ 2,334 Cost of sales (1,342 ) (1,357 ) (2,259 ) (Loss) gain related to business divestiture (1) (1 ) 64 — Goodwill impairment charges (2) (187 ) — (909 ) Operating (loss) income from discontinued operations (101 ) 109 (834 ) Interest expense allocated to discontinued operations (2 ) (5 ) (26 ) (Loss) income from discontinued operations before income taxes (103 ) 104 (860 ) Income tax benefit (expense) 27 (13 ) 128 (Loss) income from discontinued operations net of income taxes $ (76 ) $ 91 $ (732 ) (1) For the year ended December 31, 2017, the Company recognized $1 million of trailing expenses related to the sale of NSS. The year ended December 31, 2016 included a gain of $64 million (before and after income taxes) on the sale of NSS. (2) Due to a decline in estimated fair value, the Company recorded goodwill impairment charges for the years ended December 31, 2017 and 2015. The impairment charge of $187 million recorded during 2017 relates to Vertex Aerospace. The impairment charge of $909 million recorded during 2015 consists of: (i) $571 million related to NSS and (ii) $338 million related to Vertex Aerospace.
Vertex Aerospace [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Major Classes of Assets and Liabilities Included as Discontinued Operations/Held For Sale	December 31, 2017 December 31, 2016 (in millions) Assets Current assets $ 284 $ 271 Property, plant and equipment, net 13 14 Goodwill — 187 Other Intangible Assets 7 9 Other assets 2 — Total assets of discontinued operations $ 306 $ 481 Liabilities Accounts payable, trade $ 63 $ 16 Other current liabilities 131 160 Current liabilities 194 176 Long-term liabilities 32 59 Total liabilities of discontinued operations $ 226 $ 235

Contracts in Process (Tables)

Contracts in Process (Tables)	12 Months Ended
	Dec. 31, 2017
Contracts in Process [Abstract]
Components of Contracts in Process	The unbilled contract receivables, inventoried contract costs and unliquidated progress payments principally relate to contracts with the U.S. Government and prime contractors or subcontractors of the U.S. Government. December 31, 2017 2016 (in millions) Unbilled contract receivables, gross $ 1,874 $ 1,890 Unliquidated progress payments (761 ) (827 ) Unbilled contract receivables, net 1,113 1,063 Inventoried contract costs, gross 891 998 Unliquidated progress payments (71 ) (203 ) Inventoried contract costs, net 820 795 Total contracts in process $ 1,933 $ 1,858
General and Administrative, Independent Research and Development and Bid and Proposal Costs	The table below presents a summary of G&A, IRAD and B&P costs included in inventoried contract costs and the changes to them, including amounts charged to cost of sales by the Company’s U.S. Government contractor businesses for the periods presented. Year Ended December 31, 2017 2016 2015 (in millions) Amounts included in inventoried contract costs at beginning of the year $ 173 $ 137 $ 114 Contract costs incurred: IRAD and B&P 333 304 280 Other G&A (1) 842 749 742 Total 1,175 1,053 1,022 Amounts charged to cost of sales (1,179 ) (1,017 ) (999 ) Amounts included in inventoried contract costs at end of the year $ 169 $ 173 $ 137 (1) Amounts include severance and restructuring-related costs of $91 million, $13 million and $14 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Selling, General and Administrative Expenses and Research and Development Expenses	The table below presents a summary of selling, general and administrative expenses and research and development expenses for the Company’s commercial businesses, which are expensed as incurred and included in cost of sales on the consolidated statements of operations. Year Ended December 31, 2017 2016 2015 (in millions) Selling, general and administrative expenses $ 278 $ 223 $ 261 Research and development expenses 63 54 52 Total $ 341 $ 277 $ 313

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventories [Abstract]
Inventories at Lower of Cost or Realizable Value	The table below presents the components of inventories at the lower of cost (first-in, first-out or average cost) or realizable value. December 31, 2017 2016 (in millions) Raw materials, components and sub-assemblies $ 184 $ 165 Work in process 98 106 Finished goods 107 59 Total $ 389 $ 330

Goodwill and Identifiable Int39

Goodwill and Identifiable Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Identifiable Intangible Assets [Abstract]
Changes in Goodwill by Segment	The table below presents the changes in goodwill allocated to the Company’s reporting units in each reportable segment. Electronic Systems Aerospace Systems Communication Systems Sensor Systems Consolidated Total (in millions) December 31, 2015 Goodwill $ 2,445 $ 1,167 $ 1,038 $ 1,549 $ 6,199 Accumulated impairment losses (43 ) — (35 ) (26 ) (104 ) 2,402 1,167 1,003 1,523 6,095 Business acquisitions (1) 287 — 20 28 335 Foreign currency translation adjustments (45 ) 7 — (18 ) (56 ) December 31, 2016 Goodwill 2,687 1,174 1,058 1,559 6,478 Accumulated impairment losses (43 ) — (35 ) (26 ) (104 ) 2,644 1,174 1,023 1,533 6,374 Business acquisitions (1) 131 — — 81 212 Business divestitures (2) (12 ) — — — (12 ) Foreign currency translation adjustments 60 14 — 19 93 Assets held for sale (3) (10 ) (42 ) — — (52 ) December 31, 2017 Goodwill 2,856 1,146 1,058 1,659 6,719 Accumulated impairment losses (43 ) — (35 ) (26 ) (104 ) $ 2,813 $ 1,146 $ 1,023 $ 1,633 $ 6,615 (1) For the year ended December 31, 2017, business acquisitions for the Electronic Systems segment included the acquisitions of the ETD, Doss Aviation and G-Air businesses and the purchase price allocation adjustments for the MacH and Aerosim business acquisitions. Business acquis i tions for the Sensor Systems segment included primarily the Adaptive Methods, Open Water Power, OceanServer and Kigre business acquisitions. For the year ended December 31, 2016, business acquis i tions for the Electronic Systems segment included the acquisitions of the MacH and Aerosim businesses and the final purchase price allocation for L3 CTC business acquisition. Business acquis i tion for the Communication Systems segment included the ATM business acquisition. Business acquis i tions for the Sensor Systems segment included the Micreo business acquisition and the final purchase price allocation for the L3 ForceX business acquisition. (2) The decrease for the Electronic Systems segment was due to the divestitures of Coleman and Aviation Jet Services during the quarterly period ended March 31, 2017. (3) The Aerostructures businesses from the Company’s Aerospace Systems segment are classified as held for sale as of December 31, 2017 .
Identifiable Intangible Assets	The table below presents information for the Company’s identifiable intangible assets that are subject to amortization and indefinite-lived intangible assets. December 31, 2017 December 31, 2016 Weighed Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount (in years) (in millions) Customer contractual relationships 14 $ 393 $ 257 $ 136 $ 360 $ 229 $ 131 Technology 10 189 114 75 191 102 89 Other 15 29 14 15 21 12 9 Total subject to amortization 611 385 226 572 343 229 IPR&D indefinite 66 — 66 — — — Total $ 677 $ 385 $ 292 $ 572 $ 343 $ 229
Amortization Expense	The table below presents amortization expense recorded by the Company for its identifiable intangible assets. Year Ended December 31, 2017 2016 2015 (in millions) Amortization expense $ 43 $ 33 $ 32
Estimated Amortization Expense	Based on gross carrying amounts at December 31, 2017, the Company’s estimate of amortization expense for identifiable intangible assets for the years ending December 31, 2018 through 2022 is presented in the table below. Year Ending December 31, 2018 2019 2020 2021 2022 (in millions) Estimated amortization expense $ 44 $ 39 $ 31 $ 25 $ 21

Other Current Liabilities and40

Other Current Liabilities and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2017
Other Current Liabilities and Other Liabilities [Abstract]
Other Current Liabilities	The table below presents the components of other current liabilities. December 31, 2017 2016 (in millions) Other Current Liabilities: Accrued product warranty costs $ 69 $ 68 Estimated costs in excess of estimated contract value to complete contracts in process in a loss position 63 70 Accrued interest 43 43 Deferred revenues 38 34 Estimated contingent purchase price payable for acquired businesses (see Note 3) 11 — Accruals for pending and threatened litigation 3 14 Other 140 163 Total other current liabilities $ 367 $ 392
Other Liabilities	The table below presents the components of other liabilities. December 31, 2017 2016 (in millions) Other Liabilities: Non-current income taxes payable (see Note 16) $ 164 $ 121 Deferred compensation 49 47 Accrued product warranty costs 30 41 Accrued workers’ compensation 23 25 Estimated contingent purchase price payable for acquired businesses (see Note 3) 20 29 Notes payable and capital lease obligations 16 10 Other 96 83 Total other liabilities $ 398 $ 356

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	The table below presents the components of property, plant and equipment. December 31, 2017 2016 (in millions) Land $ 34 $ 53 Buildings and improvements 404 437 Machinery, equipment, furniture and fixtures 1,959 1,857 Leasehold improvements 376 337 Gross property, plant and equipment 2,773 2,684 Accumulated depreciation and amortization (1,663 ) (1,577 ) Property, plant and equipment, net $ 1,110 $ 1,107

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt [Abstract]
Components of Debt and Reconciliation to Carrying Amount of Current and Long-Term Debt	The components of debt and a reconciliation to the carrying amount of long-term debt is presented in the table below. December 31, 2017 2016 (in millions) Borrowings under Revolving Credit Facility (1) $ — $ — 5.20% Senior Notes due 2019 1,000 1,000 4.75% Senior Notes due 2020 800 800 4.95% Senior Notes due 2021 650 650 3.95% Senior Notes due 2024 350 350 3.85% Senior Notes due 2026 550 550 Principal amount of long-term debt 3,350 3,350 Unamortized discounts (7 ) (8 ) Deferred debt issue costs (13 ) (17 ) Carrying amount of long-term debt $ 3,330 $ 3,325 (1) During 2017, L3's aggregate borrowings and repayments under the Credit Facility were $1,328 million. L3 had the full availability of its $1 billion Credit Facility at December 31, 2017 and December 31, 2016.
Information Regarding Outstanding Senior Subordinated Notes	The Senior Notes are unsecured senior obligations of L3. The terms of each outstanding Senior Note are presented in the table below. Note Date of Issuance Amount Issued Discount (1) Net Cash Proceeds Effective Interest Rate Redemption at Treasury Rate (2)(3) (in millions) 5.20% Senior Notes due October 15, 2019 October 2, 2009 $ 1,000 $ 4 $ 987 5.25 % 30 bps 4.75% Senior Notes due May 21, 2010 $ 800 $ 3 $ 790 4.79 % 25 bps 4.95% Senior Notes due February 15, 2021 February 7, 2011 $ 650 $ 4 $ 639 5.02 % 25 bps 3.95% Senior Notes due May 28, 2014 $ 650 $ 3 $ 641 4.02 % 20 bps 3.85% Senior Notes due December 15, 2026 December 5, 2016 $ 550 $ 3 $ 542 3.91 % 25 bps (1) Bond discounts are recorded as a reduction to the principal amount of the notes and are amortized as interest expense over the term of the notes. (2) The Senior Notes maturing in 2019 and 2020 may be redeemed at any time prior to their maturity and the Senior Notes maturing in 2021, 2024 and 2026 may be redeemed at any time prior to November 15, 2020, February 28, 2024 and September 15, 2026, respectively, (three months prior to their maturity) at the option of L3, in whole or in part, at a redemption price equal to the greater of: (1) 100% of the principal amount, or (2) the present value of the remaining principal and interest payments discounted to the date of redemption, on a semi-annual basis, at the Treasury Rate (as defined in the indentures governing the Senior Notes), plus the spread indicated in the table above. In addition, if the Senior Notes maturing in 2021, 2024 and 2026 are redeemed at any time on or after November 15, 2020, February 28, 2024 and September 15, 2026, respectively, the redemption price would be equal to 100% of the principal amount. (3) Upon the occurrence of a change in control (as defined in the indentures governing the Senior Notes), each holder of the notes will have the right to require L3 to repurchase all or any part of such holder’s notes at an offer price in cash equal to 101% of the aggregate principal amount plus accrued and unpaid interest, if any, to the date of purchase.
Repurchases, Redemptions and Maturities of Senior Notes	The repurchases, redemptions and maturities of Senior Notes are presented in the table below. Note Settlement Type Date Settled Aggregate Amount Debt Retirement Charge Cash Payments (in millions) 1.50% Senior Notes due 2017 (1) Redemption December 30, 2016 $ 350 $ 2 $ 351 3.95% Senior Notes due 2016 Maturity November 15, 2016 $ 200 $ — $ 200 3.95% Senior Notes due 2016 (2) Redemption May 20, 2016 $ 300 $ 5 $ 305 3.95% Senior Notes due 2024 Tender Offer December 22, 2015 $ 300 $ 1 $ 297 (1) The 1.50% Senior Notes due 2017 were redeemed at a price equal to 100.323% of the principal amount thereof, plus accrued and unpaid interest to the redemption date. Interest ceased to accrue on and after the redemption date. (2) The 3.95% Senior Notes due 2016 were redeemed at a price equal to 101.475% of the principal amount thereof, plus accrued and unpaid interest. Interest ceased to accrue on and after May 20, 2016, and the only remaining right of holders of such Notes was to receive payment of the redemption price and accrued interest.

Accumulated Other Comprehensi43

Accumulated Other Comprehensive (Loss) Income (AOCI) (Tables)	12 Months Ended
	Dec. 31, 2017
Accumulated Other Comprehensive (Loss) Income (AOCI) [Abstract]
Summary of AOCI Balances Including Amounts Reclassified from AOCI into Net Income	The changes in the AOCI balances, including amounts reclassified from AOCI into net income, are presented in the table below. Foreign currency translation Unrealized (losses) gains on hedging instruments Unrecognized (losses) gains and prior service cost, net Total accumulated other comprehensive loss (in millions) Balance at December 31, 2014 $ 19 $ (5 ) $ (598 ) $ (584 ) Other comprehensive (loss) income before reclassifications, net of tax (161 ) (15 ) 81 (95 ) Amounts reclassified from AOCI, net of tax 41 12 52 105 Net current period other comprehensive (loss) income (120 ) (3 ) 133 10 Balance at December 31, 2015 $ (101 ) $ (8 ) $ (465 ) $ (574 ) Other comprehensive (loss) income before reclassifications, net of tax (77 ) 3 (119 ) (193 ) Amounts reclassified from AOCI, net of tax — 11 30 41 Net current period other comprehensive (loss) income (77 ) 14 (89 ) (152 ) Balance at December 31, 2016 $ (178 ) $ 6 $ (554 ) $ (726 ) Other comprehensive income (loss) before reclassifications, net of tax 124 7 (137 ) (6 ) Amounts reclassified from AOCI, net of tax — (4 ) 45 41 Net current period other comprehensive income (loss) 124 3 (92 ) 35 Balance at December 31, 2017 $ (54 ) $ 9 $ (646 ) $ (691 )
Summary of Amounts Reclassified from AOCI into Net Income	Further details regarding the amounts reclassified from AOCI into net income are presented in the table below. Amount Reclassified from AOCI (a) Affected Line Item in the Audited Consolidated Statements of Operations Year Ended December 31, Details About AOCI Components 2017 2016 2015 (in millions) Foreign currency translation adjustments: MSI divestiture $ — $ — $ (41 ) Loss related to business divestitures — — (41 ) Income from continuing operations before income taxes $ — $ — $ (41 ) Income from continuing operations Gain (loss) on hedging instruments: MSI divestiture $ — $ — $ (2 ) Loss related to business divestitures Other 5 (13 ) (16 ) Cost of sales-products 5 (13 ) (18 ) Income from continuing operations before income taxes (1 ) 2 6 Provision for income taxes $ 4 $ (11 ) $ (12 ) Income from continuing operations Amortization of defined benefit pension and postretirement items: MSI divestiture $ — $ — $ (14 ) Loss related to business divestitures Net loss (59 ) (48 ) (67 ) (b) (59 ) (48 ) (81 ) Income from continuing operations before income taxes 14 18 29 Provision for income taxes $ (45 ) $ (30 ) $ (52 ) Income from continuing operations Total reclassification for the period $ (41 ) $ (41 ) $ (105 ) Income from continuing operations (a) Amounts in parentheses indicate charges to the consolidated statements of operations. (b) Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 19 for additional information).

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Measurements [Abstract]
Company's Assets and Liabilities at Fair Value on Recurring Basis	The following table presents the fair value hierarchy level for each of the Company’s assets and liabilities that are measured and recorded at fair value on a recurring basis. December 31, 2017 December 31, 2016 Description Level 1 (1) Level 2 (2) Level 3 (3) Level 1 (1) Level 2 (2) Level 3 (3) (in millions) Assets Cash equivalents $ 310 $ — $ — $ 104 $ — $ — Derivatives (foreign currency forward contracts) — 11 — — 12 — Total assets $ 310 $ 11 $ — $ 104 $ 12 $ — Liabilities Derivatives (foreign currency forward contracts) $ — $ 1 $ — $ — $ 6 $ — Contingent consideration (4) — — 31 — — 29 Total liabilities $ — $ 1 $ 31 $ — $ 6 $ 29 (1) Level 1 is based on quoted market prices available in active markets for identical assets or liabilities as of the reporting date. Cash equivalents are primarily held in registered money market funds, which are valued using quoted market prices. (2) Level 2 is based on pricing inputs other than quoted prices in active markets, which are either directly or indirectly observable. The fair value is determined using a valuation model based on observable market inputs, including quoted foreign currency forward exchange rates and consideration of non-performance risk. (3) Level 3 is based on pricing inputs that are not observable and not corroborated by market data. (4) The contingent consideration liability represents the future potential earn-out payments relating to the MacH and Open Water Power acquisitions. The fair value of the MacH contingent consideration liability is based on a Monte Carlo Simulation of the aggregate revenue of MacH for the three-year period ending December 31, 2019. The significant unobservable inputs used in calculating the fair value of the MacH contingent consideration include: (i) projected revenues of the MacH acquired business, (ii) company specific risk premium, which is a component of the discount rate applied to the revenue projections and (iii) volatility. The fair value of the Open Water Power contingent consideration liability is based on the Scenario-Based Method of the income approach using post-acquisition milestone achievements of Open Water Power through December 31, 2020. The significant unobservable inputs used in calculating the fair value of the Open Water Power contingent consideration include: (i) timing of achieving the milestones associated with the contingent consideration arrangement, (ii) probabilities of achieving each milestone and (iii) discount rate. The fair value of the contingent consideration for potential earn-out payments is reassessed quarterly, including an analysis of the significant inputs used in the evaluation, as well as the accretion of the present value discount. Changes are reflected within cost of sales in the consolidated statements of operations.
Changes to Contingent Consideration Obligations	The table below presents the changes to contingent consideration obligations during the year ended December 31, 2017. December 31, 2017 (in millions) Balance at beginning of period $ 29 Acquisitions 14 Changes in fair value of contingent consideration, net (12 ) Balance at end of period $ 31

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Financial Instruments [Abstract]
Carrying Amounts and Estimated Fair Values of Company's Long-Term Debt and Foreign Currency Forward Contracts	The carrying amounts and estimated fair values of the Company’s other financial instruments are presented in the table below. December 31, 2017 December 31, 2016 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value (in millions) Senior Notes (1) $ 3,330 $ 3,502 $ 3,325 $ 3,526 Foreign currency forward contracts (2) $ 10 $ 10 $ 6 $ 6 (1) The Company measures the fair value of its Senior Notes using Level 2 inputs based primarily on current market yields for its existing debt traded in the secondary market. (2) The Company measures the fair values of foreign currency forward contracts based on forward exchange rates. See Note 14 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative Financial Instrume46

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Financial Instruments [Abstract]
Notional Amounts of Company's Outstanding Foreign Currency Forward Contracts by Currency	The table below presents the notional amounts of the Company’s outstanding foreign currency forward contracts by currency at December 31, 2017. Currency Notional Amount (in millions) U.S. dollar $ 108 Canadian dollar 100 Euro 84 British pound 15 Total $ 307
Location of Company's Derivative Instruments Recorded at Fair Value on the Consolidated Balance Sheets	The table below presents the location of the Company’s derivative instruments recorded at fair value on the consolidated balance sheets. December 31, 2017 December 31, 2016 Other Current Assets Other Assets Other Current Liabilities Other Liabilities Other Current Assets Other Assets Other Current Liabilities Other Liabilities (in millions) Derivatives designated as hedging instruments: Foreign currency forward contracts (1) $ 11 $ — $ 1 $ — $ 10 $ 2 $ 6 $ — Total derivative instruments $ 11 $ — $ 1 $ — $ 10 $ 2 $ 6 $ — (1) See Note 12 for a description of the fair value hierarchy related to the Company's foreign currency forward contracts.

L3's Earnings Per Share (Tables

L3's Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
L3's Earnings Per Share [Abstract]
Reconciliation of Basic and Diluted Earnings per Share (EPS)	A reconciliation of basic and diluted earnings per share (EPS) is presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions, except per share data) Reconciliation of net income (loss): Net income (loss) $ 693 $ 724 $ (225 ) Net income from continuing operations attributable to noncontrolling interests (16 ) (14 ) (15 ) Net income (loss) attributable to L3’s common shareholders $ 677 $ 710 $ (240 ) Earnings (loss) attributable to L3’s common shareholders: Continuing operations $ 753 $ 619 $ 492 Discontinued operations, net of income tax (76 ) 91 (732 ) Net income (loss) attributable to L3’s common shareholders $ 677 $ 710 $ (240 ) Earnings (loss) per share attributable to L3’s common shareholders: Basic: Weighted average common shares outstanding 78.0 77.4 80.7 Basic earnings (loss) per share: Continuing operations $ 9.65 $ 7.99 $ 6.10 Discontinued operations, net of income tax (0.97 ) 1.18 (9.07 ) Net income (loss) $ 8.68 $ 9.17 $ (2.97 ) Diluted: Common and potential common shares: Weighted average common shares outstanding 78.0 77.4 80.7 Effect of dilutive securities 1.6 1.4 1.2 Common and potential common shares 79.6 78.8 81.9 Diluted earnings (loss) per share: Continuing operations $ 9.46 $ 7.86 $ 6.01 Discontinued operations, net of income tax (0.95 ) 1.15 (8.94 ) Net income (loss) $ 8.51 $ 9.01 $ (2.93 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Taxes [Abstract]
Income from Continuing Operations Before Income Taxes	Income from continuing operations before income taxes is summarized in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Domestic $ 649 $ 608 $ 509 Foreign 222 196 130 Income from continuing operations before income taxes $ 871 $ 804 $ 639
Components of Current and Deferred Portions of Provision for Income Taxes on Continuing Operations	The components of the Company’s current and deferred portions of the provision for income taxes on continuing operations are presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Current income tax provision: Federal $ 44 $ 88 $ 81 State and local 10 8 7 Foreign 56 48 26 Subtotal 110 144 114 Deferred income tax provision/(benefit): Federal (16 ) 25 9 State and local 6 2 7 Foreign 2 — 2 Subtotal (8 ) 27 18 Total provision for income taxes $ 102 $ 171 $ 132
Reconciliation of Statutory Federal Income Tax Rate to Effective Income Tax Rate on Continuing Operations	A reconciliation of the statutory federal income tax rate to the effective income tax rate on continuing operations of the Company is presented in the table below. Year Ended December 31, 2017 2016 2015 Statutory federal income tax rate 35.0 % 35.0 % 35.0 % State and local income taxes, net of federal income tax benefit 2.0 2.0 2.0 Foreign income taxes (6.7 ) (3.0 ) (7.1 ) Manufacturing benefits (1.4 ) (2.2 ) (2.2 ) Research and experimentation and other tax credits (4.1 ) (4.6 ) (6.5 ) Resolution of tax contingencies (0.4 ) (3.1 ) (1.4 ) Tax deductible dividends (0.9 ) (1.0 ) (1.2 ) Equity compensation - excess income tax benefits (2.3 ) (2.1 ) — Goodwill impairment — — 1.9 Tax Reform (9.1 ) — — Other, net (0.4 ) 0.3 0.2 Effective income tax rate on continuing operations 11.7 % 21.3 % 20.7 %
Components of Net Deferred Tax Assets and Liabilities	The significant components of the Company’s net deferred tax assets and liabilities are presented in the table below. December 31, 2017 2016 (in millions) Deferred tax assets: Inventoried costs $ 44 $ 53 Compensation and benefits 94 139 Pension and postretirement benefits 281 413 Loss carryforwards 12 19 Tax credit carryforwards 5 6 Other 57 87 Deferred tax assets 493 717 Less: valuation allowance (10 ) (12 ) Deferred tax assets, net of valuation allowance 483 705 Deferred tax liabilities: Goodwill and other intangible assets $ (514 ) $ (722 ) Income recognition on contracts in process (24 ) (22 ) Property, plant and equipment (59 ) (93 ) Other (41 ) (55 ) Deferred tax liabilities (638 ) (892 ) Total deferred tax liabilities, net of valuation allowance $ (155 ) $ (187 )
Classification of Deferred Tax Assets and Liabilities	The classification of the Company’s deferred tax assets and liabilities are presented in the table below. December 31, 2017 2016 (in millions) Non-current deferred tax assets $ 3 $ 2 Non-current deferred tax liabilities (158 ) (189 ) Total net deferred tax liabilities $ (155 ) $ (187 )
Summary of Loss and Tax Credit Carryforwards	The following table presents the Company’s loss and tax credit carryforwards at December 31, 2017 on a tax return basis. The Company has established a valuation allowance as indicated in those instances in which it does not believe that it is more likely than not it will generate sufficient taxable income, of the appropriate character and in the applicable subsidiary, to utilize the carryforwards. Year Ended December 31, 2017 Carryforwards Valuation Allowances Gross Tax Effected Gross Tax Effected Expiration Periods (in millions) Federal net operating loss carryforwards 29 6 (5 ) (1 ) 2026-2036 Foreign net operating loss carryforwards 12 3 (6 ) (2 ) Indefinite State net operating loss carryforwards 160 3 (135 ) (2 ) 2018-2037 Total loss carryforwards $ 12 $ (5 ) State tax credit carryforwards 6 5 (5 ) (4 ) 2018-2032 Total tax credit carryforwards $ 5 $ (4 )
Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties	At December 31, 2017, the total amount of unrecognized tax benefits was $178 million, $157 million of which would reduce the effective income tax rate, if recognized. A reconciliation of the change in unrecognized income tax benefits, excluding potential interest and penalties, is presented in the table below. 2017 2016 2015 (in millions) Balance at January 1 $ 110 $ 124 $ 150 Additions for tax positions related to the current year 14 16 14 Additions for tax positions related to prior years 66 2 2 Reductions for tax positions related to prior years (4 ) (24 ) (34 ) Reductions for tax positions related to settlements with taxing authorities — (1 ) (1 ) Reduction for tax positions related to prior years as a result of a lapse of statute of limitations (8 ) (7 ) (7 ) Balance at December 31 $ 178 $ 110 $ 124

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Stock-Based Compensation [Abstract]
Stock-Based Compensation Expense by Form of Award	The Company’s stock-based compensation expense by form of award, including stock-based compensation recorded in discontinued operations related to Vertex Aerospace and NSS, is presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Stock options $ 7 $ 10 $ 9 Restricted stock units 43 35 38 Performance units 7 4 2 Total before income taxes 57 49 49 Income taxes (12 ) (18 ) (18 ) Total after income taxes 45 31 31 Less: Stock-based compensation recorded in discontinued operations, net of income taxes 1 1 1 Stock-based compensation recorded in continuing operations, net of income taxes $ 44 $ 30 $ 30
Company's Stock Option Activity and Changes	The table below presents a summary of the Company’s stock option activity at December 31, 2017 and changes during the year then ended. Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in thousands) (in years) (in millions) Number of shares under option: Outstanding at January 1, 2017 2,847.5 $ 99.54 6.1 $ 150 Options granted 470.5 174.53 Options exercised (521.3 ) 90.13 Options forfeited (97.8 ) 120.59 Outstanding at December 31, 2017 2,698.9 $ 113.67 5.7 $ 227 Vested and expected to vest at December 31, 2017 (1) 2,582.5 $ 110.21 5.5 $ 226 Exercisable at December 31, 2017 1,762.4 $ 95.80 4.5 $ 180 (1) Represents outstanding options reduced by expected forfeitures for options not fully vested.
Weighted Average Assumptions in Valuation Model	The weighted average assumptions used in the valuation model are presented in the table below. 2017 Grants 2016 Grants 2015 Grants Expected holding period (in years) 5.2 5.0 5.0 Expected volatility 19.9 % 21.3 % 21.4 % Expected dividend yield 2.0 % 2.8 % 2.4 % Risk-free interest rate 2.0 % 1.1 % 1.5 %
Company's Nonvested Restricted Stock Unit Awards and Changes	The table below presents a summary of the Company’s nonvested restricted stock unit awards at December 31, 2017 and changes during the year then ended. Number of Shares Weighted Average Grant Date Fair Value (in thousands) Nonvested balance at January 1, 2017 977.9 $ 119.55 Granted 305.6 169.23 Vested (318.4 ) 114.46 Forfeited (62.4 ) 134.56 Nonvested balance at December 31, 2017 902.7 $ 137.12
Company's Performance Unit Awards Based on Expected Performance	The table below presents a summary of the Company’s performance unit awards based on expected performance at December 31, 2017 and changes during the year then ended. Payable in Shares (EPS) Number of Units Weighted Average Grant Date Fair Value (in thousands) Outstanding at January 1, 2017 124.7 $ 120.83 Granted 33.9 168.80 Increase due to expected performance 29.7 146.89 Vested (48.4 ) 129.03 Forfeited (7.8 ) 121.06 Outstanding at December 31, 2017 132.1 $ 135.99

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies [Abstract]
Future Minimum Payments under Non-Cancelable Operating Leases	The following table presents future minimum payments under non-cancelable operating leases with initial or remaining terms in excess of one year at December 31, 2017. Real Estate Equipment Total (in millions) 2018 $ 101 $ 5 $ 106 2019 81 3 84 2020 106 2 108 2021 60 — 60 2022 57 — 57 Thereafter 236 — 236 Total minimum payments required 641 10 651 Sublease rentals under non-cancelable leases (9 ) — (9 ) Net minimum payments required $ 632 $ 10 $ 642

Pension and Other Postretirem51

Pension and Other Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Pension and Other Postretirement Benefits [Abstract]
Changes in Benefit Obligations, Plan Assets and Funded Status and Aggregate Balance Sheet Impact	The following table summarizes changes in the benefit obligations, the plan assets and funded status for all of the Company’s pension and postretirement benefit plans, as well as the aggregate balance sheet impact. Pension Plans Postretirement Benefit Plans 2017 2016 2017 2016 (in millions) Change in benefit obligation: Benefit obligation at the beginning of the year $ 3,758 $ 3,448 $ 177 $ 184 Service cost 112 108 2 2 Interest cost 142 135 5 6 Plan participants’ contributions 2 2 5 4 Amendments — 15 — (3 ) Actuarial loss (gain) 376 167 (13 ) (3 ) Foreign currency exchange rate changes 22 9 2 — Curtailments and special termination benefits 2 2 — — Benefits paid (186 ) (128 ) (13 ) (13 ) Benefit obligation at the end of the year $ 4,228 $ 3,758 $ 165 $ 177 Change in plan assets: Fair value of plan assets at the beginning of the year $ 2,721 $ 2,552 $ 60 $ 57 Actual return on plan assets 391 189 8 5 Employer contributions 97 97 7 7 Plan participants’ contributions 2 2 5 4 Foreign currency exchange rate changes 22 9 — — Benefits paid (186 ) (128 ) (13 ) (13 ) Fair value of plan assets at the end of the year $ 3,047 $ 2,721 $ 67 $ 60 Unfunded status at the end of the year $ (1,181 ) $ (1,037 ) $ (98 ) $ (117 ) Assets and (liabilities) recognized on the consolidated balance sheets consist of: Non-current assets $ 48 $ 37 $ — $ — Current liabilities (6 ) (6 ) (8 ) (8 ) Non-current liabilities (1,223 ) (1,068 ) (90 ) (109 ) $ (1,181 ) $ (1,037 ) $ (98 ) $ (117 )
Net Loss and Prior Service Cost Balances in Accumulated Other Comprehensive Loss Account	The table below summarizes the net loss and prior service cost balances at December 31, in the accumulated other comprehensive loss account, before related tax effects, for all of the Company’s pension and postretirement benefit plans. Pension Plans Postretirement Benefit Plans 2017 2016 2017 2016 (in millions) Net loss (gain) $ 1,035 $ 896 $ (3 ) $ (12 ) Prior service cost (credit) 10 14 (27 ) (4 ) Total amount recognized $ 1,045 $ 910 $ (30 ) $ (16 )
Pension Plans with an Accumulated Benefit Obligation in Excess of Fair Value of Plan Assets	The table below presents information for the pension plans with an ABO in excess of the fair value of plan assets at December 31, 2017 and 2016. Pension Plans 2017 2016 (in millions) Projected benefit obligation $ 3,875 $ 3,528 Accumulated benefit obligation $ 3,490 $ 3,192 Fair value of plan assets $ 2,651 $ 2,456
Weighted Average Assumptions Used to Determine Benefit Obligations	The table below summarizes the weighted average assumptions used to determine the benefit obligations for the Company’s pension and postretirement plans disclosed at December 31, 2017 and 2016. Pension Plans Postretirement Benefit Plans 2017 2016 2017 2016 Benefit obligations: Discount rate 3.78 % (1) 4.40 % (1) 3.59 % (2) 4.05 % (2) Rate of compensation increase 3.50 % (3) 3.50 % (3) (1) The weighted average discount rate assumptions used at December 31, 2017 and 2016 were comprised of separate assumptions determined by country of 3.81% and 4.45% for the U.S. based plans, respectively, and 3.39% and 3.79% for the Canadian based plans, respectively. (2) The weighted average discount rate assumptions used at December 31, 2017 and 2016 were comprised of separate assumptions determined by country of 3.63% and 4.11% for the U.S. based plans, respectively, and 3.33% and 3.64% for the Canadian based plans, respectively. (3) The weighted average rate of compensation increase assumptions were comprised of separate assumptions determined by country of 3.5% for both the U.S. based plans and Canadian based plans at December 31, 2017 and 2016.
Components of Net Periodic Benefit Cost	The following table summarizes the components of net periodic benefit cost for the Company’s pension and postretirement benefit plans for the years ended December 31, 2017, 2016 and 2015. Pension Plans Postretirement Benefit Plans 2017 2016 2015 2017 2016 2015 (in millions) Components of net periodic benefit cost: Service cost $ 112 $ 108 $ 123 $ 2 $ 2 $ 3 Interest cost 142 135 149 5 6 7 Expected return on plan assets (212 ) (200 ) (205 ) (4 ) (4 ) (5 ) Amortization of prior service cost (credits) 1 — 1 (1 ) (2 ) (2 ) Amortization of net loss (gains) 61 52 68 (2 ) (2 ) — Curtailment loss and special termination benefits (1) 6 2 3 — — — Net periodic benefit cost $ 110 $ 97 $ 139 $ — $ — $ 3 (1) During the year ended December 31, 2017, the curtailment loss and special termination benefits charge is primarily due to a pension curtailment charge in connection with the decision to discontinue future service accruals for substantially all salaried employee defined benefit plans effective January 1, 2019.
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss)	The following table summarizes the other changes in plan assets and benefit obligations recognized in other comprehensive income for the Company’s pension and postretirement benefit plans for the years ended December 31, 2017, 2016 and 2015. Pension Plans Postretirement Benefit Plans 2017 2016 2015 2017 2016 2015 (in millions) Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss): Net loss (gain) $ 200 $ 179 $ (132 ) $ (17 ) $ (4 ) $ (7 ) Prior service (cost) credit (4 ) 15 — — (2 ) — Amortization of net (loss) gain (61 ) (52 ) (68 ) 2 2 — Amortization of prior service (cost) credit (1 ) — (1 ) 1 2 2 Total recognized in other comprehensive income (loss) 134 142 (201 ) (14 ) (2 ) (5 ) Total recognized in net periodic benefit cost and other comprehensive income (loss) $ 244 $ 239 $ (62 ) $ (14 ) $ (2 ) $ (2 )
Amounts Expected to be Amortized from Accumulated OCI and Recognized as Components of Net Periodic Benefit Costs	The following table summarizes the amounts expected to be amortized from accumulated OCI and recognized as components of net periodic benefit costs during 2018. Pension Plans Postretirement Benefit Plans Total (in millions) Net loss (gain) $ 74 $ (3 ) $ 71 Prior service credit — (1 ) (1 ) $ 74 $ (4 ) $ 70
Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost	The table below summarizes the weighted average assumptions used to determine the net periodic benefit cost for the years ended December 31, 2017, 2016 and 2015. Pension Plans Postretirement Benefit Plans 2017 2016 2015 2017 2016 2015 Discount rates: Benefit obligation 4.40 % (1) 4.67 % (1) 4.14 % (1) 4.05 % (4) 4.22 % (4) 3.70 % (4) Service cost 4.55 % 4.83 % — (5) 4.21 % 4.37 % — (5) Interest cost 3.84 % 3.95 % — (5) 3.26 % 3.26 % — (5) Expected long-term return on plan assets 7.92 % (2) 7.92 % (2) 8.14 % (2) 7.43 % 7.42 % 7.65 % Rate of compensation increase 3.50 % (3) 3.50 % (3) 3.50 % (3) (1) The weighted average discount rate assumptions used for the years ended December 31, 2017, 2016, and 2015 were comprised of separate assumptions determined by country of 4.45%, 4.73% and 4.20% for the U.S. based plans and 3.79%, 3.93% and 3.90% for the Canadian based plans, respectively. (2) The weighted average expected long-term return on plan assets assumptions used were comprised of separate assumptions determined by country of 8.00% for each of the years ended December 31, 2017 and 2016 and 8.25% for the year ended December 31, 2015 for the U.S. based plans and 7.25% for the Canadian based plans for the years ended December 31, 2017, 2016 and 2015. (3) The weighted average rate of compensation increase assumptions used for the years ended December 31, 2017, 2016 and 2015 were comprised of separate assumptions determined by country of 3.50% for both the U.S and Canadian based plans. (4) The weighted average discount rate assumptions used for the years ended December 31, 2017, 2016 and 2015 were comprised of separate assumptions determined by country of 4.11%, 4.28% and 3.70% for the U.S. based plans and 3.64%, 3.74% and 3.70% for the Canadian based plans, respectively. (5) Not applicable as the Company changed to the spot rate approach beginning in 2016 as described above.
Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates	A one percentage point change in the assumed health care cost trend rates would have the following effects: 1 percentage point Increase Decrease (in millions) Effect on total service and interest cost $ — $ — Effect on postretirement benefit obligations $ 5 $ (4 )
Allowable Range for Each Major Category of the Plans' Assets and Weighted-Average Asset Allocations by Asset Category	The table below presents the allowable range for each major category of the plans’ assets at December 31, 2017 as well as the Company’s pension plan and postretirement benefit plan weighted-average asset allocations at December 31, 2017 and 2016, by asset category. U.S. Canada Asset Category Range 2017 2016 Range 2017 2016 Domestic equity (1) 30%-60% 47 % 55 % — 15 % 15 % International equity (2) 10%-20% 11 10 — 47 62 Total equities 45%-75% 58 65 40%-80% 62 77 Fixed income securities 20%-40% 28 22 — 25 13 Other, primarily cash and cash equivalents 0%-15% 7 5 — 13 10 Total fixed income securities and cash and cash equivalents NA NA NA 20%-60% 38 23 Real estate securities 0%-15% 7 8 — — — Total 100 % 100 % 100 % 100 % (1) Domestic equities for Canadian plans refers to equities of Canadian companies. (2) International equities for Canadian plans includes equities of U.S. companies. NA - Not applicable. The Company’s Master Pension Trust Investment Policy does not provide an allocation percentage range to fixed income securities and cash and cash equivalents.
Fair Value of the Company's Pension Plans' and Postretirement Benefit Plans' Assets	The table below presents the fair value of the Company’s pension plans’ assets by asset category segregated by level within the fair value hierarchy, as described below. U.S. Pension Plans’ Assets Canadian Pension Plans’ Assets Fair Value Measured at December 31, 2017 Fair Value Measured at December 31, 2017 Asset Category Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in millions) Equity securities (1) U.S. Equity $ 1,297 $ — $ — $ 1,297 $ 71 $ — $ — $ 71 International Equity 87 — — 87 105 — — 105 Fixed Income — Investment Grade (2) 329 205 — 534 — — — — Fixed Income — High Yield (3) — 219 — 219 — — — — Real Estate Investment Trusts (4) 196 — — 196 — — — — Other (5) — 198 — 198 8 37 — 45 Total assets at fair value $ 1,909 $ 622 $ — $ 2,531 $ 184 $ 37 $ — $ 221 Liabilities for unsettled trades, net (30 ) — Other investments measured at net asset value (6)(7) 203 122 Total $ 2,704 $ 343 U.S. Pension Plans’ Assets Canadian Pension Plans’ Assets Fair Value Measured at December 31, 2016 Fair Value Measured at December 31, 2016 Asset Category Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in millions) Equity securities (1) U.S. Equity $ 1,331 $ — $ — $ 1,331 $ 79 $ — $ — $ 79 International Equity 85 — — 85 104 — — 104 Fixed Income — Investment Grade (2) 255 159 — 414 — — — — Fixed Income — High Yield (3) — 136 — 136 — — — — Real Estate Investment Trusts (4) 193 — — 193 — — — — Other (5) — 114 — 114 5 27 — 32 Total assets at fair value $ 1,864 $ 409 $ — $ 2,273 $ 188 $ 27 $ — $ 215 Liabilities for unsettled trades, net (23 ) — Other investments measured at net asset value (6)(7) 171 85 Total $ 2,421 $ 300 (1) Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the New York Stock Exchange (NYSE), National Association of Securities Dealers Automated Quotations (NASDAQ), and various international exchanges. (2) Approximately 62% at December 31, 2017 and 2016 of U.S. plan assets that are invested in the Fixed Income — Investment Grade asset category consist of a mutual fund offered by a registered investment company (the Fund) and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy, as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 38% at December 31, 2017 and 2016 of U.S. plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2. (3) Fixed Income — High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs. (4) Real Estate Investment Trusts (REITs) consist of securities that trade on the major exchanges and invest directly in real estate, either through properties or mortgages. (5) Other consists primarily of: (1) money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit, and are classified as Level 2, and (2) cash, which is classified as Level 1. (6) In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value (NAV) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position. (7) All of the U.S. plans other investments measured using NAV at December 31, 2017 and 2016 and approximately 31% and 55% at December 31, 2017 and 2016, respectively, of the Canadian plans other investments measured using NAV consist of a regulated commingled equity trust fund, for which fair value is based on the NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund’s holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV. Approximately 69% and 45% at December 31, 2017 and 2016, respectively, of the Canadian plans other investments measured using NAV are invested in regulated commingled bond funds (the “Bond Funds”). As these Bond Funds do not trade in an active market, the fair value is based on NAVs calculated by fund managers based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs as a practical expedient to estimating fair value and classified as Level 2. Withdrawals are permitted monthly, with notice between 0 and 3 days of the transaction date, based on NAV. The table below presents the fair value of the Company’s postretirement benefit plans’ assets by asset category segregated by level within the fair value hierarchy, as described below. Postretirement Benefit Plans’ Assets Fair Value Measured at December 31, 2017 Fair Value Measured at December 31, 2016 Asset Category Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total (in millions) Equity securities (1) U.S. Equity $ 38 $ — $ — $ 38 $ 37 $ — $ — $ 37 International Equity 2 — — 2 1 — — 1 Fixed Income — Investment Grade (2) 10 3 — 13 8 3 — 11 Fixed Income — High Yield (3) — 3 — 3 — 2 — 2 Real Estate Investment Trusts (4) 3 — — 3 3 — — 3 Other (5) — 5 — 5 — 3 — 3 Total assets at fair value $ 53 $ 11 $ — $ 64 $ 49 $ 8 $ — $ 57 Other investments measured at net asset value (6)(7) 3 3 Total $ 67 $ 60 (1) Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the NYSE, NASDAQ, and various international exchanges. (2) Approximately 77 % and 73% at December 31, 2017 and 2016, respectively, of the postretirement benefit plan assets that are invested in the Fixed Income — Investment Grade asset category consist of the Fund and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 23 % and 27% at December 31, 2017 and 2016, respectively, of the postretirement benefit plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2. (3) Fixed Income — High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs. (4) REITs consist of securities that trade on the major exchanges and invest directly, either through properties or mortgages. (5) Other consists primarily of money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit. (6) In accordance with ASU 2015-07, certain investments that are measured at fair value using the NAV per share (or its equivalent)practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position. (7) All of the postretirement benefit plans other investments measured using NAV at December 31, 2017 and 2016 consist of a regulated commingled equity trust fund, which fair value is based on NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund’s holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV.
Estimated Future Benefit Payments	The following table presents expected pension and postretirement benefit payments and expected postretirement subsidies due to the Medicare Prescription Drug Improvement and Modernization Act of 2003, which reflect expected future service, as appropriate. Postretirement Benefits Pension Benefits Benefit Payments Subsidy Receipts (in millions) 2018 $ 158 $ 12 $ — 2019 165 12 — 2020 175 13 — 2021 185 13 — 2022 194 12 — Years 2023 - 2027 1,128 55 1
Cash Contributions and Expenses under Multi-Employer Benefit Plans	Under these plans, the Company contributed cash and recorded expenses for each of its individually significant plans and all of its other plans in aggregate as noted in the table below. EIN/Pension Plan Number Pension Protection Act Zone Status (1) FIP/RP (2) Status Pending/ Implemented Contributions by L3 (7) Surcharge Imposed Expiration Date of Collective- Bargaining Agreement Pension Fund 2017 2016 2017 2016 2015 IAM National Pension Fund 51-6031295/002 Green Green No $ 27 (3) $ 26 (4) $ 23 (4) No 4/29/2018 to (5) Other Pension Funds (6) — — — Total contributions $ 27 $ 26 $ 23 (1) A zone status rating of green indicates the plan is at least 80% funded. (2) Funding improvement plan or rehabilitation plan. (3) At the date the audited financial statements for the Company were issued, the Form 5500 for the plan year ended December 31, 2017 was not available. (4) Represents 5% of total plan contributions for the years ended December 31, 2016 and 2015 based on Form 5500. (5) The Company is a party to multiple bargaining agreements for multiple projects that require contributions into the IAM National Pension Fund. The most significant of these agreements, expiring April 28, 2019, covers multiple programs in the Company’s Aerospace Systems reportable segment and represents 61% of 2017 contributions. (6) Consists of three pension funds in which the Company’s contributions are individually, and in the aggregate, insignificant. (7) These contributions include amounts attributable to discontinued operations of approximately $26 million for the years ended December 31, 2017 and 2016 and $22 million for the year ended December 31, 2015.

Supplemental Cash Flow Inform52

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	Year Ended December 31, 2017 2016 2015 (in millions) Interest paid $ 165 $ 162 $ 182 Income tax payments $ 163 $ 120 $ 130 Income tax refunds $ 16 $ 8 $ 8

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Information [Abstract]
Summary of Segment Information	The tables below present net sales, operating income, depreciation and amortization, capital expenditures and total assets by reportable segment. Year Ended December 31, 2017 2016 2015 (in millions) Net Sales Products Electronic Systems $ 2,234 $ 2,033 $ 2,102 Aerospace Systems 1,545 1,679 1,679 Communication Systems 1,745 1,586 1,649 Sensor Systems 1,292 1,266 1,298 Elimination of intercompany sales (83 ) (111 ) (128 ) Total products sales 6,733 6,453 6,600 Services Electronic Systems $ 848 $ 812 $ 810 Aerospace Systems 1,267 1,270 1,257 Communication Systems 510 488 441 Sensor Systems 273 235 193 Elimination of intercompany sales (58 ) (48 ) (70 ) Total services sales 2,840 2,757 2,631 Consolidated total $ 9,573 $ 9,210 $ 9,231 Year Ended December 31, 2017 2016 2015 (in millions) Operating income Electronic Systems $ 403 $ 360 $ 337 Aerospace Systems 210 255 193 Communication Systems 212 195 190 Sensor Systems 195 147 142 Segment total 1,020 957 862 Goodwill impairment charges (1) — — (46 ) Loss related to business divestitures (2) — — (31 ) Consolidated total $ 1,020 $ 957 $ 785 Depreciation and amortization Electronic Systems $ 79 $ 60 $ 59 Aerospace Systems 51 46 43 Communication Systems 49 47 50 Sensor Systems 46 45 51 Consolidated total $ 225 $ 198 $ 203 Capital Expenditures Electronic Systems $ 68 $ 76 $ 69 Aerospace Systems 43 50 53 Communication Systems 49 37 37 Sensor Systems 42 37 30 Corporate 22 10 6 Consolidated total $ 224 $ 210 $ 195 Total Assets Electronic Systems $ 4,796 $ 4,369 $ 3,968 Aerospace Systems 2,014 2,084 2,190 Communication Systems 2,063 2,031 1,984 Sensor Systems 2,706 2,433 2,458 Corporate 709 467 345 Assets held for sale 135 — — Assets of discontinued operations 306 481 1,124 Consolidated total $ 12,729 $ 11,865 $ 12,069 (1) Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment. (2) See Note 3 for information regarding the Company’s business divestitures.
Property, Plant and Equipment by Geographic Area	The table below presents property, plant and equipment, net by geographic area. Year Ended December 31, 2017 2016 (in millions) United States $ 936 $ 960 All Other 174 147 Total $ 1,110 $ 1,107
Company's Sales Attributable to U.S. Customers and International Customers	The Company’s sales attributable to U.S. and international customers, based on location of the customer, are summarized in the table below. Year Ended December 31, 2017 2016 2015 (in millions) U.S. $ 7,344 $ 6,947 $ 6,734 International: United Kingdom 335 331 336 Canada 280 297 281 Australia 268 254 321 China 167 67 83 South Korea 134 127 207 Japan 125 81 95 France 84 75 62 Other 836 1,031 1,112 Total international 2,229 2,263 2,497 Consolidated $ 9,573 $ 9,210 $ 9,231
Net Sales to Principal Customers	Net sales to principal customers are summarized in the table below. Year Ended December 31, 2017 2016 2015 (in millions) U.S. Government agencies (1) $ 6,697 $ 6,399 $ 6,120 Commercial 1,456 1,280 1,373 Foreign governments (1) 1,420 1,531 1,738 Consolidated $ 9,573 $ 9,210 $ 9,231 (1) Includes sales for which the Company is the prime contractor as well as sales based on the ultimate end customer for which the Company is a subcontractor.

Severance and Restructuring R54

Severance and Restructuring Related Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Severance and Restructuring Related Costs [Abstract]
Severance and Restructuring Costs Incurred by Reportable Segment	Severance and restructuring related costs incurred by reportable segment are presented in the table below. Year Ended December 31, 2017 2016 2015 (in millions) Electronic Systems (1) $ 14 $ 5 $ 4 Aerospace Systems (1) 24 2 4 Communication Systems (2) 48 7 6 Sensor Systems (3) 15 3 4 Consolidated $ 101 $ 17 $ 18 (1) The severance and restructuring related costs incurred during the year ended December 31, 2017 include $1 million and $5 million of salaried employee pension plan curtailment losses for Electronic Systems and Aerospace Systems segments, respectively. See Note 19 for additional information. (2) The severance and restructuring related costs incurred during the year ended December 31, 2017 exclude a pre-tax gain of $42 million on the sale of the Company's property in San Carlos, California in the second quarter of 2017. (3) The severance and restructuring related costs incurred during the year ended December 31, 2017 include a $12 million loss on the sale of a building in Garland, Texas in the fourth quarter of 2017. The Company had severance and restructuring related liabilities of $23 million and $9 million included in other current liabilities on the Company’s balance sheets at December 31, 2017 and 2016, respectively. The remaining liability balance at December 31, 2017 is expected to be paid in 2018. The table below presents the change to the Company’s severance and restructuring related liability during the year ended December 31, 2017. December 31, 2017 (in millions) Balance at beginning of period $ 9 Additional provisions 101 Cash payments (87 ) Balance at end of period $ 23

Unaudited Quarterly Financial55

Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Unaudited Quarterly Financial Data [Abstract]
Unaudited Quarterly Financial Data	Unaudited summarized financial data by quarter for the years ended December 31, 2017 and 2016 is presented in the table below. The Company’s unaudited quarterly results of operations are affected, significantly in some periods, by the Company’s business acquisitions and divestitures. See Note 3 for additional information. First Quarter Second Quarter Third Quarter (1) Fourth Quarter (2) (in millions, except per share data) 2017 Sales $ 2,321 $ 2,385 $ 2,293 $ 2,574 Operating income 236 292 229 263 Income from continuing operations 157 195 146 271 Net income 168 207 25 293 Net income attributable to L3 164 202 22 289 Basic EPS from continuing operations (3) 1.97 2.44 1.83 3.42 Basic EPS (3) 2.11 2.59 0.28 3.70 Diluted EPS from continuing operations (3) 1.93 2.39 1.79 3.34 Diluted EPS (3) 2.07 2.54 0.28 3.62 2016 Sales $ 2,065 $ 2,318 $ 2,184 $ 2,643 Operating income 244 220 211 282 Income from continuing operations 163 134 149 187 Net income 230 151 151 192 Net income attributable to L3 227 147 148 188 Basic EPS from continuing operations (3) 2.06 1.68 1.89 2.37 Basic EPS (3) 2.92 1.90 1.91 2.43 Diluted EPS from continuing operations (3) 2.02 1.66 1.85 2.32 Diluted EPS (3) 2.87 1.88 1.88 2.38 (1) The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017 , which is reported in discontinued operations . (2) Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017. (3) EPS in each quarter is computed using the weighted-average number of shares outstanding during that quarter, while EPS for the full year is computed using the weighted-average number of shares outstanding during the year. Therefore, the sum of the four quarters’ EPS may not equal the full year computed EPS.

Financial Information of L3 a56

Financial Information of L3 and Its Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2017
Financial Information of L3 and Its Subsidiaries [Abstract]
Condensed Combining Balance Sheets	The following condensed combining financial information presents the results of operations, financial position and cash flows of: (1) L3 excluding its consolidated subsidiaries (the Parent), (2) the Guarantor Subsidiaries, (3) the Non-Guarantor Subsidiaries and (4) the eliminations to arrive at the information for L3 on a consolidated basis. L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) Condensed Combining Balance Sheets: At December 31, 2017: Current assets: Cash and cash equivalents $ 432 $ 14 $ 287 $ (71 ) $ 662 Billed receivables, net 266 232 225 — 723 Contracts in process 706 891 336 — 1,933 Prepaid expenses and other current assets 330 231 128 — 689 Assets held for sale — 118 17 — 135 Assets of discontinued operations — 306 — — 306 Total current assets 1,734 1,792 993 (71 ) 4,448 Goodwill 2,248 2,652 1,715 — 6,615 Other assets 658 556 452 — 1,666 Investment in and amounts due from consolidated subsidiaries 5,593 5,270 — (10,863 ) — Total assets $ 10,233 $ 10,270 $ 3,160 $ (10,934 ) $ 12,729 Current liabilities $ 811 $ 800 $ 596 $ (71 ) $ 2,136 Liabilities held for sale — 16 1 — 17 Liabilities of discontinued operations — 226 — — 226 Amounts due to consolidated subsidiaries — — 352 (352 ) — Other long-term liabilities 1,009 714 146 — 1,869 Long-term debt 3,330 — — — 3,330 Total liabilities 5,150 1,756 1,095 (423 ) 7,578 L3 shareholders’ equity 5,083 8,514 2,065 (10,579 ) 5,083 Noncontrolling interests — — — 68 68 Total equity 5,083 8,514 2,065 (10,511 ) 5,151 Total liabilities and equity $ 10,233 $ 10,270 $ 3,160 $ (10,934 ) $ 12,729 L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) At December 31, 2016: Current assets: Cash and cash equivalents $ 291 $ 1 $ 207 $ (136 ) $ 363 Billed receivables, net 261 254 185 — 700 Contracts in process 694 928 236 — 1,858 Prepaid expenses and other current assets 236 144 125 — 505 Assets of discontinued operations — 481 — — 481 Total current assets 1,482 1,808 753 (136 ) 3,907 Goodwill 2,258 2,613 1,503 — 6,374 Other assets 705 567 312 — 1,584 Investment in and amounts due from consolidated subsidiaries 5,721 5,272 — (10,993 ) — Total assets $ 10,166 $ 10,260 $ 2,568 $ (11,129 ) $ 11,865 Current liabilities $ 789 $ 846 $ 460 $ (136 ) $ 1,959 Liabilities of discontinued operations — 235 — — 235 Amounts due to consolidated subsidiaries — — 763 (763 ) — Other long-term liabilities 1,499 191 32 — 1,722 Long-term debt 3,325 — — — 3,325 Total liabilities 5,613 1,272 1,255 (899 ) 7,241 L3 shareholders’ equity 4,553 8,988 1,313 (10,301 ) 4,553 Noncontrolling interests — — — 71 71 Total equity 4,553 8,988 1,313 (10,230 ) 4,624 Total liabilities and equity $ 10,166 $ 10,260 $ 2,568 $ (11,129 ) $ 11,865
Condensed Combining Statements of Operations	L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) Condensed Combining Statements of Operations: For the year ended December 31, 2017: Total net sales $ 3,519 $ 4,748 $ 1,690 $ (384 ) $ 9,573 Total cost of sales (3,179 ) (4,350 ) (1,408 ) 384 (8,553 ) Operating income 340 398 282 — 1,020 Interest expense (168 ) — (1 ) — (169 ) Interest and other income, net 17 — 3 — 20 Income from continuing operations before income taxes 189 398 284 — 871 Provision for income taxes (22 ) (47 ) (33 ) — (102 ) Equity in net income of consolidated subsidiaries 511 — — (511 ) — Income from continuing operations 678 351 251 (511 ) 769 Loss from discontinued operations, net of income tax (1 ) (75 ) — — (76 ) Net income 677 276 251 (511 ) 693 Net income attributable to noncontrolling interests — — — (16 ) (16 ) Net income attributable to L3 $ 677 $ 276 $ 251 $ (527 ) $ 677 Comprehensive income attributable to L3 $ 712 $ 278 $ 378 $ (656 ) $ 712 For the year ended December 31, 2016: Total net sales $ 3,350 $ 4,809 $ 1,381 $ (330 ) $ 9,210 Total cost of sales (3,069 ) (4,378 ) (1,136 ) 330 (8,253 ) Operating income 281 431 245 — 957 Interest expense (164 ) — — — (164 ) Interest and other income, net 15 — 3 — 18 Debt retirement charges (7 ) — — — (7 ) Income from continuing operations before income taxes 125 431 248 — 804 Provision for income taxes (26 ) (92 ) (53 ) — (171 ) Equity in net income of consolidated subsidiaries 611 — — (611 ) — Income from continuing operations 710 339 195 (611 ) 633 Income from discontinued operations, net of income tax — 91 — — 91 Net income 710 430 195 (611 ) 724 Net income attributable to noncontrolling interests — — — (14 ) (14 ) Net income attributable to L3 $ 710 $ 430 $ 195 $ (625 ) $ 710 Comprehensive income attributable to L3 $ 558 $ 440 $ 118 $ (558 ) $ 558 For the year ended December 31, 2015: Total net sales $ 3,267 $ 4,866 $ 1,449 $ (351 ) $ 9,231 Total cost of sales (3,031 ) (4,441 ) (1,248 ) 351 (8,369 ) Goodwill impairment charges — (26 ) (20 ) — (46 ) (Loss) gain related to business divestitures (13 ) (31 ) 13 — (31 ) Operating income 223 368 194 — 785 Interest expense (161 ) (1 ) — — (162 ) Interest and other income, net 17 — — — 17 Debt retirement charge (1 ) — — — (1 ) Income from continuing operations before income taxes 78 367 194 — 639 Provision for income taxes (16 ) (76 ) (40 ) — (132 ) Equity in net loss of consolidated subsidiaries (302 ) — — 302 — (Loss) income from continuing operations (240 ) 291 154 302 507 Loss from discontinued operations, net of income tax — (732 ) — — (732 ) Net (loss) income (240 ) (441 ) 154 302 (225 ) Net income attributable to noncontrolling interests — — — (15 ) (15 ) Net (loss) income attributable to L3 $ (240 ) $ (441 ) $ 154 $ 287 $ (240 ) Comprehensive (loss) income attributable to L3 $ (230 ) $ (445 ) $ 43 $ 402 $ (230 )
Condensed Combining Statements of Cash Flows	L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) Condensed Combining Statements of Cash Flows: For the year ended December 31, 2017: Operating activities: Net cash from operating activities from continuing operations $ 374 $ 438 $ 251 $ (78 ) $ 985 Investing activities: Business acquisitions, net of cash acquired (316 ) — — — (316 ) Proceeds from sale of businesses, net of closing date cash balances 17 — 1 — 18 Other investing activities (84 ) (41 ) (30 ) — (155 ) Net cash used in investing activities from continuing operations (383 ) (41 ) (29 ) — (453 ) Financing activities: Common stock repurchased (180 ) — — — (180 ) Dividends paid on L3’s common stock (236 ) — — — (236 ) Other financing activities 565 (496 ) (162 ) 143 50 Net cash from (used in) financing activities from continuing operations 149 (496 ) (162 ) 143 (366 ) Effect of foreign currency exchange rate changes on cash — — 20 — 20 Net increase in cash and cash equivalents of discontinued operations 1 112 — — 113 Net increase in cash 141 13 80 65 299 Cash and cash equivalents, beginning of the year 291 1 207 (136 ) 363 Cash and cash equivalents, end of the year $ 432 $ 14 $ 287 $ (71 ) $ 662 L3 Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated L3 (in millions) For the year ended December 31, 2016: Operating activities: Net cash from operating activities from continuing operations $ 441 $ 509 $ 258 $ (186 ) $ 1,022 Investing activities: Business acquisitions, net of cash acquired (388 ) — — — (388 ) Proceeds from sale of businesses, net of closing date cash cash balances 563 — (2 ) — 561 Other investing activities (60 ) (80 ) (43 ) — (183 ) Net cash from (used in) investing activities from continuing operations 115 (80 ) (45 ) — (10 ) Financing activities: Proceeds from sale of senior notes 547 — — — 547 Redemption of senior notes (856 ) — — — (856 ) Common stock repurchased (373 ) — — — (373 ) Dividends paid on L3’s common stock (220 ) — — — (220 ) Other financing activities 496 (441 ) (158 ) 149 46 Net cash used in financing activities from continuing operations (406 ) (441 ) (158 ) 149 (856 ) Effect of foreign currency exchange rate changes on cash — — (13 ) — (13 ) Net increase in cash and cash equivalents of discontinued operations — 13 — — 13 Net increase in cash 150 1 42 (37 ) 156 Cash and cash equivalents, beginning of the year 141 — 165 (99 ) 207 Cash and cash equivalents, end of the year $ 291 $ 1 $ 207 $ (136 ) $ 363 For the year ended December 31, 2015: Operating activities: Net cash from operating activities from continuing operations $ 634 $ 425 $ 161 $ (185 ) $ 1,035 Investing activities: Business acquisitions, net of cash acquired (320 ) — — — (320 ) Proceeds from sale of businesses, net of closing date cash balances 14 28 276 — 318 Other investing activities (75 ) (78 ) (35 ) — (188 ) Net cash (used in) from investing activities from continuing operations (381 ) (50 ) 241 — (190 ) Financing activities: Repurchases of senior notes (297 ) — — — (297 ) Common stock repurchased (740 ) — — — (740 ) Dividends paid on L3's common stock (214 ) — — — (214 ) Other financing activities 781 (463 ) (420 ) 148 46 Net cash used in financing activities from continuing operations (470 ) (463 ) (420 ) 148 (1,205 ) Effect of foreign currency exchange rate changes on cash — — (19 ) — (19 ) Net increase in cash and cash equivalents of discontinued operations — 83 — — 83 Change in cash balance in assets held for sale — 1 60 — 61 Net (decrease) increase in cash (217 ) (4 ) 23 (37 ) (235 ) Cash and cash equivalents, beginning of the year 358 4 142 (62 ) 442 Cash and cash equivalents, end of the year $ 141 $ — $ 165 $ (99 ) $ 207

Description of Business (Detail

Description of Business (Details) $ in Billions	12 Months Ended
	Dec. 31, 2017USD ($)Segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Description of Business [Abstract]
Number of reportable segments | Segment	4
Discontinued Operations [Member] | Vertex Aerospace [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales | $	$ 1.4	$ 1.3	$ 1.2

Summary of Significant Accoun58

Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended	12 Months Ended
		Sep. 29, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Estimates [Abstract]
Increase in operating income due to changes in contract estimates			$ 184	$ 149	$ 52
Percentage of increase in consolidated operating income due to changes in contract estimates			18.00%	16.00%	7.00%
Increase in operating income due to changes in contract estimates, diluted (in dollars per share)			$ 1.48	$ 1.23	$ 0.45
Revenue Recognition [Abstract]
Percentage of net sales accounted for under contract accounting standards			59.00%
Percentage of fixed-price type contracts			49.00%
Percentage of cost-plus type contracts			10.00%
Period of performance for contracts accounted for under the percentage-of-completion method of accounting, minimum			1 year
Accrued product warranty costs [Roll Forward]:
Balance at January 1	[1]		$ 109	$ 105
Acquisitions during this period	[1]		3	3
Accruals for product warranties issued during the period	[1]		52	51
Foreign currency translation adjustments	[1]		1	(1)
Settlements made during the period	[1]		(66)	(49)
Balance at December 31	[1]		99	109	$ 105
Goodwill and Indefinite-lived Intangible Assets [Abstract]
Goodwill impairment charges	[2]		0	$ 0	46
NSS [Member]
Goodwill and Indefinite-lived Intangible Assets [Abstract]
Goodwill impairment charges					955
NSS [Member] | Discontinued Operations [Member]
Goodwill and Indefinite-lived Intangible Assets [Abstract]
Goodwill impairment charges					909
NSS [Member] | Continuing Operations [Member]
Goodwill and Indefinite-lived Intangible Assets [Abstract]
Goodwill impairment charges					$ 46
Vertex Aerospace [Member]
Goodwill and Indefinite-lived Intangible Assets [Abstract]
Goodwill impairment charges		$ 187	187
Goodwill impairment after income taxes			$ 133
Minimum [Member] | Buildings and Improvements [Member]
Property, Plant and Equipment [Abstract]
Estimated useful life			10 years
Minimum [Member] | Machinery, Equipment, Furniture and Fixtures [Member]
Property, Plant and Equipment [Abstract]
Estimated useful life			3 years
Maximum [Member] | Buildings and Improvements [Member]
Property, Plant and Equipment [Abstract]
Estimated useful life			40 years
Maximum [Member] | Machinery, Equipment, Furniture and Fixtures [Member]
Property, Plant and Equipment [Abstract]
Estimated useful life			10 years
[1]	Warranty obligations incurred in connection with long-term production contracts that are accounted for under the POC cost-to-cost method are included within the contract estimates at completion and are excluded from the above amounts. The balances above include both the current and non-current amounts.
[2]	Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment.

Summary of Significant Accoun59

Summary of Significant Accounting Policies, Accounting Standards Issued and Not Yet Implemented (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
ASU 2017-07 [Member]
Summary of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on operating income	$ 11	$ 1
New Accounting pronouncement or change in accounting principle, effect of change on interest and other income, net	(11)	$ (1)
ASC 606 [Member]
Summary of Significant Accounting Policies [Line Items]
Reclassification from inventory to other cost	$ 50
New accounting pronouncement or change in accounting principle effect of change on current assets, percentage	(2.00%)
New accounting pronouncement or change in accounting principle effect of change on current liabilities, percentage	(2.00%)
ASC 606 [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, cumulative effect of change on shareholders equity	$ 10
New accounting pronouncement or change in accounting principle, effect of change on net sales	350
ASC 606 [Member] | Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
New accounting pronouncement or change in accounting principle, cumulative effect of change on shareholders equity	20
New accounting pronouncement or change in accounting principle, effect of change on net sales	$ 400

Acquisitions, Divestitures an60

Acquisitions, Divestitures and Discontinued Operations, Business Acquisitions (Details) £ in Millions, $ in Millions

Dec. 18, 2017USD ($)

Oct. 17, 2017USD ($)

Sep. 08, 2017USD ($)

May 19, 2017USD ($)

Jan. 05, 2017USD ($)

Nov. 22, 2016USD ($)

Nov. 22, 2016GBP (£)

Sep. 30, 2016USD ($)

Jan. 22, 2016USD ($)

Oct. 13, 2015USD ($)

May 27, 2015USD ($)

May 27, 2015GBP (£)

Jan. 21, 2015USD ($)

Dec. 31, 2017USD ($)

Sep. 29, 2017USD ($)

[2]

Jun. 30, 2017USD ($)

Mar. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Sep. 23, 2016USD ($)

[2]

Jun. 24, 2016USD ($)

Mar. 25, 2016USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Sep. 12, 2017USD ($)

Mar. 17, 2017USD ($)

Nov. 22, 2016GBP (£)

May 27, 2015GBP (£)

Business Acquisition [Line Items]

Fair value of liability, contingent consideration

$ 31

$ 29

$ 31

$ 29

Goodwill recognized

6,615

6,374

6,615

6,374

$ 6,095

Net sales

$ 2,574

[1]

$ 2,293

$ 2,385

$ 2,321

$ 2,643

[1]

$ 2,184

$ 2,318

$ 2,065

9,573

9,210

9,231

Loss before income taxes

871

$ 804

$ 639

Kigre, Inc [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 13

Goodwill recognized

$ 9

Escola De Aviacao Aerocondor, S.A [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 13

Goodwill recognized

$ 12

Doss Aviation, Inc. [Member]

Business Acquisition [Line Items]

Goodwill recognized

$ 37

Goodwill deductible for income tax purposes

$ 13

Adaptive Methods, Inc. [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 33

Goodwill recognized

$ 28

Open Water Power Inc [Member]

Business Acquisition [Line Items]

Fair value of liability, contingent consideration

$ 14

Goodwill recognized

25

Open Water Power Inc [Member] | Maximum [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

17

Open Water Power Inc [Member] | IPR&D [Member]

Business Acquisition [Line Items]

Identifiable intangible assets

$ 65

OceanServer Technology, Inc. [Member]

Business Acquisition [Line Items]

Goodwill recognized

$ 19

Explosive Trace Detection Business of Implant Sciences [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 118

Goodwill recognized

$ 80

Kigre, G-Air, Doss Aviation, Adaptive Methods, Open Water Power, OceanServer and ETD Business [Member]

Business Acquisition [Line Items]

Net sales

80

Loss before income taxes

$ (1)

MacDonald Humfrey (Automation) Limited [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 327

£ 263

Fair value of liability, contingent consideration

26

£ 21

Goodwill recognized

255

204

Identifiable intangible assets

$ 56

45

Weighted average useful life

10 years

10 years

MacDonald Humfrey (Automation) Limited [Member] | Maximum [Member]

Business Acquisition [Line Items]

Business acquisition contingent consideration

$ 38

30

MacDonald Humfrey (Automation) Limited [Member] | Trade Names [Member]

Business Acquisition [Line Items]

Identifiable intangible assets

8

6

MacDonald Humfrey (Automation) Limited [Member] | Technology [Member]

Business Acquisition [Line Items]

Identifiable intangible assets

12

10

MacDonald Humfrey (Automation) Limited [Member] | Customer Relationships [Member]

Business Acquisition [Line Items]

Identifiable intangible assets

$ 36

£ 29

Micreo Limited and Aerosim [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 86

Goodwill recognized

59

Goodwill deductible for income tax purposes

$ 6

Advanced Technical Materials, Inc. [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 27

Goodwill recognized

$ 20

ForceX, Inc. [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 61

Goodwill recognized

53

Goodwill deductible for income tax purposes

$ 52

CTC Aviation Group [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 236

£ 153

Goodwill recognized

$ 182

£ 118

MITEQ, Inc. [Member]

Business Acquisition [Line Items]

Purchase price of acquisition

$ 41

Goodwill recognized

11

Goodwill deductible for income tax purposes

$ 4

[1]

Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.

[2]

The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.

Acquisitions, Divestitures an61

Acquisitions, Divestitures and Discontinued Operations, Unaudited Pro Forma Statements of Operations Data (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Acquisitions, Divestitures and Discontinued Operations [Abstract]
Pro forma net sales	$ 9,638	$ 9,493
Pro forma income from continuing operations attributable to L3	753	621
Pro forma net income attributable to L3	$ 677	$ 712
Pro forma diluted earnings per share from continuing operations (in dollars per share)	$ 9.46	$ 7.88
Pro forma diluted earnings per share (in dollars per share)	$ 8.51	$ 9.03

Acquisitions, Divestitures an62

Acquisitions, Divestitures and Discontinued Operations, Business Divestitures (Details) € in Millions, $ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2017USD ($)

[2]

Sep. 29, 2017USD ($)

[3]

Jun. 30, 2017USD ($)

Mar. 31, 2017USD ($)

Dec. 31, 2016USD ($)

[2]

Sep. 23, 2016USD ($)

[3]

Jun. 24, 2016USD ($)

Mar. 25, 2016USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Mar. 01, 2017USD ($)

Mar. 01, 2017EUR (€)

Feb. 24, 2017USD ($)

Feb. 23, 2017USD ($)

Jul. 27, 2015USD ($)

May 29, 2015USD ($)

May 29, 2015EUR (€)

Apr. 24, 2015USD ($)

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

[1]

$ 0

$ 0

$ (31)

Proceeds received

358

Net sales

209

Net sales

$ 2,574

$ 2,293

$ 2,385

$ 2,321

$ 2,643

$ 2,184

$ 2,318

$ 2,065

9,573

9,210

9,231

Income before income taxes

871

804

639

Income (Loss) from Continuing Operations [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(4)

Proceeds received

25

Net sales

10

Discontinued Operations [Member]

Business Divestiture [Abstract]

Net sales

10

59

259

Income before income taxes

2

$ 8

8

Aviation Jet Services Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(5)

Proceeds received

1

Net sales

1

Sale of business, sale price

$ 1

€ 1

Coleman Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(3)

Proceeds received

17

Net sales

9

Sale of business, sale price

$ 15

Display Product Line Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

4

Proceeds received

7

Net sales

$ 0

Sale of business, sale price

$ 7

MSI Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(17)

Proceeds received

318

Net sales

185

Sale of business, sale price

$ 318

€ 295

Estimated employee pension related liabilities | €

€ 60

BSI Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(4)

Proceeds received

26

Net sales

7

Sale of business, sale price

$ 26

Tinsley Product Line Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(8)

Proceeds received

4

Net sales

9

Sale of business, sale price

$ 4

Klein Divestiture [Member]

Business Divestiture [Abstract]

(Loss) gain related to business divestitures

(2)

Proceeds received

10

Net sales

8

Sale of business, sale price

$ 10

[1]

See Note 3 for information regarding the Company's business divestitures.

[2]

Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.

[3]

The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.

Acquisitions, Divestitures an63

Acquisitions, Divestitures and Discontinued Operations, Discontinued Operations (Details) - USD ($) $ in Millions		Feb. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Discontinued Operations [Abstract]
Proceeds from sale of discontinued operations					$ 358
Net sales					209
(Loss) income from discontinued operations net of income taxes			$ (76)	$ 91	(732)
Gain (loss) related to business divestitures	[1]		0	0	(31)
Assets [Abstract]
Current assets			306	481	1,124
Liabilities [Abstract]
Current liabilities			226	235
Vertex Aerospace [Member] | Discontinued Operations, Disposed of by Sale [Member]
Discontinued Operations [Abstract]
Net sales			1,400	1,300	1,200
Goodwill impairment charges					338
Assets [Abstract]
Current assets			284	271
Property, plant and equipment, net			13	14
Goodwill			0	187
Other Intangible Assets			7	9
Other assets			2	0
Total assets of discontinued operations			306	481
Liabilities [Abstract]
Accounts payable, trade			63	16
Other current liabilities			131	160
Current liabilities			194	176
Long-term liabilities			32	59
Total liabilities of discontinued operations			226	235
NSS [Member] | Discontinued Operations, Disposed of by Sale [Member]
Discontinued Operations [Abstract]
Goodwill impairment charges					571
Gain (loss) related to business divestitures				64
Trailing expenses related to sale			1
NSS [Member] | Discontinued Operations, Disposed of by Sale [Member] | CACI International Inc [Member]
Discontinued Operations [Abstract]
Proceeds from sale of discontinued operations		$ 547
Vertex Aerospace and NSS [Member] | Discontinued Operations, Disposed of by Sale [Member]
Discontinued Operations [Abstract]
Net sales			1,429	1,402	2,334
Cost of sales			(1,342)	(1,357)	(2,259)
(Loss) gain related to business divestiture	[2]		(1)	64	0
Goodwill impairment charges	[3]		(187)	0	(909)
Operating (loss) income from discontinued operations			(101)	109	(834)
Interest expense allocated to discontinued operations			(2)	(5)	(26)
(Loss) income from discontinued operations before income taxes			(103)	104	(860)
Income tax benefit (expense)			27	(13)	128
(Loss) income from discontinued operations net of income taxes			$ (76)	$ 91	$ (732)
[1]	See Note 3 for information regarding the Company's business divestitures.
[2]	For the year ended December 31, 2017, the Company recognized $1 million of trailing expenses related to the sale of NSS. The year ended December 31, 2016 included a gain of $64 million (before and after income taxes) on the sale of NSS.
[3]	Due to a decline in estimated fair value, the Company recorded goodwill impairment charges for the years ended December 31, 2017 and 2015. The impairment charge of $187 million recorded during 2017 relates to Vertex Aerospace. The impairment charge of $909 million recorded during 2015 consists of: (i) $571 million related to NSS and (ii) $338 million related to Vertex Aerospace.

Acquisitions, Divestitures an64

Acquisitions, Divestitures and Discontinued Operations, Assets Held for Sale (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets [Abstract]
Total current assets	$ 306	$ 481	$ 1,124
Liabilities [Abstract]
Current liabilities	226	$ 235
Assets Held for Sale [Member]
Assets [Abstract]
Billed receivables	14
Contracts in process	33
Total current assets	47
Property, plant and equipment, net	34
Goodwill	52
Indentifiable intangible assets	2
Total assets of discontinued operations	135
Liabilities [Abstract]
Accounts payable, trade	3
Accrued employment costs	2
Accrued expenses	3
Other current liabilities	5
Current liabilities	13
Deferred income taxes	4
Total liabilities of discontinued operations	$ 17

Contracts in Process (Details)

Contracts in Process (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Contracts Receivable [Abstract]
Unbilled contract receivables, gross		$ 1,874	$ 1,890
Unliquidated progress payments		(761)	(827)
Unbilled contract receivables, net		1,113	1,063
Inventoried contract costs, gross		891	998
Unliquidated progress payments		(71)	(203)
Inventoried contract costs, net		820	795
Total contracts in process		$ 1,933	1,858
Percentage of unbilled contract receivables, net billed and collected within one year		92.00%
Contracts Receivable [Line Items]
Percentage of incurred costs billed		80.00%
Summary of Inventory for Long Term Contracts or Programs [Roll Forward]
Amounts included in inventoried contract costs at beginning of the year		$ 173	137	$ 114
Contract costs incurred [Abstract]:
IRAD and B&P		333	304	280
Other G&A	[1]	842	749	742
Total		1,175	1,053	1,022
Amounts charged to cost of sales		(1,179)	(1,017)	(999)
Amounts included in inventoried contract costs at end of the year		169	173	137
Severance and restructuring cost		91	13	14
Operating Expenses [Abstract]
Selling, general and administrative expenses		278	223	261
Research and development expenses		63	54	52
Total		$ 341	$ 277	$ 313
Maximum [Member]
Contracts Receivable [Line Items]
Number of years for billed and collected, unbilled contract receivables		1 year
[1]	Amounts include severance and restructuring-related costs of $91 million, $13 million and $14 million for the years ended December 31, 2017, 2016 and 2015, respectively.

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Inventories [Abstract]
Raw materials, components and sub-assemblies	$ 184	$ 165
Work in process	98	106
Finished goods	107	59
Total	$ 389	$ 330

Goodwill and Identifiable Int67

Goodwill and Identifiable Intangible Assets, Allocated by Reportable Segment (Details) $ in Millions		12 Months Ended
		Dec. 31, 2017USD ($)Employee	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Goodwill [Line Items]
Approximate number of employees | Employee		31,000
Goodwill [Roll Forward]
Goodwill		$ 6,719	$ 6,478	$ 6,199
Accumulated impairment losses		(104)	(104)	(104)
Balance, Beginning		6,374	6,095
Business acquisitions	[1]	212	335
Business divestitures	[2]	(12)
Foreign currency translation adjustments		93	(56)
Assets held for sale	[3]	(52)
Balance, Ending		6,615	6,374
Electronic Systems [Member]
Goodwill [Roll Forward]
Goodwill		2,856	2,687	2,445
Accumulated impairment losses		(43)	(43)	(43)
Balance, Beginning		2,644	2,402
Business acquisitions	[1]	131	287
Business divestitures	[2]	(12)
Foreign currency translation adjustments		60	(45)
Assets held for sale	[3]	(10)
Balance, Ending		2,813	2,644
Aerospace Systems [Member]
Goodwill [Roll Forward]
Goodwill		1,146	1,174	1,167
Accumulated impairment losses		0	0	0
Balance, Beginning		1,174	1,167
Business acquisitions	[1]	0	0
Business divestitures	[2]	0
Foreign currency translation adjustments		14	7
Assets held for sale	[3]	(42)
Balance, Ending		1,146	1,174
Communication Systems [Member]
Goodwill [Roll Forward]
Goodwill		1,058	1,058	1,038
Accumulated impairment losses		(35)	(35)	(35)
Balance, Beginning		1,023	1,003
Business acquisitions	[1]	0	20
Business divestitures	[2]	0
Foreign currency translation adjustments		0	0
Assets held for sale	[3]	0
Balance, Ending		1,023	1,023
Sensor Systems [Member]
Goodwill [Roll Forward]
Goodwill		1,659	1,559	1,549
Accumulated impairment losses		(26)	(26)	$ (26)
Balance, Beginning		1,533	1,523
Business acquisitions	[1]	81	28
Business divestitures	[2]	0
Foreign currency translation adjustments		19	(18)
Assets held for sale	[3]	0
Balance, Ending		$ 1,633	$ 1,533
[1]	For the year ended December 31, 2017, business acquisitions for the Electronic Systems segment included the acquisitions of the ETD, Doss Aviation and G-Air businesses and the purchase price allocation adjustments for the MacH and Aerosim business acquisitions. Business acquisitions for the Sensor Systems segment included primarily the Adaptive Methods, Open Water Power, OceanServer and Kigre business acquisitions. For the year ended December 31, 2016, business acquisitions for the Electronic Systems segment included the acquisitions of the MacH and Aerosim businesses and the final purchase price allocation for L3 CTC business acquisition. Business acquisition for the Communication Systems segment included the ATM business acquisition. Business acquisitions for the Sensor Systems segment included the Micreo business acquisition and the final purchase price allocation for the L3 ForceX business acquisition.
[2]	The decrease for the Electronic Systems segment was due to the divestitures of Coleman and Aviation Jet Services during the quarterly period ended March 31, 2017.
[3]	The Aerostructures businesses within the Company's Aerospace Systems segment are classified as held for sale as of December 31, 2017.

Goodwill and Identifiable Int68

Goodwill and Identifiable Intangible Assets, Identifiable Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets Subject to Amortization [Abstract]
Finite-lived intangible assets, gross carrying amount	$ 611	$ 572
Finite-lived intangible assets, accumulated amortization	385	343
Net carrying amount	226	229
Amortization expense	43	33	$ 32
Estimated Amortization Expense for Identifiable Intangible Assets [Abstract]
Estimated amortization expense, 2018	44
Estimated amortization expense, 2019	39
Estimated amortization expense, 2020	31
Estimated amortization expense, 2021	25
Estimated amortization expense, 2022	21
Indefinite-lived Intangible Assets [Line Items]
Intangible assets, gross carrying amount	677	572
Intangible assets, net carrying amount	292	229
IPR&D [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 66	0
Customer Contractual Relationships [Member]
Finite-Lived Intangible Assets Subject to Amortization [Abstract]
Finite lived intangible assets, weighted average amortization period	14 years
Finite-lived intangible assets, gross carrying amount	$ 393	360
Finite-lived intangible assets, accumulated amortization	257	229
Net carrying amount	$ 136	131
Technology [Member]
Finite-Lived Intangible Assets Subject to Amortization [Abstract]
Finite lived intangible assets, weighted average amortization period	10 years
Finite-lived intangible assets, gross carrying amount	$ 189	191
Finite-lived intangible assets, accumulated amortization	114	102
Net carrying amount	$ 75	89
Other [Member]
Finite-Lived Intangible Assets Subject to Amortization [Abstract]
Finite lived intangible assets, weighted average amortization period	15 years
Finite-lived intangible assets, gross carrying amount	$ 29	21
Finite-lived intangible assets, accumulated amortization	14	12
Net carrying amount	$ 15	$ 9

Other Current Liabilities and69

Other Current Liabilities and Other Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Current Liabilities [Abstract]
Accrued product warranty costs	$ 69	$ 68
Estimated costs in excess of estimated contract value to complete contracts in process in a loss position	63	70
Accrued interest	43	43
Deferred revenues	38	34
Estimated contingent purchase price payable for acquired businesses (see Note 3)	11	0
Accruals for pending and threatened litigation	3	14
Other	140	163
Total other current liabilities	367	392
Other Liabilities [Abstract]
Non-current income taxes payable (see Note 16)	164	121
Deferred compensation	49	47
Accrued product warranty costs	30	41
Accrued workers' compensation	23	25
Estimated contingent purchase price payable for acquired businesses (see Note 3)	20	29
Notes payable and capital lease obligations	16	10
Other	96	83
Total other liabilities	$ 398	$ 356

Property, Plant and Equipment70

Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Land	$ 34	$ 53
Buildings and improvements	404	437
Machinery, equipment, furniture and fixtures	1,959	1,857
Leasehold improvements	376	337
Gross property, plant and equipment	2,773	2,684
Accumulated depreciation and amortization	(1,663)	(1,577)
Property, plant and equipment, net	$ 1,110	$ 1,107

Debt, Components of Debt and Re

Debt, Components of Debt and Reconciliation to Carrying Amount of Current and Long-Term Debt (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 31, 2016
Components of Debt [Abstract]
Repayments under the credit facility		$ 1,328	$ 819	$ 1,194
Proceeds under the credit facility		1,328	819	$ 1,194
Available borrowings under credit facility		1,000
3.95% Senior Notes due 2016 [Member]
Components of Debt [Abstract]
Principal amount of long-term debt		200
5.20% Senior Notes due 2019 [Member]
Components of Debt [Abstract]
Unamortized discounts	[1]	(4)
4.75% Senior Notes due 2020 [Member]
Components of Debt [Abstract]
Unamortized discounts	[1]	(3)
4.95% Senior Notes due 2021 [Member]
Components of Debt [Abstract]
Unamortized discounts	[1]	(4)
3.95% Senior Notes due 2024 [Member]
Components of Debt [Abstract]
Unamortized discounts	[1]	(3)
3.85% Senior Notes due 2026 [Member]
Components of Debt [Abstract]
Unamortized discounts	[1]	$ (3)
Revolving Credit Facility [Member]
Amended and Restated Revolving Credit Facility [Abstract]
Revolving credit facility expiration period		5 years
Total aggregate borrowings under revolving credit facility					$ 1,000
Revolving credit facility expiration date		Oct. 31, 2021
Uncommitted incremental revolving facilities and additional term loan facilities					$ 600
Revolving Credit Facility [Member] | Federal Funds Rate [Member] | Minimum [Member]
Amended and Restated Revolving Credit Facility [Abstract]
Applicable spread on base rate		0.125%
Revolving Credit Facility [Member] | Federal Funds Rate [Member] | Maximum [Member]
Amended and Restated Revolving Credit Facility [Abstract]
Applicable spread on base rate		1.00%
Revolving Credit Facility [Member] | Eurodollar Rate [Member] | Minimum [Member]
Amended and Restated Revolving Credit Facility [Abstract]
Applicable spread on base rate		1.125%
Revolving Credit Facility [Member] | Eurodollar Rate [Member] | Maximum [Member]
Amended and Restated Revolving Credit Facility [Abstract]
Applicable spread on base rate		2.00%
L3 Technologies [Member]
Components of Debt [Abstract]
Borrowings under Revolving Credit Facility	[2]	$ 0	0
Principal amount of long-term debt		3,350	3,350
Unamortized discounts		(7)	(8)
Deferred debt issue costs		(13)	(17)
Carrying amount of long-term debt		$ 3,330	3,325
L3 Technologies [Member] | 3.95% Senior Notes due 2016 [Member]
Components of Debt [Abstract]
Interest rate on senior notes		3.95%
L3 Technologies [Member] | 1.50% Senior Notes due 2017 [Member]
Components of Debt [Abstract]
Interest rate on senior notes		1.50%
L3 Technologies [Member] | 5.20% Senior Notes due 2019 [Member]
Components of Debt [Abstract]
Borrowings under Revolving Credit Facility		$ 1,000	1,000
Interest rate on senior notes		5.20%
Debt instrument maturity period		2,019
L3 Technologies [Member] | 4.75% Senior Notes due 2020 [Member]
Components of Debt [Abstract]
Borrowings under Revolving Credit Facility		$ 800	800
Interest rate on senior notes		4.75%
Debt instrument maturity period		2,020
L3 Technologies [Member] | 4.95% Senior Notes due 2021 [Member]
Components of Debt [Abstract]
Borrowings under Revolving Credit Facility		$ 650	650
Interest rate on senior notes		4.95%
Debt instrument maturity period		2,021
L3 Technologies [Member] | 3.95% Senior Notes due 2024 [Member]
Components of Debt [Abstract]
Borrowings under Revolving Credit Facility		$ 350	350
Interest rate on senior notes		3.95%
Debt instrument maturity period		2,024
L3 Technologies [Member] | 3.85% Senior Notes due 2026 [Member]
Components of Debt [Abstract]
Borrowings under Revolving Credit Facility		$ 550	550
Interest rate on senior notes		3.85%
Debt instrument maturity period		2,026
L3 Technologies [Member] | Revolving Credit Facility [Member]
Components of Debt [Abstract]
Repayments under the credit facility		$ 1,328
Proceeds under the credit facility		1,328
Available borrowings under credit facility		$ 1,000	$ 1,000
[1]	Bond discounts are recorded as a reduction to the principal amount of the notes and are amortized as interest expense over the term of the notes.
[2]	During 2017, L3's aggregate borrowings and repayments under the Credit Facility were $1,328 million. L3 had the full availability of its $1 billion Credit Facility at December 31, 2017 and December 31, 2016.

Debt, Outstanding Senior Subord

Debt, Outstanding Senior Subordinated Notes (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding Senior Note Terms [Abstract]
Net Cash Proceeds		$ 0	$ 547	$ 0
Senior Notes Redemption [Abstract]
Debt Retirement Charge		0	(7)	(1)
Cash payments of senior notes		$ 0	856	297
3.95% Senior Notes due 2016 [Member]
Outstanding Senior Note Terms [Abstract]
Redemption price as percentage of principal amount		101.475%
Senior Notes due		Nov. 15, 2016
Senior Notes Redemption [Abstract]
Redemption Date	[1]	May 20, 2016
Maturity date		Nov. 15, 2016
Redemption amount	[1]	$ 300
Principal Amount		200
Debt Retirement Charge	[1]	5
Redemption cash payments	[1]	305
Cash payments of senior notes		$ 200
1.50% Senior Notes due 2017 [Member]
Outstanding Senior Note Terms [Abstract]
Redemption price as percentage of principal amount		100.323%
Senior Notes Redemption [Abstract]
Redemption Date	[2]	Dec. 30, 2016
Redemption amount	[2]	$ 350
Debt Retirement Charge	[2]	2
Redemption cash payments	[2]	$ 351
5.20% Senior Notes due 2019 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		Oct. 2, 2009
Amount Issued		$ 1,000
Discount	[3]	4
Net Cash Proceeds		$ 987
Effective Interest Rate		5.25%
Redemption at Treasury Rate	[4],[5]	30.00%
4.75% Senior Notes due 2020 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		May 21, 2010
Amount Issued		$ 800
Discount	[3]	3
Net Cash Proceeds		$ 790
Effective Interest Rate		4.79%
Redemption at Treasury Rate	[4],[5]	25.00%
4.95% Senior Notes due 2021 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		Feb. 7, 2011
Amount Issued		$ 650
Discount	[3]	4
Net Cash Proceeds		$ 639
Effective Interest Rate		5.02%
Redemption at Treasury Rate	[4],[5]	25.00%
Senior Notes due		Nov. 15, 2020
Senior Notes Redemption [Abstract]
Maturity date		Nov. 15, 2020
3.95% Senior Notes due 2024 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		May 28, 2014
Amount Issued		$ 650
Discount	[3]	3
Net Cash Proceeds		$ 641
Effective Interest Rate		4.02%
Redemption at Treasury Rate	[4],[5]	20.00%
Senior Notes Redemption [Abstract]
Tender date		Dec. 22, 2015
Tender amount		$ 300
Debt Retirement Charge		1
Tender cash payments		$ 297
3.85% Senior Notes due 2026 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		Dec. 5, 2016
Amount Issued		$ 550
Discount	[3]	3
Net Cash Proceeds		$ 542
Effective Interest Rate		3.91%
Redemption at Treasury Rate	[4],[5]	25.00%
L3 Technologies [Member]
Outstanding Senior Note Terms [Abstract]
Discount		$ 7	8
Net Cash Proceeds			547
Redemption price as percentage of principal amount		101.00%
Senior Notes Redemption [Abstract]
Principal Amount		$ 3,350	3,350
Debt Retirement Charge			(7)	(1)
Cash payments of senior notes			$ 856	$ 297
L3 Technologies [Member] | Minimum [Member]
Outstanding Senior Note Terms [Abstract]
Redemption price as percentage of principal amount		100.00%
L3 Technologies [Member] | 3.95% Senior Notes due 2016 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.95%
L3 Technologies [Member] | 1.50% Senior Notes due 2017 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		1.50%
L3 Technologies [Member] | 5.20% Senior Notes due 2019 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		5.20%
L3 Technologies [Member] | 4.75% Senior Notes due 2020 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		4.75%
L3 Technologies [Member] | 4.95% Senior Notes due 2021 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		4.95%
L3 Technologies [Member] | 3.95% Senior Notes due 2024 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.95%
L3 Technologies [Member] | 3.95% Senior Notes due 2024 [Member] | Minimum [Member]
Outstanding Senior Note Terms [Abstract]
Senior Notes due		Feb. 28, 2024
Senior Notes Redemption [Abstract]
Maturity date		Feb. 28, 2024
L3 Technologies [Member] | 3.85% Senior Notes due 2026 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.85%
L3 Technologies [Member] | 3.85% Senior Notes due 2026 [Member] | Minimum [Member]
Outstanding Senior Note Terms [Abstract]
Senior Notes due		Sep. 15, 2026
Senior Notes Redemption [Abstract]
Maturity date		Sep. 15, 2026
[1]	The 3.95% Senior Notes due 2016 were redeemed at a price equal to 101.475% of the principal amount thereof, plus accrued and unpaid interest. Interest ceased to accrue on and after May 20, 2016, and the only remaining right of holders of such Notes was to receive payment of the redemption price and accrued interest.
[2]	The 1.50% Senior Notes due 2017 were redeemed at a price equal to 100.323% of the principal amount thereof, plus accrued and unpaid interest to the redemption date. Interest ceased to accrue on and after the redemption date.
[3]	Bond discounts are recorded as a reduction to the principal amount of the notes and are amortized as interest expense over the term of the notes.
[4]	The Senior Notes maturing in 2019 and 2020 may be redeemed at any time prior to their maturity and the Senior Notes maturing in 2021, 2024 and 2026 may be redeemed at any time prior to November 15, 2020, February 28, 2024 and September 15, 2026, respectively, (three months prior to their maturity) at the option of L3, in whole or in part, at a redemption price equal to the greater of: (1) 100% of the principal amount, or (2) the present value of the remaining principal and interest payments discounted to the date of redemption, on a semi-annual basis, at the Treasury Rate (as defined in the indentures governing the Senior Notes), plus the spread indicated in the table above. In addition, if the Senior Notes maturing in 2021, 2024 and 2026 are redeemed at any time on or after November 15, 2020, February 28, 2024 and September 15, 2026, respectively, the redemption price would be equal to 100% of the principal amount.
[5]	Upon the occurrence of a change in control (as defined in the indentures governing the Senior Notes), each holder of the notes will have the right to require L3 to repurchase all or any part of such holder's notes at an offer price in cash equal to 101% of the aggregate principal amount plus accrued and unpaid interest, if any, to the date of purchase.

Debt, Guarantees and Covenants

Debt, Guarantees and Covenants (Details) - L3 Technologies [Member] $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Ownership percentage	100.00%
Minimum consolidated interest coverage ratio under revolving credit facility covenants	300.00%
Minimum consolidated senior leverage ratio under revolving credit facility covenants	375.00%
Maximum consolidated senior leverage ratio under revolving credit facility covenants	400.00%
Minimum aggregate amount of indebtedness, swap contracts or guarantees to trigger cross default provisions	$ 75
Maximum days to cure defaults triggering cross default provisions	10 days
Minimum aggregate amount of senior notes accelerated to trigger cross default provisions	$ 100

Accumulated Other Comprehensi74

Accumulated Other Comprehensive (Loss) Income (AOCI), Summary of AOCI Balances Including Amounts Reclassified from AOCI into Net Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 4,553
Other comprehensive (loss) income before reclassifications, net of tax	(6)	$ (193)	$ (95)
Amounts reclassified from AOCI, net of tax	41	41	105
Net current period other comprehensive (loss) income	35	(152)	10
Ending Balance	5,083	4,553
Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(726)	(574)	(584)
Ending Balance	(691)	(726)	(574)
Foreign Currency Translation [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(178)	(101)	19
Other comprehensive (loss) income before reclassifications, net of tax	124	(77)	(161)
Amounts reclassified from AOCI, net of tax	0	0	41
Net current period other comprehensive (loss) income	124	(77)	(120)
Ending Balance	(54)	(178)	(101)
Unrealized (Losses) Gains on Hedging Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	6	(8)	(5)
Other comprehensive (loss) income before reclassifications, net of tax	7	3	(15)
Amounts reclassified from AOCI, net of tax	(4)	11	12
Net current period other comprehensive (loss) income	3	14	(3)
Ending Balance	9	6	(8)
Unrecognized (Losses) Gains and Prior Service Cost, Net [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(554)	(465)	(598)
Other comprehensive (loss) income before reclassifications, net of tax	(137)	(119)	81
Amounts reclassified from AOCI, net of tax	45	30	52
Net current period other comprehensive (loss) income	(92)	(89)	133
Ending Balance	$ (646)	$ (554)	$ (465)

Accumulated Other Comprehensi75

Accumulated Other Comprehensive (Loss) Income (AOCI), Summary of Amounts Reclassified from AOCI into Net Income (Details) - USD ($) $ in Millions		3 Months Ended												12 Months Ended
		Dec. 31, 2017	[2]	Sep. 29, 2017	[3]	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	[2]	Sep. 23, 2016	[3]	Jun. 24, 2016	Mar. 25, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss related to business divestitures	[1]													$ 0	$ 0	$ (31)
Cost of sales-products														(5,999)	(5,818)	(6,036)
Income from continuing operations before income taxes														871	804	639
Provision for income taxes														(102)	(171)	(132)
Income from continuing operations		$ 271		$ 146		$ 195	$ 157	$ 187		$ 149		$ 134	$ 163	769	633	507
MSI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss related to business divestitures																(17)
Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations	[4]													(41)	(41)	(105)
Foreign Currency Translation Adjustments [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	[4]													0	0	(41)
Income from continuing operations	[4]													0	0	(41)
Foreign Currency Translation Adjustments [Member] | Amount Reclassified from AOCI [Member] | MSI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss related to business divestitures	[4]													0	0	(41)
Losses on Hedging Instruments [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales-products	[4]													5	(13)	(16)
Income from continuing operations before income taxes	[4]													5	(13)	(18)
Provision for income taxes	[4]													(1)	2	6
Income from continuing operations	[4]													4	(11)	(12)
Losses on Hedging Instruments [Member] | Amount Reclassified from AOCI [Member] | MSI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss related to business divestitures	[4]													0	0	(2)
Amortization of Defined Benefit Pension Items [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net loss	[4],[5]													(59)	(48)	(67)
Income from continuing operations before income taxes	[4]													(59)	(48)	(81)
Provision for income taxes	[4]													14	18	29
Income from continuing operations	[4]													(45)	(30)	(52)
Amortization of Defined Benefit Pension Items [Member] | Amount Reclassified from AOCI [Member] | MSI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss related to business divestitures	[4]													$ 0	$ 0	$ (14)
[1]	See Note 3 for information regarding the Company's business divestitures.
[2]	Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.
[3]	The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.
[4]	Amounts in parentheses indicate charges to the consolidated statements of operations.
[5]	Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 19 for additional information).

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 12, 2018	Feb. 16, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 08, 2017	Dec. 04, 2014
Class of Stock [Line Items]
Aggregate amount of repurchased shares			$ 180	$ 373	$ 740
Cash dividends declared per common share (in dollars per share)			$ 3	$ 2.80	$ 2.60
Cash dividends			$ 236	$ 220	$ 213
Subsequent Event [Member]
Class of Stock [Line Items]
Average price per share of repurchased shares (in dollars per share)		$ 203.33
Aggregate amount of repurchased shares		$ 88
Cash dividends declared per common share (in dollars per share)	$ 0.80
Dividend declared date	Feb. 12, 2018
Dividend paid date	Mar. 15, 2018
Dividend paid, record date	Mar. 1, 2018
Treasury Stock [Member]
Class of Stock [Line Items]
Aggregate amount of repurchased shares			$ 180	$ 373	$ 740
Share Repurchase Program December 4, 2014 [Member]
Class of Stock [Line Items]
Amount of shares authorized to be repurchased							$ 1,500
Share Repurchase Program December 4, 2014 [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Number of common shares repurchased (in shares)		433,039
Share Repurchase Program December 4, 2014 [Member] | Treasury Stock [Member]
Class of Stock [Line Items]
Number of common shares repurchased (in shares)			1,000,000
Average price per share of repurchased shares (in dollars per share)			$ 183.67
Aggregate amount of repurchased shares			$ 180
Share Repurchase Program May 8, 2017 [Member]
Class of Stock [Line Items]
Amount of shares authorized to be repurchased						$ 1,500

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Liabilities [Abstract]
Contingent consideration		$ 29	$ 31	$ 29
Contingent Consideration, Liability [Abstract]
Balance at beginning of period		29
Acquisitions		14
Changes in fair value of contingent consideration, net		(12)
Balance at end of period		31
Recurring [Member] | Level 1 [Member]
Assets [Abstract]
Cash equivalents	[1]		310	104
Derivatives (foreign currency forward contracts)	[1]		0	0
Total assets	[1]		310	104
Liabilities [Abstract]
Derivatives (foreign currency forward contracts)	[1]		0	0
Contingent consideration	[1],[2]	0	0	0
Total liabilities	[1]		0	0
Contingent Consideration, Liability [Abstract]
Balance at beginning of period	[1],[2]	0
Balance at end of period	[1],[2]	0
Recurring [Member] | Level 2 [Member]
Assets [Abstract]
Cash equivalents	[3]		0	0
Derivatives (foreign currency forward contracts)	[3]		11	12
Total assets	[3]		11	12
Liabilities [Abstract]
Derivatives (foreign currency forward contracts)	[3]		1	6
Contingent consideration	[2],[3]	0	0	0
Total liabilities	[3]		1	6
Contingent Consideration, Liability [Abstract]
Balance at beginning of period	[2],[3]	0
Balance at end of period	[2],[3]	0
Recurring [Member] | Level 3 [Member]
Assets [Abstract]
Cash equivalents	[4]		0	0
Derivatives (foreign currency forward contracts)	[4]		0	0
Total assets	[4]		0	0
Liabilities [Abstract]
Derivatives (foreign currency forward contracts)	[4]		0	0
Contingent consideration	[2],[4]	29	31	29
Total liabilities	[4]		$ 31	$ 29
Contingent Consideration, Liability [Abstract]
Balance at beginning of period	[2],[4]	29
Balance at end of period	[2],[4]	$ 31
[1]	Level 1 is based on quoted market prices available in active markets for identical assets or liabilities as of the reporting date. Cash equivalents are primarily held in registered money market funds, which are valued using quoted market prices.
[2]	The contingent consideration liability represents the future potential earn-out payments relating to the L3 MacDonald Humfrey acquisition. The fair value of the contingent consideration liability is based on a Monte Carlo Simulation of the aggregate revenue of L3 MacDonald Humfrey for the three-year period ending December 31, 2019. The significant unobservable inputs used in calculating the fair value of the contingent consideration include: (i) projected revenues of the L3 MacDonald Humfrey acquired business, (ii) company specific risk premium, which is a component of the discount rate applied to the revenue projections, (iii) and volatility. The fair value of the contingent consideration for potential earn-out payments is reassessed quarterly, including an analysis of the significant inputs used in the evaluation, as well as the accretion of the present value discount. Changes are reflected within cost of sales in the consolidated statements of operations.
[3]	Level 2 is based on pricing inputs other than quoted prices in active markets, which are either directly or indirectly observable. The fair value is determined using a valuation model based on observable market inputs, including quoted foreign currency forward exchange rates and consideration of non-performance risk.
[4]	Level 3 is based on pricing inputs that are not observable and not corroborated by market data.

Financial Instruments (Details)

Financial Instruments (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	[1]	$ 3,330	$ 3,325
Foreign currency forward contracts	[2]	10	6
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes	[1]	3,502	3,526
Foreign currency forward contracts	[2]	$ 10	$ 6
[1]	The Company measures the fair value of its Senior Notes using Level 2 inputs based primarily on current market yields for its existing debt traded in the secondary market.
[2]	The Company measures the fair values of foreign currency forward contracts based on forward exchange rates. See Note 14 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative Financial Instrume79

Derivative Financial Instruments, Outstanding Forward Contracts By Currency (Details) - Foreign Currency Forward Contracts [Member] $ in Millions	Dec. 31, 2017USD ($)
Derivative [Line Items]
Notional amount	$ 307
U.S. Dollar [Member]
Derivative [Line Items]
Notional amount	108
Canadian Dollar [Member]
Derivative [Line Items]
Notional amount	100
Euro [Member]
Derivative [Line Items]
Notional amount	84
British Pound [Member]
Derivative [Line Items]
Notional amount	$ 15

Derivative Financial Instrume80

Derivative Financial Instruments, Fair Value on Consolidated Balance Sheet (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Realized pre-tax gain (loss) on forward contract		$ 5	$ (13)	$ (18)
Estimated net amount of existing gains expected to be reclassified into income within the next 12 months		2
Other Current Assets [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets		11	10
Other Current Assets [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets	[1]	11	10
Other Assets [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets		0	2
Other Assets [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets	[1]	0	2
Other Current Liabilities [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities		1	6
Other Current Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities	[1]	1	6
Other Liabilities [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities		0	0
Other Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities	[1]	$ 0	$ 0
[1]	See Note 12 for a description of the fair value hierarchy related to the Company's foreign currency forward contracts.

L3's Earnings Per Share, Reconc

L3's Earnings Per Share, Reconciliation of Basic and Diluted Earnings Per Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2017	[1]	Sep. 29, 2017	[2]	Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016	[1]	Sep. 23, 2016	[2]	Jun. 24, 2016		Mar. 25, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of net income (loss) [Abstract]
Net income (loss)	$ 293		$ 25		$ 207		$ 168		$ 192		$ 151		$ 151		$ 230		$ 693	$ 724	$ (225)
Net income from continuing operations attributable to noncontrolling interests																	(16)	(14)	(15)
Net income (loss) attributable to L-3	289		22		202		164		188		148		147		227		677	710	(240)
Earnings (loss) attributable to L3's common shareholders: [Abstract]
Continuing operations																	753	619	492
Discontinued operations, net of income tax																	(76)	91	(732)
Net income (loss) attributable to L-3	$ 289		$ 22		$ 202		$ 164		$ 188		$ 148		$ 147		$ 227		$ 677	$ 710	$ (240)
Basic [Abstract]
Weighted average common shares outstanding (in shares)																	78	77.4	80.7
Basic earnings (loss) per share: [Abstract]
Continuing operations (in dollars per share)	$ 3.42	[3]	$ 1.83	[3]	$ 2.44	[3]	$ 1.97	[3]	$ 2.37	[3]	$ 1.89	[3]	$ 1.68	[3]	$ 2.06	[3]	$ 9.65	$ 7.99	$ 6.10
Discontinued operations, net of income tax (in dollars per share)																	(0.97)	1.18	(9.07)
Basic earnings (loss) per share (in dollars per share)	3.70	[3]	0.28	[3]	2.59	[3]	2.11	[3]	2.43	[3]	1.91	[3]	1.90	[3]	2.92	[3]	$ 8.68	$ 9.17	$ (2.97)
Common and potential common shares [Abstract]
Weighted average common shares outstanding (in shares)																	78	77.4	80.7
Effect of dilutive securities																	1.6	1.4	1.2
Common and potential common shares (in shares)																	79.6	78.8	81.9
Diluted earnings (loss) per share: [Abstract]
Continuing operations (in dollars per share)	3.34	[3]	1.79	[3]	2.39	[3]	1.93	[3]	2.32	[3]	1.85	[3]	1.66	[3]	2.02	[3]	$ 9.46	$ 7.86	$ 6.01
Discontinued operations, net of income tax (in dollars per share)																	(0.95)	1.15	(8.94)
Diluted earnings (loss) per share (in dollars per share)	$ 3.62	[3]	$ 0.28	[3]	$ 2.54	[3]	$ 2.07	[3]	$ 2.38	[3]	$ 1.88	[3]	$ 1.88	[3]	$ 2.87	[3]	$ 8.51	$ 9.01	$ (2.93)
[1]	Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.
[2]	The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.
[3]	EPS in each quarter is computed using the weighted-average number of shares outstanding during that quarter, while EPS for the full year is computed using the weighted-average number of shares outstanding during the year. Therefore, the sum of the four quarters' EPS may not equal the full year computed EPS.

L3's Earnings Per Share (Detail

L3's Earnings Per Share (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsidiary, Sale of Stock [Line Items]
Shares excluded from computation of diluted earnings per share (in shares)	0.3	0.4	0.6

Income Taxes, Income from Conti

Income Taxes, Income from Continuing Operations Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Federal corporate tax rate			35.00%	35.00%	35.00%
Estimated tax benefit amount	$ (79)		$ (79)
Benefit amount from remeasurement of deferred tax assets			(101)
Estimated toll charge			22
Domestic			649	$ 608	$ 509
Foreign			222	196	130
Income from continuing operations before income taxes			$ 871	$ 804	$ 639
Plan [Member]
Income Tax Disclosure [Line Items]
Federal corporate tax rate		21.00%

Income Taxes, Components of Cur

Income Taxes, Components of Current and Deferred Portions of Provision for Income Taxes on Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current income tax provision [Abstract]
Federal	$ 44	$ 88	$ 81
State and local	10	8	7
Foreign	56	48	26
Subtotal	110	144	114
Deferred income tax provision/(benefit) [Abstract]
Federal	(16)	25	9
State and local	6	2	7
Foreign	2	0	2
Subtotal	(8)	27	18
Total provision for income taxes	$ 102	$ 171	$ 132

Income Taxes, Reconciliation of

Income Taxes, Reconciliation of Statutory Federal Income Tax Rate to Effective Income Tax Rate on Continuing Operations (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefit	2.00%	2.00%	2.00%
Foreign income taxes	(6.70%)	(3.00%)	(7.10%)
Manufacturing benefits	(1.40%)	(2.20%)	(2.20%)
Research and experimentation and other tax credits	(4.10%)	(4.60%)	(6.50%)
Resolution of tax contingencies	(0.40%)	(3.10%)	(1.40%)
Tax deductible dividends	(0.90%)	(1.00%)	(1.20%)
Equity compensation - excess income tax benefits	(2.30%)	(2.10%)	0.00%
Goodwill impairment	0.00%	0.00%	1.90%
Tax Reform	(9.10%)	0.00%	0.00%
Other, net	(0.40%)	0.30%	0.20%
Effective income tax rate on continuing operations	11.70%	21.30%	20.70%

Income Taxes, Components of Net

Income Taxes, Components of Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets [Abstract]
Inventoried costs	$ 44	$ 53
Compensation and benefits	94	139
Pension and postretirement benefits	281	413
Loss carryforwards	12	19
Tax credit carryforwards	5	6
Other	57	87
Deferred tax assets	493	717
Less: valuation allowance	(10)	(12)
Deferred tax assets, net of valuation allowance	483	705
Deferred tax liabilities [Abstract]
Goodwill and other intangible assets	(514)	(722)
Income recognition on contracts in process	(24)	(22)
Property, plant and equipment	(59)	(93)
Other	(41)	(55)
Deferred tax liabilities	(638)	(892)
Total deferred tax liabilities, net of valuation allowance	$ (155)	$ (187)

Income Taxes, Classification of

Income Taxes, Classification of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Abstract]
Non-current deferred tax assets	$ 3	$ 2
Non-current deferred tax liabilities	(158)	(189)
Total deferred tax liabilities, net of valuation allowance	$ (155)	$ (187)

Income Taxes, Summary of Loss a

Income Taxes, Summary of Loss and Tax Credit Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Tax Effected	$ 12	$ 19
Capital loss carryforwards, Valuation Allowance, Tax Effected	(10)	(12)
Total loss carryforwards, Tax Effected	12
Tax credit carryforwards, Tax Effected	5	$ 6
Total loss carryforwards, Valuation Allowance Tax Effected	(5)
Tax credit carryforwards, Valuation Allowances Tax Effected	(4)
Federal [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Gross	29
Capital loss carryforwards, Tax Effected	6
Capital loss carryforwards, Valuation Allowance, Gross	(5)
Capital loss carryforwards, Valuation Allowance, Tax Effected	$ (1)
Federal [Member] | Minimum [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Expiration Period	2,026
Federal [Member] | Maximum [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Expiration Period	2,036
Foreign [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Gross	$ 12
Capital loss carryforwards, Tax Effected	3
Capital loss carryforwards, Valuation Allowance, Gross	(6)
Capital loss carryforwards, Valuation Allowance, Tax Effected	(2)
State [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Gross	160
Capital loss carryforwards, Tax Effected	3
Capital loss carryforwards, Valuation Allowance, Gross	(135)
Capital loss carryforwards, Valuation Allowance, Tax Effected	(2)
Tax credit carryforwards, Tax Effected	5
Tax credit carryforwards, Gross	6
Tax credit carryforwards, Valuation Allowances Gross	(5)
Tax credit carryforwards, Valuation Allowances Tax Effected	$ (4)
State [Member] | Minimum [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Expiration Period	2,018
Tax credit carryforwards, Expiration Periods	2,018
State [Member] | Maximum [Member]
Tax Credit Carryforward [Line Items]
Capital loss carryforwards, Expiration Period	2,037
Tax credit carryforwards, Expiration Periods	2,032

Income Taxes, Reconciliation 89

Income Taxes, Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Income Taxes [Abstract]
Unrecognized tax benefits	$ 178	$ 124	$ 124	$ 178
Unrecognized tax benefits that would reduce the effective income tax rate				$ 157
Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties [Roll Forward]
Balance at January 1	110	124	150
Additions for tax positions related to the current year	14	16	14
Additions for tax positions related to prior years	66	2	2
Reductions for tax positions related to prior years	(4)	(24)	(34)
Reductions for tax positions related to settlements with taxing authorities	0	(1)	(1)
Reduction for tax positions related to prior years as a result of a lapse of statute of limitations	(8)	(7)	(7)
Balance at December 31	$ 178	$ 110	$ 124

Income Taxes, Income Tax Return

Income Taxes, Income Tax Returns (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Abstract]
Anticipated decrease in unrecognized tax benefits over the next 12 months	$ 6
Reversal of previously accrued income tax expense, including interest and penalties	4	$ 25	$ 9
Accrued potential interest included within current and non-current income taxes payable	15	11
Accrued potential interest included within current and non-current income taxes payable after income taxes	11	7
Potential penalties	8	7
Benefit (Expense) Related Items Included in Income Taxes Expenses	5	$ (3)
Deferred taxes for the repatriation of earnings from certain subsidiaries			$ 17
Undistributed earnings of non-U.S. Companies	$ 844

Stock-Based Compensation, Stock

Stock-Based Compensation, Stock-Based Compensation Plans (Details) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	May 03, 2016	Feb. 23, 2016	Feb. 22, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of L-3 Holdings common stock available to be awarded (in shares)					4,260	3,690
Share-based Compensation Arrangement by Share-based Payment Award [Abstract]
Stock based compensation	$ 57	$ 49	$ 49
Income taxes	(12)	(18)	(18)
Total after income taxes	45	31	31
Less: Stock-based compensation recorded in discontinued operations, net of income taxes	1	1	1
Stock-based compensation recorded in continuing operations, net of income taxes	44	30	30
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Abstract]
Stock based compensation	7	10	9
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Abstract]
Stock based compensation	43	35	38
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Abstract]
Stock based compensation	$ 7	$ 4	$ 2
2008 Long Term Performance Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of additional shares authorized for issuance under the amendment (in shares)				6,800
Number of shares authorized for issuance under the amendment (in shares)				26,000
Maximum number of shares of L-3 Holdings common stock may be issued pursuant to "full value" awards under the amendment (in shares)	7,900

Stock-Based Compensation, Sto92

Stock-Based Compensation, Stock Options (Details) - Stock Options [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period of stock options granted from date of grant		10 years
Vesting period		3 years
Weighted average grant date fair value of stock options (in dollars per share)		$ 28.35	$ 15.90	$ 19.76
Intrinsic value of stock options exercised		$ 44	$ 34	$ 35
Unrecognized compensation costs related to stock awards		7
Unrecognized compensation costs related to equity awards after income taxes		$ 6
Weighted average remaining period for recognition of unrecognized costs related to equity awards		1 year 3 months 18 days
Actual income tax benefit realized related to compensation deductions arising from the exercise of stock options		$ 16	$ 12	$ 13
Number of Options [Roll Forward]
Beginning Balance, Outstanding (in shares)		2,847,500
Options granted (in shares)		470,500
Options exercised (in shares)		(521,300)
Options forfeited (in shares)		(97,800)
Ending Balance, Outstanding (in shares)		2,698,900	2,847,500
Vested and expected to vest (in shares)	[1]	2,582,500
Exercisable (in shares)		1,762,400
Weighted Average Exercise Price [Abstract]
Beginning Balance, Outstanding (in dollars per share)		$ 99.54
Options granted (in dollars per share)		174.53
Options exercised (in dollars per share)		90.13
Options forfeited (in dollars per share)		120.59
Ending Balance, Outstanding (in dollars per share)		113.67	$ 99.54
Vested and expected to vest (in dollars per share)	[1]	110.21
Exercisable (in dollars per share)		$ 95.80
Weighted Average Remaining Contractual Term [Abstract]
Weighted Average Remaining Contractual Term, Outstanding		5 years 8 months 12 days	6 years 1 month 6 days
Vested and expected to vest	[1]	5 years 6 months
Exercisable		4 years 6 months
Aggregate Intrinsic Value [Abstract]
Beginning Balance, Outstanding		$ 150
Ending Balance, Outstanding		227	$ 150
Vested and expected to Vest	[1]	226
Exercisable		$ 180
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected holding period		5 years 2 months 12 days	5 years	5 years
Expected volatility		19.90%	21.30%	21.40%
Expected dividend yield		2.00%	2.80%	2.40%
Risk-free interest rate		2.00%	1.10%	1.50%
[1]	Represents outstanding options reduced by expected forfeitures for options not fully vested.

Stock-Based Compensation, Restr

Stock-Based Compensation, Restricted Stock Units (Details) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Weighted average grant date fair value (in dollars per share)	$ 169.23	$ 116.72	$ 128.59
Length of service after grant date	1 year
Retirement eligibility, employee age	60 years
Service period, minimum	5 years
Retirement eligibility, employee age with no service requirement	65 years
Unrecognized compensation costs related to stock awards	$ 34
Unrecognized compensation costs related to equity awards after income taxes	$ 26
Weighted average remaining period for recognition of unrecognized costs related to equity awards	1 year 1 month 6 days
Fair value of restricted stock unit awards vested	$ 53	$ 57	$ 82
Nonvested, Number of Shares [Roll Forward]
Beginning Balance, Nonvested (in shares)	977,900
Granted (in shares)	305,600
Vested (in shares)	(318,400)
Forfeited (in shares)	(62,400)
Ending Balance, Nonvested (in shares)	902,700	977,900
Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning Balance, Nonvested (in dollars per share)	$ 119.55
Granted (in dollars per share)	169.23	$ 116.72	$ 128.59
Vested (in dollars per share)	114.46
Forfeited (in dollars per share)	134.56
Ending Balance, Nonvested (in dollars per share)	$ 137.12	$ 119.55
Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year

Stock-Based Compensation, Perfo

Stock-Based Compensation, Performance Units (Details) - Performance Units [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in dollars per share)	$ 168.80	$ 116.20	$ 129.03
Length of service after grant date	3 years	3 years	3 years
Unrecognized compensation costs related to stock awards	$ 5
Unrecognized compensation costs related to equity awards after income taxes	$ 5
Weighted average remaining period for recognition of unrecognized costs related to equity awards	1 year 8 months 12 days
Total performance units earned (in shares)	48,365
Fair market value performance units earned as of their vesting date	$ 10
Nonvested, Number of Shares [Roll Forward]
Beginning Balance, Nonvested (in shares)	124,700
Granted (in shares)	33,900
Increase due to expected performance (in shares)	29,700
Vested (in shares)	(48,400)
Forfeited (in shares)	(7,800)
Ending Balance, Nonvested (in shares)	132,100	124,700
Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning Balance, Nonvested (in dollars per share)	$ 120.83
Granted (in dollars per share)	168.80	$ 116.20	$ 129.03
Increase due to expected performance (in dollars per share)	146.89
Vested (in dollars per share)	129.03
Forfeited (in dollars per share)	121.06
Ending Balance, Nonvested (in dollars per share)	$ 135.99	$ 120.83
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout Range	200.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payout Range	0.00%

Stock-Based Compensation, Emplo

Stock-Based Compensation, Employee Stock Purchase Plan (Details) - USD ($) $ / shares in Units, shares in Millions	Jan. 31, 2018	Dec. 31, 2017	May 03, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee discount on the purchase of common stock		5.00%
2008 Long Term Performance Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance under the amendment (in shares)			26
2009 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value for offering period		95.00%
Offering period to purchase shares		6 months
Share purchases funded through payroll deductions, value		$ 21,250
Issued shares under the ESPP (in shares)		0.1
Average price of issued shares under the ESPP (in dollars per share)		$ 158.59
Number of shares authorized for issuance under the amendment (in shares)		3.5
2009 Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share purchases funded through payroll deductions, percentage		10.00%
2009 Employee Stock Purchase Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issued shares under the ESPP (in shares)	0.1
Average price of issued shares under the ESPP (in dollars per share)	$ 188.72

Commitments and Contingencies,

Commitments and Contingencies, Non-Cancelable Operating Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Future Minimum Payments under Non-Cancelable Operating Leases [Abstract]
2,018	$ 106
2,019	84
2,020	108
2,021	60
2,022	57
Thereafter	236
Total minimum payments required	651
Sublease rentals under non-cancelable leases	(9)
Net minimum payments required	642
Rent expense, net of sublease income	103	$ 97	$ 102
Sublease rental income	1	$ 2	$ 2
Real Estate [Member]
Future Minimum Payments under Non-Cancelable Operating Leases [Abstract]
2,018	101
2,019	81
2,020	106
2,021	60
2,022	57
Thereafter	236
Total minimum payments required	641
Sublease rentals under non-cancelable leases	(9)
Net minimum payments required	632
Equipment [Member]
Future Minimum Payments under Non-Cancelable Operating Leases [Abstract]
2,018	5
2,019	3
2,020	2
2,021	0
2,022	0
Thereafter	0
Total minimum payments required	10
Sublease rentals under non-cancelable leases	0
Net minimum payments required	$ 10

Commitments and Contingencies97

Commitments and Contingencies, Letters of Credit and Guarantees (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)Agreement	Dec. 31, 2016USD ($)
Loss Contingencies [Line Items]
Total outstanding letters of credit		$ 416	$ 402
Available borrowings under Credit Facility		$ 1,000
Number of existing real estate lease agreements | Agreement		3
Real estate lease agreements, expiry date		Aug. 31, 2020
Purchase price of property on or before expiration date		$ 45
Residual guarantee amount		39
Maximum amount of supplemental rent payment		6
Aggregate residual guarantee amount		$ 39
Simulator Systems [Member]
Loss Contingencies [Line Items]
Operating lease agreements, term of contract		15 years
Simulator Systems [Member] | Forecast [Member]
Loss Contingencies [Line Items]
Purchase of simulator systems	$ 15

Commitments and Contingencies98

Commitments and Contingencies, Litigation Matters (Details) - HVC Alkmaar [Member] € in Millions	Jul. 23, 2014EUR (€)
Property Damages [Member]
Contingencies And Commitments [Line Items]
Claims for estimated damages	€ 11
Business Interruption [Member]
Contingencies And Commitments [Line Items]
Claims for estimated damages	€ 35

Pension and Other Postretirem99

Pension and Other Postretirement Benefits, Changes in Benefit Obligations, Plan Assets and Funded Status and Aggregate Balance Sheet Impact (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Assets and (liabilities) recognized on the consolidated balance sheets consist of [Abstract]
Non-current liabilities	$ (1,313)		$ (1,177)
Pension Plans [Member]
Change in benefit obligation [Abstract]
Benefit obligation at the beginning of the year	3,758		3,448
Service cost	112		108		$ 123
Interest cost	142		135		149
Plan participants' contributions	2		2
Amendments	0		15
Actuarial loss (gain)	376		167
Foreign currency exchange rate changes	22		9
Curtailments and special termination benefits	2		2
Benefits paid	(186)		(128)
Benefit obligation at the end of the year	4,228		3,758		3,448
Change in plan assets [Abstract]
Fair value of plan assets at the beginning of the year	2,721		2,552
Actual return on plan assets	391		189
Employer contributions	97		97
Plan participants' contributions	2		2
Foreign currency exchange rate changes	22		9
Benefits paid	(186)		(128)
Fair value of plan assets at the end of the year	3,047		2,721		2,552
Unfunded status at the end of the year	(1,181)		(1,037)
Assets and (liabilities) recognized on the consolidated balance sheets consist of [Abstract]
Non-current assets	48		37
Current liabilities	(6)		(6)
Non-current liabilities	(1,223)		(1,068)
Total	(1,181)		(1,037)
Postretirement Benefit Plans [Member]
Change in benefit obligation [Abstract]
Benefit obligation at the beginning of the year	177		184
Service cost	2		2		3
Interest cost	5		6		7
Plan participants' contributions	5		4
Amendments	0		(3)
Actuarial loss (gain)	(13)		(3)
Foreign currency exchange rate changes	2		0
Curtailments and special termination benefits	0		0
Benefits paid	(13)		(13)
Benefit obligation at the end of the year	165		177		184
Change in plan assets [Abstract]
Fair value of plan assets at the beginning of the year	60	[1]	57
Actual return on plan assets	8		5
Employer contributions	7		7
Plan participants' contributions	5		4
Foreign currency exchange rate changes	0		0
Benefits paid	(13)		(13)
Fair value of plan assets at the end of the year	67	[1]	60	[1]	$ 57
Unfunded status at the end of the year	(98)		(117)
Assets and (liabilities) recognized on the consolidated balance sheets consist of [Abstract]
Non-current assets	0		0
Current liabilities	(8)		(8)
Non-current liabilities	(90)		(109)
Total	$ (98)		$ (117)
[1]	Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the NYSE, NASDAQ, and various international exchanges.

Pension and Other Postretire100

Pension and Other Postretirement Benefits, Net Loss and Prior Service Cost Balances in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	$ 1,035	$ 896
Prior service cost (credit)	10	14
Total amount recognized	1,045	910
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	(3)	(12)
Prior service cost (credit)	(27)	(4)
Total amount recognized	$ (30)	$ (16)

Pension and Other Postretire101

Pension and Other Postretirement Benefits, Aggregate Accumulated Benefit Obligation in Excess of Fair Value (Details) - Pension Plans [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Aggregate accumulated benefit obligation (ABO)	$ 3,813	$ 3,413
Projected benefit obligation	3,875	3,528
Accumulated benefit obligation	3,490	3,192
Fair value of plan assets	$ 2,651	$ 2,456

Pension and Other Postretire102

Pension and Other Postretirement Benefits, Weighted Average Assumptions Used to Determine Benefit Obligations (Details)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Pension Plans [Member]
Benefit obligations [Abstract]
Discount rate	[1]	3.78%	4.40%
Rate of compensation increase	[2]	3.50%	3.50%
Pension Plans [Member] | U.S. [Member]
Benefit obligations [Abstract]
Rate of compensation increase		3.50%	3.50%
Assumptions used to determine net periodic benefit cost, weighted average discount rate		3.81%	4.45%
Pension Plans [Member] | Canada [Member]
Benefit obligations [Abstract]
Rate of compensation increase		3.50%	3.50%
Assumptions used to determine net periodic benefit cost, weighted average discount rate		3.39%	3.79%
Postretirement Benefit Plans [Member]
Benefit obligations [Abstract]
Discount rate	[3]	3.59%	4.05%
Postretirement Benefit Plans [Member] | U.S. [Member]
Benefit obligations [Abstract]
Assumptions used to determine net periodic benefit cost, weighted average discount rate		3.63%	4.11%
Postretirement Benefit Plans [Member] | Canada [Member]
Benefit obligations [Abstract]
Assumptions used to determine net periodic benefit cost, weighted average discount rate		3.33%	3.64%
[1]	The weighted average discount rate assumptions used at December 31, 2017 and 2016 were comprised of separate assumptions determined by country of 3.81% and 4.45% for the U.S. based plans, respectively, and 3.39% and 3.79% for the Canadian based plans, respectively.
[2]	The weighted average rate of compensation increase assumptions were comprised of separate assumptions determined by country of 3.5% for both the U.S. based plans and Canadian based plans at December 31, 2017 and 2016.
[3]	The weighted average discount rate assumptions used at December 31, 2017 and 2016 were comprised of separate assumptions determined by country of 3.63% and 4.11% for the U.S. based plans, respectively, and 3.33% and 3.64% for the Canadian based plans, respectively.

Pension and Other Postretire103

Pension and Other Postretirement Benefits, Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans [Member]
Components of net periodic benefit cost [Abstract]
Service cost		$ 112	$ 108	$ 123
Interest cost		142	135	149
Expected return on plan assets		(212)	(200)	(205)
Amortization of prior service cost (credits)		1	0	1
Amortization of net loss (gains)		61	52	68
Curtailment loss and special termination benefits	[1]	6	2	3
Net periodic benefit cost		110	97	139
Postretirement Benefit Plans [Member]
Components of net periodic benefit cost [Abstract]
Service cost		2	2	3
Interest cost		5	6	7
Expected return on plan assets		(4)	(4)	(5)
Amortization of prior service cost (credits)		(1)	(2)	(2)
Amortization of net loss (gains)		(2)	(2)	0
Curtailment loss and special termination benefits	[1]	0	0	0
Net periodic benefit cost		$ 0	$ 0	$ 3
[1]	During the year ended December 31, 2017, the curtailment loss and special termination benefits charge is primarily due to a pension curtailment charge in connection with the decision to discontinue future service accruals for substantially all salaried employee defined benefit plans effective January 1, 2019.

Pension and Other Postretire104

Pension and Other Postretirement Benefits, Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) [Abstract]
Net loss (gain)	$ 71
Prior service credit	(1)
Total amount expected to be amortized	70
Pension Plans [Member]
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) [Abstract]
Net loss (gain)	200	$ 179	$ (132)
Prior service (cost) credit	(4)	15	0
Amortization of net (loss) gain	(61)	(52)	(68)
Amortization of prior service (cost) credit	(1)	0	(1)
Total recognized in other comprehensive income (loss)	134	142	(201)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	244	239	(62)
Net loss (gain)	74
Prior service credit	0
Total amount expected to be amortized	74
Postretirement Benefit Plans [Member]
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss) [Abstract]
Net loss (gain)	(17)	(4)	(7)
Prior service (cost) credit	0	(2)	0
Amortization of net (loss) gain	2	2	0
Amortization of prior service (cost) credit	1	2	2
Total recognized in other comprehensive income (loss)	(14)	(2)	(5)
Total recognized in net periodic benefit cost and other comprehensive income (loss)	(14)	$ (2)	$ (2)
Net loss (gain)	(3)
Prior service credit	(1)
Total amount expected to be amortized	$ (4)

Pension and Other Postretire105

Pension and Other Postretirement Benefits, Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Effect of one percentage point increase on total service and interest cost		$ 0
Effect of one percentage point decrease on total service and interest cost		0
Effect of one percentage point increase on postretirement benefit obligations		5
Effect of one percentage point decrease on postretirement benefit obligations		$ (4)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	[1]	4.40%	4.67%	4.14%
Service cost		4.55%	4.83%	0.00%	[2]
Interest cost		3.84%	3.95%	0.00%	[2]
Expected long-term return on plan assets	[3]	7.92%	7.92%	8.14%
Rate of compensation increase	[4]	3.50%	3.50%	3.50%
Pension Plans [Member] | U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation		4.45%	4.73%	4.20%
Expected long-term return on plan assets		8.00%	8.00%	8.25%
Rate of compensation increase		3.50%	3.50%	3.50%
Health care cost trend rate, covering retirees under 65 years of age next fiscal year		6.50%
Health care cost trend rate, covering retirees over 65 years of age next fiscal year		8.00%
Pension Plans [Member] | U.S. [Member] | 2021 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate, covering retirees under 65 years of age		5.00%
Pension Plans [Member] | U.S. [Member] | 2024 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate, covering retirees over 65 years of age		5.00%
Pension Plans [Member] | Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation		3.79%	3.93%	3.90%
Expected long-term return on plan assets		7.25%	7.25%	7.25%
Rate of compensation increase		3.50%	3.50%	3.50%
Health care cost trend rate next fiscal year		6.25%
Pension Plans [Member] | Canada [Member] | 2023 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate		5.00%
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	[5]	4.05%	4.22%	3.70%
Service cost		4.21%	4.37%	0.00%	[2]
Interest cost		3.26%	3.26%	0.00%	[2]
Expected long-term return on plan assets		7.43%	7.42%	7.65%
Postretirement Benefit Plans [Member] | U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation		4.11%	4.28%	3.70%
Postretirement Benefit Plans [Member] | Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation		3.64%	3.74%	3.70%
[1]	The weighted average discount rate assumptions used for the years ended December 31, 2017, 2016, and 2015 were comprised of separate assumptions determined by country of 4.45%, 4.73% and 4.20% for the U.S. based plans and 3.79%, 3.93% and 3.90% for the Canadian based plans, respectively.
[2]	Not applicable as the Company changed to the spot rate approach beginning in 2016 as described above.
[3]	The weighted average expected long-term return on plan assets assumptions used were comprised of separate assumptions determined by country of 8.00% for each of the years ended December 31, 2017 and 2016 and 8.25% for the year ended December 31, 2015 for the U.S. based plans and 7.25% for the Canadian based plans for the years ended December 31, 2017, 2016 and 2015.
[4]	The weighted average rate of compensation increase assumptions used for the years ended December 31, 2017, 2016 and 2015 were comprised of separate assumptions determined by country of 3.50% for both the U.S and Canadian based plans.
[5]	The weighted average discount rate assumptions used for the years ended December 31, 2017, 2016 and 2015 were comprised of separate assumptions determined by country of 4.11%, 4.28% and 3.70% for the U.S. based plans and 3.64%, 3.74% and 3.70% for the Canadian based plans, respectively.

Pension and Other Postretire106

Pension and Other Postretirement Benefits, Weighted Average Asset Allocations by Asset Category (Details) - Pension and Postemployment Retirement Benefit Plans [Member]		Dec. 31, 2017	Dec. 31, 2016
U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	[1],[2]	100.00%	100.00%
U.S. [Member] | Total Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		58.00%	65.00%
U.S. [Member] | Total Equities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		45.00%
U.S. [Member] | Total Equities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		75.00%
U.S. [Member] | Domestic Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	[1]	47.00%	55.00%
U.S. [Member] | Domestic Equity [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[1]	30.00%
U.S. [Member] | Domestic Equity [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[1]	60.00%
U.S. [Member] | International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	[2]	11.00%	10.00%
U.S. [Member] | International Equity [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[2]	10.00%
U.S. [Member] | International Equity [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[2]	20.00%
U.S. [Member] | Total Fixed Income Securities and Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[3]
Weighted-average asset allocations	[3]
U.S. [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		28.00%	22.00%
U.S. [Member] | Fixed Income Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		20.00%
U.S. [Member] | Fixed Income Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		40.00%
U.S. [Member] | Other, Primarily Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		7.00%	5.00%
U.S. [Member] | Other, Primarily Cash and Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[1],[2]	0.00%
U.S. [Member] | Other, Primarily Cash and Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets	[1],[2]	15.00%
U.S. [Member] | Real Estate Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		7.00%	8.00%
U.S. [Member] | Real Estate Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		0.00%
U.S. [Member] | Real Estate Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		15.00%
Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	[1],[2]	100.00%	100.00%
Canada [Member] | Total Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		62.00%	77.00%
Canada [Member] | Total Equities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		40.00%
Canada [Member] | Total Equities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		80.00%
Canada [Member] | Domestic Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	[1]	15.00%	15.00%
Canada [Member] | International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	[2]	47.00%	62.00%
Canada [Member] | Total Fixed Income Securities and Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		38.00%	23.00%
Canada [Member] | Total Fixed Income Securities and Cash and Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		20.00%
Canada [Member] | Total Fixed Income Securities and Cash and Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets		60.00%
Canada [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		25.00%	13.00%
Canada [Member] | Other, Primarily Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		13.00%	10.00%
Canada [Member] | Real Estate Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations		0.00%	0.00%
[1]	Domestic equities for Canadian plans refers to equities of Canadian companies.
[2]	International equities for Canadian plans includes equities of U.S. companies.
[3]	Not applicable. The Company's Master Pension Trust Investment Policy does not provide an allocation percentage range to fixed income securities and cash and cash equivalents.

Pension and Other Postretire107

Pension and Other Postretirement Benefits, Fair Value of Pension Plan Assets (Details) - Pension Plans [Member] - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Equity securities [Abstract]
Fair value of company's plan assets		$ 3,047	$ 2,721		$ 2,552
U.S. [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net		(30)	(23)
Fair value of company's plan assets	[1]	$ 2,704	$ 2,421	[2],[3]
Percentage of mutual fund in total investment in fixed income - investment grade securities		62.00%	62.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities		38.00%	38.00%
U.S. [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		$ 1,909	$ 1,864	[1]
U.S. [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		622	409	[1]
U.S. [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		0	0	[1]
U.S. [Member] | U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	1,297	1,331
U.S. [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	1,297	1,331
U.S. [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. [Member] | International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	87	85
U.S. [Member] | International Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	87	85
U.S. [Member] | International Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. [Member] | International Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
U.S. [Member] | Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	534	414
U.S. [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	329	255
U.S. [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	205	159
U.S. [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
U.S. [Member] | Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	219	136
U.S. [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
U.S. [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	219	136
U.S. [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
U.S. [Member] | Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	196	193
U.S. [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	196	193
U.S. [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	0	0
U.S. [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	0	0
U.S. [Member] | Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	198	114
U.S. [Member] | Other [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	0	0
U.S. [Member] | Other [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	198	114
U.S. [Member] | Other [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	0	0
U.S. [Member] | Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets		2,531	2,273
U.S. [Member] | Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2],[3]	203	171
Canada [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net		0	0
Fair value of company's plan assets	[1]	$ 343	$ 300	[2],[3]
Percentage of mutual fund investment in equity trust funds		31.00%	55.00%
Percentage of pooled bond fund investment in equity trust funds		69.00%	45.00%
Canada [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		$ 184	$ 188	[1]
Canada [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		37	27	[1]
Canada [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets		0	0	[1]
Canada [Member] | U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	71	79
Canada [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	71	79
Canada [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canada [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canada [Member] | International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	105	104
Canada [Member] | International Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	105	104
Canada [Member] | International Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canada [Member] | International Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0	0
Canada [Member] | Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canada [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canada [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canada [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0	0
Canada [Member] | Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
Canada [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
Canada [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
Canada [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0	0
Canada [Member] | Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	0	0
Canada [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	0	0
Canada [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	0	0
Canada [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[6]	0	0
Canada [Member] | Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	45	32
Canada [Member] | Other [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	8	5
Canada [Member] | Other [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	37	27
Canada [Member] | Other [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[7]	0	0
Canada [Member] | Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets		221	215
Canada [Member] | Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2],[3]	$ 122	$ 85
[1]	Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the New York Stock Exchange (NYSE), National Association of Securities Dealers Automated Quotations (NASDAQ), and various international exchanges.
[2]	All of the U.S. plans other investments measured using NAV at December 31, 2017 and 2016 and approximately 31% and 55% at December 31, 2017 and 2016, respectively, of the Canadian plans other investments measured using NAV consist of a regulated commingled equity trust fund, for which fair value is based on the NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund's holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV. Approximately 69% and 45% at December 31, 2017 and 2016, respectively, of the Canadian plans other investments measured using NAV are invested in regulated commingled bond funds (the "Bond Funds"). As these Bond Funds do not trade in an active market, the fair value is based on NAVs calculated by fund managers based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs as a practical expedient to estimating fair value and classified as Level 2. Withdrawals are permitted monthly, with notice between 0 and 3 days of the transaction date, based on NAV.
[3]	In accordance with ASU 2015-07, certain investments that are measured at fair value using the net asset value (NAV) per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position.
[4]	Approximately 62% at December 31, 2017 and 2016 of U.S. plan assets that are invested in the Fixed Income - Investment Grade asset category consist of a mutual fund offered by a registered investment company (the Fund) and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy, as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 38% at December 31, 2017 and 2016 of U.S. plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2.
[5]	Fixed Income - High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs.
[6]	Real Estate Investment Trusts (REITs) consist of securities that trade on the major exchanges and invest directly in real estate, either through properties or mortgages.
[7]	Other consists primarily of: (1) money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit, and are classified as Level 2, and (2) cash, which is classified as Level 1.

Pension and Other Postretire108

Pension and Other Postretirement Benefits, Fair Value of Postretirement Benefit Plans Assets (Details) - Postretirement Benefit Plans [Member] - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Equity securities [Abstract]
Fair value of company's plan assets		$ 67	[1]	$ 60	[1]	$ 57
Percentage of mutual fund in total investment in fixed income - investment grade securities		77.00%		73.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities		23.00%		27.00%
Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	$ 53		$ 49
Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	11		8
Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0		0
U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	38		37
U.S. Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	38		37
U.S. Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0		0
U.S. Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0		0
International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	2		1
International Equity [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	2		1
International Equity [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0		0
International Equity [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[1]	0		0
Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	13		11
Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	10		8
Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	3		3
Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[2]	0		0
Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	3		2
Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0		0
Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	3		2
Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[3]	0		0
Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	3		3
Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	3		3
Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0		0
Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[4]	0		0
Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	5		3
Other [Member] | Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0		0
Other [Member] | Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	5		3
Other [Member] | Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	[5]	0		0
Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets		64		57
Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net	[6],[7]	$ 3		$ 3
[1]	Equity securities consist of investments in common stock of U.S. and international companies. The fair value of equity securities is based on quoted market prices available in active markets at the close of a trading day, primarily the NYSE, NASDAQ, and various international exchanges.
[2]	Approximately 77% and 73% at December 31, 2017 and 2016, respectively, of the postretirement benefit plan assets that are invested in the Fixed Income - Investment Grade asset category consist of the Fund and fixed income securities. The Fund invests in investment grade fixed income securities, mortgaged-backed securities, U.S. treasury and agency bonds and corporate bonds. These investments are classified by the Company as a Level 1 measurement within the fair value hierarchy as the mutual fund trades on an active market and daily, quoted prices are available. The remaining 23% and 27% at December 31, 2017 and 2016, respectively, of the postretirement benefit plan assets are fixed income securities, primarily investment grade corporate bonds from various industries held directly by the plan. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs and are classified as Level 2.
[3]	Fixed Income - High Yield consists of investments in corporate high-yield bonds from various industries. The fair values of these investments are based on yields currently available on comparable bonds of issuers with similar credit ratings, quoted prices of similar bonds in an active market, or cash flows based on observable inputs.
[4]	REITs consist of securities that trade on the major exchanges and invest directly, either through properties or mortgages.
[5]	Other consists primarily of money market accounts, which invest primarily in short-term, high quality money market securities such as government obligations, commercial paper, time deposits and certificates of deposit.
[6]	All of the postretirement benefit plans other investments measured using NAV at December 31, 2017 and 2016 consist of a regulated commingled equity trust fund, which fair value is based on NAV at the end of each month. The NAV is calculated by the fund manager based on the fair value of the fund's holdings, primarily equity securities traded in active markets, determined as of the end of each month as a practical expedient to estimating fair value. This practical expedient is not used when it is determined to be probable that the fund will sell the investment for an amount different than the reported NAV. Withdrawals are permitted, with notice by the 20th day of each month, based on NAV.
[7]	In accordance with ASU 2015-07, certain investments that are measured at fair value using the NAV per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statements of financial position.

Pension and Other Postretire109

Pension and Other Postretirement Benefits, Contributions (Details) $ in Millions	Dec. 31, 2017USD ($)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to plans in 2018	$ 100
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to plans in 2018	$ 10

Pension and Other Postretire110

Pension and Other Postretirement Benefits, Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2017USD ($)
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,018	$ 158
2,019	165
2,020	175
2,021	185
2,022	194
Years 2023-2027	1,128
Postretirement Benefit Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,018	12
2,019	12
2,020	13
2,021	13
2,022	12
Years 2023-2027	55
Subsidy Receipts, 2018	0
Subsidy Receipts, 2019	0
Subsidy Receipts, 2020	0
Subsidy Receipts, 2021	0
Subsidy Receipts, 2022	0
Subsidy Receipts, Years 2023-2027	$ 1

Pension and Other Postretire111

Pension and Other Postretirement Benefits, Employee Savings Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Continuing Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions in L-3 Holdings' common stock and cash	$ 115	$ 118	$ 131
Discontinued Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions in L-3 Holdings' common stock and cash	$ 8	$ 12	$ 24

Pension and Other Postretire112

Pension and Other Postretirement Benefits, Multi-Employer Benefit Plans (Details) $ in Millions		12 Months Ended
		Dec. 31, 2017USD ($)PensionFunds		Dec. 31, 2016USD ($)		Dec. 31, 2015USD ($)
Multiemployer Plans [Line Items]
Contributions by L-3 Communications	[1]	$ 27		$ 26		$ 23
Minimum percentage funded to have green zone status rating		80.00%
Percentage of total plan contributions				5.00%		5.00%
Percentage of contributions from reportable segment		61.00%
Expiration date of multiple bargaining agreements		Apr. 28, 2019
Number of pension funds included in Other Pension Funds | PensionFunds		3
Discontinued Operations [Member]
Multiemployer Plans [Line Items]
Contributions by L-3 Communications	[1]	$ 26		$ 26		$ 22
IAM National Pension Fund [Member]
Multiemployer Plans [Line Items]
Contributions by L-3 Communications	[1]	$ 27	[2]	$ 26	[3]	23	[3]
EIN/Pension Plan Number		51-6031295/002
Pension Protection Act Zone Status	[4]	Green		Green
FIP/RP Status Pending/Implemented	[5]	No
Surcharge Imposed		No
Expiration Date of Collective-Bargaining Agreement, First		Apr. 29, 2018
Expiration Date of Collective-Bargaining Agreement, Last	[6]	Sep. 30, 2020
Other Pension Funds [Member]
Multiemployer Plans [Line Items]
Contributions by L-3 Communications	[1],[7]	$ 0		$ 0		$ 0
[1]	These contributions include amounts attributable to discontinued operations of approximately $26 million for the years ended December 31, 2017 and 2016 and $22 million for the year ended December 31, 2015.
[2]	At the date the audited financial statements for the Company were issued, the Form 5500 for the plan year ended December 31, 2017 was not available.
[3]	Represents 5% of total plan contributions for the years ended December 31, 2016 and 2015 based on Form 5500.
[4]	A zone status rating of green indicates the plan is at least 80% funded.
[5]	Funding improvement plan or rehabilitation plan.
[6]	The Company is a party to multiple bargaining agreements for multiple projects that require contributions into the IAM National Pension Fund. The most significant of these agreements, expiring April 28, 2019, covers multiple programs in the Company's Aerospace Systems reportable segment and represents 61% of 2017 contributions.
[7]	Consists of three pension funds in which the Company's contributions are individually, and in the aggregate, insignificant.

Supplemental Cash Flow Infor113

Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Interest paid	$ 165	$ 162	$ 182
Income tax payments	163	120	130
Income tax refunds	$ 16	$ 8	$ 8

Segment Information, Products a

Segment Information, Products and Services (Details) $ in Millions		3 Months Ended												12 Months Ended
		Dec. 31, 2017USD ($)		Sep. 29, 2017USD ($)	[2]	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)		Sep. 23, 2016USD ($)	[2]	Jun. 24, 2016USD ($)	Mar. 25, 2016USD ($)	Dec. 31, 2017USD ($)Segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment														4
Corporate expenses														$ 32	$ 29	$ 29
Net Sales [Abstract]
Products														6,733	6,453	6,600
Services														2,840	2,757	2,631
Total net sales		$ 2,574	[1]	$ 2,293		$ 2,385	$ 2,321	$ 2,643	[1]	$ 2,184		$ 2,318	$ 2,065	9,573	9,210	9,231
Operating income [Abstract]
Operating income		263	[1]	$ 229		$ 292	$ 236	282	[1]	$ 211		$ 220	$ 244	1,020	957	785
Goodwill impairment charge	[3]													0	0	(46)
Loss related to business divestitures	[4]													0	0	(31)
Depreciation and amortization [Abstract]
Depreciation and amortization														225	198	203
Capital Expenditures [Abstract]
Capital Expenditures														224	210	195
Total Assets [Abstract]
Total Assets		12,729						11,865						12,729	11,865	12,069
Assets held for sale		135						0						135	0	0
Assets of discontinued operations		306						481						306	481	1,124
NSS Including Business Retained [Member] | Continuing Operations [Member]
Operating income [Abstract]
Goodwill impairment charge																(46)
Operating Segments [Member]
Operating income [Abstract]
Operating income														1,020	957	862
Operating Segments [Member] | Electronic Systems [Member]
Net Sales [Abstract]
Products														2,234	2,033	2,102
Services														848	812	810
Operating income [Abstract]
Operating income														403	360	337
Depreciation and amortization [Abstract]
Depreciation and amortization														79	60	59
Capital Expenditures [Abstract]
Capital Expenditures														68	76	69
Total Assets [Abstract]
Total Assets		4,796						4,369						4,796	4,369	3,968
Operating Segments [Member] | Aerospace Systems [Member]
Net Sales [Abstract]
Products														1,545	1,679	1,679
Services														1,267	1,270	1,257
Operating income [Abstract]
Operating income														210	255	193
Depreciation and amortization [Abstract]
Depreciation and amortization														51	46	43
Capital Expenditures [Abstract]
Capital Expenditures														43	50	53
Total Assets [Abstract]
Total Assets		2,014						2,084						2,014	2,084	2,190
Operating Segments [Member] | Communication Systems [Member]
Net Sales [Abstract]
Products														1,745	1,586	1,649
Services														510	488	441
Operating income [Abstract]
Operating income														212	195	190
Depreciation and amortization [Abstract]
Depreciation and amortization														49	47	50
Capital Expenditures [Abstract]
Capital Expenditures														49	37	37
Total Assets [Abstract]
Total Assets		2,063						2,031						2,063	2,031	1,984
Operating Segments [Member] | Sensor Systems [Member]
Net Sales [Abstract]
Products														1,292	1,266	1,298
Services														273	235	193
Operating income [Abstract]
Operating income														195	147	142
Depreciation and amortization [Abstract]
Depreciation and amortization														46	45	51
Capital Expenditures [Abstract]
Capital Expenditures														42	37	30
Total Assets [Abstract]
Total Assets		2,706						2,433						2,706	2,433	2,458
Corporate [Member]
Capital Expenditures [Abstract]
Capital Expenditures														22	10	6
Total Assets [Abstract]
Total Assets		$ 709						$ 467						709	467	345
Elimination of Intercompany Sales [Member]
Net Sales [Abstract]
Products														(83)	(111)	(128)
Services														$ (58)	$ (48)	$ (70)
[1]	Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.
[2]	The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.
[3]	Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment.
[4]	See Note 3 for information regarding the Company's business divestitures.

Segment Information, Geographic

Segment Information, Geographic Location (Details) - USD ($) $ in Millions		3 Months Ended												12 Months Ended
		Dec. 31, 2017		Sep. 29, 2017	[2]	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016		Sep. 23, 2016	[2]	Jun. 24, 2016	Mar. 25, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Property, plant and equipment, net		$ 1,110						$ 1,107						$ 1,110	$ 1,107
Net sales		2,574	[1]	$ 2,293		$ 2,385	$ 2,321	2,643	[1]	$ 2,184		$ 2,318	$ 2,065	9,573	9,210	$ 9,231
U.S. Government Agencies [Member]
Segment Reporting Information [Line Items]
Net sales	[3]													6,697	6,399	6,120
Commercial [Member]
Segment Reporting Information [Line Items]
Net sales														1,456	1,280	1,373
Foreign Governments [Member]
Segment Reporting Information [Line Items]
Net sales	[3]													1,420	1,531	1,738
Reportable Geographical Components [Member] | United States [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net		936						960						936	960
Net sales														7,344	6,947	6,734
Reportable Geographical Components [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Net sales														335	331	336
Reportable Geographical Components [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Net sales														280	297	281
Reportable Geographical Components [Member] | Australia [Member]
Segment Reporting Information [Line Items]
Net sales														268	254	321
Reportable Geographical Components [Member] | China [Member]
Segment Reporting Information [Line Items]
Net sales														167	67	83
Reportable Geographical Components [Member] | South Korea [Member]
Segment Reporting Information [Line Items]
Net sales														134	127	207
Reportable Geographical Components [Member] | Japan [Member]
Segment Reporting Information [Line Items]
Net sales														125	81	95
Reportable Geographical Components [Member] | France [Member]
Segment Reporting Information [Line Items]
Net sales														84	75	62
Reportable Geographical Components [Member] | Other [Member]
Segment Reporting Information [Line Items]
Property, plant and equipment, net		$ 174						$ 147						174	147
Net sales														836	1,031	1,112
Reportable Geographical Components [Member] | Total International [Member]
Segment Reporting Information [Line Items]
Net sales														$ 2,229	$ 2,263	$ 2,497
[1]	Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.
[2]	The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.
[3]	Includes sales for which the Company is the prime contractor as well as sales based on the ultimate end customer for which the Company is a subcontractor.

Severance and Restructuring 116

Severance and Restructuring Related Costs (Details) $ in Millions		3 Months Ended		12 Months Ended
		Dec. 31, 2017USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)Employee	Dec. 31, 2016USD ($)Employee	Dec. 31, 2015USD ($)Employee
Restructuring Cost and Reserve [Line Items]
Severance and restructuring costs				$ 91	$ 13	$ 14
Number of employees of restructuring costs | Employee				1,500	700	800
Gain (loss) on sale of property		$ (12)	$ 42
Severance and Restructuring Related Liability [Roll Forward]
Balance at beginning of period				$ 9
Additional provisions				101
Cash payments				(87)
Balance at end of period		$ 23		23	$ 9
Electronic Systems [Member]
Restructuring Cost and Reserve [Line Items]
Severance and restructuring costs	[1]			14	5	$ 4
Curtailment loss				1
Aerospace Systems [Member]
Restructuring Cost and Reserve [Line Items]
Severance and restructuring costs	[1]			24	2	4
Curtailment loss				5
Communication Systems [Member]
Restructuring Cost and Reserve [Line Items]
Severance and restructuring costs	[2]			48	7	6
Sensor Systems [Member]
Restructuring Cost and Reserve [Line Items]
Severance and restructuring costs	[3]			15	3	4
Consolidated [Member]
Restructuring Cost and Reserve [Line Items]
Severance and restructuring costs				$ 101	$ 17	$ 18
[1]	The severance and restructuring related costs incurred during the year ended December 31, 2017 include $1 million and $5 million of salaried employee pension plan curtailment losses for Electronic Systems and Aerospace Systems segments, respectively. See Note 19 for additional information.
[2]	The severance and restructuring related costs incurred during the year ended December 31, 2017 exclude a pre-tax gain of $42 million on the sale of the Company's property in San Carlos, California in the second quarter of 2017.
[3]	The severance and restructuring related costs incurred during the year ended December 31, 2017 include a $12 million loss on the sale of a building in Garland, Texas in the fourth quarter of 2017.

Unaudited Quarterly Financia117

Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2017		Sep. 29, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016	[1]	Sep. 23, 2016	[2]	Jun. 24, 2016		Mar. 25, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data [Line Items]
Sales		$ 2,574	[1]	$ 2,293	[2]	$ 2,385		$ 2,321		$ 2,643		$ 2,184		$ 2,318		$ 2,065		$ 9,573	$ 9,210	$ 9,231
Operating income		263	[1]	229	[2]	292		236		282		211		220		244		1,020	957	785
Income from continuing operations		271	[1]	146	[2]	195		157		187		149		134		163		769	633	507
Net income		293	[1]	25	[2]	207		168		192		151		151		230		693	724	(225)
Net income attributable to L3		$ 289	[1]	$ 22	[2]	$ 202		$ 164		$ 188		$ 148		$ 147		$ 227		$ 677	$ 710	$ (240)
Basic EPS from continuing operations (in dollars per share)		$ 3.42	[1],[3]	$ 1.83	[2],[3]	$ 2.44	[3]	$ 1.97	[3]	$ 2.37	[3]	$ 1.89	[3]	$ 1.68	[3]	$ 2.06	[3]	$ 9.65	$ 7.99	$ 6.10
Basic EPS (in dollars per share)		3.70	[1],[3]	0.28	[2],[3]	2.59	[3]	2.11	[3]	2.43	[3]	1.91	[3]	1.90	[3]	2.92	[3]	8.68	9.17	(2.97)
Diluted EPS from continuing operations (in dollars per share)		3.34	[1],[3]	1.79	[2],[3]	2.39	[3]	1.93	[3]	2.32	[3]	1.85	[3]	1.66	[3]	2.02	[3]	9.46	7.86	6.01
Diluted EPS (in dollars per share)		$ 3.62	[1],[3]	0.28	[2],[3]	$ 2.54	[3]	$ 2.07	[3]	$ 2.38	[3]	$ 1.88	[3]	$ 1.88	[3]	$ 2.87	[3]	$ 8.51	$ 9.01	$ (2.93)
Goodwill impairment charges	[4]																	$ 0	$ 0	$ 46
Estimated tax benefit amount		$ (79)																(79)
Earnings per share, diluted (in dollars per share)		$ 0.99
Vertex Aerospace [Member]
Quarterly Financial Data [Line Items]
Diluted EPS (in dollars per share)				$ 1.67
Goodwill impairment charges				$ 187														$ 187
[1]	Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.
[2]	The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.
[3]	EPS in each quarter is computed using the weighted-average number of shares outstanding during that quarter, while EPS for the full year is computed using the weighted-average number of shares outstanding during the year. Therefore, the sum of the four quarters' EPS may not equal the full year computed EPS.
[4]	Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment.

Financial Information of L3 118

Financial Information of L3 and Its Subsidiaries, Condensed Combining Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 662	$ 363	$ 207	$ 442
Billed receivables, net	723	700
Contracts in process	1,933	1,858
Prepaid expenses and other current assets	689	505
Assets held for sale	135	0	0
Assets of discontinued operations	306	481	1,124
Total current assets	4,448	3,907
Goodwill	6,615	6,374	6,095
Other assets	1,666	1,584
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	12,729	11,865	12,069
Current liabilities	2,136	1,959
Liabilities held for sale	17	0
Liabilities of discontinued operations	226	235
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,869	1,722
Long-term debt	3,330	3,325
Total liabilities	7,578	7,241
L3 shareholders' equity	5,083	4,553
Noncontrolling interests	68	71
Total equity	5,151	4,624	4,429	5,360
Total liabilities and equity	12,729	11,865
L-3 Communications Corporation [Member]
Current assets:
Cash and cash equivalents	432	291	141	358
Billed receivables, net	266	261
Contracts in process	706	694
Prepaid expenses and other current assets	330	236
Assets held for sale	0
Assets of discontinued operations	0	0
Total current assets	1,734	1,482
Goodwill	2,248	2,258
Other assets	658	705
Investment in and amounts due from consolidated subsidiaries	5,593	5,721
Total assets	10,233	10,166
Current liabilities	811	789
Liabilities held for sale	0
Liabilities of discontinued operations	0	0
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,009	1,499
Long-term debt	3,330	3,325
Total liabilities	5,150	5,613
L3 shareholders' equity	5,083	4,553
Noncontrolling interests	0	0
Total equity	5,083	4,553
Total liabilities and equity	10,233	10,166
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	14	1	0	4
Billed receivables, net	232	254
Contracts in process	891	928
Prepaid expenses and other current assets	231	144
Assets held for sale	118
Assets of discontinued operations	306	481
Total current assets	1,792	1,808
Goodwill	2,652	2,613
Other assets	556	567
Investment in and amounts due from consolidated subsidiaries	5,270	5,272
Total assets	10,270	10,260
Current liabilities	800	846
Liabilities held for sale	16
Liabilities of discontinued operations	226	235
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	714	191
Long-term debt	0	0
Total liabilities	1,756	1,272
L3 shareholders' equity	8,514	8,988
Noncontrolling interests	0	0
Total equity	8,514	8,988
Total liabilities and equity	10,270	10,260
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	287	207	165	142
Billed receivables, net	225	185
Contracts in process	336	236
Prepaid expenses and other current assets	128	125
Assets held for sale	17
Assets of discontinued operations	0	0
Total current assets	993	753
Goodwill	1,715	1,503
Other assets	452	312
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	3,160	2,568
Current liabilities	596	460
Liabilities held for sale	1
Liabilities of discontinued operations	0	0
Amounts due to consolidated subsidiaries	352	763
Other long-term liabilities	146	32
Long-term debt	0	0
Total liabilities	1,095	1,255
L3 shareholders' equity	2,065	1,313
Noncontrolling interests	0	0
Total equity	2,065	1,313
Total liabilities and equity	3,160	2,568
Eliminations [Member]
Current assets:
Cash and cash equivalents	(71)	(136)	$ (99)	$ (62)
Billed receivables, net	0	0
Contracts in process	0	0
Prepaid expenses and other current assets	0	0
Assets held for sale	0
Assets of discontinued operations	0	0
Total current assets	(71)	(136)
Goodwill	0	0
Other assets	0	0
Investment in and amounts due from consolidated subsidiaries	(10,863)	(10,993)
Total assets	(10,934)	(11,129)
Current liabilities	(71)	(136)
Liabilities held for sale	0
Liabilities of discontinued operations	0	0
Amounts due to consolidated subsidiaries	(352)	(763)
Other long-term liabilities	0	0
Long-term debt	0	0
Total liabilities	(423)	(899)
L3 shareholders' equity	(10,579)	(10,301)
Noncontrolling interests	68	71
Total equity	(10,511)	(10,230)
Total liabilities and equity	$ (10,934)	$ (11,129)

Financial Information of L3 119

Financial Information of L3 and Its Subsidiaries, Condensed Combining Statements of Operations (Details) - USD ($) $ in Millions		3 Months Ended												12 Months Ended
		Dec. 31, 2017	[1]	Sep. 29, 2017	[2]	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	[1]	Sep. 23, 2016	[2]	Jun. 24, 2016	Mar. 25, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Total net sales		$ 2,574		$ 2,293		$ 2,385	$ 2,321	$ 2,643		$ 2,184		$ 2,318	$ 2,065	$ 9,573	$ 9,210	$ 9,231
Total cost of sales														(8,553)	(8,253)	(8,369)
Goodwill impairment charges	[3]													0	0	(46)
(Loss) gain related to business divestitures	[4]													0	0	(31)
Operating income		263		229		292	236	282		211		220	244	1,020	957	785
Interest expense														(169)	(164)	(162)
Interest and other income, net														20	18	17
Debt retirement charge														0	(7)	(1)
Income from continuing operations before income taxes														871	804	639
Provision for income taxes														(102)	(171)	(132)
Equity in net income (loss) of consolidated subsidiaries														0	0	0
Income from continuing operations		271		146		195	157	187		149		134	163	769	633	507
(Loss) income from discontinued operations, net of income taxes														(76)	91	(732)
Net (loss) income		293		25		207	168	192		151		151	230	693	724	(225)
Net income attributable to noncontrolling interests														(16)	(14)	(15)
Net income (loss) attributable to L-3		$ 289		$ 22		$ 202	$ 164	$ 188		$ 148		$ 147	$ 227	677	710	(240)
Comprehensive (loss) income attributable to L3														712	558	(230)
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales														3,519	3,350	3,267
Total cost of sales														(3,179)	(3,069)	(3,031)
Goodwill impairment charges																0
(Loss) gain related to business divestitures																(13)
Operating income														340	281	223
Interest expense														(168)	(164)	(161)
Interest and other income, net														17	15	17
Debt retirement charge															(7)	(1)
Income from continuing operations before income taxes														189	125	78
Provision for income taxes														(22)	(26)	(16)
Equity in net income (loss) of consolidated subsidiaries														511	611	(302)
Income from continuing operations														678	710	(240)
(Loss) income from discontinued operations, net of income taxes														(1)	0	0
Net (loss) income														677	710	(240)
Net income attributable to noncontrolling interests														0	0	0
Net income (loss) attributable to L-3														677	710	(240)
Comprehensive (loss) income attributable to L3														712	558	(230)
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales														4,748	4,809	4,866
Total cost of sales														(4,350)	(4,378)	(4,441)
Goodwill impairment charges																(26)
(Loss) gain related to business divestitures																(31)
Operating income														398	431	368
Interest expense														0	0	(1)
Interest and other income, net														0	0	0
Debt retirement charge															0	0
Income from continuing operations before income taxes														398	431	367
Provision for income taxes														(47)	(92)	(76)
Equity in net income (loss) of consolidated subsidiaries														0	0	0
Income from continuing operations														351	339	291
(Loss) income from discontinued operations, net of income taxes														(75)	91	(732)
Net (loss) income														276	430	(441)
Net income attributable to noncontrolling interests														0	0	0
Net income (loss) attributable to L-3														276	430	(441)
Comprehensive (loss) income attributable to L3														278	440	(445)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales														1,690	1,381	1,449
Total cost of sales														(1,408)	(1,136)	(1,248)
Goodwill impairment charges																(20)
(Loss) gain related to business divestitures																13
Operating income														282	245	194
Interest expense														(1)	0	0
Interest and other income, net														3	3	0
Debt retirement charge															0	0
Income from continuing operations before income taxes														284	248	194
Provision for income taxes														(33)	(53)	(40)
Equity in net income (loss) of consolidated subsidiaries														0	0	0
Income from continuing operations														251	195	154
(Loss) income from discontinued operations, net of income taxes														0	0	0
Net (loss) income														251	195	154
Net income attributable to noncontrolling interests														0	0	0
Net income (loss) attributable to L-3														251	195	154
Comprehensive (loss) income attributable to L3														378	118	43
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total net sales														(384)	(330)	(351)
Total cost of sales														384	330	351
Goodwill impairment charges																0
(Loss) gain related to business divestitures																0
Operating income														0	0	0
Interest expense														0	0	0
Interest and other income, net														0	0	0
Debt retirement charge															0	0
Income from continuing operations before income taxes														0	0	0
Provision for income taxes														0	0	0
Equity in net income (loss) of consolidated subsidiaries														(511)	(611)	302
Income from continuing operations														(511)	(611)	302
(Loss) income from discontinued operations, net of income taxes														0	0	0
Net (loss) income														(511)	(611)	302
Net income attributable to noncontrolling interests														(16)	(14)	(15)
Net income (loss) attributable to L-3														(527)	(625)	287
Comprehensive (loss) income attributable to L3														$ (656)	$ (558)	$ 402
[1]	Provision for income taxes for the fourth quarter of 2017, includes estimated tax benefits of $79 million or $0.99 per diluted share, related to the enactment of the U.S. Tax Cuts and Jobs Act (U.S. Tax Reform) in December 2017.
[2]	The Company recorded a goodwill impairment charge of $187 million or $1.67 per diluted share for the Vertex Aerospace reporting unit in 2017, which is reported in discontinued operations.
[3]	Represents non-cash goodwill impairment charges recorded during 2015 of $46 million related to a business retained by L3 in connection with the sale of the NSS segment.
[4]	See Note 3 for information regarding the Company's business divestitures.

Financial Information of L3 120

Financial Information of L3 and Its Subsidiaries, Condensed Combining Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net cash from operating activities from continuing operations	$ 985	$ 1,022	$ 1,035
Investing activities:
Business acquisitions, net of cash acquired	(316)	(388)	(320)
Proceeds from sale of business, net of closing date cash balances	18	561	318
Other investing activities	(155)	(183)	(188)
Net cash used in investing activities from continuing operations	(453)	(10)	(190)
Financing activities:
Proceeds from sale of senior notes	0	547	0
Redemption of senior notes	0	(856)	(297)
Common stock repurchased	(180)	(373)	(740)
Dividends paid on L3's common stock	(236)	(220)	(214)
Other financing activities	50	46	46
Net cash used in financing activities from continuing operations	(366)	(856)	(1,205)
Effect of foreign currency exchange rate changes on cash	20	(13)	(19)
Net increase in cash and cash equivalents of discontinued operations	113	13	83
Change in cash balance in assets held for sale	0	0	61
Net (decrease) increase in cash	299	156	(235)
Cash and cash equivalents, beginning of the year	363	207	442
Cash and cash equivalents, end of the year	662	363	207
L-3 Communications Corporation [Member]
Operating activities:
Net cash from operating activities from continuing operations	374	441	634
Investing activities:
Business acquisitions, net of cash acquired	(316)	(388)	(320)
Proceeds from sale of business, net of closing date cash balances	17	563	14
Other investing activities	(84)	(60)	(75)
Net cash used in investing activities from continuing operations	(383)	115	(381)
Financing activities:
Proceeds from sale of senior notes		547
Redemption of senior notes		(856)	(297)
Common stock repurchased	(180)	(373)	(740)
Dividends paid on L3's common stock	(236)	(220)	(214)
Other financing activities	565	496	781
Net cash used in financing activities from continuing operations	149	(406)	(470)
Effect of foreign currency exchange rate changes on cash	0	0	0
Net increase in cash and cash equivalents of discontinued operations	1	0	0
Change in cash balance in assets held for sale			0
Net (decrease) increase in cash	141	150	(217)
Cash and cash equivalents, beginning of the year	291	141	358
Cash and cash equivalents, end of the year	432	291	141
Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities from continuing operations	438	509	425
Investing activities:
Business acquisitions, net of cash acquired	0	0	0
Proceeds from sale of business, net of closing date cash balances	0	0	28
Other investing activities	(41)	(80)	(78)
Net cash used in investing activities from continuing operations	(41)	(80)	(50)
Financing activities:
Proceeds from sale of senior notes		0
Redemption of senior notes		0	0
Common stock repurchased	0	0	0
Dividends paid on L3's common stock	0	0	0
Other financing activities	(496)	(441)	(463)
Net cash used in financing activities from continuing operations	(496)	(441)	(463)
Effect of foreign currency exchange rate changes on cash	0	0	0
Net increase in cash and cash equivalents of discontinued operations	112	13	83
Change in cash balance in assets held for sale			1
Net (decrease) increase in cash	13	1	(4)
Cash and cash equivalents, beginning of the year	1	0	4
Cash and cash equivalents, end of the year	14	1	0
Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities from continuing operations	251	258	161
Investing activities:
Business acquisitions, net of cash acquired	0	0	0
Proceeds from sale of business, net of closing date cash balances	1	(2)	276
Other investing activities	(30)	(43)	(35)
Net cash used in investing activities from continuing operations	(29)	(45)	241
Financing activities:
Proceeds from sale of senior notes		0
Redemption of senior notes		0	0
Common stock repurchased	0	0	0
Dividends paid on L3's common stock	0	0	0
Other financing activities	(162)	(158)	(420)
Net cash used in financing activities from continuing operations	(162)	(158)	(420)
Effect of foreign currency exchange rate changes on cash	20	(13)	(19)
Net increase in cash and cash equivalents of discontinued operations	0	0	0
Change in cash balance in assets held for sale			60
Net (decrease) increase in cash	80	42	23
Cash and cash equivalents, beginning of the year	207	165	142
Cash and cash equivalents, end of the year	287	207	165
Eliminations [Member]
Operating activities:
Net cash from operating activities from continuing operations	(78)	(186)	(185)
Investing activities:
Business acquisitions, net of cash acquired	0	0	0
Proceeds from sale of business, net of closing date cash balances	0	0	0
Other investing activities	0	0	0
Net cash used in investing activities from continuing operations	0	0	0
Financing activities:
Proceeds from sale of senior notes		0
Redemption of senior notes		0	0
Common stock repurchased	0	0	0
Dividends paid on L3's common stock	0	0	0
Other financing activities	143	149	148
Net cash used in financing activities from continuing operations	143	149	148
Effect of foreign currency exchange rate changes on cash	0	0	0
Net increase in cash and cash equivalents of discontinued operations	0	0	0
Change in cash balance in assets held for sale			0
Net (decrease) increase in cash	65	(37)	(37)
Cash and cash equivalents, beginning of the year	(136)	(99)	(62)
Cash and cash equivalents, end of the year	$ (71)	$ (136)	$ (99)