L3 10-K 26 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 20, 2015	Jun. 27, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	LLL
Entity Registrant Name	L 3 COMMUNICATIONS HOLDINGS INC
Entity Central Index Key	1056239
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		82,526,828
Entity Public Float			$10.20

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$442	$500
Billed receivables, net of allowances of $14 in 2014 and $26 in 2013	852	991
Contracts in process	2,295	2,442
Inventories	288	366
Deferred income taxes	127	147
Other current assets	186	167
Assets held for sale	547
Total current assets	4,737	4,613
Property, plant and equipment, net	1,088	1,042
Goodwill	7,501	7,796
Identifiable intangible assets	243	285
Deferred debt issue costs	27	24
Other assets	240	247
Total assets	13,836	14,007
Current liabilities:
Accounts payable, trade	382	535
Accrued employment costs	510	545
Accrued expenses	402	464
Advance payments and billings in excess of costs incurred	573	576
Income taxes	23	31
Other current liabilities	398	402
Liabilities held for sale	237
Total current liabilities	2,525	2,553
Pension and postretirement benefits	1,187	727
Deferred income taxes	443	635
Other liabilities	382	406
Long-term debt	3,939	3,630
Total liabilities	8,476	7,951
Commitments and contingencies (see Note 19)
L-3 shareholders' equity:
L-3 Communications Holdings, Inc.'s common stock: $.01 par value; 300,000,000 shares authorized, 82,040,525 shares outstanding at December 31, 2014 and 85,828,485 shares outstanding at December 31, 2013 (L-3 Communications Corporation's common stock: $.01 par value, 100 shares authorized, issued and outstanding)	5,799	5,653
L-3 Communications Holdings, Inc.'s treasury stock (at cost), 73,005,891 shares at December 31, 2014 and 66,118,406 shares at December 31, 2013	-6,111	-5,288
Retained earnings	6,181	5,726
Accumulated other comprehensive loss	-584	-110
Total L-3 shareholders' equity	5,285	5,981
Noncontrolling interests	75	75
Total equity	5,360	6,056
Total liabilities and equity	$13,836	$14,007

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Class of Stock [Line Items]
Net allowances for billed receivables	$14	$26
Treasury stock (at cost), shares	73,005,891	66,118,406
L-3 Communications Holdings, Inc. [Member]
Class of Stock [Line Items]
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares outstanding	82,040,525	85,828,485
L-3 Communications Corporation [Member]
Class of Stock [Line Items]
Common stock, par value	$0.01	$0.01
Common stock, shares authorized	100	100
Common stock, shares issued	100	100
Common stock, shares outstanding	100	100

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net sales:
Products	$6,909	$7,189	$7,586
Services	5,215	5,433	5,521
Total net sales	12,124	12,622	13,107
Cost of sales:
Products	-6,219	-6,409	-6,782
Services	-4,820	-5,001	-5,017
Total cost of sales	-11,039	-11,410	-11,799
Operating income	1,085	1,212	1,308
Interest expense	-178	-177	-184
Interest and other income, net	18	20	11
Debt Retirement Charge			-13
Income from continuing operations before income taxes	925	1,055	1,122
Provision for income taxes	-248	-295	-360
Income from continuing operations	677	760	762
Income from discontinued operations, net of income tax			32
Net income	677	760	794
Net income attributable to noncontrolling interests	-13	-9	-10
Net income attributable to L-3	$664	$751	$784
Basic earnings per share attributable to L-3 Holdings' common shareholders:
Continuing operations	$7.78	$8.40	$7.85
Discontinued operations			$0.29
Basic earnings per share	$7.78	$8.40	$8.14
Diluted earnings per share attributable to L-3 Holdings' common shareholders:
Continuing operations	$7.56	$8.24	$7.74
Discontinued operations			$0.29
Diluted earnings per share	$7.56	$8.24	$8.03
Cash dividends declared per common share	$2.40	$2.20	$2
L-3 Holdings' weighted average common shares outstanding:
Basic	85.4	89.4	96.3
Diluted	87.8	91.1	97.6

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$677		$760		$794
Other comprehensive (loss) income:
Foreign currency translation adjustments	-123		-25		34
Unrealized (losses) gains on hedging instruments	-6	[1]	-2	[1]	3	[1]
Pension and postretirement benefit plans:
Amortization of net loss and prior service cost previously recognized	9	[2]	53	[2]	42	[2]
Net prior service (costs) credit arising during the period			-9	[3]	3	[3]
Net gain (loss) arising during the period	-354	[4]	423	[4]	-178	[4]
Net change in pension and postretirement benefit plans	-345		467		-133
Total other comprehensive (loss) gain	-474		440		-96
Comprehensive income	203		1,200		698
Comprehensive income attributable to noncontrolling interests	-13		-9		-10
Comprehensive income attributable to L-3	$190		$1,191		$688
[1]	Net of income tax benefits of $1 million in 2014 and $3 million in 2013 and income taxes of $2 million in 2012
[2]	Net of income taxes of $6 million in 2014, $30 million in 2013 and $26 million in 2012
[3]	Net of an income tax benefit of $5 million in 2013 and income taxes of $2 million in 2012
[4]	Net of an income tax benefit of $211 million in 2014, income taxes of $243 million in 2013 and an income tax benefit of $105 million in 2012

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Income tax expenses (benefits) on unrealized (losses) gains on hedging instruments	($1)	($3)	$2
Income tax effect on amortization of net loss and prior service cost previously recognized	6	30	26
Income tax expense (benefit) on net prior service (costs) credit arising during the period		-5	2
Income tax expense (benefit) on net gain(loss) arising during the period	($211)	$243	($105)

Consolidated_Statements_of_Equ

Consolidated Statements of Equity (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interests [Member]
In Millions, except Share data, unless otherwise specified
Beginning Balance at Dec. 31, 2011	$6,733	$1	$5,063	($3,616)	$5,650	($454)	$89
Beginning Balance, Shares at Dec. 31, 2011		99,000,000
Class of Stock [Line Items]
Net income	794				784		10
Other comprehensive income (loss)	-96					-96
Distributions to noncontrolling interests	-10						-10
Cash dividends declared	-196				-196
Shares issued:
Employee savings plans	141		141
Employee savings plans, Shares		2,100,000
Exercise of stock options	19		19
Exercise of stock options, Shares		400,000
Employee stock purchase plan	39		39
Employee stock purchase plan, Shares		700,000
Stock-based compensation expense	60		60
Contribution received from the spin-off of Engility	335				335
Spin-off of Engility	-1,411				-1,398		-13
Treasury stock purchased	-872			-872
Treasury stock purchased, Shares		-12,100,000
Other	-9		-9
Other, Shares		300,000
Ending Balance at Dec. 31, 2012	5,527	1	5,313	-4,488	5,175	-550	76
Ending Balance, Shares at Dec. 31, 2012		90,400,000
Class of Stock [Line Items]
Net income	760				751		9
Other comprehensive income (loss)	440					440
Distributions to noncontrolling interests	-10						-10
Cash dividends declared	-201				-201
Shares issued:
Employee savings plans	121		121
Employee savings plans, Shares		1,500,000
Exercise of stock options	128		128
Exercise of stock options, Shares		1,800,000
Employee stock purchase plan	36		36
Employee stock purchase plan, Shares		500,000
Stock-based compensation expense	59		59
Treasury stock purchased	-800			-800
Treasury stock purchased, Shares		-8,700,000
Other	-4		-5		1
Other, Shares		300,000
Ending Balance at Dec. 31, 2013	6,056	1	5,652	-5,288	5,726	-110	75
Ending Balance, Shares at Dec. 31, 2013		85,800,000
Class of Stock [Line Items]
Net income	677				664		13
Other comprehensive income (loss)	-474					-474
Distributions to noncontrolling interests	-13						-13
Cash dividends declared	-209				-209
Shares issued:
Employee savings plans	130		130
Employee savings plans, Shares		1,200,000
Exercise of stock options	109		109
Exercise of stock options, Shares	1,183,400	1,200,000
Employee stock purchase plan	35		35
Employee stock purchase plan, Shares		300,000
Stock-based compensation expense	52		52
Treasury stock purchased	-823			-823
Treasury stock purchased, Shares		-6,900,000
Retirement of Convertible Contingent Debt Securities	-161		-161
Other	-19		-19
Other, Shares		400,000
Ending Balance at Dec. 31, 2014	$5,360	$1	$5,798	($6,111)	$6,181	($584)	$75
Ending Balance, Shares at Dec. 31, 2014		82,000,000

Consolidated_Statements_of_Equ1

Consolidated Statements of Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Class of Stock [Line Items]
Cash dividends declared per share	$2.40	$2.20	$2
Retained Earnings [Member]
Class of Stock [Line Items]
Cash dividends declared per share	$2.40	$2.20	$2

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$677	$760	$794
Income from discontinued operations, net of tax			-32
Income from continuing operations	677	760	762
Depreciation of property, plant and equipment	172	166	170
Amortization of intangibles and other assets	53	48	58
Deferred income tax provision	121	42	97
Stock-based employee compensation expense	52	59	59
Contributions to employee savings plans in L-3 Holdings' common stock	130	114	125
Amortization of pension and postretirement benefit plans net loss and prior service cost	15	83	68
Amortization of bond discounts and deferred debt issue costs (included in interest expense)	7	6	7
Equity in losses of unconsolidated subsidiaries			3
Other non-cash items		2	9
Changes in operating assets and liabilities, excluding amounts from acquisitions, divestitures, and discontinued operations:
Billed receivables	51	-18	147
Contracts in process	6	86	-67
Inventories		1	-35
Other assets	-18	-88	8
Accounts payable, trade	-112	28	92
Accrued employment costs	-10	-5	-10
Accrued expenses	-17	1	-100
Advance payments and billings in excess of costs incurred	66	-44	37
Income taxes	7	31	-47
Excess income tax benefits related to share-based payment arrangements	-17	-4	-3
Other current liabilities	12	15	-46
Pension and postretirement benefits	-44	14	-64
All other operating activities	-26	-34	-39
Net cash from operating activities from continuing operations	1,125	1,263	1,231
Investing activities:
Contribution received from the spin-off of Engility			335
Business acquisitions, net of cash acquired	-57	-62	-348
Proceeds from sale of a business	6	4	5
Capital expenditures	-183	-209	-210
Dispositions of property, plant and equipment	4	12	5
Cash from equity investees			20
Other investing activities	1	-6	-7
Net cash used in investing activities from continuing operations	-229	-261	-200
Financing activities:
Proceeds from sale of senior notes	996
Redemption of senior subordinated notes			-500
Redemption of CODES	-935
Borrowings under revolving credit facility	1,367	1,893	596
Repayment of borrowings under revolving credit facility	-1,367	-1,893	-596
Common stock repurchased	-823	-800	-872
Dividends paid on L-3 Holdings' common stock	-208	-199	-195
Proceeds from exercise of stock options	93	128	19
Proceeds from employee stock purchase plan	35	36	39
Debt issue costs	-8		-6
Excess income tax benefits related to share-based payment arrangements	17	4	3
Other financing activities	-43	-18	-15
Net cash used in financing activities from continuing operations	-876	-849	-1,527
Effect of foreign currency exchange rate changes on cash and cash equivalents	-17	-2	7
Cash from (used in) discontinued operations:
Operating activities			75
Financing activities			-1
Cash from discontinued operations			74
Change in cash balance in assets held for sale	-61
Net (decrease) increase in cash and cash equivalents	-58	151	-415
Cash and cash equivalents, beginning of the year	500	349	764
Cash and cash equivalents, end of the year	$442	$500	$349

Description_of_Business

Description of Business	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Description of Business	1. Description of Business
	L-3 Communications Holdings, Inc. derives all of its operating income and cash flows from its wholly-owned subsidiary, L-3 Communications Corporation (L-3 Communications). L-3 Communications Holdings, Inc. (L-3 Holdings and, together with its subsidiaries, referred to herein as L-3 or the Company) is a prime contractor in Intelligence, Surveillance and Reconnaissance (ISR) systems, aircraft sustainment (including modifications, logistics and maintenance), simulation and training, night vision and image intensification equipment, enterprise and mission information technology (IT) solutions and cyber operations. L-3 is also a leading provider of a broad range of communication and electronic systems and products used on military 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 international commercial customers.
	The Company has the following four reportable segments: (1) Electronic Systems, (2) Aerospace Systems, (3) Communication Systems, and (4) National Security Solutions (NSS). Electronic Systems provides a broad range of components, products, subsystems, systems, and related services for military and commercial customers in several niche markets across several business areas. These business areas include precision engagement & training, sensor systems, power & propulsion systems, marine systems, aviation products, warrior systems and security & detection systems. Aerospace Systems delivers integrated solutions for the global ISR market and provides modernization, upgrade, sustainment, and maintenance and logistics support for a wide variety of aircraft and ground systems. Communication Systems delivers products and services for the global communications market, specializing in strategic and tactical airborne, space, ground and sea-based communication systems. NSS provides 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. Financial information with respect to each of our segments is included in Note 22.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies
	Basis of Presentation: The accompanying financial statements comprise the consolidated financial statements of L-3 Holdings and L-3 Communications. L-3 Holdings’ only asset is its investment in the common stock of L-3 Communications, its wholly-owned subsidiary, and its only obligations are: (1) its guarantee of borrowings under the Amended and Restated Revolving Credit Facility (“Credit Facility”) of L-3 Communications and (2) its guarantee of other contractual obligations of L-3 Communications and its subsidiaries. As of June 20, 2014, L-3 Holdings’ obligation for its 3% Convertible Contingent Debt Securities (CODES) due 2035, which were issued on July 29, 2005, have been fully retired. L-3 Holdings’ obligations relating to the CODES were jointly, severally, fully and unconditionally guaranteed by L-3 Communications and certain of its wholly-owned domestic subsidiaries. Accordingly, such debt was reflected as debt of L-3 Communications in its consolidated financial statements at December 31, 2013 in accordance with the accounting standards for pushdown accounting. All issuances of and conversions into L-3 Holdings’ equity securities, including grants of stock options, restricted stock units and performance units by L-3 Holdings to employees and directors of L-3 Communications and its subsidiaries, have been reflected in the consolidated financial statements of L-3 Communications. As a result, the consolidated financial positions, results of operations and cash flows of L-3 Holdings and L-3 Communications are substantially the same. See Note 25 for additional information regarding the audited financial information of L-3 Communications and its subsidiaries.
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of sales and costs of sales during the reporting period. The most significant of these estimates and assumptions relate to contract revenue, profit and loss recognition, fair values of assets acquired and liabilities assumed in business combinations, market values for inventories reported at lower of cost or market, pension and post-retirement benefit obligations, stock-based employee compensation expense, income taxes, including the valuations of deferred tax assets, litigation reserves and environmental obligations, accrued product warranty costs, and the recoverability, useful lives and valuation of recorded amounts of long-lived assets, identifiable intangible assets and goodwill. Changes in estimates are reflected in the periods during which they become known. Actual amounts will differ from these estimates and could differ materially.
	Certain reclassifications have been made to conform prior-year amounts to the current-year presentation.
	Principles of Consolidation: The consolidated financial statements of the Company include all wholly-owned and majority-owned subsidiaries. All significant intercompany transactions are eliminated in consolidation. Investments in equity securities, joint ventures and limited liability corporations over which the Company has significant influence but does not have voting control are accounted for using the equity method. Investments over which the Company does not have significant influence are accounted for using the cost method.
	Revenue Recognition: Substantially all of the Company’s sales are generated from written contractual (revenue) arrangements. The sales price for the Company’s revenue arrangements are either fixed-price, cost-plus or time-and-material type. Depending on the contractual scope of work, the Company utilizes either contract accounting standards or accounting standards for revenue arrangements with commercial customers to account for these contracts. Approximately 46% of the Company’s 2014 sales were accounted for under contract accounting standards, of which approximately 40% were fixed-price type contracts and approximately 6% were cost-plus type contracts. For contracts that are accounted for under contract accounting standards, sales and profits are recognized based on: (1) a Percentage-of-Completion (POC) method of accounting (fixed-price contracts), (2) allowable costs incurred plus the estimated profit on those costs (cost-plus contracts), or (3) direct labor hours expended multiplied by the contractual fixed rate per hour plus incurred costs for material (time-and-material contracts). Aggregate net changes in contract estimates increased operating income by $66 million, or 6%, for the year ended December 31, 2014, $114 million, or 9%, for the year ended December 31, 2013, and $72 million, or 6%, for the year ended December 31, 2012.
	Sales and profits on fixed-price type contracts 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. 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 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. Incentive and award fees are the primary variable fee contractual arrangements. 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 us 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 to perform services 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 awarded by the customer.
	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: Independent research and development (IRAD) costs sponsored by the Company and bid and proposal (B&P) costs relate to both U.S. Government contracts and those for international and commercial customers. The IRAD and B&P costs for certain of the Company’s businesses that are U.S. Government contractors are recoverable indirect contract costs that are allocated to U.S. Government contracts in accordance with U.S. Government procurement regulations, and are specifically excluded from research and development accounting standards. The Company includes the recoverable IRAD and B&P costs allocated to U.S. Government contracts in inventoried contract costs, and charges them to costs of sales when the related contract sales are recognized as revenue. Research and development costs that are not recoverable on U.S. Government contracts are accounted for in accordance with research and development accounting standards and are expensed to cost of sales as incurred.
	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 warranty costs are accrued when revenue is recognized for the covered products. Product warranty expense is recognized based on the terms of the product warranty and the related estimated costs. Accrued warranty costs are reduced as product warranty costs are incurred or as warranty periods expire.
	The table below presents the changes in the Company’s accrued product warranty costs.
			Year Ended December 31,
			2014		2013
			(in millions)
	Accrued product warranty costs(1):
	Balance at January 1		$	99	$	99
	Acquisitions during this period			—		2
	Accruals for product warranties issued during the period			71		71
	Changes to accruals for product warranties existing before January 1			1		3
	Foreign currency translation adjustments			(2)		—
	Settlements made during the period			(67)		(76)
	Liabilities held for sale(2)			(9)		—
	Balance at December 31		$	93	$	99
		(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)	On December 16, 2014, the Company entered into a definitive agreement with Wärtsilä Corporation to sell its Marine Systems International business.
	Deferred Debt Issue Costs: Costs to issue debt are capitalized and deferred when incurred, and subsequently amortized to interest expense over the term of the related debt using the effective interest rate method.
	Stock-Based Compensation: The Company follows the fair value based method of accounting for stock-based employee compensation, which requires the Company to expense all stock-based employee compensation. Stock-based employee compensation is primarily a non-cash expense because the Company settles these obligations by issuing shares of L-3 Holdings common stock instead of settling such obligations with cash payments.
	Compensation expense for all restricted stock unit and stock option awards is 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 L-3 Holdings 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.
	Income Taxes: The Company provides for income taxes using the liability method. Deferred income tax assets and liabilities reflect tax carryforwards and the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting and income tax purposes, as determined under enacted tax laws and rates. The effect of changes in tax laws or rates is accounted for in the period of enactment. Valuation allowances for deferred tax assets are provided when it is more likely than not that the assets will not be realized, considering, when appropriate, tax planning strategies.
	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 on its financial statements.
	Cash and Cash Equivalents: Cash equivalents consist of highly liquid investments with an original maturity of three months or less at the time of purchase.
	Contracts in Process: Contracts in Process include unbilled contract receivables and inventoried contract costs for which sales and profits are recognized primarily using a POC method of accounting. Unbilled Contract Receivables represent accumulated incurred costs and earned profits on contracts in process that have been recorded as sales, primarily using the cost-to-cost method, but have not been billed to customers. Inventoried Contract Costs primarily represent incurred costs on contracts using the units-of-delivery method of accounting and include direct costs and indirect costs, including overhead costs, and materials acquired for U.S. Government service contracts. As discussed in Note 5, the Company’s inventoried contract costs for U.S. Government contracts, and contracts with prime contractors or subcontractors of the U.S. Government include allocated general and administrative costs (G&A), IRAD costs and B&P costs. Contracts in Process contain amounts relating to contracts and programs with long performance cycles, a portion of which may not be realized within one year. For contracts in a loss position, the unrecoverable costs expected to be incurred in future periods are recorded in Estimated Costs in Excess of Estimated Contract Value to Complete Contracts in Process in a Loss Position, which is a component of Other Current Liabilities. Under the terms of certain revenue arrangements (contracts) with the U.S. Government, the Company is entitled to receive progress payments as costs are incurred or milestone payments as work is performed. The U.S. Government has a security interest in the Unbilled Contract Receivables and Inventoried Contract Costs to which progress payments have been applied, and such progress payments are reflected as a reduction of the related amounts. Milestone payments that have been received in excess of contract costs incurred and related estimated profits are reported on the Company’s balance sheet as Advance Payments and Billings in Excess of Costs Incurred.
	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, other than Inventoried Contract Costs, are stated at cost (first-in, first-out or average cost), but not in excess of realizable value. A provision for excess or inactive inventory is recorded based upon an analysis that considers current inventory levels, historical usage patterns and future sales expectations.
	Property, Plant and Equipment: Property, plant and equipment are stated at cost, less accumulated depreciation. Depreciation is computed by applying principally the straight-line method to the estimated useful lives of the related assets. Useful lives range substantially from 10 to 40 years for buildings and improvements and three to 10 years for machinery, equipment, furniture and fixtures. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the improvements. When property or equipment is retired or otherwise disposed of, the net book value of the asset is removed from the Company’s balance sheet and the net gain or loss is included in the determination of operating income. Property, plant and equipment acquired as part of a business acquisition is valued at fair value.
	Goodwill: The carrying value of goodwill and indefinite lived identifiable intangible assets are not amortized, but are tested for impairment annually as of November 30 and, additionally on an interim basis, whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable. The accounting standards for goodwill allow for the assessment of qualitative factors to determine whether it is more likely or not that the fair value of a reporting unit is less than its carrying amount. The Company did not utilize a qualitative assessment approach for the November 30, 2014 goodwill impairment test, as the Company chose instead to complete the quantitative two-step testing process for each reporting unit. The first step in the process is to identify any potential impairment by comparing the carrying value of a reporting unit to its fair value. The Company determines the fair value of its reporting units using a discounted cash flows valuation approach. If a potential impairment is identified, the second step is to measure the impairment loss by comparing the implied fair value of goodwill with the carrying value of goodwill of the reporting unit. There were no impairment charges that resulted from the annual impairment assessment or change in circumstances during the years ended December 31, 2014, 2013 and 2012. See Note 7 for additional information on the accumulated goodwill impairment losses.
	Identifiable Intangible Assets: Identifiable intangible assets represent assets acquired as part of the Company’s business acquisitions and include customer contractual relationships, technology, favorable leasehold interests and trade names. The initial measurement of these intangible assets is based on their fair values. Identifiable intangible assets are: (1) tested for impairment whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable and (2) amortized over their estimated useful lives as the economic benefits are consumed. The Company reviews and updates its estimates of the duration of its customer contractual relationships. If such estimates indicate that the duration of the Company’s customer contractual relationships has decreased compared to the estimates made as of the date the Company acquired these intangible assets, then the Company accelerates the amortization period for its customer contractual relationships over their remaining useful economic life.
	Derivative Financial Instruments: The Company’s derivative financial instruments include foreign currency forward contracts, which are entered into for risk management purposes, and an embedded derivative representing the contingent interest payment provision related to the CODES, which was retired as of June 20, 2014. See Note 10 for information on the CODES retirement.
	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 Canadian dollar, the U.S. 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.
	The embedded derivative related to the issuance of the CODES was recorded at fair value with changes reflected in the Consolidated Statements of Operations.
	Translation of Foreign Currency and Foreign Currency Transactions: Transactions in foreign currencies are translated into the local (functional) currency of the respective business at the approximate prevailing rate at the time of the transaction. Foreign exchange transaction gains and losses in the years ended December 31, 2014, 2013 and 2012 are not material to the Company’s results of operations. The operations of the Company’s foreign subsidiaries are translated from the local (functional) currencies into U.S. dollars using weighted average rates of exchange during each reporting period. The rates of exchange at each balance sheet date are used for translating the assets and liabilities of the Company’s foreign subsidiaries. Gains or losses resulting from these translation adjustments are included in the balance sheets as a component of accumulated other comprehensive income (loss) and are only recognized in income when a foreign subsidiary is divested.
	Accounting Standards Issued and Not Yet Implemented: In February 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-2, which changes the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. This update is effective for the interim and annual periods beginning after December 15, 2015. The adoption of this standard will not have an impact on the Company’s financial position, results of operations or cash flows.
	In January 2015, the FASB issued ASU 2015-1, which eliminates from GAAP the concept of extraordinary items. The update is effective for the Company for the interim and annual periods beginning after December 15, 2015. The adoption of this standard will not have an impact on the Company’s financial position, results of operations or cash flows.
	In June 2014, the FASB issued ASU 2014-12, which provides new guidance on accounting for share-based payments when the terms of an award provide that a performance target could be achieved after the requisite service period. The update requires a reporting entity to treat a performance target that affects vesting and that could be achieved after the requisite service period as a performance condition under Accounting Standards Codification (ASC) 718 Compensation — Stock Compensation, and apply existing guidance as it relates to awards with performance conditions that affect vesting to account for such awards. The update is effective for the Company for the interim and annual periods beginning after December 15, 2015. The adoption of this standard will not have an impact on the Company’s financial position, results of operations or cash flows.
	In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which will replace numerous requirements in U.S. GAAP, including industry-specific requirements, provide companies with a single revenue recognition model for recognizing revenue from contracts with customers and significantly expand the disclosure requirements for revenue arrangements. The new standard will be effective for the Company for interim and annual reporting periods beginning January 1, 2017. The two permitted transition methods under the new standard are the full retrospective method, in which case the standard would be applied to each prior reporting period presented, or the modified retrospective method, in which case the cumulative effect of applying the standard would be recognized at the date of initial application. The Company is currently evaluating the expected impact of the adoption of this standard on its consolidated financial statements and related disclosures and the transition alternatives available. As the new standard will supersede substantially all existing revenue guidance, it could impact revenue and cost recognition on substantially all of the Company’s contracts, in addition to the Company’s business processes and our information technology systems. As a result, the Company’s evaluation of the impact of the standard will extend over future periods.

New_Accounting_Standards_Imple

New Accounting Standards Implemented	12 Months Ended
	Dec. 31, 2014
Accounting Changes and Error Corrections [Abstract]
New Accounting Standards Implemented	3. New Accounting Standards Implemented
	In April 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, that provides new guidance on the accounting and reporting of discontinued operations. Under the new guidance, only disposals representing a strategic shift in operations should be presented as discontinued operations. Those strategic shifts should have a major effect on the organization’s operations and financial results. Additionally, the new guidance requires additional disclosures about discontinued operations. The Company early adopted the standard as of December 31, 2014 for its pending divestiture of L-3 MSI. In accordance with ASU 2014-08, L-3 MSI’s assets and liabilities are classified as held for sale in the Company’s audited consolidated balance sheet at December 31, 2014. Also, in accordance with ASU 2014-08, L-3 MSI’s results of operations are included in the Company’s income from continuing operations for all periods presented and are not classified within discontinued operations. See Note 4 for additional information regarding the Company’s business divestitures.
	Effective January 1, 2014, the Company adopted FASB issued amendments to an accounting standard that require an unrecognized tax benefit or portion of an unrecognized tax benefit to be presented as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except when certain conditions exist. The adoption of this standard did not have an impact on the Company’s financial position, results of operations or cash flows.

Acquisitions_and_Divestitures

Acquisitions and Divestitures	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisitions and Divestitures	4. Acquisitions and Divestitures
	Business Acquisitions
	All business acquisitions are included in the Company’s results of operations from their respective acquisition dates.
	2014 Business Acquisition
	On March 4, 2014, the Company acquired Data Tactics Corporation, renamed L-3 Data Tactics, for a purchase price of $57 million, which was financed with cash on hand. The purchase price and purchase price allocation for L-3 Data Tactics was finalized as of December 31, 2014, with no significant changes from preliminary amounts. L-3 Data Tactics is a specialized provider of large-scale data analytics, cybersecurity and cloud computing solution services, primarily to the DoD. Based on the final purchase price allocation, the aggregate goodwill recognized for this business was $39 million, substantially all of which is expected to be deductible for income tax purposes. The goodwill was assigned to the NSS reportable segment.
	2013 Business Acquisition
	On December 19, 2013, the Company acquired Mustang Technology Group, L.P. (Mustang) business for a purchase price of $54 million, which was financed with cash on hand. The purchase price and purchase price allocation for Mustang was finalized as of June 27, 2014, with no significant changes from preliminary amounts. Mustang develops and manufactures radar-based sensors and systems used in precision-guided weapons, electronic warfare, unmanned systems and other military applications. Based on the final purchase price allocation, the aggregate goodwill recognized for this business was $41 million, substantially all of which is expected to be deductible for income tax purposes. The goodwill was assigned to the Electronic Systems reportable segment.
	2012 Business Acquisitions
	During the year ended December 31, 2012, in separate transactions, the Company acquired three businesses for an aggregate purchase price of $349 million, which were financed with cash on hand. Based on the final purchase price allocations, the aggregate goodwill recognized for these businesses was $278 million, of which $182 million is expected to be deductible for income tax purposes. The goodwill was assigned to the Electronic Systems reportable segment. A description of each business acquisition made by the Company during the year ended December 31, 2012 is listed below:
		•		On February 6, 2012, the Company acquired the Kollmorgen Electro-Optical business (named L-3 KEO). L-3 KEO develops and manufactures specialized equipment, including submarine photonics systems and periscopes, ship fire control systems, visual landing aids and ground electro-optical and sensor-cueing systems for the U.S. military and foreign governments.
		•		On April 13, 2012, the Company acquired the assets and liabilities of MAVCO, Inc. (MAVCO). MAVCO is an audio, video, lighting and broadcast systems integrations business primarily for cruise lines.
		•		On August 6, 2012, the Company acquired the commercial aircraft simulation business from Thales Group (named Link Simulation & Training U.K. Limited (Link U.K.)). Link U.K. is a leading manufacturer of flight simulation systems for the commercial aviation market.
	The purchase prices and purchase price allocations for L-3 KEO and MAVCO were finalized as of June 28, 2013 and December 31, 2012, respectively, with no significant changes from the preliminary amounts. The Link U.K. purchase price allocation was finalized as of September 27, 2013 based on the results of the final appraisals and valuations of the assets and liabilities acquired and estimated final closing date net working capital. The final purchase price allocations resulted in certain adjustments to the preliminary valuations, the most significant of which included an increase to goodwill of $32 million, which included $4 million for foreign currency translation adjustments, an increase to other liabilities of $17 million, and a decrease of $16 million to contracts in process. The purchase price for Link U.K. was finalized in the fourth quarter of 2013 and resulted in a $6 million final net working capital adjustment that had been previously accrued.
	Business Acquisitions Completed After December 31, 2014
	On January 21, 2015, the Company acquired the assets of Miteq, Inc. (Miteq) for a purchase price of $41 million (subject to customary adjustments), which was financed with cash on hand. Miteq was combined with the Company’s Narda Microwave-East business and the new organization was re-named L-3 Narda-Miteq. Miteq offers a broad product line of active and passive radio frequency (RF) microwave components and low-power satellite communications (SATCOM) products for space and military applications that complement the existing Narda Microwave East product line. The combined L-3 Narda-Miteq business will provide products for the DoD, other U.S. Government agencies, prime contractors and commercial customers.
	Business Divestitures
	On December 16, 2014, the Company entered into a definitive agreement with Wärtsilä Corporation to sell its Marine Systems International (L-3 MSI) business for a base purchase price of €285 million, subject to customary adjustments and an estimated reduction of €60 million for L-3 MSI employee pension-related liabilities to be assumed by Wärtsilä Corporation. L-3 MSI is a sector within the Company’s Electronic Systems segment, primarily selling to the commercial ship industry. L-3 MSI is a turnkey supplier of complete electrical systems, as well as integrated navigation, automation, communications and power and propulsion systems for all types of ships, including cruise liners, ferries and offshore and specialty vessels. The transaction is anticipated to be completed in the second quarter of 2015, subject to customary closing conditions and regulatory approvals. Therefore, in accordance with ASU 2014-08, L-3 MSI’s assets and liabilities are classified as held for sale in the Company’s audited consolidated balance sheet, as of December 31, 2014. Also, in accordance with ASU 2014-08, L-3 MSI’s results of operations are included in income from continuing operations for all periods presented and are not classified within discontinued operations.
	The accounting standards for long-lived assets to be disposed of by sale require that the Company measure assets and liabilities of disposal group, classified as held for sale, at the lower of its carrying amount or fair value less costs to sell, at the end of each reporting period. At December 31, 2014, the fair value of the L-3 MSI disposal group exceeded its carrying value and no adjustment to carrying value was required. At the end of each future reporting period, the Company will adjust the carrying value of the L-3 MSI disposal group to the lower of its carrying amount or fair value less cost to sell, with any losses recognized through cost of sales. The Company may recognize a gain in subsequent periods not to exceed the cumulative losses previously recognized if the fair value of the L-3 MSI disposal group subsequently recovers. The Company will recognize any unrealized gains of the L-3 MSI disposal group upon completion of the L-3 MSI divesture.
	The major classes of assets and liabilities included as held for sale related to L-3 MSI are presented in the table below:
			December 31,
			2014
				(in millions)
	Assets
	Cash and cash equivalents		$	61
	Billed receivables, net of allowance of $6			77
	Contracts in process			70
	Inventories			70
	Other current assets			10
	Total current assets			288
	Goodwill			231
	Other assets			28
	Total assets classified as held for sale		$	547
	Liabilities
	Accounts payable, trade		$	31
	Accrued employment costs			22
	Accrued expenses			33
	Advance payments and billings in excess of costs incurred			55
	Other current liabilities			21
	Total current liabilities			162
	Pension and postretirement benefits			56
	Other liabilities			19
	Total liabilities classified as held for sale		$	237
	2012 Spin-off of Engility
	The Company completed the spin-off of its subsidiary, Engility Holdings, Inc. (Engility), on July 17, 2012. In connection with the spin-off, Engility made a cash distribution of $335 million to L-3. A portion of the proceeds were used to redeem $250 million of L-3 Communications 6 3⁄8% Senior Subordinated Notes due 2015 (6 3⁄8% 2015 Notes) on July 26, 2013. There was no gain or loss recognized by L-3 as a result of the spin-off transaction.
	Prior to the completion of the spin-off, L-3 and Engility entered into a Distribution Agreement dated July 16, 2012 and several other agreements that govern certain aspects of L-3’s relationship with Engility following the spin-off. These agreements generally provide that each party is responsible for its respective assets, liabilities and obligations, including employee benefits, insurance and tax-related assets and liabilities, following the spin-off, whether accrued or contingent.
	L-3 incurred transaction expenses in connection with the spin-off of $19 million ($14 million after income taxes) for the year ended December 31, 2012 which have been included in discontinued operations. In addition, L-3 allocated interest expense for debt not directly attributable or related to L-3’s other operations of $14 million to discontinued operations for the year ended December 31, 2012. Interest expense was allocated in accordance with the accounting standards for discontinued operations and was based on the ratio of Engility’s net assets to the sum of: (1) total L-3 consolidated net assets and (2) L-3 consolidated total debt.
	Engility’s statement of operations data, which has been classified as discontinued operations, is provided in the table below.
			January 1
			to July 17,
			2012
			(in millions)
	Product and service revenues		$	911
	Operating income from discontinued operations before income tax			68
	Interest expense allocated to discontinued operations			(14)
	Income from discontinued operations before income tax		$	54
	Income tax expense			(22)
	Income from discontinued operations, net of income tax		$	32
	Net income from discontinued operations attributable to noncontrolling interests			(4)
	Net income from discontinued operations attributable to L-3		$	28
	Unaudited Pro Forma Statements of Operations Data
	The following unaudited pro forma Statements of Operations data presents the combined results of the Company and its business acquisitions completed during the years ended December 31, 2014, 2013 and 2012 assuming that the business acquisitions completed during 2014, 2013 and 2012 had occurred on January 1, 2012.
			Year Ended December 31,
			2014		2013		2012
			(in millions, except per share data)
Pro forma net sales		$	12,131	$	12,701	$	13,276
Pro forma income from continuing operations		$	676	$	760	$	764
Pro forma net income attributable to L-3		$	663	$	751	$	786
Pro forma diluted earnings per share from continuing operations		$	7.55	$	8.24	$	7.76
Pro forma diluted earnings per share		$	7.55	$	8.24	$	8.05
The unaudited pro forma results disclosed in the table above are based on various assumptions and are not necessarily indicative of the results of operations that would have occurred had the Company completed these acquisitions on the dates indicated above.

Contracts_in_Process

Contracts in Process	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Contracts in Process	5. 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. In connection with contracts in process assumed by the Company in its business acquisitions, the underlying contractual customer relationships are separately recognized as identifiable intangible assets at the date of acquisition, and are discussed and presented in Note 7.
		December 31,
		2014		2013
		(in millions)
	Unbilled contract receivables, gross	$	2,280	$	2,493
	Unliquidated progress payments		(887)		(1,008)
	Unbilled contract receivables, net		1,393		1,485
	Inventoried contract costs, gross		997		1,037
	Unliquidated progress payments		(95)		(80)
	Inventoried contract costs, net		902		957
	Total contracts in process	$	2,295	$	2,442
	Unbilled Contract Receivables. Unbilled contract receivables represent accumulated incurred costs and earned profits on contracts (revenue arrangements), which have been recorded as sales, but have not yet been billed to customers. Unbilled contract receivables arise from the cost-to-cost method of revenue recognition that is used to record sales on certain fixed-price contracts. Unbilled contract receivables from fixed-price type contracts are converted to billed receivables when amounts are invoiced to customers according to contractual billing terms, which generally occur when deliveries or other performance milestones are completed. Unbilled contract receivables also arise from cost-plus type contracts, time-and-material type contracts and fixed-price service type contracts for revenue amounts that have not been billed by the end of the accounting period due to the timing of preparation of invoices to customers. The Company believes that approximately 97% of the unbilled contract receivables, net at December 31, 2014 will be billed and collected within one year.
	Unliquidated Progress Payments. Unliquidated progress payments arise from fixed-price type contracts with the U.S. Government that contain progress payment clauses, and represent progress payments on invoices that have been collected in cash, but have not yet been liquidated. Progress payment invoices are billed to the customer as contract costs are incurred at an amount generally equal to 75% to 80% of incurred costs. Unliquidated progress payments are liquidated as deliveries or other contract performance milestones are completed, at an amount equal to a percentage of the contract sales price for the items delivered or work performed, based on a contractual liquidation rate. Therefore, unliquidated progress payments are a contra asset account, and are classified against unbilled contract receivables if revenue for the underlying contract is recorded using the cost-to-cost method, and against inventoried contract costs if revenue is recorded using the units-of-delivery method.
	Inventoried Contract Costs. In accordance with contract accounting standards, the Company’s U.S. Government contractor businesses account for the portion of their G&A, IRAD and B&P costs that are allowable and reimbursable indirect contract costs under U.S. Government procurement regulations on their U.S. Government contracts (revenue arrangements) as inventoried contract costs. G&A, IRAD and B&P costs are allocated to contracts for which the U.S. Government is the end customer and are charged to costs of sales when sales on the related contracts are recognized. The Company’s U.S. Government contractor businesses record the unallowable portion of their G&A, IRAD and B&P costs to expense as incurred, and do not include them in 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,
		2014		2013		2012
		(in millions)
	Amounts included in inventoried contract costs at beginning of the year	$	138	$	110	$	91
	IRAD and B&P costs incurred		280		294		334
	Other G&A costs incurred		850		876		876
	Total contract costs incurred		1,130		1,170		1,210
	Amounts charged to cost of sales		(1,130)		(1,142)		(1,191)
	Amounts included in inventoried contract costs at end of the year	$	138	$	138	$	110
	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,
		2014		2013		2012
		(in millions)
	Selling, general and administrative expenses	$	295	$	310	$	322
	Research and development expenses		67		76		90
	Total	$	362	$	386	$	412

Inventories

Inventories	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories	6. Inventories
	Inventories at Lower of Cost or Market. 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,
		2014		2013
		(in millions)
	Raw materials, components and sub-assemblies	$	127	$	164
	Work in process		97		124
	Finished goods		64		78
	Total	$	288	$	366

Goodwill_and_Identifiable_Inta

Goodwill and Identifiable Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Identifiable Intangible Assets	7. Goodwill and Identifiable Intangible Assets
	Goodwill. In accordance with the accounting standards for business combinations, the Company records the assets acquired and liabilities assumed based on their estimated fair values at the date of acquisition (commonly referred to as the purchase price allocation). As part of the purchase price allocations for the Company’s business acquisitions, identifiable intangible assets are recognized as assets apart from goodwill if they arise from contractual or other legal rights, or if they are capable of being separated or divided from the acquired business and sold, transferred, licensed, rented or exchanged. However, the Company does not recognize any intangible assets apart from goodwill for the assembled workforces of its business acquisitions. At December 31, 2014, the Company had approximately 45,000 employees, and the substantial majority of the sales generated by the Company’s businesses were from the productive labor efforts of its employees, as compared to selling manufactured products or right-to-use technology.
	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				Aerospace				Communication				NSS				Consolidated
			Systems				Systems				Systems								Total
			(in millions)
	Balance at December 31, 2012		$	4,046			$	1,770			$	992			$	968			$	7,776
	Business acquisition(1)			44				—				—				—				44
	Business disposition			(2)				—				—				—				(2)
	Foreign currency translation  adjustments(2)			(3)				(19)				—				—				(22)
	Balance at December 31, 2013		$	4,085			$	1,751			$	992			$	968			$	7,796
	Business acquisitions(1)			(3)				—				—				39				36
	Business disposition			(1)				—				—				—				(1)
	Foreign currency translation  adjustments(2)			(77)				(21)				—				(1)				(99)
	Assets held for sale(3)			(231)				—				—				—				(231)
	Balance at December 31, 2014		$	3,773			$	1,730			$	992			$	1,006			$	7,501
		(1)	For the year ended December 31, 2014, the decrease in goodwill for the Electronic Systems segment was due to the final purchase price allocation for the Mustang business acquisition. The increase in goodwill for the NSS segment was due to the L-3 Data Tactics business acquisition. For the year ended December 31, 2013, the increase in goodwill for the Electronic Systems segment was due to the Mustang business acquisition.
		(2)	During 2014, the decrease in goodwill presented in the Electronic Systems segment was primarily due to the strengthening of the U.S. dollar against the Euro, the Canadian dollar and the British pound. During 2014 and 2013, the decreases in goodwill presented in the Aerospace Systems segment were due to the strengthening of the U.S. dollar against the Canadian dollar. During 2013, the decrease in goodwill presented in the Electronic Systems segment was primarily due to the strengthening of the U.S. dollar against the Canadian dollar and Australian dollar, partially offset by the weakening of the U.S. dollar against the Euro and the British pound.
		(3)	On December 16, 2014, the Company entered into a definitive agreement with Wärtsilä Corporation to sell its Marine Systems International business.
	As discussed in Note 2, the carrying value of goodwill is tested for impairment annually as of November 30 and on an interim basis, using a two-step process, whenever events or changes in circumstances indicate that the carrying amount may not be recoverable.
	The first step of the November 30, 2014 and November 30, 2013 annual impairment tests did not indicate any impairments. The Company’s accumulated goodwill impairment losses were $58 million at December 31, 2014 and 2013, of which $43 million and $15 million were recorded in the Electronic Systems and Communication Systems segments, respectively.
	Identifiable Intangible Assets. The most significant identifiable intangible asset that is separately recognized for the Company’s business acquisitions is customer contractual relationships. All of the Company’s customer relationships are established through written customer contracts (revenue arrangements). The fair value for customer contractual relationships is determined, as of the date of acquisition, based on estimates and judgments regarding expectations for the estimated future after-tax earnings and cash flows (including cash flows for working capital) arising from the follow-on sales on contract (revenue arrangement) renewals expected from the customer contractual relationships over their estimated lives, including the probability of expected future contract renewals and sales, less a contributory assets charge, all of which is discounted to present value.
	Information on the Company’s identifiable intangible assets that are subject to amortization is presented in the table below.
			December 31, 2014														December 31, 2013
			Weighted		Gross				Accumulated				Net				Gross				Accumulated		Net
			Average		Carrying				Amortization				Carrying				Carrying				Amortization		Carrying
			Amortization		Amount								Amount				Amount						Amount
			Period
			(in years)		(in millions)
	Customer contractual   relationships(1)		20		$	440			$	262			$	178			$	466			$	253	$	213
	Technology(1)		11			165				111				54				168				108		60
	Other		18			27				16				11				27				15		12
	Total		18		$	632			$	389			$	243			$	661			$	376	$	285
		(1)	Amounts reclassified to assets held for sale at December 31, 2014 relating to L-3 MSI include gross carrying amounts of $28 million and $7 million for customer contractual relationships and technology intangible assets, respectively, and accumulated amortization of $20 million and $6 million for customer contractual relationships and technology intangible assets, respectively.
	Amortization expense recorded by the Company for its identifiable intangible assets is presented in the table below.
			Year Ended December 31,
			2014				2013				2012
			(in millions)
	Amortization expense		$	43			$	39			$	47
	Based on gross carrying amounts at December 31, 2014, excluding assets held for sale relating to L-3 MSI, the Company’s estimate of amortization expense for identifiable intangible assets for the years ending December 31, 2015 through 2019 is presented in the table below.
			Year Ending December 31,
			2015				2016				2017				2018				2019
			(in millions)
	Estimated amortization expense		$	37			$	33			$	29			$	25			$	22

Other_Current_Liabilities_and_

Other Current Liabilities and Other Liabilities	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Other Current Liabilities and Other Liabilities	8. Other Current Liabilities and Other Liabilities
	The table below presents the components of other current liabilities.
		December 31,
		2014		2013
		(in millions)
	Other Current Liabilities:
	Accruals for pending and threatened litigation (see Note 19)	$	38	$	6
	Estimated costs in excess of estimated contract value to complete contracts in  process in a loss position		75		78
	Accrued product warranty costs		59		75
	Accrued interest		46		52
	Deferred revenues		30		35
	Other		150		156
	Total other current liabilities	$	398	$	402
	The table below presents the components of other liabilities.
		December 31,
		2014		2013
		(in millions)
	Other Liabilities:
	Non-current income taxes payable (see Note 17)	$	196	$	177
	Deferred compensation		43		45
	Accrued workers’ compensation		38		46
	Accrued product warranty costs		34		24
	Notes payable and capital lease obligations		1		15
	Other		70		99
	Total other liabilities	$	382	$	406

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	9. Property, Plant and Equipment
	The table below presents the components of Property, Plant and Equipment.
		December 31,
		2014		2013
		(in millions)
	Land	$	62	$	62
	Buildings and improvements		420		405
	Machinery, equipment, furniture and fixtures		1,707		1,643
	Leasehold improvements		327		338
	Gross property, plant and equipment		2,516		2,448
	Accumulated depreciation and amortization		(1,428)		(1,406)
	Property, plant and equipment, net	$	1,088	$	1,042

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Debt	10. Debt
	The components of long-term debt and a reconciliation to the carrying amount of long-term debt are presented in the table below.
			December 31,
			2014		2013
			(in millions)
	L-3 Communications:
	Borrowings under Amended and Restated Revolving Credit Facility(1)		$	—	$	—
	3.95% Senior Notes due 2016			500		500
	1.50% Senior Notes due 2017			350		—
	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			650		—
	Subtotal			3,950		2,950
	L-3 Holdings:
	3% Convertible Contingent Debt Securities due 2035			—		689
	Principal amount of long-term debt			3,950		3,639
	Unamortized discounts			(11)		(9)
	Carrying amount of long-term debt		$	3,939	$	3,630
		(1)	During 2014, L-3 Communications’ aggregate borrowings and repayments under the Credit Facility were $1,367 million. L-3 Communications had the full availability of its $1 billion Credit Facility at December 31, 2014 and had the availability of substantially all of its $1 billion Credit Facility at December 31, 2013.
	L-3 Communications Amended and Restated Revolving Credit Facility
	On February 3, 2012, L-3 Communications amended and restated its $1 billion Revolving Credit Facility, which extended the expiration date to February 3, 2017. The terms of the Credit Facility are substantially consistent with the terms of this facility prior to its amendment and restatement except that: (1) provisions that previously limited the ability of L-3 Communications to pay dividends, repurchase L-3 Holdings’ common stock and make other distributions with respect to any capital stock were eliminated, (2) a provision that previously limited the ability of L-3 Communications to make investments in L-3 Holdings was made less restrictive and (3) the cost of borrowings, loan commitment fees and letter of credit fees were reduced. In addition, the Credit Facility provides for uncommitted incremental revolving facilities and additional term loan facilities in an aggregate principal amount of up to $500 million. Borrowings under the Credit Facility bear interest, at L-3 Communications’ option, at either (1) the “base rate” equal to the highest of (a) 0.50% per annum above the latest federal funds rate, (b) the Bank of America “prime rate” (as defined in the Credit Facility), and (c) 1.00% per annum above a “Eurodollar Rate” (as defined in the Credit Facility), plus a spread ranging from 0.25% to 1.00% per annum, or (2) a “Eurodollar Rate” (as defined in the Credit Facility) plus a spread ranging from 1.25% to 2.00% per annum. L-3 Communications pays: (1) commitment fees calculated on the daily amounts of the available unused commitments at a rate ranging from 0.15% to 0.325% per annum, (2) letter of credit fees ranging from 0.675% to 1.20% per annum for commercial and performance letters of credit and (3) letter of credit fees ranging from 1.25% to 2.00% for financial letters of credit. The interest rate spread and the commitment fee rate, in all cases, depend on L-3 Communications’ debt rating at the time of determination. The debt rating is based on the credit ratings as determined by Standard & Poor’s Rating Services, Moody’s Investors Service, Inc. and Fitch Ratings of L-3 Communications’ non-credit enhanced senior, unsecured long-term debt.
	L-3 Communications Senior Notes
	The Senior Notes are unsecured senior obligations of L-3 Communications. The terms of each outstanding Senior Note are presented in the table below.
	Note		Date of Issuance		Amount		Discount(1)		Net			Effective			Redemption
					Issued				Cash			Interest			at Treasury
									Proceeds			Rate			Rate(2)(3)
					(in millions)
	3.95% Senior Notes due   November 15, 2016			November 22, 2011	$	500	$	4	$	491			4.11	%		50 bps
	1.50% Senior Notes due   May 28, 2017			May 28, 2014	$	350	$	1	$	347	(4)		1.55	%		10 bps
	5.20% Senior Notes due   October 15, 2019			2-Oct-09	$	1,000	$	4	$	987			5.25	%		30 bps
	4.75% Senior Notes due   July 15, 2020			21-May-10	$	800	$	3	$	790			4.79	%		25 bps
	4.95% Senior Notes due   February 15, 2021			7-Feb-11	$	650	$	4	$	639			5.02	%		25 bps
	3.95% Senior Notes due   May 28, 2024			May 28, 2014	$	650	$	3	$	641	(4)		4.02	%		20 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 2016, 2017, 2019, 2020 and 2021 may be redeemed at any time prior to their maturity and the Senior Notes maturing in 2024 may be redeemed at any time prior to February 28, 2024 (three months prior to their maturity) at the option of L-3 Communications, 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 2024 are redeemed at any time on or after February 28, 2024, 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 L-3 Communications 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.
		(4)	The net cash proceeds of $988 million (after deduction of the bond discount, underwriting expenses and commissions and other related expenses) were used primarily to fund the CODES retirement as discussed below. The remaining net proceeds were used for general corporate purposes.
	Information on the Senior Subordinated Notes redeemed by the Company during the year ended December 31, 2012 is presented in the table below. There were no redemptions of L-3 Communications Senior Subordinated Notes during the years ended December 31, 2014 and 2013.
	Note		Redemption Date		Principal		Debt		Redemption Price
					Amount		Retirement		% of Principal
					Redeemed		Charge
					(in millions)
	6 3⁄8% Senior Subordinated Notes due October 15, 2015			October 15, 2012	$	250	$	5		101.06%
	6 3⁄8% Senior Subordinated Notes due October 15, 2015(1)			26-Jul-12	$	250	$	8		102.13%
		(1)	In connection with the spin-off, Engility made a cash distribution of $335 million to L-3, a portion of which was used to redeem $250 million of the 6  3⁄8% 2015 Notes.
	L-3 Holdings
	In 2005, L-3 Holdings sold $700 million of 3% Convertible Contingent Debt Securities (CODES) due August 1, 2035. On February 2, 2011, L-3 Holdings repurchased approximately $11 million of the CODES as a result of the exercise by the holders of their contractual right to require L-3 Holdings to repurchase their CODES. At December 31, 2013, the remaining $689 million principal amount of CODES was classified as long-term debt.
	Interest expense recognized for the CODES was $2 million for the year ended December 31, 2014 and $21 million for each of the years ended December 31, 2013 and 2012, a portion of which was allocated to discontinued operations in 2012 as a result of the spin-off of Engility.
	On May 13, 2014, L-3 Holdings called for the full redemption of all of its outstanding CODES effective on June 2, 2014 (the Redemption Date). The redemption price for the CODES was $1,000 per $1,000 principal amount of the CODES, plus accrued and unpaid interest to, but excluding, the Redemption Date. Holders of the CODES were entitled to convert all or a portion thereof (in integral multiples of $1,000) at any time prior to the close of business on the business day immediately preceding the Redemption Date. The conversion value of CODES of $935 million was calculated in accordance with the indenture governing the CODES. L-3 Holdings settled the entire conversion value with respect to converted CODES in cash. As of June 20, 2014, the CODES have been retired. As a result of the conversion, the Company recorded a reduction to shareholders’ equity of $161 million, related to the excess conversion value over the fair value of the debt component of the CODES, net of deferred tax liability.
	Guarantees
	The borrowings under the Credit Facility are fully and unconditionally guaranteed by L-3 Holdings and by substantially all of the material 100% owned domestic subsidiaries of L-3 Communications 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 L-3 Communications’ material 100% owned domestic subsidiaries that guarantee any of its other indebtedness.
	Subordination
	The guarantees of the Credit Facility and the Senior Notes rank pari passu with each other.
	Covenants
	Financial and other restrictive covenants. The Credit Facility contains financial and other restrictive covenants that limit, among other things, the ability of the subsidiaries of L-3 Communications to borrow additional funds, and the ability of L-3 Communications and its subsidiaries to incur liens, make investments, merge or consolidate or dispose of assets. The Company’s Credit Facility contains covenants that require that (1) the Company’s consolidated leverage ratio be less than or equal to 4.0 to 1.0, (2) the Company’s consolidated interest coverage ratio be greater than or equal to 3.0 to 1.0, and (3) the Company’s consolidated senior leverage ratio be less than or equal to 3.5 to 1.0, in each case, as of the end of any fiscal quarter. Calculations of the financial covenants are to exclude, among other things, certain items such as impairment losses on goodwill or other intangible assets, non-cash gains or losses from discontinued operations, gains or losses in connection with asset dispositions, and gains or losses with respect to judgments or settlements in connection with litigation matters. As of December 31, 2014, the Company was in compliance with its 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 L-3 Communications 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 L-3 Communications and its subsidiaries to enter into certain sale and leaseback transactions (as defined in the Senior Indentures).
	Cross default provisions. The Credit Facility contains cross default provisions that are triggered when a payment default occurs or certain other defaults occur that would allow the acceleration of indebtedness, swap contracts or guarantees of L-3 Holdings, L-3 Communications or its subsidiaries, so long as the aggregate amount of such indebtedness, swap contracts or guarantees is at least $50 million and such defaults (other than payment defaults and defaults that have resulted in acceleration) have not been cured within 10 days. The Senior Notes indenture contains a cross acceleration provision that is triggered when a default or acceleration occurs under any indenture or instrument of L-3 Communications or its subsidiaries or the payment of which is guaranteed by L-3 Communications or its subsidiaries in an aggregate amount of at least $100 million.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive (Loss) Income (AOCI)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Accumulated Other Comprehensive (Loss) Income (AOCI)	11. 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		Unrealized		Unrecognized		Total
			currency		gains		(losses) gains		accumulated
			translation		(losses) on		and prior service		other
					hedging		cost, net		comprehensive
					instruments(1)				(loss) income
			(in millions)
	Balance at December 31, 2011		$	133	$	—	$	(587)	$	(454)
	Other comprehensive income (loss) before   reclassifications, net of tax			34				(175)
	Amounts reclassified from AOCI, net of tax			—				42
	Net current period other comprehensive   income (loss)			34		3		(133)		(96)
	Balance at December 31, 2012		$	167	$	3	$	(720)	$	(550)
	Other comprehensive (loss) income before   reclassifications, net of tax			(25)		(1)		414		388
	Amounts reclassified from AOCI, net of tax			—		(1)		53		52
	Net current period other comprehensive   (loss) income			(25)		(2)		467		440
	Balance at December 31, 2013		$	142	$	1	$	(253)	$	(110)
	Other comprehensive (loss) before reclassifications,   net of tax			(123)		(13)		(354)		(490)
	Amounts reclassified from AOCI, net of tax			—		7		9		16
	Net current period other comprehensive (loss)			(123)		(6)		(345)		(474)
	Balance at December 31, 2014		$	19	$	(5)	$	(598)	$	(584)
		(1)	Information related to amounts reclassified from AOCI for hedging instruments is unavailable for the year ended December 31, 2012.
	Further details regarding the amounts reclassified from AOCI into net income are presented in the table below.
			Amount Reclassified from
			AOCI(a)
			Year Ended December 31,						Affected Line Item in the
									Audited Consolidated
	Details About AOCI Components		2014		2013		2012(b)		Statements of Operations
			(in millions)
	(Loss) gains on hedging instruments		$	(8)	$	1			Cost of sales-products
				(8)		1			Income from continuing operations before income taxes
				1		—			Provision for income taxes
			$	(7)	$	1			Income from continuing operations
	Amortization of defined benefit pension items:
	Net loss		$	(15)	$	(83)	$	(68)	(c)
				(15)		(83)		(68)	Income from continuing operations before income taxes
				6		30		26	Provision for income taxes
			$	(9)	$	(53)	$	(42)	Income from continuing operations
	Total reclassification for the period		$	(16)	$	(52)			Income from continuing operations
		(a)	Amounts in parentheses indicate charges to the consolidated statements of operations.
		(b)	Information related to amounts reclassified from AOCI for hedging instruments is unavailable for the year ended December 31, 2012.
		(c)	Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 20 for additional information).

Equity

Equity	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Equity	12. Equity
	On February 5, 2013, L-3 Holdings’ Board of Directors approved a share repurchase program that authorizes L-3 Holdings to repurchase up to $1.5 billion of its common stock through June 30, 2015. On December 4, 2014, L-3 Holdings’ Board of Directors approved a new share repurchase program that authorizes L-3 Holdings to repurchase up to an additional $1.5 billion of its common stock through June 30, 2017. Repurchases of L-3 Holdings’ 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. L-3 Holdings, pursuant to the February 5, 2013 share repurchase program, repurchased 6.9 million shares of its common stock at an average price of $119.42 per share for an aggregate amount of $823 million from January 1, 2014 through December 31, 2014. All share repurchases of L-3 Holdings’ common stock have been recorded as treasury shares. At December 31, 2014, the remaining dollar value of authorization under the February 5, 2013 share repurchase program was $45 million and the Company had the full authorization of the December 4, 2014 $1.5 billion share repurchase program available.
	From January 1, 2015 through February 20, 2015, L-3 Holdings repurchased 613,789 shares of its common stock at an average price of $126.99 per share for an aggregate amount of approximately $78 million. During this period, the February 5, 2013 share repurchase program was fully utilized. The remaining dollar value of authorization under our December 4, 2014 share repurchase program available at February 20, 2015 is summarized in the table below.
		Share Authorization
		(in millions)
	Remaining authorization at December 31, 2014	$	1,545
	Share repurchases from January 1, 2015 to February 20, 2015 under February 5, 2013 share repurchase program		(45	)
	Share repurchases from January 1, 2015 to February 20, 2015 under December 4, 2014 share repurchase program		(33	)
	Remaining authorization at February 20, 2015 under the December 4, 2014 share repurchase program	$	1,467

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Measurements	13. Fair Value Measurements
	L-3 applies the accounting standards for fair value measurements to all of the Company’s assets and liabilities that are measured and recorded at fair value. 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,
			2014						2013
	Description		Level 1(1)		Level 2(2)		Level 3(3)		Level 1(1)		Level 2(2)		Level 3(3)
			(in millions)
	Assets
	Cash equivalents		$	416	$	—	$	—	$	299	$	—	$	—
	Derivatives (foreign currency forward contracts)			—		5		—		—		6		—
	Total assets		$	416	$	5	$	—	$	299	$	6	$	—
	Liabilities
	Derivatives (foreign currency forward contracts)		$	—	$	11	$	—	$	—	$	5	$	—
		(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. The Company has no Level 3 assets or liabilities.

Financial_Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2014
Investments, All Other Investments [Abstract]
Financial Instruments	14. Financial Instruments
	At December 31, 2014 and 2013, the Company’s financial instruments consisted primarily of cash and cash equivalents, billed receivables, trade accounts payable, Senior Notes, CODES 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, 2014				December 31, 2013
			Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value
			(in millions)
	Senior Notes(1)		$	3,939	$	4,178	$	2,941	$	3,121
	CODES(1)		$	—	$	—	$	689	$	830
	Foreign currency forward contracts(2)		$	(6)	$	(6)	$	1	$	1
		(1)	The Company measures the fair value of its Senior Notes and its CODES prior to their redemption 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 15 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative_Financial_Instrumen

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	15. 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 as of December 31, 2014.
	Currency		Notional Amount
			(in millions)
	Canadian dollar		$	123
	U.S. dollar			101
	Euro			47
	British pound			9
	Total		$	280
	At December 31, 2014, the Company’s foreign currency forward contracts had maturities through 2018.
	The table below presents the location of the Company’s derivative instruments recorded at fair value on the consolidated balance sheets.
			December 31, 2014								December 31, 2013
			Other		Other		Other		Other		Other		Other		Other		Other
			Current		Assets		Current		Liabilities		Current		Assets		Current		Liabilities
			Assets				Liabilities				Assets				Liabilities
			(in millions)
	Derivatives designated as hedging instruments:
	Foreign currency forward   contracts(1) (2)		$	4	$	1	$	10	$	1	$	5	$	1	$	3	$	2
	Total derivative instruments		$	4	$	1	$	10	$	1	$	5	$	1	$	3	$	2
		(1)	See Note 13 for a description of the fair value hierarchy related to the Company’s foreign currency forward contracts.
		(2)	Assets held for sale at December 31, 2014 include $2 million of other current assets relating to the fair value of derivative instruments and liabilities held for sale at December 31, 2014 include $2 million of other current liabilities relating to the fair value of derivative instruments.
	The effect of gains or losses from foreign currency forward contracts was not material to the consolidated statements of operations for the years ended December 31, 2014, 2013 and 2012. At December 31, 2014, the estimated net amount of existing losses that are expected to be reclassified into income within the next 12 months is $4 million.

L3_Holdings_Earnings_Per_Share

L-3 Holdings' Earnings Per Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
L-3 Holdings' Earnings Per Share	16. L-3 Holdings’ Earnings Per Share
	A reconciliation of basic and diluted earnings per share (EPS) is presented in the table below.
			Year Ended December 31,
			2014		2013		2012
			(in millions, except per share data)
	Reconciliation of net income:
	Net income		$	677	$	760	$	794
	Net income from continuing operations attributable to noncontrolling interests			(13)		(9)		(6)
	Net income from discontinued operations attributable to noncontrolling interests			—		—		(4)
	Net income attributable to L-3 Holdings common shareholders		$	664	$	751	$	784
	Earnings attributable to L-3 Holdings’ common shareholders:
	Continuing operations		$	664	$	751	$	756
	Discontinued operations, net of income tax			—		—		28
	Net income attributable to L-3 Holdings common shareholders		$	664	$	751	$	784
	Earnings per share attributable to L-3 Holdings’ common shareholders:
	Basic:
	Weighted average common shares outstanding			85.4		89.4		96.3
	Basic earnings per share attributable to L-3 Holdings’ common shareholders:
	Continuing operations		$	7.78	$	8.40	$	7.85
	Discontinued operations, net of income tax			—		—		0.29
	Basic earnings per share		$	7.78	$	8.40	$	8.14
	Diluted:
	Common and potential common shares:
	Weighted average common shares outstanding			85.4		89.4		96.3
	Assumed exercise of stock options			3.0		3.9		1.9
	Unvested restricted stock awards			1.6		1.8		2.0
	Employee stock purchase plan contributions			—		0.2		0.3
	Performance unit awards			0.1		0.1		0.1
	Assumed purchase of common shares for treasury			(3.1)		(4.5)		(3.0)
	Assumed conversion of the CODES(1)			0.8		0.2		—
	Common and potential common shares			87.8		91.1		97.6
	Diluted earnings per share attributable to L-3 Holdings’ common shareholders:
	Continuing operations		$	7.56	$	8.24	$	7.74
	Discontinued operations, net of income tax			—		—		0.29
	Diluted earnings per share		$	7.56	$	8.24	$	8.03
		(1)	The CODES were retired on June 20, 2014 and were dilutive for the years ended December 31, 2014 and 2013 as the average market price of L-3 Holdings’ common stock during the periods that the CODES were outstanding was greater than the price at which the CODES would have been convertible into L-3 Holdings’ common stock. L-3 Holdings’ CODES had no impact on diluted EPS for the year ended December 31, 2012 because the average market price of L-3 Holdings’ common stock during this period was less than the price at which the CODES would have been convertible into L-3 Holdings’ common stock. As of June 18, 2014, the final date of conversion, the conversion price during the year-to-date period ended June 27, 2014 was $88.71. As of December 31, 2013 and 2012, the conversion prices were $90.24, and $91.21, respectively.
	The computation of diluted EPS excluded shares for stock options and employee stock purchase plan contributions of 0.5 million, 0.9 million and 3.2 million for the years ended December 31, 2014, 2013 and 2012, respectively, as they were anti-dilutive.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	17. Income Taxes
	Income from continuing operations before income taxes is summarized in the table below.
			Year Ended December 31,
			2014		2013		2012
			(in millions)
	Domestic		$	760	$	858	$	892
	Foreign			165		197		230
	Income from continuing operations before income taxes		$	925	$	1,055	$	1,122
	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,
			2014		2013		2012
			(in millions)
	Current income tax provision:
	Federal		$	87	$	181	$	198
	State and local			4		34		21
	Foreign			36		38		44
	Subtotal			127		253		263
	Deferred income tax provision:
	Federal			107		35		80
	State and local			13		—		8
	Foreign			1		7		9
	Subtotal			121		42		97
	Total provision for income taxes		$	248	$	295	$	360
	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,
			2014		2013		2012
	Statutory federal income tax rate			35.0%		35.0%		35.0%
	State and local income taxes, net of federal income tax benefit			2.3		2.1		1.7
	Foreign income taxes			(3.4)		(1.6)		(2.0)
	Manufacturing benefits			(1.7)		(1.9)		(1.8)
	Research and experimentation and other tax credits			(4.1)		(3.6)		(0.5)
	Resolution of tax contingencies			(0.9)		(1.0)		(0.9)
	Other, net			(0.4)		(1.0)		0.6
	Effective income tax rate on continuing operations			26.8%		28.0%		32.1%
	The significant components of the Company’s net deferred tax assets and liabilities are presented in the table below.
			December 31,
			2014		2013
			(in millions)
	Deferred tax assets:
	Inventoried costs		$	86	$	72
	Compensation and benefits			152		164
	Pension and postretirement benefits			402		207
	Loss carryforwards			15		24
	Tax credit carryforwards			10		7
	Other			84		75
	Gross deferred tax assets			749		549
	Less: valuation allowance			(9)		(22)
	Net deferred tax assets			740		527
	Deferred tax liabilities:
	Goodwill and other intangible assets		$	792	$	726
	Income recognition on contracts in process			78		58
	Property, plant and equipment			98		85
	Long-term debt-CODES			—		81
	Other			88		65
	Gross deferred tax liabilities			1,056		1,015
	Total net deferred tax liabilities		$	(316)	$	(488)
	The classification of the Company’s deferred tax assets and liabilities are presented in the table below.
			December 31,
			2014		2013
			(in millions)
	Current deferred tax assets		$	127	$	147
	Non-current deferred tax liabilities			(443)		(635)
	Total net deferred tax liabilities		$	(316)	$	(488)
	The following table presents the Company’s loss and tax credit carryforwards as of December 31, 2014 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, 2014
		Carryforwards				Valuation
						Allowances
		Gross		Tax		Gross		Tax		Expiration
				Effected				Effected		Periods
		(in millions)				(in millions)
Capital loss carryforwards(1)		$	25	$	9	$	14	$	5	2016-2017
Federal net operating loss carryforwards			5		2		5		2	2026-2030
Foreign net operating loss carryforwards			7		2		2		1	Indefinite
State net operating loss carryforwards			94		2		48		1	2016-2033
Total loss carryforwards				$	15			$	9
State tax credit carryforwards			11		7		—		—	2016-2033
Foreign tax credit carryforwards			3		3		—		—	Indefinite
Total tax credit carryforwards				$	10			$	—
(1)	During 2014, the Company reduced its valuation allowance for capital loss carryforwards by $4 million because it now believes that it will more likely than not have sufficient capital gains to realize this portion of the underlying deferred tax asset.
As of December 31, 2014, the total amount of unrecognized tax benefits was $180 million, $114 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.
		2014		2013		2012
		(in millions)
Balance at January 1		$	169	$	138	$	150
Additions for tax positions related to the current year			20		18		8
Additions for tax positions related to prior years			13		41		9
Reductions for tax positions related to prior years			(15)		(8)		(13)
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			(6)		(20)		(15)
Balance at December 31		$	180	$	169	$	138
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. The statutes of limitations for the Company’s U.S. Federal income tax returns for the years ended December 31, 2010 through 2013 are open as of December 31, 2014. The U.S. Internal Revenue Service (IRS) commenced audits of the Company’s U.S. Federal income tax returns for 2010 and 2011. The Company cannot predict the outcome of the audits at this time. As of December 31, 2014, the Company anticipates that unrecognized tax benefits will decrease by approximately $20 million over the next 12 months due to the potential resolution of unrecognized tax benefits involving several jurisdictions and tax periods. The actual amount could vary significantly depending on the ultimate timing and nature of any settlements.
During the year ended December 31, 2014, the Company settled various state and local tax audits. As a result, the Company reduced its income tax provision by $8 million for the reversal of previously accrued amounts.
During the years ended December 31, 2013 and 2012, the statutes of limitations for several of the Company’s tax returns, including its 2009 and 2008 U.S. Federal income tax returns, respectively, as well as certain foreign tax returns expired. As a result, the Company reduced its income tax provision by $10 million in both years ended December 31, 2013 and 2012 for the reversal of previously accrued amounts.
As of December 31, 2014 and 2013, current and non-current income taxes payable include accrued potential interest of $15 million ($9 million after income taxes) and $11 million ($7 million after income taxes), respectively, and potential penalties of $9 million and $8 million, respectively. With respect to the interest related items, the Company’s income tax expense included an expense of $2 million for the year ended December 31, 2014 and a benefit of $2 million for the year ended December 31, 2012.
At December 31, 2014, the Company has not provided deferred U.S. income taxes and foreign withholding taxes for $331 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.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	18. Stock-Based Compensation
	Stock-Based Compensation Plans. The Company has adopted stock-based compensation plans in order to provide incentives to directors, officers, employees and other individuals providing services to or on behalf of the Company and its subsidiaries. The Company believes that its stock-based compensation awards encourage high levels of performance by individuals who contribute to the success of the Company and enable the Company to attract, retain and reward talented and experienced individuals. This is accomplished by providing eligible individuals with an opportunity to obtain or increase a proprietary interest in the Company and/or by providing eligible individuals with additional incentives to join or remain with the Company. The stock-based compensation plans serve to better align the interests of management and its employees with those of the Company’s shareholders. During the year ended December 31, 2014, the Company awarded stock-based compensation under its Amended and Restated 2008 Long Term Performance Plan (2008 LTPP). Awards under the 2008 LTPP may be granted to any officer or employee of the Company or any of its subsidiaries, non-employee directors, or to any other individual who provides services to or on behalf of the Company or any of its subsidiaries. To date, awards under the 2008 LTPP have been in the form of L-3 Holdings’ restricted stock units, performance units and options to purchase L-3 Holdings’ common stock.
	On April 30, 2013, the stockholders of L-3 Holdings approved an amendment to the 2008 LTPP to increase the number of shares authorized for issuance to approximately 19.2 million shares. Each share of L-3 Holdings’ common stock issued under a full value award granted on or after February 26, 2013 is counted as 3.69 shares for purposes of this share limit. Each share issued under full value awards granted between March 1, 2010 and February 25, 2013 is counted as 2.6 shares for purposes of the share limit. At December 31, 2014, 6.0 million shares of L-3 Holdings’ common stock remained available for future awards under the 2008 LTPP.
	The Company’s stock-based compensation by form of award, including stock-based compensation recorded in discontinued operations for the spin-off of Engility in 2012, is presented in the table below.
			Year Ended December 31,
			2014		2013		2012
			(in millions)
	Stock options		$	9	$	10	$	10
	Restricted stock units			40		41		46
	Performance units			3		7		8
	Total before income taxes			52		58		64
	Income taxes			(20)		(22)		(24)
	Total after income taxes			32		36		40
	Less: Stock based compensation recorded in discontinued   operations, net of income taxes			—		—		1
	Stock based compensation recorded in continuing operations,   net of income taxes		$	32	$	36	$	39
	Stock Options. The exercise price of stock options granted under the 2008 LTPP may not be less than the fair market value of L-3 Holdings’ common stock on the date of grant. Options expire after 10 years from the date of grant and vest ratably over a three year period on the annual anniversary of the date of grant. All unvested options are subject to forfeiture upon termination of employment (subject to customary exceptions for death or disability). All of the stock option awards issued under the 2008 LTPP are non-qualified stock options for U.S. income tax regulations. The table below presents a summary of the Company’s stock option activity as of December 31, 2014 and changes during the year then ended.
			Number of		Weighted		Weighted		Aggregate
			Options		Average		Average		Intrinsic
					Exercise		Remaining		Value
					Price		Contractual
							Term
			(in thousands)				(in years)		(in millions)
	Number of shares under option:
	Outstanding at January 1, 2014			3,882.9	$	77.90		6.2	$	112
	Options granted			473.0		113.67
	Options exercised			(1,183.4)		77.94
	Options forfeited			(71.3)		91.59
	Outstanding at December 31, 2014			3,101.2	$	83.02		6.2	$	134
	Vested and expected to vest at December 31, 2014(1)			3,090.3	$	82.96		6.2	$	134
	Exercisable at December 31, 2014			1,962.8	$	79.46		4.9	$	92
		(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 2014, 2013 and 2012 was $20.02, $12.09 and $11.32, respectively. The aggregate intrinsic value, disclosed in the table above, represents the difference between L-3 Holdings’ 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 L-3 Holdings’ stock price at the time of exercise and the related exercise price, was $43 million, $32 million and $7 million for the years ended December 31, 2014, 2013 and 2012, respectively. At December 31, 2014, unrecognized compensation costs related to stock options were $10 million ($6 million after income taxes), which are expected to be recognized over a weighted average remaining period of 1.2 years.
	The actual income tax benefit realized related to compensation deductions arising from the exercise of stock options by the Company’s employees totaled $14 million, $10 million and $2 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	Stock Option Fair Value Estimation Assumptions. The Company estimates the fair value of its stock options at the date of grant using the Black-Scholes option-pricing valuation model. The Company’s valuation model is affected by L-3 Holdings’ stock price as well as weighted average assumptions for a number of subjective variables described below.
		•		Expected Holding Period. The expected holding period represents the period of time that granted stock options are expected to be outstanding until they are exercised. The Company uses historical stock option exercise data to estimate the expected holding period.
		•		Expected Volatility. Expected volatility is based on L-3 Holdings’ historical share price volatility matching the expected holding period.
		•		Expected Dividend Yield. Expected dividend yield is based on L-3 Holdings’ anticipated dividend payments and historical pattern of dividend increases over the expected holding period.
		•		Risk-Free Interest Rates. The risk-free interest rates for stock options are based on U.S. Treasuries for a maturity period matching the expected holding period.
	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.
			2014		2013		2012
			Grants		Grants		Grants
	Expected holding period (in years)			5.5		5.6		5.4
	Expected volatility			24.40%		26.40%		27.00%
	Expected dividend yield			2.70%		3.60%		3.60%
	Risk-free interest rate			1.70%		1.00%		1.00%
	Restricted Stock Units. The Company awards restricted stock units that automatically convert into shares of L-3 Holdings’ common stock upon vesting (in the case of awards granted to employees) or upon the date on which the recipient ceases to be a director (in the case of awards granted to directors). These awards are subject to forfeiture until certain restrictions have lapsed, including a three year cliff vesting period for employees and a one year cliff vesting period for directors, in each case starting on the date of grant. The weighted average grant date fair value of the restricted stock units awarded during 2014, 2013 and 2012 was $113.58, $77.12 and $70.42, respectively. The grant date fair value of the restricted stock unit awards is based on L-3 Holdings’ closing stock price at the date of grant, and is generally recognized as compensation expense on a straight-line basis over the vesting period. However, for employees who attain retirement eligibility status prior to the end of the three year cliff vesting period, and who have provided at least one year of service after the date of grant, compensation expense is recognized over the shorter period from the date of grant to the retirement eligibility date. Retirement eligible employees are those employees that have attained the age of 65 and have completed at least five years of service (which service must be continuous through the date of termination except for a single break in service that does not exceed one year in length).
	The table below presents a summary of the Company’s nonvested restricted stock unit awards as of December 31, 2014 and changes during the year then ended.
			Number of		Weighted
			Shares		Average
					Grant Date
					Fair Value
			(in thousands)
	Nonvested balance at January 1, 2014			1,773.8	$	73.51
	Granted			416.7		113.58
	Vested			(570.8)		77.07
	Forfeited			(102.1)		80.36
	Nonvested balance at December 31, 2014			1,517.6	$	82.72
	As of December 31, 2014, total unrecognized compensation costs related to nonvested restricted stock unit awards were $40 million ($25 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, 2014, 2013 and 2012 as of their vesting dates was $66 million, $37 million and $44 million, respectively.
	Performance Units. The Company grants performance unit awards, with each unit having a value at the time of grant equal to a share of L-3 Holdings’ common stock. The number of units ultimately earned can range from zero to 200% of the original award based upon the level of performance achieved by the Company over the associated performance period in relation to pre-determined performance goals. Units earned under the program are converted into shares of L-3 Holdings’ common stock, or are paid in cash based on the closing price of L-3 Holdings’ common stock at the end of the performance period, as determined at the time of grant by the Compensation Committee of the Board of Directors of L-3 Holdings.
	During the years ended December 31, 2014, 2013, and 2012, the Company granted performance unit awards with a weighted average grant date fair value per unit of $113.67, $77.00 and $70.43, respectively. All the awards granted in 2014, 2013, and 2012 have performance conditions based on L-3’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 award are convertible into shares of L-3 Holdings’ common stock. As of December 31, 2014, total unrecognized compensation costs related to the awards were $5 million ($3 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 as of December 31, 2014 and changes during the year then ended.
			Payable in Shares (EPS)
			Number of		Weighted Average
Units			Grant Date
			Fair Value
		(in thousands)
Outstanding at January 1, 2014			175.5	$	70.84
Granted			47.5		113.67
Decrease due to expected performance			(45.6)		71.78
Vested			(87.3)		67.49
Forfeited			(4.9)		89.90
Outstanding at December 31, 2014			85.2	$	96.53
The performance period for awards granted in 2012 ended on December 31, 2014. Based on L-3’s cumulative diluted EPS during the performance period, a total of 87,309 performance units having a fair market value of $11 million as of their vesting date were earned by the participants on December 31, 2014.
Employee Stock Purchase Plan. Effective July 1, 2009, the Company adopted the 2009 Employee Stock Purchase Plan (2009 ESPP). Under the 2009 ESPP, eligible employees are offered options to purchase shares of L-3 Holdings’ 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.
As of December 31, 2014, 4.3 million shares were available for future issuance under the 2009 ESPP (i.e., excluding the effect of shares issued in January 2014 as described below). In July 2014, the Company issued 0.2 million shares under the 2009 ESPP at an average price of $115.03 per share, which covered employee contributions for the six months ended June 30, 2014. In January 2015, the Company issued 0.1 million shares under the 2009 ESPP at an average price of $120.94 per share, which covered employee contributions for the six months ended December 31, 2014. 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, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	19. Commitments and Contingencies
	Non-Cancelable Operating Leases
	The Company leases certain facilities and equipment under agreements expiring at various dates through 2033. 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, 2014.
		Real Estate		Equipment		Total
				(in millions)
	2015	$	142	$	9	$	151
	2016		100		6		106
	2017		90		4		94
	2018		78		3		81
	2019		58		2		60
	Thereafter		113		2		115
	Total minimum payments required		581		26		607
	Less: Sublease rentals under non-cancelable leases		5		—		5
	Net minimum payments required	$	576	$	26	$	602
	Rent expense was $140 million for 2014, $141 million for 2013, and $145 million for 2012. Sublease rental income was $4 million for 2014, $6 million for 2013 and $5 million for 2012.
	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 $615 million and $634 million at December 31, 2014 and 2013, respectively. The Company had the full availability of its $1 billion Credit Facility at December 31, 2014 and had the availability of substantially all of its $1 billion Credit Facility at December 31, 2013. 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, L-3 entered into a Distribution Agreement and several other agreements that govern certain aspects of L-3’s relationship with Engility, including employee matters, tax matters, transition services, and the future supplier/customer relationship between L-3 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 L-3 to the U.S. Internal Revenue Service (IRS) for the consolidated U.S. Federal income taxes of L-3’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 L-3 and Engility will each bear responsibility, and L-3 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 L-3 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 two existing real estate lease agreements, which include residual guarantee amounts, expiring on August 31, 2015 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 both properties for $28 million, or sell both 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 $23 million for both properties, on or before the lease expiration date. In addition, at the time both 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 $5 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 $23 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 U.S. Air Force (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. At the end of the lease term, the Company may elect to purchase the simulator systems at fair market value, which can be no less than $7 million and no greater than $21 million. If the Company does not elect to purchase the simulator systems on the date of expiration (during the first quarter of 2018), the Company shall pay to the lessor, as additional rent, $7 million and return the simulator systems to the lessors.
	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 U.S. Government and foreign government customers. 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. In that regard, an ongoing government investigation resulted in an $18 million charge in connection with an anticipated settlement relating to a product specifications matter. We have other ongoing government investigations, 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 and 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 8. Amounts recoverable from insurance contracts or third parties are recorded as assets when deemed probable. At December 31, 2014, the Company recorded approximately $11 million of receivables 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 quarterly and adjusts 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. Accordingly, our current judgment as to the likelihood of our loss (or our current estimate as to the potential range of loss, if applicable) with respect to any particular litigation matter may turn out to be wrong. Therefore, it is possible that the financial position, results of operations or cash flows of the Company could be materially adversely affected in any particular period by the unfavorable resolution of one or more of these or other contingencies.
	Class Action. In August 2014, three separate, putative class actions were filed in the United States District Court for the Southern District of New York (the District Court) against the Company and certain of its officers. These cases were consolidated into a single action on October 24, 2014, and a consolidated amended complaint was filed in the District Court on December 22, 2014. The complaint alleges violations of federal securities laws related to misconduct and accounting errors identified by the Company at its Aerospace Systems segment, and seeks monetary damages, pre- and post-judgment interest, and fees and expenses. The Company believes the action lacks merit and intends to defend itself vigorously. On February 20, 2015, the Company filed a motion to dismiss the action. The Company is unable to reasonably estimate any amount or range of loss, if any, that may be incurred in connection with this matter because the proceedings are in their early stages.
	Government Inquiries. On July 30, 2014, the Company voluntarily contacted the Securities and Exchange Commission (SEC) to report information concerning its internal review related to misconduct and accounting errors identified by the Company at its Aerospace Systems segment. The Company is in contact with the SEC and the U.S. Department of Justice, has received subpoenas for documents and other materials from both agencies concerning these self-reported matters, and is fully cooperating. The Company is unable to reasonably estimate any amount or range of loss, if any, that may be incurred in connection with these inquiries based on the nature of the inquiries to date.
	Bashkirian Airways. On July 1, 2004, lawsuits were filed on behalf of the estates of 31 Russian children in the state courts of Washington, Arizona, California, Florida, New York and New Jersey against Honeywell, Honeywell TCAS, Thales USA, Thales France, the Company and Aviation Communications & Surveillance Systems (ACSS), which is a joint venture of L-3 and Thales. The suits relate to the crash over southern Germany of a Bashkirian Airways Tupelov TU 154M aircraft and a DHL Boeing 757 cargo aircraft. On-board the Tupelov aircraft were 9 crew members and 60 passengers, including 45 children. The Boeing aircraft carried a crew of two. Both aircraft were equipped with Honeywell/ACSS Model 2000, Change 7 Traffic Collision and Avoidance Systems (TCAS). Sensing the other aircraft, the on-board DHL TCAS instructed the DHL pilot to descend, and the Tupelov on-board TCAS instructed the Tupelov pilot to climb. However, the Swiss air traffic controller ordered the Tupelov pilot to descend. The Tupelov pilot disregarded the on-board TCAS and put the Tupelov aircraft into a descent striking the DHL aircraft in midair at approximately 35,000 feet. All crew and passengers of both planes were lost. Investigations by the National Transportation Safety Board after the crash revealed that both TCAS units were performing as designed. The suits allege negligence and strict product liability based upon the design of the units and the training provided to resolve conflicting commands. The Company’s insurers accepted defense of these matters and retained counsel. The matters were consolidated in the U.S. District Court for the District of New Jersey, which then dismissed the actions on the basis of forum non conveniens. Plaintiffs representing 30 of the estates re-filed their complaint against ACSS on April 23, 2007 with the Barcelona Court’s Registry in Spain. On March 9, 2010, the court ruled in favor of the plaintiffs and entered judgment against ACSS in the amount of approximately $6.7 million, all of which represented compensatory damages. Both ACSS and the plaintiffs appealed the judgment. In May 2012, the appellate court ruled in favor of the plaintiffs and entered judgment against ACSS in the amount of $48 million. ACSS filed an appeal of the judgment with the Supreme Court of Spain on September 28, 2012. During the Supreme Court’s consideration of the appeal, 18 of 30 plantiffs released their claims against ACSS in consideration for payments made by the Company’s insurance carriers. On February 10, 2015, the Supreme Court issued a ruling that awarded the remaining 12 plantiffs approximately $11 million in the aggregate (including interest), plus certain legal expenses incurred by the plantiffs in connection with the appeal to the Supreme Court. The Company’s insurers have confirmed that they will pay the full amount of the awards on behalf of the Company when due.
	HVC Alkmaar. On July 23, 2014, a notice of claim was received by our JovyAtlas business unit. The notice relates to losses resulting from a fire that occurred at an HVC Alkmaar bio-energy plant on July 21, 2013. The notice states that the fire resulted from the failure of an uninterruptible power supply (UPS) to provide sufficient power to act as a back-up energy supply, alleges that JovyAtlas was the manufacturer and service provider for the UPS and claims €11 million in estimated property damages and €35 million in estimated business interruption damages. The Company has tendered the notice of claim to its insurance carriers, who have commenced their own investigation.

Pensions_and_Other_Employee_Be

Pensions and Other Employee Benefits	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Pensions and Other Employee Benefits	20. Pensions and Other Employee Benefits
	The Company maintains multiple pension plans, both contributory and non-contributory, covering employees at certain locations. Eligibility for participation in these plans varies and benefits are generally based on the participant’s compensation and/or years of service. The Company’s funding policy is generally to contribute in accordance with cost accounting standards that affect government contractors, subject to the Internal Revenue Code and regulations thereon. Plan assets are invested primarily in listed stocks, mutual funds, corporate bonds, U.S. Government obligations and U.S. Government agency 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 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 as of December 31.
	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
			2014			2013			2014			2013
			(in millions)
	Change in benefit obligation:
	Benefit obligation at the beginning of the year		$	2,973		$	3,222		$	194		$	218
	Service cost			106			126			3			4
	Interest cost			147			132			8			7
	Plan participants’ contributions			2			2			4			4
	Amendments			1			14			(1)			—
	Actuarial loss (gain)			579			(402)			5			(23)
	Foreign currency exchange rate changes			(34)			(21)			(2)			(3)
	Curtailments, settlements and special termination benefits			1			3			—			—
	Benefits paid			(112)			(103)			(12)			(13)
	Benefit obligation at the end of the year		$	3,663		$	2,973		$	199		$	194
	Change in plan assets:
	Fair value of plan assets at the beginning of the year		$	2,403		$	2,026		$	55		$	47
	Actual return on plan assets			205			394			6			9
	Employer contributions			97			105			7			8
	Plan participants’ contributions			2			2			4			4
	Foreign currency exchange rate changes			(25)			(21)			—			—
	Benefits paid			(112)			(103)			(12)			(13)
	Fair value of plan assets at the end of the year		$	2,570		$	2,403		$	60		$	55
	Unfunded status at the end of the year		$	(1,093)		$	(570)		$	(139)		$	(139)
	Assets and (liabilities) recognized in the consolidated balance sheets consist of:
	Non-current assets		$	26		$	35		$	—		$	—
	Current liabilities			(4)			(8)			(8)			(9)
	Non-current liabilities			(1,056)			(597)			(131)			(130)
	Liabilities held for sale(1)			(59)			—			—			—
			$	(1,093)		$	(570)		$	(139)		$	(139)
		(1)	Liabilities held for sale consists of $3 million of current liabilities and $56 million of non-current liabilities relating to L-3 MSI.
	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
			2014			2013			2014			2013
			(in millions)
	Net loss (gain)		$	968		$	425		$	(6)		$	(9)
	Prior service cost (credit)			—			1			(3)			(8)
	Total amount recognized		$	968		$	426		$	(9)		$	(17)
	The aggregate accumulated benefit obligation (ABO) for all of the Company’s pension plans was $3,272 million at December 31, 2014 and $2,657 million at December 31, 2013. The table below presents information for the pension plans with an ABO in excess of the fair value of plan assets at December 31, 2014 and 2013.
			Pension Plans
			2014			2013
			(in millions)
	Projected benefit obligation		$	3,467		$	2,408
	Accumulated benefit obligation			3,083			2,115
	Fair value of plan assets			2,349			1,815
	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, 2014 and 2013.
			Pension Plans						Postretirement
									Benefit Plans
			2014			2013			2014			2013
	Benefit obligations:
	Discount rate			4.14%	(1)		5.03%	(1)		3.70%	(2)		4.43%	(2)
	Rate of compensation increase			3.50%	(3)		3.50%	(3)
		(1)	The weighted average discount rate assumptions used at December 31, 2014 and 2013 were comprised of separate assumptions determined by country of 4.2% and 5.1% for the U.S. based plans, 3.9% and 4.7% for the Canadian based plans and 2.2% and 3.5% for the German based plans, respectively.
		(2)	The weighted average discount rate assumptions used at December 31, 2014 and 2013 were comprised of separate assumptions determined by country of 3.7% and 4.4% for the U.S. based plans and 3.7% and 4.6% 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, 2014 and 2013.
	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, 2014, 2013 and 2012.
			Pension Plans									Postretirement
												Benefit Plans
		2014			2013			2012			2014				2013				2012
		(in millions)
Components of net periodic benefit cost:
Service cost		$	106		$	126		$	113		$	3			$	4			$	4
Interest cost			147			132			134			8				7				10
Expected return on plan assets			(193)			(164)			(145)			(4)				(4)				(3)
Amortization of prior service cost (credits)			2			1			1			(2)				(3)				(3)
Amortization of net loss (gain)			17			83			69			(2)				2				1
Curtailment or settlement loss (gain)			1			3			7			(1)				—				1
Net periodic benefit cost		$	80		$	181		$	179		$	2			$	6			$	10
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, 2014, 2013 and 2012.
		Pension Plans									Postretirement
											Benefit Plans
		2014			2013			2012			2014				2013				2012
		(in millions)
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)		$	560		$	(637)		$	287		$	5			$	(29)			$	(3)
Prior service cost (credit)			1			14			(1)			(1)				—				(5)
Amortization of net (loss) gain			(17)			(83)			(69)			2				(2)				(1)
Amortization of prior service (cost) credit			(2)			(1)			(1)			2				3				3
Total recognized in other comprehensive income			542			(707)			216			8				(28)				(6)
Total recognized in net periodic benefit cost and other comprehensive income		$	622		$	(526)		$	395		$	10			$	(22)			$	4
The following table summarizes the amounts expected to be amortized from accumulated other comprehensive income (loss) and recognized as components of net periodic benefit costs during 2015.
		Pension			Postretirement			Total
		Plans			Benefit Plans
					(in millions)
Net loss		$	68		$	—		$	68
Prior service cost (credit)			1			(2)			(1)
		$	69		$	(2)		$	67
The table below summarizes the weighted average assumptions used to determine the net periodic benefit cost for the years ended December 31, 2014, 2013 and 2012.
		Pension Plans									Postretirement
											Benefit Plans
		2014			2013			2012			2014				2013				2012
Discount rate			5.03%	(1)		4.15%	(1)		5.02%	(1)		4.43%	(4)			3.37%	(4)			4.71%	(4)
Expected long-term return on plan assets			8.13%	(2)		8.13%	(2)		8.15%	(2)		7.64%				7.64%				7.64%
Rate of compensation increase			3.50%	(3)		3.50%	(3)		4.06%	(3)
	(1)	The weighted average discount rate assumptions used for the years ended December 31, 2014, 2013, and 2012 were comprised of separate assumptions determined by country of 5.1%, 4.2% and 5.1% for the U.S. based plans, 4.7%, 3.9% and 4.4% for the Canadian based plans and 3.5%, 3.4%, and 5.1% for the German 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 8.25% for the U.S. based plans for the years ended December 31, 2014, 2013 and 2012 and 7.25% for the years ended December 31, 2014 and 2013 and 7.5% for the year ended December 31, 2012 for the Canadian based plans.
	(3)	The weighted average rate of compensation increase assumptions used for the years ended December 31, 2014 and 2013 were comprised of separate assumptions determined by country of 3.5% for both the U.S. and Canadian based plans. The rate of compensation increase assumptions were 4.0% for the U.S. based plans and 4.5% for the Canadian based plans for the year ended December 31, 2012.
	(4)	The weighted average discount rate assumptions used for the years ended December 31, 2014, 2013 and 2012 were comprised of separate assumptions determined by country of 4.4%, 3.3% and 4.8% for the U.S. based plans and 4.6%, 3.7% and 4.3% for the Canadian based plans, respectively.
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 our 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 is assumed to be an average of 7.5% in 2015 and is assumed to gradually decrease to a rate of 5.0% in 2020 and thereafter. The health care cost trend rate for the Company’s Canadian based plans is assumed to be an average of 7.0% in 2015 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 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			7			(6)
Plan Assets. The Company’s Benefit Plan Committee (Committee) has the responsibility to formulate the investment policies and strategies for the plans’ assets. The Committee structures the investment of plan assets to achieve the following goals: (1) maximize the plans’ long-term rate of return on assets for an acceptable level of risk; and (2) limit the volatility of investment returns and consequent impact on the plans’ assets. In the pursuit of these goals, the Committee has formulated the following investment policies and objectives: (1) invest assets of the plans in a manner consistent with the fiduciary standards of the Employee Retirement Income Security Act of 1974 (ERISA); (2) preserve the plans’ assets; (3) maintain sufficient liquidity to fund benefit payments and pay plan expenses; (4) evaluate the performance of investment managers; and (5) achieve, on average, a minimum total rate of return equal to the established benchmarks for each asset category.
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 interest 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, 2014 as well as the Company’s pension plan and postretirement benefit plan weighted-average asset allocations at December 31, 2014 and 2013, by asset category.
		U.S.									Canada
Asset Category		2014 and 2013			2014			2013			2014 and 2013		2014				2013
		Range									Range
Domestic equity(1)			30%-60%			52%			54%		10%-25%			15%				20%
International equity(2)			10%-20%			10			10		30%-60%			55				49
Fixed income securities			20%-40%			22			23		20%-60%			20				28
Real estate securities			0%-15%			7			6		—			—				—
Other, primarily cash and cash equivalents			0%-15%			9			7		0%-15%			10				3
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.
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 at December 31, 2014 and 2013, 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													Fair Value Measured at
		December 31, 2014													December 31, 2014
Asset Category		Level 1			Level 2			Level 3			Total				Level 1				Level 2			Level 3		Total
		(in millions)
Equity securities(1):
U.S. Equity		$	1,172		$	—		$	—		$	1,172			$	58			$	33		$	—	$	91
International Equity			87			140			—			227				107				13			—		120
Fixed Income — Investment Grade(2)			237			157			—			394				—				62			—		62
Fixed Income — High Yield(3)			—			120			—			120				—				—			—		—
Real Estate Investment Trusts(4)			159			—			—			159				—				—			—		—
Other(5)			—			208			—			208				4				26			—		30
Total assets at fair value		$	1,655		$	625		$	—		$	2,280			$	169			$	134		$	—	$	303
Liabilities for unsettled trades, net												(13)													—
Total											$	2,267												$	303
		Fair Value Measured at													Fair Value Measured at
		December 31, 2013													December 31, 2013
Asset Category		Level 1			Level 2			Level 3			Total				Level 1				Level 2			Level 3		Total
		(in millions)
Equity securities(1):
U.S. Equity		$	1,144		$	—		$	—		$	1,144			$	54			$	18		$	—	$	72
International Equity			79			146			—			225				117				18			—		135
Fixed Income — Investment Grade(2)			217			149			—			366				—				82			—		82
Fixed Income — High Yield(3)			—			111			—			111				—				—			—		—
Real Estate Investment Trusts(4)			118			—			—			118				—				—			—		—
Other(5)			—			150			—			150				6				5			—		11
Total assets at fair value		$	1,558		$	556		$	—		$	2,114			$	177			$	123		$	—	$	300
Liabilities for unsettled trades, net												(11)													—
Total											$	2,103												$	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. The Level 2 investment balance is derived from a regulated commingled equity trust fund, which fair value is based on the net asset value (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.
	(2)	Approximately 60% at December 31, 2014 and 59% at December 31, 2013 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 40% at December 31, 2014 and 41% at December 31, 2013 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 as a practical expedient to estimating fair value and classified as level 2. All of the Canadian plan assets for both 2014 and 2013 are invested in regulated commingled equity trust 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)	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.
The table below presents the fair value of the Company’s postretirement benefit plans’ assets at December 31, 2014 and 2013, by asset category segregated by level within the fair value hierarchy, as described below.
		Postretirement Benefit Plans’ Assets
		Fair Value Measured at													Fair Value Measured at
		December 31, 2014													December 31, 2013
Asset Category		Level 1			Level 2			Level 3			Total				Level 1				Level 2			Level 3		Total
		(in millions)
Equity securities(1):
U.S. Equity		$	36		$	—		$	—		$	36			$	37			$	—		$	—	$	37
International Equity			1			3			—			4				1				2			—		3
Fixed Income — Investment Grade(2)			10			2			—			12				7				2			—		9
Fixed Income — High Yield(3)			—			2			—			2				—				2			—		2
Real Estate Investment Trusts(4)			2			—			—			2				2				—			—		2
Other(5)			—			4			—			4				—				2			—		2
Total		$	49		$	11		$	—		$	60			$	47			$	8		$	—	$	55
	(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. The Level 2 investment balance is derived from 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.
	(2)	Approximately 83% at December 31, 2014 and 78% at December 31, 2013 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 17% at December 31, 2014 and 22% at December 31, 2013 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 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)	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 in real estate, 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, and are classified as Level 2.
Contributions. The funding policy for the Company’s pension and postretirement benefit plans is to contribute at least the minimum required by applicable laws and regulations or to directly make benefit payments where appropriate. The Company makes voluntary, additional contributions to the pension plans depending on a number of factors, including operating cash flow levels, alternative uses for excess cash and the plans’ funded status. At December 31, 2014, all legal funding requirements had been met. For the year ending December 31, 2015, the Company currently expects to contribute between approximately $100 million and $132 million to its pension plans, and approximately $10 million to its postretirement benefit plans.
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			Benefit			Subsidy
		Benefits			Payments			Receipts
		(in millions)
2015		$	131			13			—
2016			138			13			—
2017			151			14			—
2018			159			15			—
2019			164			15			—
Years 2020-2024			991			73			1
Employee Savings Plans. Under its various employee savings plans, the Company matches the contributions of participating employees up to a designated level. The extent of the match, vesting terms and the form of the matching contributions vary among the plans. Under these plans, the Company’s matching contributions in L-3 Holdings’ common stock and cash attributable to continuing operations were $135 million for 2014, $120 million for 2013 and $126 million for 2012. The Company’s matching contributions in L-3 Holdings’ common stock and cash attributable to discontinued operations were $8 million for 2012.
Multi-employer Benefit Plans. Certain of the Company’s businesses participate in multi-employer defined benefit pension plans. The Company makes cash contributions to these plans under the terms of collective-bargaining agreements that cover its union employees based on a fixed rate per hour of service worked by the covered employees. The risks of participating in these multi-employer plans are different from single-employer plans in the following aspects: (1) assets contributed to the multi-employer plan by one employer may be used to provide benefits to employees of other participating employers, (2) if a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers and (3) if the Company chooses to stop participating in some of its multi-employer plans, the Company may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability.
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.
Pension Fund		EIN/Pension		Pension			FIP/RP(2)	Contributions by											Surcharge			Expiration
		Plan Number		Protection Act			Status Pending/	L-3 Communications											Imposed			Date of
				Zone			Implemented															Collective-
				Status(1)																		Bargaining
				2014	2013			2014			2013				2012							Agreement
								(in millions)
IAM National Pension Fund		51-6031295/002		Green	Green		No	$	19(3)		$	21(4)			$	20(4)				No		2/4/2015 to
																						4/28/2019(5)
Other Pension Funds(6)									—			—				—
					Total contributions			$	19		$	21			$	20
	(1)	A zone status rating of green indicates the plan is at least 80% funded. The funding status of the IAM National Pension Fund was impacted by a market value investment loss for the plan year ended December 31, 2009, which amortization was extended over five years.
	(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 ending December 31, 2014 was not available.
	(4)	Represents 6% of total plan contributions for both years ended December 31, 2013 and 2012 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 represent 67% of 2014 contributions.
	(6)	Consists of three pension funds in which the Company’s contributions are individually, and in the aggregate, insignificant.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	12 Months Ended
	Dec. 31, 2014
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	21. Supplemental Cash Flow Information
		Year Ended December 31,
		2014		2013		2012
		(in millions)
	Interest paid on outstanding debt	$	176	$	171	$	198
	Income tax payments		129		245		332
	Income tax refunds		9		23		22

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Information	22. 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 and operating income. All corporate expenses are allocated to the Company’s operating segments using an allocation methodology prescribed by U.S. Government regulations for government contractors. Accordingly, all costs and expenses are included in the Company’s measure of segment profitability. Certain Corporate expenses of $10 million for the year ended December 31, 2012 that had previously been allocated to the Engility businesses were retained by the Company and were allocated to L-3’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,
			2014		2013		2012
			(in millions)
	Net Sales
	Products
	Electronic Systems		$	3,685	$	3,661	$	3,754
	Aerospace Systems			1,722		1,827		1,755
	Communication Systems			1,541		1,755		2,083
	NSS			75		71		98
	Elimination of intercompany sales			(114)		(125)		(104)
	Total products sales			6,909		7,189		7,586
	Services
	Electronic Systems		$	1,029	$	1,054	$	1,011
	Aerospace Systems			2,604		2,730		2,844
	Communication Systems			499		471		445
	NSS			1,140		1,228		1,292
	Elimination of intercompany sales			(57)		(50)		(71)
	Total services sales			5,215		5,433		5,521
	Consolidated total		$	12,124	$	12,622	$	13,107
	Operating Income
	Electronic Systems		$	537	$	533	$	569
	Aerospace Systems			288		426		437
	Communication Systems			196		168		223
	NSS			64		85		79
	Consolidated total		$	1,085	$	1,212	$	1,308
	Depreciation and amortization
	Electronic Systems		$	123	$	117	$	121
	Aerospace Systems			40		38		46
	Communication Systems			51		48		47
	NSS			11		11		14
	Consolidated total		$	225	$	214	$	228
	Capital Expenditures
	Electronic Systems		$	80	$	71	$	77
	Aerospace Systems			59		54		42
	Communication Systems			29		59		84
	NSS			9		5		5
	Corporate			6		20		2
	Consolidated total		$	183	$	209	$	210
	Total Assets
	Electronic Systems		$	6,287	$	6,928	$	6,792
	Aerospace Systems			3,011		3,106		3,074
	Communication Systems			1,997		2,130		2,179
	NSS			1,287		1,247		1,228
	Corporate			707		596		527
	Assets held for sale			547		—		—
	Consolidated total		$	13,836	$	14,007	$	13,800
	Corporate assets not allocated to the reportable segments primarily include cash and cash equivalents, corporate office fixed assets, deferred income tax assets and liabilities and deferred debt issue costs. In addition, substantially all of the Company’s assets are located in North America.
	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,
			2014		2013		2012
			(in millions)
	U.S.		$	9,172	$	9,808	$	10,658
	International:
	United Kingdom			342		449		360
	Canada			289		357		314
	Australia			254		218		222
	Germany			243		272		263
	South Korea			226		178		125
	Saudi Arabia			160		132		76
	Japan			124		67		78
	Other			1,314		1,141		1,011
	Total international			2,952		2,814		2,449
Consolidated		$	12,124	$	12,622	$	13,107
Net sales to principal customers are summarized in the table below.
		Year Ended December 31,
		2014		2013		2012
		(in millions)
U.S. Government agencies(1)		$	8,584	$	9,186	$	9,986
Commercial			1,693		1,689		1,658
Foreign governments(1)			1,847		1,747		1,463
Consolidated		$	12,124	$	12,622	$	13,107
	(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.

Employee_Severance_and_Termina

Employee Severance and Termination Costs	12 Months Ended
	Dec. 31, 2014
Restructuring and Related Activities [Abstract]
Employee Severance and Termination Costs	23. Employee Severance and Termination Costs
	Consistent with the Company’s strategy to continuously improve its cost structure and right-size its businesses, especially in view of sequestration and other DoD budget reductions, L-3 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 and due to the impact of sequestration at certain affected business units, the Company recorded employee severance and other termination costs of $30 million with respect to approximately 2,000 employees during the year ended December 31, 2014, $29 million with respect to approximately 2,000 employees during the year ended December 31, 2013 and $23 million with respect to approximately 1,600 employees for the year ended December 31, 2012. Employee severance and other termination costs are reported within cost of sales on the consolidated statements of operations. The remaining balance to be paid in connection with these initiatives was $11 million at December 31, 2014, which is expected to be paid in 2015, and $11 million at December 31, 2013, which was paid during 2014. Employee severance and other termination costs incurred by reportable segment are presented in the table below.
		Year Ended December 31,
		2014		2013		2012
		(in millions)
	Electronic Systems	$	16	$	16	$	13
	Aerospace Systems		5		2		1
	Communication Systems		8		11		8
	NSS		1		—		1
	Consolidated	$	30	$	29	$	23

Unaudited_Quarterly_Financial_

Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Financial Data	24. Unaudited Quarterly Financial Data
	Unaudited summarized financial data by quarter for the years ended December 31, 2014 and 2013 is presented in the table below. The Company’s unaudited quarterly results of operations are affected, significantly in some periods, by our business acquisitions. See Note 4.
			First		Second		Third		Fourth
			Quarter		Quarter		Quarter		Quarter
			(in millions, except per share data)
	2014
	Sales		$	2,957	$	3,019	$	2,940	$	3,208
	Operating income			286		239		257		303
	Net income			172		141		157		207
	Net income attributable to L-3			170		137		154		203
	Basic EPS(1)			1.97		1.59		1.81		2.41
	Diluted EPS(1)			1.90		1.53		1.78		2.36
	2013
	Sales		$	3,197	$	3,189	$	3,002	$	3,234
	Operating income			310		290		306		306
	Net income			192		176		204		188
	Net income attributable to L-3			191		175		200		185
	Basic EPS(1)			2.12		1.95		2.23		2.10
	Diluted EPS(1)			2.09		1.92		2.19		2.04
		(1)	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_Co

Financial Information of L-3 Communications and Its Subsidiaries	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Financial Information of L-3 Communications and Its Subsidiaries	25. Financial Information of L-3 Communications and Its Subsidiaries
	Total shareholders’ equity for L-3 Communications equals that of L-3 Holdings, but the components (common stock, additional paid-in capital, treasury stock and retained earnings) are different. The table below presents information regarding the balances and changes in common stock, additional paid-in capital, treasury stock and retained earnings of L-3 Communications for each of the three years ended December 31, 2014.
		L-3				Additional		Treasury		Retained		Accumulated		Total
		Communications				Paid-in		Stock		Earnings		Other
		Common Stock				Capital						Comprehensive
												(Loss)
		Shares		Par								Income
		Issued		Value
				(in millions, except shares issued)
	Balance at December 31, 2011		100	$	—	$	5,064	$	—	$	2,034	$	(454)	$	6,644
	Net income attributable to L-3		—		—		—		—		784		—		784
	Contributions from L-3 Holdings		—		—		250		—		—		—		250
	Dividends to L-3 Holdings		—		—		—		—		(1,068)		—		(1,068)
	Comprehensive loss		—		—		—		—		—		(96)		(96)
	Net change of equity due to spin-off of Engility		—		—		—		—		(1,063)		—		(1,063)
	Balance at December 31, 2012		100	$	—	$	5,314	$	—	$	687	$	(550)	$	5,451
	Net income attributable to L-3		—		—		—		—		751		—		751
	Contributions from L-3 Holdings		—		—		339		—		—		—		339
	Dividends to L-3 Holdings		—		—		—		—		(1,001)		—		(1,001)
	Comprehensive income		—		—		—		—		—		440		440
	Other		—		—		—		—		1		—		1
	Balance at December 31, 2013		100	$	—	$	5,653	$	—	$	438	$	(110)	$	5,981
	Net income attributable to L-3		—		—		—		—		664		—		664
	Contributions from L-3 Holdings		—		—		146		—		—		—		146
	Dividends to L-3 Holdings		—		—		—		—		(1,032)		—		(1,032)
	Comprehensive loss		—		—		—		—		—		(474)		(474)
	Balance at December 31, 2014		100	$	—	$	5,799	$	—	$	70	$	(584)	$	5,285
	The net proceeds received by L-3 Holdings from (i) the sale of its common stock, (ii) exercise of L-3 Holdings’ employee and director stock options, and related tax benefits, and (iii) L-3 Holdings’ common stock contributed to the Company’s savings plans are contributed to L-3 Communications. The amounts paid by L-3 Holdings for dividends and share repurchases are generated from dividends received from L-3 Communications.
	L-3 Communications is a 100% owned subsidiary of L-3 Holdings. The debt of L-3 Communications, 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”) and, in the case of the Credit Facility, by L-3 Holdings. The CODES, prior to the CODES Retirement, were guaranteed on a joint and several, full and unconditional basis, by L-3 Communications and the Guarantor Subsidiaries. See Note 10 for additional information. The foreign subsidiaries and certain domestic subsidiaries of L-3 Communications (the “Non-Guarantor Subsidiaries”) do not guarantee the debt of L-3 Communications or L-3 Holdings. None of the debt of L-3 Communications has been issued by its subsidiaries. There are no restrictions on the payment of dividends from the Guarantor Subsidiaries to L-3 Communications or from L-3 Communications to L-3 Holdings.
	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 L-3 Communications Corporation, 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.
	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) L-3 Holdings, excluding L-3 Communications and its consolidated subsidiaries (the “Parent”), (2) L-3 Communications, excluding its consolidated subsidiaries, (3) the Guarantor Subsidiaries, (4) the Non-Guarantor Subsidiaries and (5) the eliminations to arrive at the information for L-3 on a consolidated basis.
		L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
		Holdings		Communications		Subsidiaries		Guarantor				L-3
		(Parent)						Subsidiaries
		(in millions)
	Condensed Combining Balance Sheets:
	At December 31, 2014:
	Current assets:
	Cash and cash equivalents	$	—	$	361	$	1	$	142	$	(62)	$	442
	Billed receivables, net		—		320		329		203		—		852
	Contracts in process		—		867		1,144		284		—		2,295
	Other current assets		—		365		141		95		—		601
	Assets held for sale		—		—		52		495		—		547
	Total current assets		—		1,913		1,667		1,219		(62)		4,737
	Goodwill		—		2,350		4,246		905		—		7,501
	Other assets		—		817		576		205		—		1,598
	Investment in and amounts due from consolidated subsidiaries		5,285		6,813		4,191		—		(16,289)		—
	Total assets	$	5,285	$	11,893	$	10,680	$	2,329	$	(16,351)	$	13,836
	Current liabilities	$	—	$	878	$	1,017	$	455	$	(62)	$	2,288
	Liabilities held for sale		—		—		10		227		—		237
	Amounts due to consolidated subsidiaries		—		—		—		325		(325)		—
	Other long-term liabilities		—		1,791		190		31		—		2,012
	Long-term debt		—		3,939		—		—		—		3,939
	Total liabilities		—		6,608		1,217		1,038		(387)		8,476
	L-3 shareholders’ equity		5,285		5,285		9,463		1,291		(16,039)		5,285
	Noncontrolling interests		—		—		—		—		75		75
	Total equity		5,285		5,285		9,463		1,291		(15,964)		5,360
	Total liabilities and equity	$	5,285	$	11,893	$	10,680	$	2,329	$	(16,351)	$	13,836
	At December 31, 2013:
	Current assets:
	Cash and cash equivalents	$	—	$	258	$	—	$	261	$	(19)	$	500
	Billed receivables, net		—		364		401		226		—		991
	Contracts in process		—		919		1,169		354		—		2,442
Other current assets		—		350		162		168		—		680
Total current assets		—		1,891		1,732		1,009		(19)		4,613
Goodwill		—		2,350		4,247		1,199		—		7,796
Other assets		—		838		532		228		—		1,598
Investment in and amounts due from consolidated subsidiaries		6,670		6,897		3,822		—		(17,389)		—
Total assets	$	6,670	$	11,976	$	10,333	$	2,436	$	(17,408)	$	14,007
Current liabilities	$	—	$	914	$	1,030	$	628	$	(19)	$	2,553
Amounts due to consolidated subsidiaries		—		—		—		305		(305)		—
Other long-term liabilities		—		1,451		193		124		—		1,768
Long-term debt		689		3,630		—		—		(689)		3,630
Total liabilities		689		5,995		1,223		1,057		(1,013)		7,951
L-3 shareholders’ equity		5,981		5,981		9,110		1,379		(16,470)		5,981
Noncontrolling interests		—		—		—		—		75		75
Total equity		5,981		5,981		9,110		1,379		(16,395)		6,056
Total liabilities and equity	$	6,670	$	11,976	$	10,333	$	2,436	$	(17,408)	$	14,007
	L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
	Holdings		Communications		Subsidiaries		Guarantor				L-3
	(Parent)						Subsidiaries
Condensed Combining Statements of Operations:
For the year ended December 31, 2014:
Net sales	$	—	$	3,556	$	6,618	$	2,256	$	(306)	$	12,124
Cost of sales		(52)		(3,211)		(6,117)		(2,017)		358		(11,039)
Operating (loss) income		(52)		345		501		239		52		1,085
Interest expense		(2)		(176)		(2)		—		2		(178)
Interest and other income (expense), net		—		15		—		3		—		18
(Loss) income from continuing operations before income taxes		(54)		184		499		242		54		925
Benefit (provision) for income taxes		14		(49)		(134)		(65)		(14)		(248)
Equity in net income of consolidated subsidiaries		704		529		—		—		(1,233)		—
Net income		664		664		365		177		(1,193)		677
Net income attributable to noncontrolling interests		—		—		—		—		(13)		(13)
Net income attributable to L-3	$	664	$	664	$	365	$	177	$	(1,206)	$	664
Comprehensive income attributable to L-3	$	190	$	190	$	363	$	46	$	(599)	$	190
For the year ended December 31, 2013:
Net sales	$	—	$	3,842	$	6,804	$	2,363	$	(387)	$	12,622
Cost of sales		(59)		(3,549)		(6,139)		(2,109)		446		(11,410)
Operating (loss) income		(59)		293		665		254		59		1,212
Interest expense		(21)		(176)		—		(1)		21		(177)
Interest and other income (expense), net		—		15		—		5		—		20
(Loss) income from continuing operations before income taxes		(80)		132		665		258		80		1,055
Benefit (provision) for income taxes		22		(38)		(184)		(73)		(22)		(295)
Equity in net income of consolidated subsidiaries		809		657		—		—		(1,466)		—
Net income		751		751		481		185		(1,408)		760
Net income attributable to noncontrolling interests		—		—		—		—		(9)		(9)
Net income attributable to L-3	$	751	$	751	$	481	$	185	$	(1,417)	$	751
Comprehensive income attributable to L-3	$	1,191	$	1,191	$	480	$	159	$	(1,830)	$	1,191
For the year ended December 31, 2012:
Net sales	$	—	$	3,737	$	7,475	$	2,278	$	(383)	$	13,107
Cost of sales		(59)		(3,434)		(6,749)		(1,999)		442		(11,799)
Operating (loss) income		(59)		303		726		279		59		1,308
Interest expense		(21)		(183)		—		(1)		21		(184)
Interest and other income (expense), net		—		14		(5)		2		—		11
Debt retirement charge		—		(13)		—		—		—		(13)
(Loss) income from continuing operations before income taxes		(80)		121		721		280		80		1,122
Benefit (provision) for income taxes		26		(37)		(230)		(93)		(26)		(360)
Equity in net income of consolidated subsidiaries		838		668		—		—		(1,506)		—
Income from continuing operations		784		752		491		187		(1,452)		762
Income from discontinued operations, net of income tax		—		32		—		—		—		32
Net income		784		784		491		187		(1,452)		794
Net income attributable to noncontrolling interests		—		—		—		—		(10)		(10)
Net income attributable to L-3	$	784	$	784	$	491	$	187	$	(1,462)	$	784
Comprehensive income attributable to L-3	$	688	$	688	$	493	$	215	$	(1,396)	$	688
	L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
	Holdings		Communications		Subsidiaries		Guarantor				L-3
	(Parent)						Subsidiaries
	(in millions)
Condensed Combining Statements of Cash
Flows: For the year ended December 31,
2014:00:00
Operating activities:
Net cash from operating activities	$	1,966	$	478	$	599	$	141	$	(2,059)	$	1,125
Investing activities:
Business acquisitions, net of cash acquired		—		(57)		—		—		—		(57)
Investments in L-3 Communications		(102)		—		—		—		102		—
Other investing activities		—		(57)		(94)		(21)		—		(172)
Net cash used in investing activities		(102)		(114)		(94)		(21)		102		(229)
Financing activities:
Proceeds from sale of senior notes		—		996		—		—		—		996
Redemption of CODES		(935)		—		—		—		—		(935)
Common stock repurchased		(823)		—		—		—		—		(823)
Dividends paid on L-3 Holdings’ common stock		(208)		—		—		—		—		(208)
Dividends paid to L-3 Holdings		—		(1,966)		—		—		1,966		—
Investments from L-3 Holdings		—		102		—		—		(102)		—
Other financing activities		102		607		(503)		(162)		50		94
Net cash used in financing activities		(1,864)		(261)		(503)		(162)		1,914		(876)
Effect of foreign currency exchange rate changes on cash		—		—		—		(17)		—		(17)
Change in cash balance in assets held for sale		—		—		(1)		(60)		—		(61)
Net increase (decrease) in cash		—		103		1		(119)		(43)		(58)
Cash and cash equivalents, beginning of the year		—		258		—		261		(19)		500
Cash and cash equivalents, end of the year	$	—	$	361	$	1	$	142	$	(62)	$	442
For the year ended December 31, 2013:
Operating activities:
Net cash from operating activities	$	999	$	437	$	776	$	231	$	(1,180)	$	1,263
Investing activities:
Business acquisitions, net of cash acquired		—		(62)		—		—		—		(62)
Investments in L-3 Communications		(149)		—		—		—		149		—
Other investing activities		—		(88)		(89)		(22)		—		(199)
Net cash used in investing activities		(149)		(150)		(89)		(22)		149		(261)
Financing activities:
Common stock repurchased		(800)		—		—		—		—		(800)
Dividends paid on L-3 Holdings’ common stock		(199)		—		—		—		—		(199)
Dividends paid to L-3 Holdings		—		(999)		—		—		999		—
Investments from L-3 Holdings		—		149		—		—		(149)		—
Other financing activities		149		575		(687)		(188)		301		150
Net cash used in financing activities		(850)		(275)		(687)		(188)		1,151		(849)
Effect of foreign currency exchange rate changes on cash		—		—		—		(2)		—		(2)
Net increase in cash		—		12		—		19		120		151
Cash and cash equivalents, beginning of the year		—		246		—		242		(139)		349
Cash and cash equivalents, end of the year	$	—	$	258	$	—	$	261	$	(19)	$	500
	L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
	Holdings		Communications		Subsidiaries		Guarantor				L-3
	(Parent)						Subsidiaries
	(in millions)
For the year ended December 31, 2012:
Operating activities:
Net cash from operating activities from continuing operations	$	1,067	$	252	$	858	$	265	$	(1,211)	$	1,231
Investing activities:
Business acquisitions, net of cash acquired		—		(348)		—		—		—		(348)
Investments in L-3 Communications		(42)		—		—		—		42		—
Other investing activities		—		225		(59)		(18)		—		148
Net cash used in investing activities from continuing operations		(42)		(123)		(59)		(18)		42		(200)
Financing activities:
Redemption of senior subordinated notes		—		(500)		—		—		—		(500)
Common stock repurchased		(872)		—		—		—		—		(872)
Dividends paid on L-3 Holdings’ common stock		(195)		—		—		—		—		(195)
Dividends paid to L-3 Holdings		—		(1,067)		—		—		1,067		—
Investments from L-3 Holdings		—		42		—		—		(42)		—
Other financing activities		42		924		(799)		(234)		107		40
Net cash used in financing activities from continuing operations		(1,025)		(601)		(799)		(234)		1,132		(1,527)
Effect of foreign currency exchange rate changes on cash		—		—		—		7		—		7
Net increase in cash and cash equivalents of discontinued operations		—		74		—		—		—		74
Net (decrease) increase in cash		—		(398)		—		20		(37)		(415)
Cash and cash equivalents, beginning of the year		—		644		—		222		(102)		764
Cash and cash equivalents, end of the year	$	—	$	246	$	—	$	242	$	(139)	$	349

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation: The accompanying financial statements comprise the consolidated financial statements of L-3 Holdings and L-3 Communications. L-3 Holdings’ only asset is its investment in the common stock of L-3 Communications, its wholly-owned subsidiary, and its only obligations are: (1) its guarantee of borrowings under the Amended and Restated Revolving Credit Facility (“Credit Facility”) of L-3 Communications and (2) its guarantee of other contractual obligations of L-3 Communications and its subsidiaries. As of June 20, 2014, L-3 Holdings’ obligation for its 3% Convertible Contingent Debt Securities (CODES) due 2035, which were issued on July 29, 2005, have been fully retired. L-3 Holdings’ obligations relating to the CODES were jointly, severally, fully and unconditionally guaranteed by L-3 Communications and certain of its wholly-owned domestic subsidiaries. Accordingly, such debt was reflected as debt of L-3 Communications in its consolidated financial statements at December 31, 2013 in accordance with the accounting standards for pushdown accounting. All issuances of and conversions into L-3 Holdings’ equity securities, including grants of stock options, restricted stock units and performance units by L-3 Holdings to employees and directors of L-3 Communications and its subsidiaries, have been reflected in the consolidated financial statements of L-3 Communications. As a result, the consolidated financial positions, results of operations and cash flows of L-3 Holdings and L-3 Communications are substantially the same. See Note 25 for additional information regarding the audited financial information of L-3 Communications and its subsidiaries.
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of sales and costs of sales during the reporting period. The most significant of these estimates and assumptions relate to contract revenue, profit and loss recognition, fair values of assets acquired and liabilities assumed in business combinations, market values for inventories reported at lower of cost or market, pension and post-retirement benefit obligations, stock-based employee compensation expense, income taxes, including the valuations of deferred tax assets, litigation reserves and environmental obligations, accrued product warranty costs, and the recoverability, useful lives and valuation of recorded amounts of long-lived assets, identifiable intangible assets and goodwill. Changes in estimates are reflected in the periods during which they become known. Actual amounts will differ from these estimates and could differ materially.
	Certain reclassifications have been made to conform prior-year amounts to the current-year presentation.
Principles of Consolidation
	Principles of Consolidation: The consolidated financial statements of the Company include all wholly-owned and majority-owned subsidiaries. All significant intercompany transactions are eliminated in consolidation. Investments in equity securities, joint ventures and limited liability corporations over which the Company has significant influence but does not have voting control are accounted for using the equity method. Investments over which the Company does not have significant influence are accounted for using the cost method.
Revenue Recognition	Revenue Recognition: Substantially all of the Company’s sales are generated from written contractual (revenue) arrangements. The sales price for the Company’s revenue arrangements are either fixed-price, cost-plus or time-and-material type. Depending on the contractual scope of work, the Company utilizes either contract accounting standards or accounting standards for revenue arrangements with commercial customers to account for these contracts. Approximately 46% of the Company’s 2014 sales were accounted for under contract accounting standards, of which approximately 40% were fixed-price type contracts and approximately 6% were cost-plus type contracts. For contracts that are accounted for under contract accounting standards, sales and profits are recognized based on: (1) a Percentage-of-Completion (POC) method of accounting (fixed-price contracts), (2) allowable costs incurred plus the estimated profit on those costs (cost-plus contracts), or (3) direct labor hours expended multiplied by the contractual fixed rate per hour plus incurred costs for material (time-and-material contracts). Aggregate net changes in contract estimates increased operating income by $66 million, or 6%, for the year ended December 31, 2014, $114 million, or 9%, for the year ended December 31, 2013, and $72 million, or 6%, for the year ended December 31, 2012.
	Sales and profits on fixed-price type contracts 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. 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 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. Incentive and award fees are the primary variable fee contractual arrangements. 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 us 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 to perform services 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 awarded by the customer.
	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: Independent research and development (IRAD) costs sponsored by the Company and bid and proposal (B&P) costs relate to both U.S. Government contracts and those for international and commercial customers. The IRAD and B&P costs for certain of the Company’s businesses that are U.S. Government contractors are recoverable indirect contract costs that are allocated to U.S. Government contracts in accordance with U.S. Government procurement regulations, and are specifically excluded from research and development accounting standards. The Company includes the recoverable IRAD and B&P costs allocated to U.S. Government contracts in inventoried contract costs, and charges them to costs of sales when the related contract sales are recognized as revenue. Research and development costs that are not recoverable on U.S. Government contracts are accounted for in accordance with research and development accounting standards and are expensed to cost of sales as incurred.
	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: Product warranty costs are accrued when revenue is recognized for the covered products. Product warranty expense is recognized based on the terms of the product warranty and the related estimated costs. Accrued warranty costs are reduced as product warranty costs are incurred or as warranty periods expire.
	The table below presents the changes in the Company’s accrued product warranty costs.
			Year Ended December 31,
			2014		2013
			(in millions)
	Accrued product warranty costs(1):
	Balance at January 1		$	99	$	99
	Acquisitions during this period			—		2
	Accruals for product warranties issued during the period			71		71
	Changes to accruals for product warranties existing before January 1			1		3
	Foreign currency translation adjustments			(2)		—
	Settlements made during the period			(67)		(76)
	Liabilities held for sale(2)			(9)		—
	Balance at December 31		$	93	$	99
		(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)	On December 16, 2014, the Company entered into a definitive agreement with Wärtsilä Corporation to sell its Marine Systems International business.
Deferred Debt Issue Costs	Deferred Debt Issue Costs: Costs to issue debt are capitalized and deferred when incurred, and subsequently amortized to interest expense over the term of the related debt using the effective interest rate method.
Stock-Based Compensation	Stock-Based Compensation: The Company follows the fair value based method of accounting for stock-based employee compensation, which requires the Company to expense all stock-based employee compensation. Stock-based employee compensation is primarily a non-cash expense because the Company settles these obligations by issuing shares of L-3 Holdings common stock instead of settling such obligations with cash payments.
	Compensation expense for all restricted stock unit and stock option awards is 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 L-3 Holdings 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.
Income Taxes	Income Taxes: The Company provides for income taxes using the liability method. Deferred income tax assets and liabilities reflect tax carryforwards and the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting and income tax purposes, as determined under enacted tax laws and rates. The effect of changes in tax laws or rates is accounted for in the period of enactment. Valuation allowances for deferred tax assets are provided when it is more likely than not that the assets will not be realized, considering, when appropriate, tax planning strategies.
	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 on its financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents: Cash equivalents consist of highly liquid investments with an original maturity of three months or less at the time of purchase.
Contracts in Process	Contracts in Process: Contracts in Process include unbilled contract receivables and inventoried contract costs for which sales and profits are recognized primarily using a POC method of accounting. Unbilled Contract Receivables represent accumulated incurred costs and earned profits on contracts in process that have been recorded as sales, primarily using the cost-to-cost method, but have not been billed to customers. Inventoried Contract Costs primarily represent incurred costs on contracts using the units-of-delivery method of accounting and include direct costs and indirect costs, including overhead costs, and materials acquired for U.S. Government service contracts. As discussed in Note 5, the Company’s inventoried contract costs for U.S. Government contracts, and contracts with prime contractors or subcontractors of the U.S. Government include allocated general and administrative costs (G&A), IRAD costs and B&P costs. Contracts in Process contain amounts relating to contracts and programs with long performance cycles, a portion of which may not be realized within one year. For contracts in a loss position, the unrecoverable costs expected to be incurred in future periods are recorded in Estimated Costs in Excess of Estimated Contract Value to Complete Contracts in Process in a Loss Position, which is a component of Other Current Liabilities. Under the terms of certain revenue arrangements (contracts) with the U.S. Government, the Company is entitled to receive progress payments as costs are incurred or milestone payments as work is performed. The U.S. Government has a security interest in the Unbilled Contract Receivables and Inventoried Contract Costs to which progress payments have been applied, and such progress payments are reflected as a reduction of the related amounts. Milestone payments that have been received in excess of contract costs incurred and related estimated profits are reported on the Company’s balance sheet as Advance Payments and Billings in Excess of Costs Incurred.
	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: Inventories, other than Inventoried Contract Costs, are stated at cost (first-in, first-out or average cost), but not in excess of realizable value. A provision for excess or inactive inventory is recorded based upon an analysis that considers current inventory levels, historical usage patterns and future sales expectations.
Property, Plant and Equipment	Property, Plant and Equipment: Property, plant and equipment are stated at cost, less accumulated depreciation. Depreciation is computed by applying principally the straight-line method to the estimated useful lives of the related assets. Useful lives range substantially from 10 to 40 years for buildings and improvements and three to 10 years for machinery, equipment, furniture and fixtures. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the improvements. When property or equipment is retired or otherwise disposed of, the net book value of the asset is removed from the Company’s balance sheet and the net gain or loss is included in the determination of operating income. Property, plant and equipment acquired as part of a business acquisition is valued at fair value.
Goodwill	Goodwill: The carrying value of goodwill and indefinite lived identifiable intangible assets are not amortized, but are tested for impairment annually as of November 30 and, additionally on an interim basis, whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable. The accounting standards for goodwill allow for the assessment of qualitative factors to determine whether it is more likely or not that the fair value of a reporting unit is less than its carrying amount. The Company did not utilize a qualitative assessment approach for the November 30, 2014 goodwill impairment test, as the Company chose instead to complete the quantitative two-step testing process for each reporting unit. The first step in the process is to identify any potential impairment by comparing the carrying value of a reporting unit to its fair value. The Company determines the fair value of its reporting units using a discounted cash flows valuation approach. If a potential impairment is identified, the second step is to measure the impairment loss by comparing the implied fair value of goodwill with the carrying value of goodwill of the reporting unit. There were no impairment charges that resulted from the annual impairment assessment or change in circumstances during the years ended December 31, 2014, 2013 and 2012. See Note 7 for additional information on the accumulated goodwill impairment losses.
Identifiable Intangible Assets	Identifiable Intangible Assets: Identifiable intangible assets represent assets acquired as part of the Company’s business acquisitions and include customer contractual relationships, technology, favorable leasehold interests and trade names. The initial measurement of these intangible assets is based on their fair values. Identifiable intangible assets are: (1) tested for impairment whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable and (2) amortized over their estimated useful lives as the economic benefits are consumed. The Company reviews and updates its estimates of the duration of its customer contractual relationships. If such estimates indicate that the duration of the Company’s customer contractual relationships has decreased compared to the estimates made as of the date the Company acquired these intangible assets, then the Company accelerates the amortization period for its customer contractual relationships over their remaining useful economic life.
Derivative Financial Instruments	Derivative Financial Instruments: The Company’s derivative financial instruments include foreign currency forward contracts, which are entered into for risk management purposes, and an embedded derivative representing the contingent interest payment provision related to the CODES, which was retired as of June 20, 2014. See Note 10 for information on the CODES retirement.
	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 Canadian dollar, the U.S. 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.
	The embedded derivative related to the issuance of the CODES was recorded at fair value with changes reflected in the Consolidated Statements of Operations.
Translation of Foreign Currency and Foreign Currency Transactions	Translation of Foreign Currency and Foreign Currency Transactions: Transactions in foreign currencies are translated into the local (functional) currency of the respective business at the approximate prevailing rate at the time of the transaction. Foreign exchange transaction gains and losses in the years ended December 31, 2014, 2013 and 2012 are not material to the Company’s results of operations. The operations of the Company’s foreign subsidiaries are translated from the local (functional) currencies into U.S. dollars using weighted average rates of exchange during each reporting period. The rates of exchange at each balance sheet date are used for translating the assets and liabilities of the Company’s foreign subsidiaries. Gains or losses resulting from these translation adjustments are included in the balance sheets as a component of accumulated other comprehensive income (loss) and are only recognized in income when a foreign subsidiary is divested.
Accounting Standards Issued and Not Yet Implemented	Accounting Standards Issued and Not Yet Implemented: In February 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-2, which changes the analysis that a reporting entity must perform to determine whether it should consolidate certain types of legal entities. This update is effective for the interim and annual periods beginning after December 15, 2015. The adoption of this standard will not have an impact on the Company’s financial position, results of operations or cash flows.
	In January 2015, the FASB issued ASU 2015-1, which eliminates from GAAP the concept of extraordinary items. The update is effective for the Company for the interim and annual periods beginning after December 15, 2015. The adoption of this standard will not have an impact on the Company’s financial position, results of operations or cash flows.
	In June 2014, the FASB issued ASU 2014-12, which provides new guidance on accounting for share-based payments when the terms of an award provide that a performance target could be achieved after the requisite service period. The update requires a reporting entity to treat a performance target that affects vesting and that could be achieved after the requisite service period as a performance condition under Accounting Standards Codification (ASC) 718 Compensation — Stock Compensation, and apply existing guidance as it relates to awards with performance conditions that affect vesting to account for such awards. The update is effective for the Company for the interim and annual periods beginning after December 15, 2015. The adoption of this standard will not have an impact on the Company’s financial position, results of operations or cash flows.
	In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers, which will replace numerous requirements in U.S. GAAP, including industry-specific requirements, provide companies with a single revenue recognition model for recognizing revenue from contracts with customers and significantly expand the disclosure requirements for revenue arrangements. The new standard will be effective for the Company for interim and annual reporting periods beginning January 1, 2017. The two permitted transition methods under the new standard are the full retrospective method, in which case the standard would be applied to each prior reporting period presented, or the modified retrospective method, in which case the cumulative effect of applying the standard would be recognized at the date of initial application. The Company is currently evaluating the expected impact of the adoption of this standard on its consolidated financial statements and related disclosures and the transition alternatives available. As the new standard will supersede substantially all existing revenue guidance, it could impact revenue and cost recognition on substantially all of the Company’s contracts, in addition to the Company’s business processes and our information technology systems. As a result, the Company’s evaluation of the impact of the standard will extend over future periods.
Adoption of New Accounting Standards	In April 2014, the FASB issued ASU 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, that provides new guidance on the accounting and reporting of discontinued operations. Under the new guidance, only disposals representing a strategic shift in operations should be presented as discontinued operations. Those strategic shifts should have a major effect on the organization’s operations and financial results. Additionally, the new guidance requires additional disclosures about discontinued operations. The Company early adopted the standard as of December 31, 2014 for its pending divestiture of L-3 MSI. In accordance with ASU 2014-08, L-3 MSI’s assets and liabilities are classified as held for sale in the Company’s audited consolidated balance sheet at December 31, 2014. Also, in accordance with ASU 2014-08, L-3 MSI’s results of operations are included in the Company’s income from continuing operations for all periods presented and are not classified within discontinued operations. See Note 4 for additional information regarding the Company’s business divestitures.
	Effective January 1, 2014, the Company adopted FASB issued amendments to an accounting standard that require an unrecognized tax benefit or portion of an unrecognized tax benefit to be presented as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward, except when certain conditions exist. The adoption of this standard did not have an impact on the Company’s financial position, results of operations or cash flows.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
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,
			2014		2013
			(in millions)
	Accrued product warranty costs(1):
	Balance at January 1		$	99	$	99
	Acquisitions during this period			—		2
	Accruals for product warranties issued during the period			71		71
	Changes to accruals for product warranties existing before January 1			1		3
	Foreign currency translation adjustments			(2)		—
	Settlements made during the period			(67)		(76)
	Liabilities held for sale(2)			(9)		—
	Balance at December 31		$	93	$	99
		(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)	On December 16, 2014, the Company entered into a definitive agreement with Wärtsilä Corporation to sell its Marine Systems International business.

Acquisitions_and_Divestitures_

Acquisitions and Divestitures (Tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Schedule of Major Classes of Assets and Liabilities Included as Held For Sale	The major classes of assets and liabilities included as held for sale related to L-3 MSI are presented in the table below:
		December 31,
		2014
			(in millions)
	Assets
	Cash and cash equivalents	$	61
	Billed receivables, net of allowance of $6		77
	Contracts in process		70
	Inventories		70
	Other current assets		10
	Total current assets		288
	Goodwill		231
	Other assets		28
	Total assets classified as held for sale	$	547
	Liabilities
	Accounts payable, trade	$	31
	Accrued employment costs		22
	Accrued expenses		33
	Advance payments and billings in excess of costs incurred		55
	Other current liabilities		21
	Total current liabilities		162
	Pension and postretirement benefits		56
	Other liabilities		19
	Total liabilities classified as held for sale	$	237
Statement of Operations Data Classified as Discontinued Operations	Engility’s statement of operations data, which has been classified as discontinued operations, is provided in the table below.
		January 1
		to July 17,
		2012
		(in millions)
	Product and service revenues	$	911
	Operating income from discontinued operations before income tax		68
	Interest expense allocated to discontinued operations		(14)
	Income from discontinued operations before income tax	$	54
	Income tax expense		(22)
	Income from discontinued operations, net of income tax	$	32
	Net income from discontinued operations attributable to noncontrolling interests		(4)
	Net income from discontinued operations attributable to L-3	$	28
Unaudited Pro Forma Statements of Operations Data	The following unaudited pro forma Statements of Operations data presents the combined results of the Company and its business acquisitions completed during the years ended December 31, 2014, 2013 and 2012 assuming that the business acquisitions completed during 2014, 2013 and 2012 had occurred on January 1, 2012.
		Year Ended December 31,
		2014		2013		2012
		(in millions, except per share data)
	Pro forma net sales	$	12,131	$	12,701	$	13,276
	Pro forma income from continuing operations	$	676	$	760	$	764
	Pro forma net income attributable to L-3	$	663	$	751	$	786
	Pro forma diluted earnings per share from continuing operations	$	7.55	$	8.24	$	7.76
	Pro forma diluted earnings per share	$	7.55	$	8.24	$	8.05

Contracts_in_Process_Tables

Contracts in Process (Tables)	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Components of Contracts in Process	The components of contracts in process are presented in the table below.
		December 31,
		2014		2013
		(in millions)
	Unbilled contract receivables, gross	$	2,280	$	2,493
	Unliquidated progress payments		(887)		(1,008)
	Unbilled contract receivables, net		1,393		1,485
	Inventoried contract costs, gross		997		1,037
	Unliquidated progress payments		(95)		(80)
	Inventoried contract costs, net		902		957
	Total contracts in process	$	2,295	$	2,442
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,
		2014		2013		2012
		(in millions)
	Amounts included in inventoried contract costs at beginning of the year	$	138	$	110	$	91
	IRAD and B&P costs incurred		280		294		334
	Other G&A costs incurred		850		876		876
	Total contract costs incurred		1,130		1,170		1,210
	Amounts charged to cost of sales		(1,130)		(1,142)		(1,191)
	Amounts included in inventoried contract costs at end of the year	$	138	$	138	$	110
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,
		2014		2013		2012
		(in millions)
	Selling, general and administrative expenses	$	295	$	310	$	322
	Research and development expenses		67		76		90
	Total	$	362	$	386	$	412

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories at Lower of Cost or Market	Inventories at Lower of Cost or Market. 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,
		2014		2013
		(in millions)
	Raw materials, components and sub-assemblies	$	127	$	164
	Work in process		97		124
	Finished goods		64		78
	Total	$	288	$	366

Goodwill_and_Identifiable_Inta1

Goodwill and Identifiable Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [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				Aerospace				Communication				NSS				Consolidated
			Systems				Systems				Systems								Total
			(in millions)
	Balance at December 31, 2012		$	4,046			$	1,770			$	992			$	968			$	7,776
	Business acquisition(1)			44				—				—				—				44
	Business disposition			(2)				—				—				—				(2)
	Foreign currency translation  adjustments(2)			(3)				(19)				—				—				(22)
	Balance at December 31, 2013		$	4,085			$	1,751			$	992			$	968			$	7,796
	Business acquisitions(1)			(3)				—				—				39				36
	Business disposition			(1)				—				—				—				(1)
	Foreign currency translation  adjustments(2)			(77)				(21)				—				(1)				(99)
	Assets held for sale(3)			(231)				—				—				—				(231)
	Balance at December 31, 2014		$	3,773			$	1,730			$	992			$	1,006			$	7,501
		(1)	For the year ended December 31, 2014, the decrease in goodwill for the Electronic Systems segment was due to the final purchase price allocation for the Mustang business acquisition. The increase in goodwill for the NSS segment was due to the L-3 Data Tactics business acquisition. For the year ended December 31, 2013, the increase in goodwill for the Electronic Systems segment was due to the Mustang business acquisition.
		(2)	During 2014, the decrease in goodwill presented in the Electronic Systems segment was primarily due to the strengthening of the U.S. dollar against the Euro, the Canadian dollar and the British pound. During 2014 and 2013, the decreases in goodwill presented in the Aerospace Systems segment were due to the strengthening of the U.S. dollar against the Canadian dollar. During 2013, the decrease in goodwill presented in the Electronic Systems segment was primarily due to the strengthening of the U.S. dollar against the Canadian dollar and Australian dollar, partially offset by the weakening of the U.S. dollar against the Euro and the British pound.
		(3)	On December 16, 2014, the Company entered into a definitive agreement with Wärtsilä Corporation to sell its Marine Systems International business.
Identifiable Intangible Assets	Information on the Company’s identifiable intangible assets that are subject to amortization is presented in the table below.
			December 31, 2014														December 31, 2013
			Weighted		Gross				Accumulated				Net				Gross				Accumulated		Net
			Average		Carrying				Amortization				Carrying				Carrying				Amortization		Carrying
			Amortization		Amount								Amount				Amount						Amount
			Period
			(in years)		(in millions)
	Customer contractual   relationships(1)		20		$	440			$	262			$	178			$	466			$	253	$	213
	Technology(1)		11			165				111				54				168				108		60
	Other		18			27				16				11				27				15		12
	Total		18		$	632			$	389			$	243			$	661			$	376	$	285
		(1)	Amounts reclassified to assets held for sale at December 31, 2014 relating to L-3 MSI include gross carrying amounts of $28 million and $7 million for customer contractual relationships and technology intangible assets, respectively, and accumulated amortization of $20 million and $6 million for customer contractual relationships and technology intangible assets, respectively.
Amortization Expense	Amortization expense recorded by the Company for its identifiable intangible assets is presented in the table below.
			Year Ended December 31,
			2014				2013				2012
			(in millions)
	Amortization expense		$	43			$	39			$	47
Estimated Amortization Expense	Based on gross carrying amounts at December 31, 2014, excluding assets held for sale relating to L-3 MSI, the Company’s estimate of amortization expense for identifiable intangible assets for the years ending December 31, 2015 through 2019 is presented in the table below.
			Year Ending December 31,
			2015				2016				2017				2018				2019
			(in millions)
	Estimated amortization expense		$	37			$	33			$	29			$	25			$	22

Other_Current_Liabilities_and_1

Other Current Liabilities and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Other Current Liabilities	The table below presents the components of other current liabilities.
		December 31,
		2014		2013
		(in millions)
	Other Current Liabilities:
	Accruals for pending and threatened litigation (see Note 19)	$	38	$	6
	Estimated costs in excess of estimated contract value to complete contracts in  process in a loss position		75		78
	Accrued product warranty costs		59		75
	Accrued interest		46		52
	Deferred revenues		30		35
	Other		150		156
	Total other current liabilities	$	398	$	402
Other Liabilities	The table below presents the components of other liabilities.
		December 31,
		2014		2013
		(in millions)
	Other Liabilities:
	Non-current income taxes payable (see Note 17)	$	196	$	177
	Deferred compensation		43		45
	Accrued workers’ compensation		38		46
	Accrued product warranty costs		34		24
	Notes payable and capital lease obligations		1		15
	Other		70		99
	Total other liabilities	$	382	$	406

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	The table below presents the components of Property, Plant and Equipment.
		December 31,
		2014		2013
		(in millions)
	Land	$	62	$	62
	Buildings and improvements		420		405
	Machinery, equipment, furniture and fixtures		1,707		1,643
	Leasehold improvements		327		338
	Gross property, plant and equipment		2,516		2,448
	Accumulated depreciation and amortization		(1,428)		(1,406)
	Property, plant and equipment, net	$	1,088	$	1,042

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Components of Long-Term Debt and Reconciliation to Carrying Amount of Long-Term Debt	The components of long-term debt and a reconciliation to the carrying amount of long-term debt are presented in the table below.
			December 31,
			2014		2013
			(in millions)
	L-3 Communications:
	Borrowings under Amended and Restated Revolving Credit Facility(1)		$	—	$	—
	3.95% Senior Notes due 2016			500		500
	1.50% Senior Notes due 2017			350		—
	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			650		—
	Subtotal			3,950		2,950
	L-3 Holdings:
	3% Convertible Contingent Debt Securities due 2035			—		689
	Principal amount of long-term debt			3,950		3,639
	Unamortized discounts			(11)		(9)
	Carrying amount of long-term debt		$	3,939	$	3,630
		(1)	During 2014, L-3 Communications’ aggregate borrowings and repayments under the Credit Facility were $1,367 million. L-3 Communications had the full availability of its $1 billion Credit Facility at December 31, 2014 and had the availability of substantially all of its $1 billion Credit Facility at December 31, 2013.
Information Regarding Outstanding Senior Subordinated Notes	The terms of each outstanding Senior Note are presented in the table below.
	Note		Date of Issuance		Amount		Discount(1)		Net			Effective			Redemption
					Issued				Cash			Interest			at Treasury
									Proceeds			Rate			Rate(2)(3)
					(in millions)
	3.95% Senior Notes due   November 15, 2016			November 22, 2011	$	500	$	4	$	491			4.11	%		50 bps
	1.50% Senior Notes due   May 28, 2017			May 28, 2014	$	350	$	1	$	347	(4)		1.55	%		10 bps
	5.20% Senior Notes due   October 15, 2019			2-Oct-09	$	1,000	$	4	$	987			5.25	%		30 bps
	4.75% Senior Notes due   July 15, 2020			21-May-10	$	800	$	3	$	790			4.79	%		25 bps
	4.95% Senior Notes due   February 15, 2021			7-Feb-11	$	650	$	4	$	639			5.02	%		25 bps
	3.95% Senior Notes due   May 28, 2024			May 28, 2014	$	650	$	3	$	641	(4)		4.02	%		20 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 2016, 2017, 2019, 2020 and 2021 may be redeemed at any time prior to their maturity and the Senior Notes maturing in 2024 may be redeemed at any time prior to February 28, 2024 (three months prior to their maturity) at the option of L-3 Communications, 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 2024 are redeemed at any time on or after February 28, 2024, 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 L-3 Communications 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.
		(4)	The net cash proceeds of $988 million (after deduction of the bond discount, underwriting expenses and commissions and other related expenses) were used primarily to fund the CODES retirement as discussed below. The remaining net proceeds were used for general corporate purposes.
Redemptions of Senior Subordinated Notes	Information on the Senior Subordinated Notes redeemed by the Company during the year ended December 31, 2012 is presented in the table below. There were no redemptions of L-3 Communications Senior Subordinated Notes during the years ended December 31, 2014 and 2013.
	Note		Redemption Date		Principal		Debt		Redemption Price
					Amount		Retirement		% of Principal
					Redeemed		Charge
					(in millions)
	6 3⁄8% Senior Subordinated Notes due October 15, 2015			October 15, 2012	$	250	$	5		101.06%
	6 3⁄8% Senior Subordinated Notes due October 15, 2015(1)			26-Jul-12	$	250	$	8		102.13%
		(1)	In connection with the spin-off, Engility made a cash distribution of $335 million to L-3, a portion of which was used to redeem $250 million of the 6  3⁄8% 2015 Notes.

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive (Loss) Income (AOCI) (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Summary of 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		Unrealized		Unrecognized		Total
			currency		gains		(losses) gains		accumulated
			translation		(losses) on		and prior service		other
					hedging		cost, net		comprehensive
					instruments(1)				(loss) income
			(in millions)
	Balance at December 31, 2011		$	133	$	—	$	(587)	$	(454)
	Other comprehensive income (loss) before   reclassifications, net of tax			34				(175)
	Amounts reclassified from AOCI, net of tax			—				42
	Net current period other comprehensive   income (loss)			34		3		(133)		(96)
	Balance at December 31, 2012		$	167	$	3	$	(720)	$	(550)
	Other comprehensive (loss) income before   reclassifications, net of tax			(25)		(1)		414		388
	Amounts reclassified from AOCI, net of tax			—		(1)		53		52
	Net current period other comprehensive   (loss) income			(25)		(2)		467		440
	Balance at December 31, 2013		$	142	$	1	$	(253)	$	(110)
	Other comprehensive (loss) before reclassifications,   net of tax			(123)		(13)		(354)		(490)
	Amounts reclassified from AOCI, net of tax			—		7		9		16
	Net current period other comprehensive (loss)			(123)		(6)		(345)		(474)
	Balance at December 31, 2014		$	19	$	(5)	$	(598)	$	(584)
		(1)	Information related to amounts reclassified from AOCI for hedging instruments is unavailable for the year ended December 31, 2012.
	Further details regarding the amounts reclassified from AOCI into net income are presented in the table below.
			Amount Reclassified from
			AOCI(a)
			Year Ended December 31,						Affected Line Item in the
									Audited Consolidated
	Details About AOCI Components		2014		2013		2012(b)		Statements of Operations
			(in millions)
	(Loss) gains on hedging instruments		$	(8)	$	1			Cost of sales-products
				(8)		1			Income from continuing operations before income taxes
				1		—			Provision for income taxes
			$	(7)	$	1			Income from continuing operations
	Amortization of defined benefit pension items:
	Net loss		$	(15)	$	(83)	$	(68)	(c)
				(15)		(83)		(68)	Income from continuing operations before income taxes
				6		30		26	Provision for income taxes
			$	(9)	$	(53)	$	(42)	Income from continuing operations
	Total reclassification for the period		$	(16)	$	(52)			Income from continuing operations
		(a)	Amounts in parentheses indicate charges to the consolidated statements of operations.
		(b)	Information related to amounts reclassified from AOCI for hedging instruments is unavailable for the year ended December 31, 2012.
		(c)	Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 20 for additional information).

Equity_Tables

Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Remaining Value of Authorization under Share Repurchase Programs	The remaining dollar value of authorization under our December 4, 2014 share repurchase program available at February 20, 2015 is summarized in the table below.
		Share Authorization
		(in millions)
	Remaining authorization at December 31, 2014	$	1,545
	Share repurchases from January 1, 2015 to February 20, 2015 under February 5, 2013 share repurchase program		(45	)
	Share repurchases from January 1, 2015 to February 20, 2015 under December 4, 2014 share repurchase program		(33	)
	Remaining authorization at February 20, 2015 under the December 4, 2014 share repurchase program	$	1,467

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [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,
			2014						2013
	Description		Level 1(1)		Level 2(2)		Level 3(3)		Level 1(1)		Level 2(2)		Level 3(3)
			(in millions)
	Assets
	Cash equivalents		$	416	$	—	$	—	$	299	$	—	$	—
	Derivatives (foreign currency forward contracts)			—		5		—		—		6		—
	Total assets		$	416	$	5	$	—	$	299	$	6	$	—
	Liabilities
	Derivatives (foreign currency forward contracts)		$	—	$	11	$	—	$	—	$	5	$	—
		(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. The Company has no Level 3 assets or liabilities.

Financial_Instruments_Tables

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Investments, All Other Investments [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, 2014				December 31, 2013
			Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value
			(in millions)
	Senior Notes(1)		$	3,939	$	4,178	$	2,941	$	3,121
	CODES(1)		$	—	$	—	$	689	$	830
	Foreign currency forward contracts(2)		$	(6)	$	(6)	$	1	$	1
		(1)	The Company measures the fair value of its Senior Notes and its CODES prior to their redemption 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 15 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [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 as of December 31, 2014.
	Currency		Notional Amount
			(in millions)
	Canadian dollar		$	123
	U.S. dollar			101
	Euro			47
	British pound			9
	Total		$	280
Location of the 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, 2014								December 31, 2013
			Other		Other		Other		Other		Other		Other		Other		Other
			Current		Assets		Current		Liabilities		Current		Assets		Current		Liabilities
			Assets				Liabilities				Assets				Liabilities
			(in millions)
	Derivatives designated as hedging instruments:
	Foreign currency forward   contracts(1) (2)		$	4	$	1	$	10	$	1	$	5	$	1	$	3	$	2
	Total derivative instruments		$	4	$	1	$	10	$	1	$	5	$	1	$	3	$	2
		(1)	See Note 13 for a description of the fair value hierarchy related to the Company’s foreign currency forward contracts.
		(2)	Assets held for sale at December 31, 2014 include $2 million of other current assets relating to the fair value of derivative instruments and liabilities held for sale at December 31, 2014 include $2 million of other current liabilities relating to the fair value of derivative instruments.

L3_Holdings_Earnings_Per_Share1

L-3 Holdings' Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2014
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,
			2014		2013		2012
			(in millions, except per share data)
	Reconciliation of net income:
	Net income		$	677	$	760	$	794
	Net income from continuing operations attributable to noncontrolling interests			(13)		(9)		(6)
	Net income from discontinued operations attributable to noncontrolling interests			—		—		(4)
	Net income attributable to L-3 Holdings common shareholders		$	664	$	751	$	784
	Earnings attributable to L-3 Holdings’ common shareholders:
	Continuing operations		$	664	$	751	$	756
	Discontinued operations, net of income tax			—		—		28
	Net income attributable to L-3 Holdings common shareholders		$	664	$	751	$	784
	Earnings per share attributable to L-3 Holdings’ common shareholders:
	Basic:
	Weighted average common shares outstanding			85.4		89.4		96.3
	Basic earnings per share attributable to L-3 Holdings’ common shareholders:
	Continuing operations		$	7.78	$	8.40	$	7.85
	Discontinued operations, net of income tax			—		—		0.29
	Basic earnings per share		$	7.78	$	8.40	$	8.14
	Diluted:
	Common and potential common shares:
	Weighted average common shares outstanding			85.4		89.4		96.3
	Assumed exercise of stock options			3.0		3.9		1.9
	Unvested restricted stock awards			1.6		1.8		2.0
	Employee stock purchase plan contributions			—		0.2		0.3
	Performance unit awards			0.1		0.1		0.1
	Assumed purchase of common shares for treasury			(3.1)		(4.5)		(3.0)
	Assumed conversion of the CODES(1)			0.8		0.2		—
	Common and potential common shares			87.8		91.1		97.6
	Diluted earnings per share attributable to L-3 Holdings’ common shareholders:
	Continuing operations		$	7.56	$	8.24	$	7.74
	Discontinued operations, net of income tax			—		—		0.29
	Diluted earnings per share		$	7.56	$	8.24	$	8.03
		(1)	The CODES were retired on June 20, 2014 and were dilutive for the years ended December 31, 2014 and 2013 as the average market price of L-3 Holdings’ common stock during the periods that the CODES were outstanding was greater than the price at which the CODES would have been convertible into L-3 Holdings’ common stock. L-3 Holdings’ CODES had no impact on diluted EPS for the year ended December 31, 2012 because the average market price of L-3 Holdings’ common stock during this period was less than the price at which the CODES would have been convertible into L-3 Holdings’ common stock. As of June 18, 2014, the final date of conversion, the conversion price during the year-to-date period ended June 27, 2014 was $88.71. As of December 31, 2013 and 2012, the conversion prices were $90.24, and $91.21, respectively.

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [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,
			2014		2013		2012
			(in millions)
	Domestic		$	760	$	858	$	892
	Foreign			165		197		230
	Income from continuing operations before income taxes		$	925	$	1,055	$	1,122
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,
			2014		2013		2012
			(in millions)
	Current income tax provision:
	Federal		$	87	$	181	$	198
	State and local			4		34		21
	Foreign			36		38		44
	Subtotal			127		253		263
	Deferred income tax provision:
	Federal			107		35		80
	State and local			13		—		8
	Foreign			1		7		9
	Subtotal			121		42		97
	Total provision for income taxes		$	248	$	295	$	360
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,
			2014		2013		2012
	Statutory federal income tax rate			35.0%		35.0%		35.0%
	State and local income taxes, net of federal income tax benefit			2.3		2.1		1.7
	Foreign income taxes			(3.4)		(1.6)		(2.0)
	Manufacturing benefits			(1.7)		(1.9)		(1.8)
	Research and experimentation and other tax credits			(4.1)		(3.6)		(0.5)
	Resolution of tax contingencies			(0.9)		(1.0)		(0.9)
	Other, net			(0.4)		(1.0)		0.6
	Effective income tax rate on continuing operations			26.8%		28.0%		32.1%
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,
			2014		2013
			(in millions)
	Deferred tax assets:
	Inventoried costs		$	86	$	72
	Compensation and benefits			152		164
	Pension and postretirement benefits			402		207
	Loss carryforwards			15		24
	Tax credit carryforwards			10		7
	Other			84		75
	Gross deferred tax assets			749		549
	Less: valuation allowance			(9)		(22)
	Net deferred tax assets			740		527
	Deferred tax liabilities:
	Goodwill and other intangible assets		$	792	$	726
	Income recognition on contracts in process			78		58
	Property, plant and equipment			98		85
	Long-term debt-CODES			—		81
	Other			88		65
	Gross deferred tax liabilities			1,056		1,015
	Total net deferred tax liabilities		$	(316)	$	(488)
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,
			2014		2013
			(in millions)
	Current deferred tax assets		$	127	$	147
	Non-current deferred tax liabilities			(443)		(635)
	Total net deferred tax liabilities		$	(316)	$	(488)
Summary of Loss and Tax Credit Carryforwards	The following table presents the Company’s loss and tax credit carryforwards as of December 31, 2014 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, 2014
			Carryforwards				Valuation
							Allowances
			Gross		Tax		Gross		Tax		Expiration
					Effected				Effected		Periods
			(in millions)				(in millions)
	Capital loss carryforwards(1)		$	25	$	9	$	14	$	5	2016-2017
	Federal net operating loss carryforwards			5		2		5		2	2026-2030
	Foreign net operating loss carryforwards			7		2		2		1	Indefinite
	State net operating loss carryforwards			94		2		48		1	2016-2033
	Total loss carryforwards				$	15			$	9
	State tax credit carryforwards			11		7		—		—	2016-2033
	Foreign tax credit carryforwards			3		3		—		—	Indefinite
	Total tax credit carryforwards				$	10			$	—
	(1)	During 2014, the Company reduced its valuation allowance for capital loss carryforwards by $4 million because it now believes that it will more likely than not have sufficient capital gains to realize this portion of the underlying deferred tax asset.
Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties	A reconciliation of the change in unrecognized income tax benefits, excluding potential interest and penalties, is presented in the table below.
			2014		2013		2012
			(in millions)
	Balance at January 1		$	169	$	138	$	150
	Additions for tax positions related to the current year			20		18		8
	Additions for tax positions related to prior years			13		41		9
	Reductions for tax positions related to prior years			(15)		(8)		(13)
	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			(6)		(20)		(15)
	Balance at December 31		$	180	$	169	$	138

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation by Form of Award	The Company’s stock-based compensation by form of award, including stock-based compensation recorded in discontinued operations for the spin-off of Engility in 2012, is presented in the table below.
			Year Ended December 31,
			2014		2013		2012
			(in millions)
	Stock options		$	9	$	10	$	10
	Restricted stock units			40		41		46
	Performance units			3		7		8
	Total before income taxes			52		58		64
	Income taxes			(20)		(22)		(24)
	Total after income taxes			32		36		40
	Less: Stock based compensation recorded in discontinued   operations, net of income taxes			—		—		1
	Stock based compensation recorded in continuing operations,   net of income taxes		$	32	$	36	$	39
Company's Stock Option Activity and Changes	The table below presents a summary of the Company’s stock option activity as of December 31, 2014 and changes during the year then ended.
			Number of		Weighted		Weighted		Aggregate
			Options		Average		Average		Intrinsic
					Exercise		Remaining		Value
					Price		Contractual
							Term
			(in thousands)				(in years)		(in millions)
	Number of shares under option:
	Outstanding at January 1, 2014			3,882.9	$	77.90		6.2	$	112
	Options granted			473.0		113.67
	Options exercised			(1,183.4)		77.94
	Options forfeited			(71.3)		91.59
	Outstanding at December 31, 2014			3,101.2	$	83.02		6.2	$	134
	Vested and expected to vest at December 31, 2014(1)			3,090.3	$	82.96		6.2	$	134
	Exercisable at December 31, 2014			1,962.8	$	79.46		4.9	$	92
		(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.
			2014		2013		2012
			Grants		Grants		Grants
	Expected holding period (in years)			5.5		5.6		5.4
	Expected volatility			24.40%		26.40%		27.00%
	Expected dividend yield			2.70%		3.60%		3.60%
	Risk-free interest rate			1.70%		1.00%		1.00%
Company's Nonvested Restricted Stock Unit Awards and Changes	The table below presents a summary of the Company’s nonvested restricted stock unit awards as of December 31, 2014 and changes during the year then ended.
			Number of		Weighted
			Shares		Average
					Grant Date
					Fair Value
			(in thousands)
	Nonvested balance at January 1, 2014			1,773.8	$	73.51
	Granted			416.7		113.58
	Vested			(570.8)		77.07
	Forfeited			(102.1)		80.36
	Nonvested balance at December 31, 2014			1,517.6	$	82.72
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 as of December 31, 2014 and changes during the year then ended.
			Payable in Shares (EPS)
			Number of		Weighted Average
			Units		Grant Date
					Fair Value
			(in thousands)
	Outstanding at January 1, 2014			175.5	$	70.84
	Granted			47.5		113.67
	Decrease due to expected performance			(45.6)		71.78
	Vested			(87.3)		67.49
	Forfeited			(4.9)		89.90
	Outstanding at December 31, 2014			85.2	$	96.53

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [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, 2014.
		Real Estate		Equipment		Total
				(in millions)
	2015	$	142	$	9	$	151
	2016		100		6		106
	2017		90		4		94
	2018		78		3		81
	2019		58		2		60
	Thereafter		113		2		115
	Total minimum payments required		581		26		607
	Less: Sublease rentals under non-cancelable leases		5		—		5
	Net minimum payments required	$	576	$	26	$	602

Pensions_and_Other_Employee_Be1

Pensions and Other Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [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
			2014			2013			2014			2013
			(in millions)
	Change in benefit obligation:
	Benefit obligation at the beginning of the year		$	2,973		$	3,222		$	194		$	218
	Service cost			106			126			3			4
	Interest cost			147			132			8			7
	Plan participants’ contributions			2			2			4			4
	Amendments			1			14			(1)			—
	Actuarial loss (gain)			579			(402)			5			(23)
	Foreign currency exchange rate changes			(34)			(21)			(2)			(3)
	Curtailments, settlements and special termination benefits			1			3			—			—
	Benefits paid			(112)			(103)			(12)			(13)
	Benefit obligation at the end of the year		$	3,663		$	2,973		$	199		$	194
	Change in plan assets:
	Fair value of plan assets at the beginning of the year		$	2,403		$	2,026		$	55		$	47
	Actual return on plan assets			205			394			6			9
	Employer contributions			97			105			7			8
	Plan participants’ contributions			2			2			4			4
	Foreign currency exchange rate changes			(25)			(21)			—			—
	Benefits paid			(112)			(103)			(12)			(13)
	Fair value of plan assets at the end of the year		$	2,570		$	2,403		$	60		$	55
	Unfunded status at the end of the year		$	(1,093)		$	(570)		$	(139)		$	(139)
	Assets and (liabilities) recognized in the consolidated balance sheets consist of:
	Non-current assets		$	26		$	35		$	—		$	—
	Current liabilities			(4)			(8)			(8)			(9)
	Non-current liabilities			(1,056)			(597)			(131)			(130)
	Liabilities held for sale(1)			(59)			—			—			—
			$	(1,093)		$	(570)		$	(139)		$	(139)
		(1)	Liabilities held for sale consists of $3 million of current liabilities and $56 million of non-current liabilities relating to L-3 MSI.
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
			2014			2013			2014			2013
			(in millions)
	Net loss (gain)		$	968		$	425		$	(6)		$	(9)
	Prior service cost (credit)			—			1			(3)			(8)
	Total amount recognized		$	968		$	426		$	(9)		$	(17)
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, 2014 and 2013.
			Pension Plans
			2014			2013
			(in millions)
	Projected benefit obligation		$	3,467		$	2,408
	Accumulated benefit obligation			3,083			2,115
	Fair value of plan assets			2,349			1,815
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, 2014 and 2013.
			Pension Plans						Postretirement
									Benefit Plans
			2014			2013			2014			2013
	Benefit obligations:
	Discount rate			4.14%	(1)		5.03%	(1)		3.70%	(2)		4.43%	(2)
	Rate of compensation increase			3.50%	(3)		3.50%	(3)
		(1)	The weighted average discount rate assumptions used at December 31, 2014 and 2013 were comprised of separate assumptions determined by country of 4.2% and 5.1% for the U.S. based plans, 3.9% and 4.7% for the Canadian based plans and 2.2% and 3.5% for the German based plans, respectively.
		(2)	The weighted average discount rate assumptions used at December 31, 2014 and 2013 were comprised of separate assumptions determined by country of 3.7% and 4.4% for the U.S. based plans and 3.7% and 4.6% 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, 2014 and 2013.
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, 2014, 2013 and 2012.
			Pension Plans									Postretirement
												Benefit Plans
			2014			2013			2012			2014				2013				2012
			(in millions)
	Components of net periodic benefit cost:
	Service cost		$	106		$	126		$	113		$	3			$	4			$	4
	Interest cost			147			132			134			8				7				10
	Expected return on plan assets			(193)			(164)			(145)			(4)				(4)				(3)
	Amortization of prior service cost (credits)			2			1			1			(2)				(3)				(3)
	Amortization of net loss (gain)			17			83			69			(2)				2				1
	Curtailment or settlement loss (gain)			1			3			7			(1)				—				1
	Net periodic benefit cost		$	80		$	181		$	179		$	2			$	6			$	10
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income	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, 2014, 2013 and 2012.
			Pension Plans									Postretirement
												Benefit Plans
			2014			2013			2012			2014				2013				2012
			(in millions)
	Other changes in plan assets and benefit obligations recognized in other comprehensive income:
	Net loss (gain)		$	560		$	(637)		$	287		$	5			$	(29)			$	(3)
	Prior service cost (credit)			1			14			(1)			(1)				—				(5)
	Amortization of net (loss) gain			(17)			(83)			(69)			2				(2)				(1)
	Amortization of prior service (cost) credit			(2)			(1)			(1)			2				3				3
	Total recognized in other comprehensive income			542			(707)			216			8				(28)				(6)
	Total recognized in net periodic benefit cost and other comprehensive income		$	622		$	(526)		$	395		$	10			$	(22)			$	4
Amounts Expected to be Amortized from Accumulated Other Comprehensive Income (Loss) and Recognized as Components of Net Periodic Benefit Costs	The following table summarizes the amounts expected to be amortized from accumulated other comprehensive income (loss) and recognized as components of net periodic benefit costs during 2015.
			Pension			Postretirement			Total
			Plans			Benefit Plans
						(in millions)
	Net loss		$	68		$	—		$	68
	Prior service cost (credit)			1			(2)			(1)
			$	69		$	(2)		$	67
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, 2014, 2013 and 2012.
			Pension Plans									Postretirement
												Benefit Plans
			2014			2013			2012			2014				2013				2012
	Discount rate			5.03%	(1)		4.15%	(1)		5.02%	(1)		4.43%	(4)			3.37%	(4)			4.71%	(4)
	Expected long-term return on plan assets			8.13%	(2)		8.13%	(2)		8.15%	(2)		7.64%				7.64%				7.64%
	Rate of compensation increase			3.50%	(3)		3.50%	(3)		4.06%	(3)
		(1)	The weighted average discount rate assumptions used for the years ended December 31, 2014, 2013, and 2012 were comprised of separate assumptions determined by country of 5.1%, 4.2% and 5.1% for the U.S. based plans, 4.7%, 3.9% and 4.4% for the Canadian based plans and 3.5%, 3.4%, and 5.1% for the German 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 8.25% for the U.S. based plans for the years ended December 31, 2014, 2013 and 2012 and 7.25% for the years ended December 31, 2014 and 2013 and 7.5% for the year ended December 31, 2012 for the Canadian based plans.
		(3)	The weighted average rate of compensation increase assumptions used for the years ended December 31, 2014 and 2013 were comprised of separate assumptions determined by country of 3.5% for both the U.S. and Canadian based plans. The rate of compensation increase assumptions were 4.0% for the U.S. based plans and 4.5% for the Canadian based plans for the year ended December 31, 2012.
		(4)	The weighted average discount rate assumptions used for the years ended December 31, 2014, 2013 and 2012 were comprised of separate assumptions determined by country of 4.4%, 3.3% and 4.8% for the U.S. based plans and 4.6%, 3.7% and 4.3% for the Canadian based plans, respectively.
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			7			(6)
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, 2014 as well as the Company’s pension plan and postretirement benefit plan weighted-average asset allocations at December 31, 2014 and 2013, by asset category.
			U.S.									Canada
	Asset Category		2014 and 2013			2014			2013			2014 and 2013		2014				2013
			Range									Range
	Domestic equity(1)			30%-60%			52%			54%		10%-25%			15%				20%
	International equity(2)			10%-20%			10			10		30%-60%			55				49
	Fixed income securities			20%-40%			22			23		20%-60%			20				28
	Real estate securities			0%-15%			7			6		—			—				—
	Other, primarily cash and cash equivalents			0%-15%			9			7		0%-15%			10				3
	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.
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 at December 31, 2014 and 2013, 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													Fair Value Measured at
			December 31, 2014													December 31, 2014
	Asset Category		Level 1			Level 2			Level 3			Total				Level 1				Level 2			Level 3		Total
			(in millions)
	Equity securities(1):
	U.S. Equity		$	1,172		$	—		$	—		$	1,172			$	58			$	33		$	—	$	91
	International Equity			87			140			—			227				107				13			—		120
	Fixed Income — Investment Grade(2)			237			157			—			394				—				62			—		62
	Fixed Income — High Yield(3)			—			120			—			120				—				—			—		—
	Real Estate Investment Trusts(4)			159			—			—			159				—				—			—		—
	Other(5)			—			208			—			208				4				26			—		30
	Total assets at fair value		$	1,655		$	625		$	—		$	2,280			$	169			$	134		$	—	$	303
	Liabilities for unsettled trades, net												(13)													—
	Total											$	2,267												$	303
			Fair Value Measured at													Fair Value Measured at
			December 31, 2013													December 31, 2013
	Asset Category		Level 1			Level 2			Level 3			Total				Level 1				Level 2			Level 3		Total
			(in millions)
	Equity securities(1):
	U.S. Equity		$	1,144		$	—		$	—		$	1,144			$	54			$	18		$	—	$	72
	International Equity			79			146			—			225				117				18			—		135
	Fixed Income — Investment Grade(2)			217			149			—			366				—				82			—		82
	Fixed Income — High Yield(3)			—			111			—			111				—				—			—		—
	Real Estate Investment Trusts(4)			118			—			—			118				—				—			—		—
	Other(5)			—			150			—			150				6				5			—		11
	Total assets at fair value		$	1,558		$	556		$	—		$	2,114			$	177			$	123		$	—	$	300
	Liabilities for unsettled trades, net												(11)													—
	Total											$	2,103												$	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. The Level 2 investment balance is derived from a regulated commingled equity trust fund, which fair value is based on the net asset value (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.
		(2)	Approximately 60% at December 31, 2014 and 59% at December 31, 2013 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 40% at December 31, 2014 and 41% at December 31, 2013 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 as a practical expedient to estimating fair value and classified as level 2. All of the Canadian plan assets for both 2014 and 2013 are invested in regulated commingled equity trust 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)	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.
	The table below presents the fair value of the Company’s postretirement benefit plans’ assets at December 31, 2014 and 2013, by asset category segregated by level within the fair value hierarchy, as described below.
			Postretirement Benefit Plans’ Assets
			Fair Value Measured at													Fair Value Measured at
			December 31, 2014													December 31, 2013
	Asset Category		Level 1			Level 2			Level 3			Total				Level 1				Level 2			Level 3		Total
			(in millions)
	Equity securities(1):
	U.S. Equity		$	36		$	—		$	—		$	36			$	37			$	—		$	—	$	37
	International Equity			1			3			—			4				1				2			—		3
	Fixed Income — Investment Grade(2)			10			2			—			12				7				2			—		9
	Fixed Income — High Yield(3)			—			2			—			2				—				2			—		2
	Real Estate Investment Trusts(4)			2			—			—			2				2				—			—		2
	Other(5)			—			4			—			4				—				2			—		2
	Total		$	49		$	11		$	—		$	60			$	47			$	8		$	—	$	55
		(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. The Level 2 investment balance is derived from 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.
		(2)	Approximately 83% at December 31, 2014 and 78% at December 31, 2013 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 17% at December 31, 2014 and 22% at December 31, 2013 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 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)	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 in real estate, 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, and are classified as Level 2.
Estimated Future Benefit Payments	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			Benefit			Subsidy
			Benefits			Payments			Receipts
			(in millions)
	2015		$	131			13			—
	2016			138			13			—
	2017			151			14			—
	2018			159			15			—
	2019			164			15			—
	Years 2020-2024			991			73			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.
	Pension Fund		EIN/Pension		Pension			FIP/RP(2)	Contributions by											Surcharge			Expiration
			Plan Number		Protection Act			Status Pending/	L-3 Communications											Imposed			Date of
					Zone			Implemented															Collective-
					Status(1)																		Bargaining
					2014	2013			2014			2013				2012							Agreement
									(in millions)
	IAM National Pension Fund		51-6031295/002		Green	Green		No	$	19(3)		$	21(4)			$	20(4)				No		2/4/2015 to
																							4/28/2019(5)
	Other Pension Funds(6)									—			—				—
						Total contributions			$	19		$	21			$	20
		(1)	A zone status rating of green indicates the plan is at least 80% funded. The funding status of the IAM National Pension Fund was impacted by a market value investment loss for the plan year ended December 31, 2009, which amortization was extended over five years.
		(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 ending December 31, 2014 was not available.
		(4)	Represents 6% of total plan contributions for both years ended December 31, 2013 and 2012 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 represent 67% of 2014 contributions.
		(6)	Consists of three pension funds in which the Company’s contributions are individually, and in the aggregate, insignificant.

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2014
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information
		Year Ended December 31,
		2014		2013		2012
		(in millions)
	Interest paid on outstanding debt	$	176	$	171	$	198
	Income tax payments		129		245		332
	Income tax refunds		9		23		22

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [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,
			2014		2013		2012
			(in millions)
	Net Sales
	Products
	Electronic Systems		$	3,685	$	3,661	$	3,754
	Aerospace Systems			1,722		1,827		1,755
	Communication Systems			1,541		1,755		2,083
	NSS			75		71		98
	Elimination of intercompany sales			(114)		(125)		(104)
	Total products sales			6,909		7,189		7,586
	Services
	Electronic Systems		$	1,029	$	1,054	$	1,011
	Aerospace Systems			2,604		2,730		2,844
	Communication Systems			499		471		445
	NSS			1,140		1,228		1,292
	Elimination of intercompany sales			(57)		(50)		(71)
	Total services sales			5,215		5,433		5,521
	Consolidated total		$	12,124	$	12,622	$	13,107
	Operating Income
	Electronic Systems		$	537	$	533	$	569
	Aerospace Systems			288		426		437
	Communication Systems			196		168		223
	NSS			64		85		79
	Consolidated total		$	1,085	$	1,212	$	1,308
	Depreciation and amortization
	Electronic Systems		$	123	$	117	$	121
	Aerospace Systems			40		38		46
	Communication Systems			51		48		47
	NSS			11		11		14
	Consolidated total		$	225	$	214	$	228
	Capital Expenditures
	Electronic Systems		$	80	$	71	$	77
	Aerospace Systems			59		54		42
	Communication Systems			29		59		84
	NSS			9		5		5
	Corporate			6		20		2
	Consolidated total		$	183	$	209	$	210
	Total Assets
	Electronic Systems		$	6,287	$	6,928	$	6,792
	Aerospace Systems			3,011		3,106		3,074
	Communication Systems			1,997		2,130		2,179
	NSS			1,287		1,247		1,228
	Corporate			707		596		527
	Assets held for sale			547		—		—
	Consolidated total		$	13,836	$	14,007	$	13,800
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,
			2014		2013		2012
			(in millions)
	U.S.		$	9,172	$	9,808	$	10,658
	International:
	United Kingdom			342		449		360
	Canada			289		357		314
	Australia			254		218		222
	Germany			243		272		263
	South Korea			226		178		125
	Saudi Arabia			160		132		76
	Japan			124		67		78
	Other			1,314		1,141		1,011
	Total international			2,952		2,814		2,449
	Consolidated		$	12,124	$	12,622	$	13,107
Net Sales to Principal Customers	Net sales to principal customers are summarized in the table below.
			Year Ended December 31,
			2014		2013		2012
			(in millions)
	U.S. Government agencies(1)		$	8,584	$	9,186	$	9,986
	Commercial			1,693		1,689		1,658
	Foreign governments(1)			1,847		1,747		1,463
	Consolidated		$	12,124	$	12,622	$	13,107
		(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.

Employee_Severance_and_Termina1

Employee Severance and Termination Costs (Tables)	12 Months Ended
	Dec. 31, 2014
Restructuring and Related Activities [Abstract]
Employee Severance and Other Termination Costs Incurred by Reportable Segment	Employee severance and other termination costs incurred by reportable segment are presented in the table below.
		Year Ended December 31,
		2014		2013		2012
		(in millions)
	Electronic Systems	$	16	$	16	$	13
	Aerospace Systems		5		2		1
	Communication Systems		8		11		8
	NSS		1		—		1
	Consolidated	$	30	$	29	$	23

Unaudited_Quarterly_Financial_1

Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Company's Unaudited Quarterly Results of Operations	The Company’s unaudited quarterly results of operations are affected, significantly in some periods, by our business acquisitions. See Note 4.
			First		Second		Third		Fourth
			Quarter		Quarter		Quarter		Quarter
			(in millions, except per share data)
	2014
	Sales		$	2,957	$	3,019	$	2,940	$	3,208
	Operating income			286		239		257		303
	Net income			172		141		157		207
	Net income attributable to L-3			170		137		154		203
	Basic EPS(1)			1.97		1.59		1.81		2.41
	Diluted EPS(1)			1.90		1.53		1.78		2.36
	2013
	Sales		$	3,197	$	3,189	$	3,002	$	3,234
	Operating income			310		290		306		306
	Net income			192		176		204		188
	Net income attributable to L-3			191		175		200		185
	Basic EPS(1)			2.12		1.95		2.23		2.10
	Diluted EPS(1)			2.09		1.92		2.19		2.04
		(1)	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_Co1

Financial Information of L-3 Communications and Its Subsidiaries (Tables)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Condensed Combining Statements of Equity	The table below presents information regarding the balances and changes in common stock, additional paid-in capital, treasury stock and retained earnings of L-3 Communications for each of the three years ended December 31, 2014.
		L-3				Additional		Treasury		Retained		Accumulated		Total
		Communications				Paid-in		Stock		Earnings		Other
		Common Stock				Capital						Comprehensive
												(Loss)
		Shares		Par								Income
		Issued		Value
				(in millions, except shares issued)
	Balance at December 31, 2011		100	$	—	$	5,064	$	—	$	2,034	$	(454)	$	6,644
	Net income attributable to L-3		—		—		—		—		784		—		784
	Contributions from L-3 Holdings		—		—		250		—		—		—		250
	Dividends to L-3 Holdings		—		—		—		—		(1,068)		—		(1,068)
	Comprehensive loss		—		—		—		—		—		(96)		(96)
	Net change of equity due to spin-off of Engility		—		—		—		—		(1,063)		—		(1,063)
	Balance at December 31, 2012		100	$	—	$	5,314	$	—	$	687	$	(550)	$	5,451
	Net income attributable to L-3		—		—		—		—		751		—		751
	Contributions from L-3 Holdings		—		—		339		—		—		—		339
	Dividends to L-3 Holdings		—		—		—		—		(1,001)		—		(1,001)
	Comprehensive income		—		—		—		—		—		440		440
	Other		—		—		—		—		1		—		1
	Balance at December 31, 2013		100	$	—	$	5,653	$	—	$	438	$	(110)	$	5,981
	Net income attributable to L-3		—		—		—		—		664		—		664
	Contributions from L-3 Holdings		—		—		146		—		—		—		146
	Dividends to L-3 Holdings		—		—		—		—		(1,032)		—		(1,032)
	Comprehensive loss		—		—		—		—		—		(474)		(474)
	Balance at December 31, 2014		100	$	—	$	5,799	$	—	$	70	$	(584)	$	5,285
Condensed Combining Balance Sheets	The following condensed combining financial information presents the results of operations, financial position and cash flows of (1) L-3 Holdings, excluding L-3 Communications and its consolidated subsidiaries (the “Parent”), (2) L-3 Communications, excluding its consolidated subsidiaries, (3) the Guarantor Subsidiaries, (4) the Non-Guarantor Subsidiaries and (5) the eliminations to arrive at the information for L-3 on a consolidated basis.
		L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
		Holdings		Communications		Subsidiaries		Guarantor				L-3
		(Parent)						Subsidiaries
		(in millions)
	Condensed Combining Balance Sheets:
	At December 31, 2014:
	Current assets:
	Cash and cash equivalents	$	—	$	361	$	1	$	142	$	(62)	$	442
	Billed receivables, net		—		320		329		203		—		852
	Contracts in process		—		867		1,144		284		—		2,295
	Other current assets		—		365		141		95		—		601
	Assets held for sale		—		—		52		495		—		547
	Total current assets		—		1,913		1,667		1,219		(62)		4,737
	Goodwill		—		2,350		4,246		905		—		7,501
	Other assets		—		817		576		205		—		1,598
	Investment in and amounts due from consolidated subsidiaries		5,285		6,813		4,191		—		(16,289)		—
	Total assets	$	5,285	$	11,893	$	10,680	$	2,329	$	(16,351)	$	13,836
	Current liabilities	$	—	$	878	$	1,017	$	455	$	(62)	$	2,288
	Liabilities held for sale		—		—		10		227		—		237
	Amounts due to consolidated subsidiaries		—		—		—		325		(325)		—
	Other long-term liabilities		—		1,791		190		31		—		2,012
	Long-term debt		—		3,939		—		—		—		3,939
	Total liabilities		—		6,608		1,217		1,038		(387)		8,476
	L-3 shareholders’ equity		5,285		5,285		9,463		1,291		(16,039)		5,285
	Noncontrolling interests		—		—		—		—		75		75
	Total equity		5,285		5,285		9,463		1,291		(15,964)		5,360
	Total liabilities and equity	$	5,285	$	11,893	$	10,680	$	2,329	$	(16,351)	$	13,836
	At December 31, 2013:
	Current assets:
	Cash and cash equivalents	$	—	$	258	$	—	$	261	$	(19)	$	500
	Billed receivables, net		—		364		401		226		—		991
	Contracts in process		—		919		1,169		354		—		2,442
	Other current assets		—		350		162		168		—		680
	Total current assets		—		1,891		1,732		1,009		(19)		4,613
	Goodwill		—		2,350		4,247		1,199		—		7,796
	Other assets		—		838		532		228		—		1,598
	Investment in and amounts due from consolidated subsidiaries		6,670		6,897		3,822		—		(17,389)		—
	Total assets	$	6,670	$	11,976	$	10,333	$	2,436	$	(17,408)	$	14,007
	Current liabilities	$	—	$	914	$	1,030	$	628	$	(19)	$	2,553
	Amounts due to consolidated subsidiaries		—		—		—		305		(305)		—
	Other long-term liabilities		—		1,451		193		124		—		1,768
	Long-term debt		689		3,630		—		—		(689)		3,630
	Total liabilities		689		5,995		1,223		1,057		(1,013)		7,951
	L-3 shareholders’ equity		5,981		5,981		9,110		1,379		(16,470)		5,981
	Noncontrolling interests		—		—		—		—		75		75
	Total equity		5,981		5,981		9,110		1,379		(16,395)		6,056
	Total liabilities and equity	$	6,670	$	11,976	$	10,333	$	2,436	$	(17,408)	$	14,007
Condensed Combining Statements of Operations		L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
		Holdings		Communications		Subsidiaries		Guarantor				L-3
		(Parent)						Subsidiaries
	Condensed Combining Statements of Operations:
	For the year ended December 31, 2014:
	Net sales	$	—	$	3,556	$	6,618	$	2,256	$	(306)	$	12,124
	Cost of sales		(52)		(3,211)		(6,117)		(2,017)		358		(11,039)
	Operating (loss) income		(52)		345		501		239		52		1,085
	Interest expense		(2)		(176)		(2)		—		2		(178)
	Interest and other income (expense), net		—		15		—		3		—		18
	(Loss) income from continuing operations before income taxes		(54)		184		499		242		54		925
	Benefit (provision) for income taxes		14		(49)		(134)		(65)		(14)		(248)
	Equity in net income of consolidated subsidiaries		704		529		—		—		(1,233)		—
	Net income		664		664		365		177		(1,193)		677
	Net income attributable to noncontrolling interests		—		—		—		—		(13)		(13)
	Net income attributable to L-3	$	664	$	664	$	365	$	177	$	(1,206)	$	664
	Comprehensive income attributable to L-3	$	190	$	190	$	363	$	46	$	(599)	$	190
	For the year ended December 31, 2013:
	Net sales	$	—	$	3,842	$	6,804	$	2,363	$	(387)	$	12,622
	Cost of sales		(59)		(3,549)		(6,139)		(2,109)		446		(11,410)
	Operating (loss) income		(59)		293		665		254		59		1,212
	Interest expense		(21)		(176)		—		(1)		21		(177)
	Interest and other income (expense), net		—		15		—		5		—		20
	(Loss) income from continuing operations before income taxes		(80)		132		665		258		80		1,055
	Benefit (provision) for income taxes		22		(38)		(184)		(73)		(22)		(295)
	Equity in net income of consolidated subsidiaries		809		657		—		—		(1,466)		—
	Net income		751		751		481		185		(1,408)		760
	Net income attributable to noncontrolling interests		—		—		—		—		(9)		(9)
	Net income attributable to L-3	$	751	$	751	$	481	$	185	$	(1,417)	$	751
	Comprehensive income attributable to L-3	$	1,191	$	1,191	$	480	$	159	$	(1,830)	$	1,191
	For the year ended December 31, 2012:
	Net sales	$	—	$	3,737	$	7,475	$	2,278	$	(383)	$	13,107
	Cost of sales		(59)		(3,434)		(6,749)		(1,999)		442		(11,799)
	Operating (loss) income		(59)		303		726		279		59		1,308
	Interest expense		(21)		(183)		—		(1)		21		(184)
	Interest and other income (expense), net		—		14		(5)		2		—		11
	Debt retirement charge		—		(13)		—		—		—		(13)
	(Loss) income from continuing operations before income taxes		(80)		121		721		280		80		1,122
	Benefit (provision) for income taxes		26		(37)		(230)		(93)		(26)		(360)
	Equity in net income of consolidated subsidiaries		838		668		—		—		(1,506)		—
	Income from continuing operations		784		752		491		187		(1,452)		762
	Income from discontinued operations, net of income tax		—		32		—		—		—		32
	Net income		784		784		491		187		(1,452)		794
	Net income attributable to noncontrolling interests		—		—		—		—		(10)		(10)
	Net income attributable to L-3	$	784	$	784	$	491	$	187	$	(1,462)	$	784
	Comprehensive income attributable to L-3	$	688	$	688	$	493	$	215	$	(1,396)	$	688
Condensed Combining Statements of Cash Flows		L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
		Holdings		Communications		Subsidiaries		Guarantor				L-3
		(Parent)						Subsidiaries
		(in millions)
	Condensed Combining Statements of Cash
	Flows: For the year ended December 31,
	2014:00:00
	Operating activities:
	Net cash from operating activities	$	1,966	$	478	$	599	$	141	$	(2,059)	$	1,125
	Investing activities:
	Business acquisitions, net of cash acquired		—		(57)		—		—		—		(57)
	Investments in L-3 Communications		(102)		—		—		—		102		—
	Other investing activities		—		(57)		(94)		(21)		—		(172)
	Net cash used in investing activities		(102)		(114)		(94)		(21)		102		(229)
	Financing activities:
	Proceeds from sale of senior notes		—		996		—		—		—		996
	Redemption of CODES		(935)		—		—		—		—		(935)
	Common stock repurchased		(823)		—		—		—		—		(823)
	Dividends paid on L-3 Holdings’ common stock		(208)		—		—		—		—		(208)
	Dividends paid to L-3 Holdings		—		(1,966)		—		—		1,966		—
	Investments from L-3 Holdings		—		102		—		—		(102)		—
	Other financing activities		102		607		(503)		(162)		50		94
	Net cash used in financing activities		(1,864)		(261)		(503)		(162)		1,914		(876)
	Effect of foreign currency exchange rate changes on cash		—		—		—		(17)		—		(17)
	Change in cash balance in assets held for sale		—		—		(1)		(60)		—		(61)
	Net increase (decrease) in cash		—		103		1		(119)		(43)		(58)
	Cash and cash equivalents, beginning of the year		—		258		—		261		(19)		500
	Cash and cash equivalents, end of the year	$	—	$	361	$	1	$	142	$	(62)	$	442
	For the year ended December 31, 2013:
	Operating activities:
	Net cash from operating activities	$	999	$	437	$	776	$	231	$	(1,180)	$	1,263
	Investing activities:
	Business acquisitions, net of cash acquired		—		(62)		—		—		—		(62)
	Investments in L-3 Communications		(149)		—		—		—		149		—
	Other investing activities		—		(88)		(89)		(22)		—		(199)
	Net cash used in investing activities		(149)		(150)		(89)		(22)		149		(261)
	Financing activities:
	Common stock repurchased		(800)		—		—		—		—		(800)
	Dividends paid on L-3 Holdings’ common stock		(199)		—		—		—		—		(199)
	Dividends paid to L-3 Holdings		—		(999)		—		—		999		—
	Investments from L-3 Holdings		—		149		—		—		(149)		—
	Other financing activities		149		575		(687)		(188)		301		150
	Net cash used in financing activities		(850)		(275)		(687)		(188)		1,151		(849)
	Effect of foreign currency exchange rate changes on cash		—		—		—		(2)		—		(2)
	Net increase in cash		—		12		—		19		120		151
	Cash and cash equivalents, beginning of the year		—		246		—		242		(139)		349
	Cash and cash equivalents, end of the year	$	—	$	258	$	—	$	261	$	(19)	$	500
		L-3		L-3		Guarantor		Non-		Eliminations		Consolidated
		Holdings		Communications		Subsidiaries		Guarantor				L-3
		(Parent)						Subsidiaries
		(in millions)
	For the year ended December 31, 2012:
	Operating activities:
	Net cash from operating activities from continuing operations	$	1,067	$	252	$	858	$	265	$	(1,211)	$	1,231
	Investing activities:
	Business acquisitions, net of cash acquired		—		(348)		—		—		—		(348)
	Investments in L-3 Communications		(42)		—		—		—		42		—
	Other investing activities		—		225		(59)		(18)		—		148
	Net cash used in investing activities from continuing operations		(42)		(123)		(59)		(18)		42		(200)
	Financing activities:
	Redemption of senior subordinated notes		—		(500)		—		—		—		(500)
	Common stock repurchased		(872)		—		—		—		—		(872)
	Dividends paid on L-3 Holdings’ common stock		(195)		—		—		—		—		(195)
	Dividends paid to L-3 Holdings		—		(1,067)		—		—		1,067		—
Investments from L-3 Holdings		—		42		—		—		(42)		—
Other financing activities		42		924		(799)		(234)		107		40
Net cash used in financing activities from continuing operations		(1,025)		(601)		(799)		(234)		1,132		(1,527)
Effect of foreign currency exchange rate changes on cash		—		—		—		7		—		7
Net increase in cash and cash equivalents of discontinued operations		—		74		—		—		—		74
Net (decrease) increase in cash		—		(398)		—		20		(37)		(415)
Cash and cash equivalents, beginning of the year		—		644		—		222		(102)		764
Cash and cash equivalents, end of the year	$	—	$	246	$	—	$	242	$	(139)	$	349

Description_of_Business_Additi

Description of Business - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014
	Segment
Disclosure Description Of Business Additional Information [Abstract]
Number of reportable segments	4

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Percentage of sales accounted for under contract accounting standards	0.46%
Percentage of fixed-price type contracts	40.00%
Percentage of cost-plus type contracts	6.00%
Increase in operating income due to changes in contract estimates	$66,000,000	$114,000,000	$72,000,000
Percentage of increase in operating income due to changes in contract estimates	6.00%	9.00%	6.00%
Period of performance for contracts accounted for under the percentage-of-completion method of accounting, minimum	1 year
Goodwill impairment charges	$0	$0	$0
Minimum [Member] | Buildings and Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful life	10 years
Minimum [Member] | Machinery, Equipment, Furniture and Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful life	3 years
Maximum [Member] | Buildings and Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful life	40 years
Maximum [Member] | Machinery, Equipment, Furniture and Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, estimated useful life	10 years
CODES Due 2035 [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest rate on debt instruments	3.00%
Debt instruments, maturity year	2035

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Changes in Company's Accrued Product Warranty Costs (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accrued product warranty costs:
Balance at January 1	$99	$99
Acquisitions during this period		2
Accruals for product warranties issued during the period	71	71
Changes to accruals for product warranties existing before January 1	1	3
Foreign currency translation adjustments	-2
Settlements made during the period	-67	-76
Liabilities held for sale	-9
Balance at December 31	$93	$99

Acquisitions_and_Divestitures_1

Acquisitions and Divestitures - Additional Information (Detail)

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

3 Months Ended

12 Months Ended

0 Months Ended

Jul. 17, 2012

Dec. 31, 2014

Dec. 31, 2012

Dec. 31, 2013

Dec. 16, 2014

Jul. 26, 2013

Jul. 26, 2013

Jun. 27, 2014

Dec. 19, 2013

Dec. 31, 2012

Dec. 31, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 27, 2013

Mar. 04, 2014

Dec. 31, 2014

Dec. 31, 2014

Jan. 21, 2015

Jan. 21, 2015

USD ($)

USD ($)

USD ($)

USD ($)

L-3 MSI [Member]

6 3/8% Senior Subordinated Notes Due October 15, 2015 [Member]

6 3/8% Senior Subordinated Notes Due October 15, 2015 [Member]

2013 Business Acquisition [Member]

2013 Business Acquisition [Member]

2012 Business Acquisitions [Member]

Link U.K. [Member]

Link U.K. [Member]

Link U.K. [Member]

Link U.K. [Member]

2014 Business Acquisition [Member]

Kollmorgen Electro-Optical [Member]

MAVCO, Inc. [Member]

Miteq, Inc. [Member]

Miteq, Inc. [Member]

EUR (€)

USD ($)

USD ($)

USD ($)

USD ($)

Adjustments to Preliminary Valuations Adjustments [Member]

Adjustments to Preliminary Valuations Adjustments [Member]

Adjustments to Preliminary Valuations Adjustments [Member]

USD ($)

Subsequent Event [Member]

Subsequent Event [Member]

Business

USD ($)

USD ($)

USD ($)

USD ($)

Business Acquisition [Line Items]

Aggregate purchase price of acquisition

$54,000,000

$349,000,000

$57,000,000

$41,000,000

Amount of goodwill recognized

7,501,000,000

7,776,000,000

7,796,000,000

41,000,000

278,000,000

32,000,000

39,000,000

Goodwill deductible for income tax purposes

41,000,000

182,000,000

39,000,000

Number of businesses acquired

3

Acquisition date

6-Aug-12

6-Feb-12

13-Apr-12

21-Jan-15

Other liabilities

17,000,000

Contracts in process

16,000,000

Foreign currency translation adjustments

4,000,000

Net working capital adjustment

6,000,000

Sell of business, base purchase price

285,000,000

Estimated reduction of employee pension-related liabilities

60,000,000

Spin-off date

17-Jul-12

Net cash distribution in connection with spin-off

335,000,000

Redemption of 6 3/8% Senior Subordinated Notes due 2015

250,000,000

Interest rate on Senior Notes

6.38%

Distribution Agreement date

16-Jul-12

Transaction expenses in connection with the spin-off, before income taxes

19,000,000

Transaction expenses in connection with the spin-off, after income taxes

14,000,000

Interest expense for debt

$14,000,000

Acquisitions_and_Divestitures_2

Acquisitions and Divestitures - Schedule of Major Classes of Assets and Liabilities Included as Held For Sale (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Assets
Total current assets	$547
Total assets classified as held for sale	547
Liabilities
Total current liabilities	237
L-3 MSI [Member]
Assets
Cash and cash equivalents	61
Billed receivables, net of allowance of $6	77
Contracts in process	70
Inventories	70
Other current assets	10
Total current assets	288
Goodwill	231
Other assets	28
Total assets classified as held for sale	547
Liabilities
Accounts payable, trade	31
Accrued employment costs	22
Accrued expenses	33
Advance payments and billings in excess of costs incurred	55
Other current liabilities	21
Total current liabilities	162
Pension and postretirement benefits	56
Other liabilities	19
Total liabilities classified as held for sale	$237

Acquisitions_and_Divestitures_3

Acquisitions and Divestitures - Schedule of Major Classes of Assets and Liabilities Included as Held For Sale (Parenthetical) (Detail) (L-3 MSI [Member], USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
L-3 MSI [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Billed receivables, allowance	$6

Acquisitions_and_Divestitures_4

Acquisitions and Divestitures - Statement of Operations Data Classified as Discontinued Operations (Detail) (USD $)	12 Months Ended	6 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2012	Jul. 17, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Interest expense allocated to discontinued operations	($14)
Income from discontinued operations, net of income tax	32
Net income from discontinued operations attributable to L-3	28
Engility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Product and service revenues		911
Operating income from discontinued operations before income tax		68
Interest expense allocated to discontinued operations		-14
Income from discontinued operations before income tax		54
Income tax expense		-22
Income from discontinued operations, net of income tax		32
Net income from discontinued operations attributable to noncontrolling interests		-4
Net income from discontinued operations attributable to L-3		$28

Acquisitions_and_Divestitures_5

Acquisitions and Divestitures - Unaudited Pro Forma Statements of Operations Data (Detail) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Combinations [Abstract]
Pro forma net sales	$12,131	$12,701	$13,276
Pro forma income from continuing operations	676	760	764
Pro forma net income attributable to L-3	$663	$751	$786
Pro forma diluted earnings per share from continuing operations	$7.55	$8.24	$7.76
Pro forma diluted earnings per share	$7.55	$8.24	$8.05

Contracts_in_Process_Component

Contracts in Process - Components of Contracts in Process (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Components of contracts in process
Unbilled contract receivables, gross	$2,280	$2,493
Unliquidated progress payments	-887	-1,008
Unbilled contract receivables, net	1,393	1,485
Inventoried contract costs, gross	997	1,037
Unliquidated progress payments	-95	-80
Inventoried contract costs, net	902	957
Total contracts in process	$2,295	$2,442

Contracts_in_Process_Additiona

Contracts in Process - Additional Information (Detail)	Dec. 31, 2014
Contractors [Abstract]
Percentage of unbilled contract receivables, net billed and collected within one year	97.00%
Percentage of incurred costs billed, minimum	75.00%
Percentage of incurred costs billed, maximum	80.00%

Contracts_in_Process_General_a

Contracts in Process - General and Administrative, Independent Research and Development and Bids and Proposal Costs (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Inventory Disclosure [Abstract]
Amounts included in inventoried contract costs at beginning of the year	$138	$110	$91
IRAD and B&P costs incurred	280	294	334
Other G&A costs incurred	850	876	876
Total contract costs incurred	1,130	1,170	1,210
Amounts charged to cost of sales	-1,130	-1,142	-1,191
Amounts included in inventoried contract costs at end of the year	$138	$138	$110

Contracts_in_Process_Selling_G

Contracts in Process - Selling, General and Administrative Expenses and Research and Development Expenses (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Inventory Disclosure [Abstract]
Selling, general and administrative expenses	$295	$310	$322
Research and development expenses	67	76	90
Total	$362	$386	$412

Inventories_Inventories_at_Low

Inventories - Inventories at Lower of Cost or Market (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]
Raw materials, components and sub-assemblies	$127	$164
Work in process	97	124
Finished goods	64	78
Total	$288	$366

Goodwill_and_Identifiable_Inta2

Goodwill and Identifiable Intangible Assets - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	Employees
Goodwill [Line Items]
Approximate number of employees	45,000
Accumulated goodwill impairment losses	$58	$58
Electronic Systems [Member]
Goodwill [Line Items]
Accumulated goodwill impairment losses	43	43
Communication Systems [Member]
Goodwill [Line Items]
Accumulated goodwill impairment losses	$15	$15

Goodwill_and_Identifiable_Inta3

Goodwill and Identifiable Intangible Assets - Changes in Goodwill by Segment (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Balance, Beginning	$7,796	$7,776
Business acquisitions	36	44
Business disposition	-1	-2
Foreign currency translation adjustments	-99	-22
Assets held for sale	-231
Balance, Ending	7,501	7,796
Electronic Systems [Member]
Goodwill [Line Items]
Balance, Beginning	4,085	4,046
Business acquisitions	-3	44
Business disposition	-1	-2
Foreign currency translation adjustments	-77	-3
Assets held for sale	-231
Balance, Ending	3,773	4,085
Aerospace Systems [Member]
Goodwill [Line Items]
Balance, Beginning	1,751	1,770
Business acquisitions
Business disposition
Foreign currency translation adjustments	-21	-19
Assets held for sale
Balance, Ending	1,730	1,751
Communication Systems [Member]
Goodwill [Line Items]
Balance, Beginning	992	992
Business acquisitions
Business disposition
Foreign currency translation adjustments
Assets held for sale
Balance, Ending	992	992
NSS [Member]
Goodwill [Line Items]
Balance, Beginning	968	968
Business acquisitions	39
Business disposition
Foreign currency translation adjustments	-1
Assets held for sale
Balance, Ending	$1,006	$968

Goodwill_and_Identifiable_Inta4

Goodwill and Identifiable Intangible Assets - Identifiable Intangible Assets (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	18 years
Gross Carrying Amount	$632	$661
Accumulated Amortization	389	376
Net Carrying Amount	243	285
Customer Contractual Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	20 years
Gross Carrying Amount	440	466
Accumulated Amortization	262	253
Net Carrying Amount	178	213
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	11 years
Gross Carrying Amount	165	168
Accumulated Amortization	111	108
Net Carrying Amount	54	60
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (in years)	18 years
Gross Carrying Amount	27	27
Accumulated Amortization	16	15
Net Carrying Amount	$11	$12

Goodwill_and_Identifiable_Inta5

Goodwill and Identifiable Intangible Assets - Identifiable Intangible Assets (Parenthetical) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount reclassified to assets held for sale	$632	$661
Customer Contractual Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount reclassified to assets held for sale	440	466
Customer Contractual Relationships [Member] | L-3 MSI [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount reclassified to assets held for sale	28
Reduction in accumulated amortization	20
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount reclassified to assets held for sale	165	168
Technology [Member] | L-3 MSI [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount reclassified to assets held for sale	7
Reduction in accumulated amortization	$6

Goodwill_and_Identifiable_Inta6

Goodwill and Identifiable Intangible Assets - Amortization Expense (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$43	$39	$47

Goodwill_and_Identifiable_Inta7

Goodwill and Identifiable Intangible Assets - Estimated Amortization Expense (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
Estimated amortization expense, 2015	$37
Estimated amortization expense, 2016	33
Estimated amortization expense, 2017	29
Estimated amortization expense, 2018	25
Estimated amortization expense, 2019	$22

Other_Current_Liabilities_and_2

Other Current Liabilities and Other Liabilities - Other Current Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Current Liabilities:
Accruals for pending and threatened litigation (see Note 19)	$38	$6
Estimated costs in excess of estimated contract value to complete contracts in process in a loss position	75	78
Accrued product warranty costs	59	75
Accrued interest	46	52
Deferred revenues	30	35
Other	150	156
Total other current liabilities	$398	$402

Other_Current_Liabilities_and_3

Other Current Liabilities and Other Liabilities - Other Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Liabilities:
Non-current income taxes payable (see Note 17)	$196	$177
Deferred compensation	43	45
Accrued workers' compensation	38	46
Accrued product warranty costs	34	24
Notes payable and capital lease obligations	1	15
Other	70	99
Total other liabilities	$382	$406

Property_Plant_and_Equipment_P

Property, Plant and Equipment - Property, Plant and Equipment (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Property, Plant and Equipment [Abstract]
Land	$62	$62
Buildings and improvements	420	405
Machinery, equipment, furniture and fixtures	1,707	1,643
Leasehold improvements	327	338
Gross property, plant and equipment	2,516	2,448
Accumulated depreciation and amortization	-1,428	-1,406
Property, plant and equipment, net	$1,088	$1,042

Debt_Components_of_LongTerm_De

Debt - Components of Long-Term Debt and Reconciliation to Carrying Amount of Long-Term Debt (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Debt Instrument [Line Items]
3% Convertible Contingent Debt Securities due 2035		$689
L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Borrowings under Amended and Restated Revolving Credit Facility
3.95% Senior Notes due 2016	500	500
1.50% Senior Notes due 2017	350
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	650
Subtotal	3,950	2,950
L-3 Communications Holdings, Inc. [Member]
Debt Instrument [Line Items]
3% Convertible Contingent Debt Securities due 2035		689
Principal amount of long-term debt	3,950	3,639
Unamortized discounts	-11	-9
Carrying amount of long-term debt	$3,939	$3,630

Debt_Components_of_LongTerm_De1

Debt - Components of Long-Term Debt and Reconciliation to Carrying Amount of Long-Term Debt (Parenthetical) (Detail) (USD $)	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Aggregate borrowings and repayments under the Credit Facility	1,367,000,000		1,367,000,000
Available borrowings under Credit Facility	1,000,000,000	1,000,000,000	1,000,000,000	1,000,000,000
3.95% Senior Notes due 2016 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.95%	3.95%	3.95%	3.95%
Debt instrument maturity period	2016	2016
1.50% Senior Notes due 2017 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	1.50%	1.50%	1.50%	1.50%
Debt instrument maturity period	2017	2017
5.20% Senior Notes due 2019 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	5.20%	5.20%	5.20%	5.20%
Debt instrument maturity period	2019	2019
4.75% Senior Notes due 2020 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	4.75%	4.75%	4.75%	4.75%
Debt instrument maturity period	2020	2020
4.95% Senior Notes due 2021 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	4.95%	4.95%	4.95%	4.95%
Debt instrument maturity period	2021	2021
3.95% Senior Notes due 2024 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.95%	3.95%	3.95%	3.95%
Debt instrument maturity period	2024	2024
CODES Due 2035 [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.00%		3.00%
CODES Due 2035 [Member] | L-3 Communications Holdings, Inc. [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.00%	3.00%	3.00%	3.00%
Debt instrument maturity period	2035	2035

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	13-May-14	Feb. 03, 2012	Feb. 02, 2011	Jul. 29, 2005
Debt Instrument [Line Items]
Total aggregate borrowings under revolving credit facility					1,000,000,000
Uncommitted incremental revolving facilities and additional term loan facilities					500,000,000
Base rate above the latest federal funds rate					0.50%
Base rate above a Eurodollar Rate					1.00%
Conversion of converted securities	-161,000,000
Ownership percentage	100.00%
Maximum consolidated senior leverage ratio under revolving credit facility covenants	4
Minimum consolidated interest coverage ratio under revolving credit facility covenants	3
Maximum consolidated interest coverage ratio under revolving credit facility covenants	3.5
Minimum aggregate amount of indebtedness, swap contracts or guarantees to trigger cross default provisions	50,000,000
Maximum days to cure defaults triggering cross default provisions	10 days
Minimum aggregate amount of senior notes accelerated to trigger cross default provisions	100,000,000
L-3 Communications Holdings, Inc. [Member]
Debt Instrument [Line Items]
Interest expense recognized	2,000,000	21,000,000	21,000,000
Ownership percentage	100.00%
Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Redemptions of debt	0	0
CODES Due 2035 [Member]
Debt Instrument [Line Items]
Sale of 3% Convertible Contingent Debt Securities by L-3 Holdings							700,000,000
Interest rate on Senior Notes	3.00%
Repurchased debt						11,000,000
Redemption price for CODES				1,000
Principal amount of CODES				1,000
Conversion of converted securities				935,000,000
Redemption date	2-Jun-14
Excess of conversion value over fair value of the debt component				161,000,000
CODES Due 2035 [Member] | L-3 Communications Holdings, Inc. [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.00%	3.00%
Remaining principal amount of convertible debt securities that have been classified as long-term debt		$689,000,000
Minimum [Member]
Debt Instrument [Line Items]
Applicable spread on base rate option					0.25%
Applicable spread on Eurodollar Rate option					1.25%
Commitment fees calculated on the daily amounts of the available unused commitments					0.15%
Letter of credit fees for performance and commercial letters of credit					0.68%
Letter of credit fees for financial letters of credit					1.25%
Maximum [Member]
Debt Instrument [Line Items]
Applicable spread on base rate option					1.00%
Applicable spread on Eurodollar Rate option					2.00%
Commitment fees calculated on the daily amounts of the available unused commitments					0.33%
Letter of credit fees for performance and commercial letters of credit					1.20%
Letter of credit fees for financial letters of credit					2.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Revolving credit facility expiration date	3-Feb-17

Debt_Information_Regarding_Out

Debt - Information Regarding Outstanding Senior Subordinated Notes (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Debt Instrument [Line Items]
Net Cash Proceeds	$996,000,000
L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Net Cash Proceeds	996,000,000
L-3 Communications Corporation [Member] | 3.95% Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Date of Issuance	22-Nov-11
Amount Issued	500,000,000
Discount	4,000,000
Net Cash Proceeds	491,000,000
Effective Interest Rate	4.11%
Redemption at Treasury Rate	0.50%
L-3 Communications Corporation [Member] | 1.50% Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Date of Issuance	28-May-14
Amount Issued	350,000,000
Discount	1,000,000
Net Cash Proceeds	347,000,000
Effective Interest Rate	1.55%
Redemption at Treasury Rate	0.10%
L-3 Communications Corporation [Member] | 5.20% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Date of Issuance	2-Oct-09
Amount Issued	1,000,000,000
Discount	4,000,000
Net Cash Proceeds	987,000,000
Effective Interest Rate	5.25%
Redemption at Treasury Rate	0.30%
L-3 Communications Corporation [Member] | 4.75% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Date of Issuance	21-May-10
Amount Issued	800,000,000
Discount	3,000,000
Net Cash Proceeds	790,000,000
Effective Interest Rate	4.79%
Redemption at Treasury Rate	0.25%
L-3 Communications Corporation [Member] | 4.95% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Date of Issuance	7-Feb-11
Amount Issued	650,000,000
Discount	4,000,000
Net Cash Proceeds	639,000,000
Effective Interest Rate	5.02%
Redemption at Treasury Rate	0.25%
L-3 Communications Corporation [Member] | 3.95% Senior Notes due 2024 [Member]
Debt Instrument [Line Items]
Date of Issuance	28-May-14
Amount Issued	650,000,000
Discount	3,000,000
Net Cash Proceeds	$641,000,000
Effective Interest Rate	4.02%
Redemption at Treasury Rate	0.20%

Debt_Information_Regarding_Out1

Debt - Information Regarding Outstanding Senior Subordinated Notes (Parenthetical) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Net cash proceeds from senior unsecured notes	988
L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Redemption price as percentage of principal amount	100.00%
Senior notes redemption price	101.00%
3.95% Senior Notes due 2016 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.95%	3.95%
Senior Notes due	15-Nov-16
1.50% Senior Notes due 2017 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	1.50%	1.50%
Senior Notes due	28-May-17
5.20% Senior Notes due 2019 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	5.20%	5.20%
Senior Notes due	15-Oct-19
4.75% Senior Notes due 2020 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	4.75%	4.75%
Senior Notes due	15-Jul-20
4.95% Senior Notes due 2021 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	4.95%	4.95%
Senior Notes due	15-Feb-21
3.95% Senior Notes due 2024 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Interest rate on Senior Notes	3.95%	3.95%
Senior Notes due	28-May-24
Minimum [Member] | 3.95% Senior Notes due 2024 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Senior Notes due	28-Feb-24

Debt_Redemptions_of_Senior_Sub

Debt - Redemptions of Senior Subordinated Notes (Detail) (USD $)	0 Months Ended	12 Months Ended
	Jul. 26, 2012	Dec. 31, 2014	Dec. 31, 2012
Debt Instrument [Line Items]
Debt Retirement Charge			($13,000,000)
L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Debt Retirement Charge			-13,000,000
Redemption Price % of Principal		101.00%
L-3 Communications Corporation [Member] | 6 3/8% Senior Subordinated Notes due October 15, 2015 [Member]
Debt Instrument [Line Items]
Redemption Date		15-Oct-12
Principal Amount Redeemed			250,000,000
Debt Retirement Charge			5,000,000
Redemption Price % of Principal			101.06%
L-3 Communications Corporation [Member] | 6 3/8% Senior Subordinated Notes Due October 15, 2015 [Member]
Debt Instrument [Line Items]
Redemption Date		26-Jul-12
Principal Amount Redeemed	250,000,000		250,000,000
Debt Retirement Charge			$8,000,000
Redemption Price % of Principal			102.13%

Debt_Redemptions_of_Senior_Sub1

Debt - Redemptions of Senior Subordinated Notes (Parenthetical) (Detail) (USD $)	0 Months Ended		12 Months Ended
	Jul. 17, 2012	Jul. 26, 2012	Dec. 31, 2012
Debt Instrument [Line Items]
Net cash distribution in connection with spin-off	$335,000,000
L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Net cash distribution in connection with spin-off	335,000,000
6 3/8% Senior Subordinated Notes Due October 15, 2015 [Member] | L-3 Communications Corporation [Member]
Debt Instrument [Line Items]
Redemption of 6 3/8% Senior Subordinated Notes due 2015		$250,000,000	$250,000,000
Interest rate on Senior Notes		6.38%

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive (Loss) Income (AOCI) - Summary of Amounts Reclassified from AOCI into Net Income (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	($110)	($550)	($454)
Other comprehensive (loss) income before reclassifications, net of tax	-490	388
Amounts reclassified from AOCI, net of tax	16	52
Net current period other comprehensive (loss) income	-474	440	-96
Ending Balance	-584	-110	-550
Cost of sales-products	6,219	6,409	6,782
Income from continuing operations before income taxes	925	1,055	1,122
Provision for income taxes	-248	-295	-360
Income from continuing operations	677	760	762
Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations	-16	-52
Foreign Currency Translation [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	142	167	133
Other comprehensive (loss) income before reclassifications, net of tax	-123	-25	34
Amounts reclassified from AOCI, net of tax
Net current period other comprehensive (loss) income	-123	-25	34
Ending Balance	19	142	167
Unrealized Gains (Losses) on Hedging Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	1	3
Other comprehensive (loss) income before reclassifications, net of tax	-13	-1
Amounts reclassified from AOCI, net of tax	7	-1
Net current period other comprehensive (loss) income	-6	-2	3
Ending Balance	-5	1	3
Unrealized Gains (Losses) on Hedging Instruments [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Cost of sales-products	-8	1
Income from continuing operations before income taxes	-8	1
Provision for income taxes	1
Income from continuing operations	-7	1
Unrecognized (Losses) Gains and Prior Service Cost, Net [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	-253	-720	-587
Other comprehensive (loss) income before reclassifications, net of tax	-354	414	-175
Amounts reclassified from AOCI, net of tax	9	53	42
Net current period other comprehensive (loss) income	-345	467	-133
Ending Balance	-598	-253	-720
Amortization of Defined Benefit Pension Items [Member] | Amount Reclassified from AOCI [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net loss	-15	-83	-68
Income from continuing operations before income taxes	-15	-83	-68
Provision for income taxes	6	30	26
Income from continuing operations	($9)	($53)	($42)

Equity_Additional_Information_

Equity - Additional Information (Detail) (USD $)	12 Months Ended			2 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 20, 2015	Feb. 05, 2013	Dec. 04, 2014
Class of Stock [Line Items]
Aggregate amount of repurchased shares	$823,000,000	$800,000,000	$872,000,000
Common Stock [Member]
Class of Stock [Line Items]
Number of common shares repurchased	6,900,000	8,700,000	12,100,000
February 5, 2013 Share Repurchase Program [Member]
Class of Stock [Line Items]
Amount of shares authorized to be repurchased					1,500,000,000
Average price per share of repurchased shares	$119.42
Aggregate amount of repurchased shares	823,000,000
Remaining value under share repurchase program	45,000,000
February 5, 2013 Share Repurchase Program [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Average price per share of repurchased shares				$126.99
Aggregate amount of repurchased shares				78,000,000
February 5, 2013 Share Repurchase Program [Member] | Common Stock [Member]
Class of Stock [Line Items]
Number of common shares repurchased	6,900,000
February 5, 2013 Share Repurchase Program [Member] | Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Number of common shares repurchased				613,789
December 4, 2014 Share Repurchase Program [Member]
Class of Stock [Line Items]
Amount of shares authorized to be repurchased						1,500,000,000
Remaining value under share repurchase program	$1,500,000,000

Equity_Remaining_Value_of_Auth

Equity - Remaining Value of Authorization under Share Repurchase Programs (Detail) (USD $)	12 Months Ended			2 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 20, 2015
Equity, Class of Treasury Stock [Line Items]
Share repurchases from January 1, 2015 to February 20, 2015	($823)	($800)	($872)
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Remaining authorization at February 20, 2015	1,545
February 5, 2013 Share Repurchase Program [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Share repurchases from January 1, 2015 to February 20, 2015				-45
December 4, 2014 Share Repurchase Program [Member] | Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Share repurchases from January 1, 2015 to February 20, 2015				-33
Remaining authorization at February 20, 2015				$1,467

Fair_Value_Measurements_Compan

Fair Value Measurements - Company's Assets and Liabilities at Fair Value on Recurring Basis (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Level 1 [Member]
Assets
Cash equivalents	$416	$299
Derivatives (foreign currency forward contracts)
Total assets	416	299
Liabilities
Derivatives (foreign currency forward contracts)
Level 2 [Member]
Assets
Cash equivalents
Derivatives (foreign currency forward contracts)	5	6
Total assets	5	6
Liabilities
Derivatives (foreign currency forward contracts)	11	5
Level 3 [Member]
Assets
Cash equivalents
Derivatives (foreign currency forward contracts)
Total assets
Liabilities
Derivatives (foreign currency forward contracts)

Financial_Instruments_Carrying

Financial Instruments - Carrying Amounts and Estimated Fair Values of Company's Long-Term Debt and Foreign Currency Forward Contracts (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, Carrying Amount	$3,939	$2,941
CODES, Carrying Amount		689
Senior Notes, Estimated Fair Value	4,178	3,121
CODES, Estimated Fair Value		830
Estimated Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign currency forward contracts, liability	-6
Foreign currency forward contracts, asset		1
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Foreign currency forward contracts, liability	-6
Foreign currency forward contracts, asset		$1

Derivative_Financial_Instrumen2

Derivative Financial Instruments - Notional Amounts of Company's Outstanding Foreign Currency Forward Contracts by Currency (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	$280
Canadian Dollar [Member]
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	123
U.S. Dollar [Member]
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	101
Euro [Member]
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	47
British Pound [Member]
Derivative [Line Items]
Notional amounts of foreign currency forward contracts	$9

Derivative_Financial_Instrumen3

Derivative Financial Instruments - Location of the Company's Derivative Instruments Recorded at Fair Value on the Consolidated Balance Sheets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities	$10	$3
Other Current Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities	10	3
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities	1	2
Other Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, liabilities	1	2
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets	4	5
Other Current Assets [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets	4	5
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets	1	1
Other Assets [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Total derivative instruments, assets	$1	$1

Derivative_Financial_Instrumen4

Derivative Financial Instruments - Location of the Company's Derivative Instruments Recorded at Fair Value on the Consolidated Balance Sheets (Parenthetical) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities held for sale	$10	$3
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets held for sale	4	5
Designated as Hedging Instruments [Member] | Assets Held for Sale [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities held for sale	2
Designated as Hedging Instruments [Member] | Assets Held for Sale [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets held for sale	$2

Derivative_Financial_Instrumen5

Derivative Financial Instruments - Additional Information (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Estimated net amount of existing losses expected to be reclassified into income within the next 12 months	$4

L3_Holdings_Earnings_Per_Share2

L-3 Holdings' Earnings Per Share - Reconciliation of Basic and Diluted Earnings per Share (EPS) (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of net income:
Net income	$207	$157	$141	$172	$188	$204	$176	$192	$677	$760	$794
Net income from continuing operations attributable to noncontrolling interests									-13	-9	-6
Net income from discontinued operations attributable to noncontrolling interests											-4
Net income attributable to L-3 Holdings common shareholders									664	751	784
Earnings attributable to L-3 Holdings' common shareholders:
Continuing operations									664	751	756
Discontinued operations, net of income tax											28
Net income attributable to L-3 Holdings common shareholders									$664	$751	$784
Basic:
Weighted average common shares outstanding									85.4	89.4	96.3
Basic earnings per share attributable to L-3 Holdings' common shareholders:
Continuing operations									$7.78	$8.40	$7.85
Discontinued operations, net of income tax											$0.29
Basic earnings per share	$2.41	$1.81	$1.59	$1.97	$2.10	$2.23	$1.95	$2.12	$7.78	$8.40	$8.14
Common and potential common shares:
Weighted average common shares outstanding									85.4	89.4	96.3
Assumed purchase of common shares for treasury									-3.1	-4.5	-3
Assumed conversion of the CODES									0.8	0.2
Common and potential common shares									87.8	91.1	97.6
Diluted earnings per share attributable to L-3 Holdings' common shareholders:
Continuing operations									$7.56	$8.24	$7.74
Discontinued operations, net of income tax											$0.29
Diluted earnings per share	$2.36	$1.78	$1.53	$1.90	$2.04	$2.19	$1.92	$2.09	$7.56	$8.24	$8.03
Stock Options [Member]
Common and potential common shares:
Common and potential common shares									3	3.9	1.9
Unvested Restricted Stock Awards [Member]
Common and potential common shares:
Common and potential common shares									1.6	1.8	2
Employee Stock Purchase Plan Contributions [Member]
Common and potential common shares:
Common and potential common shares										0.2	0.3
Performance Unit Awards [Member]
Common and potential common shares:
Common and potential common shares									0.1	0.1	0.1

L3_Holdings_Earnings_Per_Share3

L-3 Holdings' Earnings Per Share - Reconciliation of Basic and Diluted Earnings per Share (EPS) (Parenthetical) (Detail) (USD $)	Jun. 27, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Conversion price of L-3 Holdings' CODES	$88.71	$90.24	$91.21

L3_Holdings_Earnings_Per_Share4

L-3 Holdings' Earnings Per Share - Additional Information (Detail)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Shares excluded from computation of diluted earnings per share and employee stock purchase plan contributions	0.5	0.9	3.2

Income_Taxes_Income_from_Conti

Income Taxes - Income from Continuing Operations Before Income Taxes (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Domestic	$760	$858	$892
Foreign	165	197	230
Income from continuing operations before income taxes	$925	$1,055	$1,122

Income_Taxes_Components_of_Cur

Income Taxes - Components of Current and Deferred Portions of Provision for Income Taxes on Continuing Operations (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current income tax provision:
Federal	$87	$181	$198
State and local	4	34	21
Foreign	36	38	44
Subtotal	127	253	263
Deferred income tax provision:
Federal	107	35	80
State and local	13		8
Foreign	1	7	9
Subtotal	121	42	97
Total provision for income taxes	$248	$295	$360

Income_Taxes_Reconciliation_of

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate to Effective Income Tax Rate on Continuing Operations (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	35.00%	35.00%	35.00%
State and local income taxes, net of federal income tax benefit	2.30%	2.10%	1.70%
Foreign income taxes	-3.40%	-1.60%	-2.00%
Manufacturing benefits	-1.70%	-1.90%	-1.80%
Research and experimentation and other tax credits	-4.10%	-3.60%	-0.50%
Resolution of tax contingencies	-0.90%	-1.00%	-0.90%
Other, net	-0.40%	-1.00%	0.60%
Effective income tax rate on continuing operations	26.80%	28.00%	32.10%

Income_Taxes_Components_of_Net

Income Taxes - Components of Net Deferred Tax Assets and Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Deferred tax assets:
Inventoried costs	$86	$72
Compensation and benefits	152	164
Pension and postretirement benefits	402	207
Loss carryforwards	15	24
Tax credit carryforwards	10	7
Other	84	75
Gross deferred tax assets	749	549
Less: valuation allowance	-9	-22
Net deferred tax assets	740	527
Deferred tax liabilities:
Goodwill and other intangible assets	792	726
Income recognition on contracts in process	78	58
Property, plant and equipment	98	85
Long-term debt-CODES		81
Other	88	65
Gross deferred tax liabilities	1,056	1,015
Total net deferred tax liabilities	($316)	($488)

Income_Taxes_Classification_of

Income Taxes - Classification of Deferred Tax Assets and Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Income Tax Disclosure [Abstract]
Current deferred tax assets	$127	$147
Non-current deferred tax liabilities	-443	-635
Total net deferred tax liabilities	($316)	($488)

Income_Taxes_Summary_of_Loss_a

Income Taxes - Summary of Loss and Tax Credit Carryforwards (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary Of Losses And Tax Credit Carryforwards [Line Items]
Total loss carryforwards, Tax Effected	$15
Capital loss carryforwards, Tax Effected	15	24
Capital loss carryforwards, Valuation Allowance, Tax Effected	9	22
Tax credit carryforwards, Tax Effected	10
Federal [Member]
Summary Of Losses And Tax Credit Carryforwards [Line Items]
Net operating loss carryforwards, Gross	5
Capital loss carryforwards, Tax Effected	2
Capital loss carryforwards, Valuation Allowance, Gross	5
Capital loss carryforwards, Valuation Allowance, Tax Effected	2
Net operating loss carryforwards, Expiration Period, Start	2026
Net operating loss carryforwards, Expiration Period, End	2030
Foreign [Member]
Summary Of Losses And Tax Credit Carryforwards [Line Items]
Net operating loss carryforwards, Gross	7
Capital loss carryforwards, Tax Effected	2
Capital loss carryforwards, Valuation Allowance, Gross	2
Capital loss carryforwards, Valuation Allowance, Tax Effected	1
Tax credit carryforwards, Gross	3
Tax credit carryforwards, Tax Effected	3
State [Member]
Summary Of Losses And Tax Credit Carryforwards [Line Items]
Net operating loss carryforwards, Gross	94
Capital loss carryforwards, Tax Effected	2
Capital loss carryforwards, Valuation Allowance, Gross	48
Capital loss carryforwards, Valuation Allowance, Tax Effected	1
Net operating loss carryforwards, Expiration Period, Start	2016
Net operating loss carryforwards, Expiration Period, End	2033
Tax credit carryforwards, Gross	11
Tax credit carryforwards, Tax Effected	7
Tax credit carryforwards, Expiration Periods, Start	2016
Tax credit carryforwards, Expiration Periods, End	2033
Capital Loss Carryforward [Member]
Summary Of Losses And Tax Credit Carryforwards [Line Items]
Net operating loss carryforwards, Gross	25
Capital loss carryforwards, Tax Effected	9
Capital loss carryforwards, Valuation Allowance, Gross	14
Capital loss carryforwards, Valuation Allowance, Tax Effected	$5
Net operating loss carryforwards, Expiration Period, Start	2016
Net operating loss carryforwards, Expiration Period, End	2017

Income_Taxes_Summary_of_Loss_a1

Income Taxes - Summary of Loss and Tax Credit Carryforwards (Parenthetical) (Detail) (Capital Loss Carryforward [Member], USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Capital Loss Carryforward [Member]
Summary Of Losses And Tax Credit Carryforwards [Line Items]
Reduction in valuation allowance for capital loss carryforwards	$4

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$180	$138	$169	$150
Unrecognized tax benefits that would reduce the effective income tax rate	114
Anticipated decrease in unrecognized tax benefit over the next 12 months	20
Change in previously accrued income tax expenses related to tax returns	8	10	10
Accrued potential interest included with in current and non-current income taxes payable	15		11
Accrued potential interest included with in current and non-current income taxes payable after income taxes	9		7
Potential penalties	9		8
Expense (benefit) for interest related items included in income taxes expenses	2	-2
Undistributed earnings of non-U.S. Companies	$331

Income_Taxes_Reconciliation_of1

Income Taxes - Reconciliation of Change in Unrecognized Income Tax Benefits, Excluding Interest and Penalties (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Balance at January 1	$169	$138	$150
Additions for tax positions related to the current year	20	18	8
Additions for tax positions related to prior years	13	41	9
Reductions for tax positions related to prior years	-15	-8	-13
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	-6	-20	-15
Balance at December 31	$180	$169	$138

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 31, 2014	Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of L-3 Holdings common stock available to be awarded	3.69	2.6
Weighted average grant date fair value	$113.58
Total performance units earned	87,309
Employee discount on the purchase of common stock	5.00%
Stock Options [Member]
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	$20.02	$12.09	$11.32
Intrinsic value of stock options exercised	$43,000,000	$32,000,000	$7,000,000
Unrecognized compensation costs related to equity awards after income taxes	10,000,000
Unrecognized compensation costs related to stock awards	6,000,000
Weighted average remaining period for recognition of unrecognized costs related to equity awards	1 year 2 months 12 days
Actual income tax benefit realized related to compensation deductions arising from the exercise of stock options	14,000,000	10,000,000	2,000,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Unrecognized compensation costs related to equity awards after income taxes	25,000,000
Unrecognized compensation costs related to stock awards	40,000,000
Weighted average remaining period for recognition of unrecognized costs related to equity awards	1 year 1 month 6 days
Vesting period of units granted for non-employee directors	1 year
Weighted average grant date fair value	$113.58	$77.12	$70.42
Length of service after grant date	1 year
Age of retirement eligible employees	65 years
Length of service for retirement eligible employees, minimum	At least five years
Fair value of restricted stock unit awards vested	66,000,000	37,000,000	44,000,000
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to equity awards after income taxes	3,000,000
Unrecognized compensation costs related to stock awards	5,000,000
Weighted average remaining period for recognition of unrecognized costs related to equity awards	1 year 8 months 12 days
Weighted average grant date fair value	$113.67	$77	$70.43
Length of service after grant date	3 years	3 years	3 years
Minimum payout range	0.00%
Maximum payout range	200.00%
Fair market value of total performance units earned as of their vesting date	11,000,000
2009 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares authorized for issuance under the amendment	4,300,000
Percentage of fair market value for offering period	95.00%
Term of plans	Eligible employees are offered options to purchase shares of L-3 Holdings' 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.
Offering period to purchase shares	6 months
Share purchases funded through payroll deductions up to a maximum percentage	10.00%
Share purchases funded through payroll deductions up to a maximum value	$21,250
Issued shares under the ESPP, per share				200,000
Issued shares under the ESPP, value				$115.03
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, per share					100,000
Issued shares under the ESPP, value					$120.94
2008 Long Term Performance Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares authorized for issuance under the amendment	19,200,000
Maximum number of shares of L-3 Holdings common stock may be issued pursuant to "full value" awards under the amendment	6,000,000

StockBased_Compensation_StockB

Stock-Based Compensation - Stock-Based Compensation by Form of Award (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	$52	$58	$64
Income taxes	-20	-22	-24
Total after income taxes	32	36	40
Less: Stock based compensation recorded in discontinued operations, net of income taxes			1
Stock based compensation recorded in continuing operations, net of income taxes	32	36	39
Total after income taxes	32	36	40
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	9	10	10
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	40	41	46
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation	$3	$7	$8

StockBased_Compensation_Compan

Stock-Based Compensation - Company's Stock Option Activity and Changes (Detail) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Beginning Balance, Number of Options Outstanding	3,882,900
Options granted, Number of Options	473,000
Options exercised, Number of Options	-1,183,400
Options forfeited, Number of Options	-71,300
Ending Balance, Number of Options Outstanding	3,101,200	3,882,900
Vested and expected to vest, Number of Options	3,090,300
Exercisable, Number of Options	1,962,800
Beginning Balance, Weighted Average Exercise Price Outstanding	$77.90
Options granted, Weighted Average Exercise Price	$113.67
Options exercised, Weighted Average Exercise Price	$77.94
Options forfeited, Weighted Average Exercise Price	$91.59
Ending Balance, Weighted Average Exercise Price Outstanding	$83.02	$77.90
Vested and expected to vest, Weighted Average Exercise Price	$82.96
Exercisable, Weighted Average Exercise Price	$79.46
Weighted Average Remaining Contractual Term Outstanding	6 years 2 months 12 days	6 years 2 months 12 days
Vested and expected to vest, Weighted Average Remaining Contractual Term	6 years 2 months 12 days
Exercisable, Weighted Average Remaining Contractual Term	4 years 10 months 24 days
Beginning Balance, Aggregate Intrinsic Value Outstanding	$112
Ending Balance, Aggregate Intrinsic Value Outstanding	134	112
Vested and expected to Vest, Aggregate Intrinsic Value	134
Exercisable, Aggregate Intrinsic Value	$92

StockBased_Compensation_Weight

Stock-Based Compensation - Weighted Average Assumptions in Valuation Model (Detail) (Stock Options [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected holding period (in years)	5 years 6 months	5 years 7 months 6 days	5 years 4 months 24 days
Expected volatility	24.40%	26.40%	27.00%
Expected dividend yield	2.70%	3.60%	3.60%
Risk-free interest rate	1.70%	1.00%	1.00%

StockBased_Compensation_Compan1

Stock-Based Compensation - Company's Nonvested Restricted Stock Unit Awards and Changes (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Beginning Balance, Number of Shares	1,773,800
Granted, Number of Shares	416,700
Vested, Number of Shares	-570,800
Forfeited, Number of Shares	-102,100
Ending Balance, Number of Shares	1,517,600
Beginning Balance, Weighted Average Grant Date Fair Value	$73.51
Granted, Weighted Average Grant Date Fair Value	$113.58
Vested, Weighted Average Grant Date Fair Value	$77.07
Forfeited, Weighted Average Grant Date Fair Value	$80.36
Ending Balance, Weighted Average Grant Date Fair Value	$82.72

StockBased_Compensation_Compan2

Stock-Based Compensation - Company's Performance Unit Awards Based on Expected Performance (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	1,773,800
Granted, Number of Shares	416,700
Vested, Number of Shares	-570,800
Forfeited, Number of Shares	-102,100
Ending Balance, Number of Shares	1,517,600
Beginning Balance, Weighted Average Grant Date Fair Value	$73.51
Granted, Weighted Average Grant Date Fair Value	$113.58
Vested, Weighted Average Grant Date Fair Value	$77.07
Forfeited, Weighted Average Grant Date Fair Value	$80.36
Ending Balance, Weighted Average Grant Date Fair Value	$82.72
EPS [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Number of Shares	175,500
Granted, Number of Shares	47,500
Decrease due to expected performance, Number of Shares	-45,600
Vested, Number of Shares	-87,300
Forfeited, Number of Shares	-4,900
Ending Balance, Number of Shares	85,200
Beginning Balance, Weighted Average Grant Date Fair Value	$70.84
Granted, Weighted Average Grant Date Fair Value	$113.67
Decrease due to expected performance, Weighted Average Grant Date Fair Value	$71.78
Vested, Weighted Average Grant Date Fair Value	$67.49
Forfeited, Weighted Average Grant Date Fair Value	$89.90
Ending Balance, Weighted Average Grant Date Fair Value	$96.53

Commitments_and_Contingencies_1

Commitments and Contingencies - Future Minimum Payments under Non-Cancelable Operating Leases (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Operating Leased Assets [Line Items]
2015	$151
2016	106
2017	94
2018	81
2019	60
Thereafter	115
Total minimum payments required	607
Less: Sublease rentals under non-cancelable leases	5
Net minimum payments required	602
Real Estate Securities [Member]
Operating Leased Assets [Line Items]
2015	142
2016	100
2017	90
2018	78
2019	58
Thereafter	113
Total minimum payments required	581
Less: Sublease rentals under non-cancelable leases	5
Net minimum payments required	576
Equipment [Member]
Operating Leased Assets [Line Items]
2015	9
2016	6
2017	4
2018	3
2019	2
Thereafter	2
Total minimum payments required	26
Less: Sublease rentals under non-cancelable leases
Net minimum payments required	$26

Commitments_and_Contingencies_2

Commitments and Contingencies - Additional Information (Detail)	0 Months Ended			12 Months Ended					0 Months Ended
	Dec. 31, 2014	Sep. 28, 2012	Apr. 23, 2007	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	31-May-12	Mar. 09, 2010	Feb. 10, 2015	Jul. 23, 2014	Jul. 23, 2014
	USD ($)	Plaintiff		USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	Subsequent Event [Member]	Property Damages [Member]	Business Interruption [Member]
				Agreement					USD ($)	EUR (€)	EUR (€)
									Plaintiff
Contingencies And Commitments [Line Items]
Rent expense, net of sublease income				$140,000,000	$141,000,000	$145,000,000
Sublease rental income				4,000,000	6,000,000	5,000,000
Total outstanding letters of credit				615,000,000	634,000,000
Available borrowings under Credit Facility				1,000,000,000	1,000,000,000
Number of existing real estate lease agreements				2
Real estate lease agreements, expiry date				31-Aug-15
Purchase price of property on or before expiration date				28,000,000
Residual guarantee amount				23,000,000
Maximum amount of supplemental rent payment				5,000,000
Aggregate residual guarantee amount				23,000,000
Term for operating lease agreements (in years)				15 years
Fair market value of simulator systems, Minimum				7,000,000
Fair market value of simulator systems, Maximum				21,000,000
Additional rent to be paid for simulator systems after expiration date				7,000,000
Charges in connection with anticipated settlement				18,000,000
Receivables for recoveries from insurance contracts	11,000,000
Number of plaintiffs re-filed their complaint against ACSS			30
Compensatory damages							48,000,000	6,700,000
Number of plaintiffs released their claims against ACSS		18
Number of plaintiffs settled their claims against ACSS									12
Aggregate expenses incurred by plaintiff									11,000,000
Claims for estimated damages										€ 11,000,000	€ 35,000,000

Pensions_and_Other_Employee_Be2

Pensions and Other Employee Benefits - Changes in Benefit Obligations, Plan Assets and Funded Status and Aggregate Balance Sheet Impact (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets and (liabilities) recognized in the consolidated balance sheets consist of:
Non-current liabilities	($1,187)	($727)
Pension Plans [Member]
Change in benefit obligation:
Benefit obligation at the beginning of the year	2,973	3,222
Service cost	106	126	113
Interest cost	147	132	134
Plan participants' contributions	2	2
Amendments	1	14
Actuarial loss (gain)	579	-402
Foreign currency exchange rate changes	-34	-21
Curtailments, settlements and special termination benefits	1	3
Benefits paid	-112	-103
Benefit obligation at the end of the year	3,663	2,973	3,222
Change in plan assets:
Fair value of plan assets at the beginning of the year	2,403	2,026
Actual return on plan assets	205	394
Employer contributions	97	105
Plan participants' contributions	2	2
Foreign currency exchange rate changes	-25	-21
Benefits paid	-112	-103
Fair value of plan assets at the end of the year	2,570	2,403	2,026
Unfunded status at the end of the year	-1,093	-570
Assets and (liabilities) recognized in the consolidated balance sheets consist of:
Non-current assets	26	35
Current liabilities	-4	-8
Non-current liabilities	-1,056	-597
Liabilities held for sale	-59
Total	-1,093	-570
Postretirement Benefit Plans [Member]
Change in benefit obligation:
Benefit obligation at the beginning of the year	194	218
Service cost	3	4	4
Interest cost	8	7	10
Plan participants' contributions	4	4
Amendments	-1
Actuarial loss (gain)	5	-23
Foreign currency exchange rate changes	-2	-3
Curtailments, settlements and special termination benefits
Benefits paid	-12	-13
Benefit obligation at the end of the year	199	194	218
Change in plan assets:
Fair value of plan assets at the beginning of the year	55	47
Actual return on plan assets	6	9
Employer contributions	7	8
Plan participants' contributions	4	4
Foreign currency exchange rate changes
Benefits paid	-12	-13
Fair value of plan assets at the end of the year	60	55	47
Unfunded status at the end of the year	-139	-139
Assets and (liabilities) recognized in the consolidated balance sheets consist of:
Non-current assets
Current liabilities	-8	-9
Non-current liabilities	-131	-130
Liabilities held for sale
Total	($139)	($139)

Pensions_and_Other_Employee_Be3

Pensions and Other Employee Benefits - Changes in Benefit Obligations, Plan Assets and Funded Status and Aggregate Balance Sheet Impact (Parenthetical) (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]
Liabilities held for sale, current	$237
Liabilities held for sale, non-current	237
L-3 MSI [Member]
Defined Benefit Plan Disclosure [Line Items]
Liabilities held for sale, current	162
Pension Plans [Member] | L-3 MSI [Member]
Defined Benefit Plan Disclosure [Line Items]
Liabilities held for sale, current	3
Liabilities held for sale, non-current	$56

Pensions_and_Other_Employee_Be4

Pensions and Other Employee Benefits - Net Loss and Prior Service Cost Balances in Accumulated Other Comprehensive Loss Account (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	$968	$425
Prior service cost (credit)		1
Total amount recognized	968	426
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	-6	-9
Prior service cost (credit)	-3	-8
Total amount recognized	($9)	($17)

Pensions_and_Other_Employee_Be5

Pensions and Other Employee Benefits - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Aggregate accumulated benefit obligation (ABO)	$3,272	$2,657
Pension Plans [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to plans in 2015	100
Pension Plans [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to plans in 2015	132
U.S. Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend in 2015	7.50%
U.S. Based Pension Plans [Member] | 2020 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend	5.00%
Canadian Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend in 2015	7.00%
Canadian Based Pension Plans [Member] | 2023 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend	5.00%
Continuing Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions in L-3 Holdings' common stock and cash	135	120	126
Discontinued Operations [Member]
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions in L-3 Holdings' common stock and cash			8
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to plans in 2015	$10

Pensions_and_Other_Employee_Be6

Pensions and Other Employee Benefits - Pension Plans with an Accumulated Benefit Obligation in Excess of Fair Value of Plan Assets (Detail) (Pension Plans [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$3,467	$2,408
Accumulated benefit obligation	3,083	2,115
Fair value of plan assets	$2,349	$1,815

Pensions_and_Other_Employee_Be7

Pensions and Other Employee Benefits - Weighted Average Assumptions Used to Determine Benefit Obligations (Detail)	Dec. 31, 2014	Dec. 31, 2013
Pension Plans [Member]
Benefit obligations:
Discount rate	4.14%	5.03%
Rate of compensation increase	3.50%	3.50%
Postretirement Benefit Plans [Member]
Benefit obligations:
Discount rate	3.70%	4.43%

Pensions_and_Other_Employee_Be8

Pensions and Other Employee Benefits - Weighted Average Assumptions Used to Determine Benefit Obligations (Parenthetical) (Detail)	Dec. 31, 2014	Dec. 31, 2013
U.S. Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine benefit obligations, weighted average discount rate	4.20%	5.10%
Canadian Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine benefit obligations, weighted average discount rate	3.90%	4.70%
U.S. Based Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine benefit obligations, weighted average discount rate	3.70%	4.40%
Rate of compensation increase	3.50%	3.50%
Canadian Based Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine benefit obligations, weighted average discount rate	3.70%	4.60%
Rate of compensation increase	3.50%	3.50%
German Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine benefit obligations, weighted average discount rate	2.20%	3.50%

Pensions_and_Other_Employee_Be9

Pensions and Other Employee Benefits - Components of Net Periodic Benefit Cost (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$106	$126	$113
Interest cost	147	132	134
Expected return on plan assets	-193	-164	-145
Amortization of prior service cost (credits)	2	1	1
Amortization of net loss (gain)	17	83	69
Curtailment or settlement loss (gain)	1	3	7
Net periodic benefit cost	80	181	179
Postretirement Benefit Plans [Member]
Components of net periodic benefit cost:
Service cost	3	4	4
Interest cost	8	7	10
Expected return on plan assets	-4	-4	-3
Amortization of prior service cost (credits)	-2	-3	-3
Amortization of net loss (gain)	-2	2	1
Curtailment or settlement loss (gain)	-1		1
Net periodic benefit cost	$2	$6	$10

Recovered_Sheet1

Pensions and Other Employee Benefits - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	$560	($637)	$287
Prior service cost (credit)	1	14	-1
Amortization of net (loss) gain	-17	-83	-69
Amortization of prior service (cost) credit	-2	-1	-1
Total recognized in other comprehensive income	542	-707	216
Total recognized in net periodic benefit cost and other comprehensive income	622	-526	395
Postretirement Benefit Plans [Member]
Other changes in plan assets and benefit obligations recognized in other comprehensive income:
Net loss (gain)	5	-29	-3
Prior service cost (credit)	-1		-5
Amortization of net (loss) gain	2	-2	-1
Amortization of prior service (cost) credit	2	3	3
Total recognized in other comprehensive income	8	-28	-6
Total recognized in net periodic benefit cost and other comprehensive income	$10	($22)	$4

Recovered_Sheet2

Pensions and Other Employee Benefits - Amounts Expected to be Amortized from Accumulated Other Comprehensive Income (Loss) and Recognized as Components of Net Periodic Benefit Costs (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Net loss	$68
Prior service cost (credit)	-1
Total amount expected to be amortized	67
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss	68
Prior service cost (credit)	1
Total amount expected to be amortized	69
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss
Prior service cost (credit)	-2
Total amount expected to be amortized	($2)

Recovered_Sheet3

Pensions and Other Employee Benefits - Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	5.03%	4.15%	5.02%
Expected long-term return on plan assets	8.13%	8.13%	8.15%
Rate of compensation increase	3.50%	3.50%	4.06%
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.43%	3.37%	4.71%
Expected long-term return on plan assets	7.64%	7.64%	7.64%

Recovered_Sheet4

Pensions and Other Employee Benefits - Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
U.S. Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine net periodic benefit cost, weighted average discount rate	5.10%	4.20%	5.10%
Assumptions used to determine net periodic benefit cost, weighted average expected long-term return on plan assets	8.25%	8.25%	8.25%
Assumptions used to determine net periodic benefit cost, Rate of compensation increase	3.50%	3.50%	4.00%
Canadian Based Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine net periodic benefit cost, weighted average discount rate	4.60%	3.70%	4.30%
Assumptions used to determine net periodic benefit cost, weighted average expected long-term return on plan assets	7.25%	7.25%	7.50%
Assumptions used to determine net periodic benefit cost, Rate of compensation increase	3.50%	3.50%	4.50%
U.S. Based Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine net periodic benefit cost, weighted average discount rate	4.40%	3.30%	4.80%
Canadian Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine net periodic benefit cost, weighted average discount rate	4.70%	3.90%	4.40%
German Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumptions used to determine net periodic benefit cost, weighted average discount rate	3.50%	3.40%	5.10%

Recovered_Sheet5

Pensions and Other Employee Benefits - Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Effect of one percentage point increase on total service and interest cost
Effect of one percentage point decrease on total service and interest cost
Effect of one percentage point increase on postretirement benefit obligations	7
Effect of one percentage point decrease on postretirement benefit obligations	($6)

Recovered_Sheet6

Pensions and Other Employee Benefits - Allowable Range for Each Major Category of the Plans' Assets and Weighted-Average Asset Allocations by Asset Category (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	100.00%	100.00%
U.S. [Member] | Domestic Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	30.00%	30.00%
Percentage of plan assets, maximum range	60.00%	60.00%
Weighted-average asset allocations	52.00%	54.00%
U.S. [Member] | International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	10.00%	10.00%
Percentage of plan assets, maximum range	20.00%	20.00%
Weighted-average asset allocations	10.00%	10.00%
U.S. [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	20.00%	20.00%
Percentage of plan assets, maximum range	40.00%	40.00%
Weighted-average asset allocations	22.00%	23.00%
U.S. [Member] | Real Estate Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	0.00%	0.00%
Percentage of plan assets, maximum range	15.00%	15.00%
Weighted-average asset allocations	7.00%	6.00%
U.S. [Member] | Other Asset [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	0.00%	0.00%
Percentage of plan assets, maximum range	15.00%	15.00%
Weighted-average asset allocations	9.00%	7.00%
Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocations	100.00%	100.00%
Canada [Member] | Domestic Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	10.00%	10.00%
Percentage of plan assets, maximum range	25.00%	25.00%
Weighted-average asset allocations	15.00%	20.00%
Canada [Member] | International Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	30.00%	30.00%
Percentage of plan assets, maximum range	60.00%	60.00%
Weighted-average asset allocations	55.00%	49.00%
Canada [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	20.00%	20.00%
Percentage of plan assets, maximum range	60.00%	60.00%
Weighted-average asset allocations	20.00%	28.00%
Canada [Member] | Real Estate Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range
Percentage of plan assets, maximum range
Weighted-average asset allocations
Canada [Member] | Other Asset [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of plan assets, minimum range	0.00%	0.00%
Percentage of plan assets, maximum range	15.00%	15.00%
Weighted-average asset allocations	10.00%	3.00%

Recovered_Sheet7

Pensions and Other Employee Benefits - Fair Value of the Company's Pension Plans' and Postretirement Benefit Plans' Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Postretirement Benefit Plans Assets [Member]
Equity securities:
Fair value of company's plan assets	$60	$55
Postretirement Benefit Plans Assets [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	49	47
Postretirement Benefit Plans Assets [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	11	8
Postretirement Benefit Plans Assets [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member]
Equity securities:
Fair value of company's plan assets	36	37
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	36	37
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | International Equity [Member]
Equity securities:
Fair value of company's plan assets	4	3
Postretirement Benefit Plans Assets [Member] | International Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	1	1
Postretirement Benefit Plans Assets [Member] | International Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	3	2
Postretirement Benefit Plans Assets [Member] | International Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member]
Equity securities:
Fair value of company's plan assets	12	9
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	10	7
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	2	2
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Other Asset [Member]
Equity securities:
Fair value of company's plan assets	4	2
Postretirement Benefit Plans Assets [Member] | Other Asset [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Postretirement Benefit Plans Assets [Member] | Other Asset [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	4	2
Postretirement Benefit Plans Assets [Member] | Other Asset [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member]
Equity securities:
Fair value of company's plan assets	2,267	2,103
U.S. Based Pension Plans [Member] | U.S. Equity [Member]
Equity securities:
Fair value of company's plan assets	1,172	1,144
U.S. Based Pension Plans [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	1,172	1,144
U.S. Based Pension Plans [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | International Equity [Member]
Equity securities:
Fair value of company's plan assets	227	225
U.S. Based Pension Plans [Member] | International Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	87	79
U.S. Based Pension Plans [Member] | International Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	140	146
U.S. Based Pension Plans [Member] | International Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member]
Equity securities:
Fair value of company's plan assets	394	366
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	237	217
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	157	149
U.S. Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member]
Equity securities:
Fair value of company's plan assets	120	111
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	120	111
U.S. Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member]
Equity securities:
Fair value of company's plan assets	159	118
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	159	118
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Other Asset [Member]
Equity securities:
Fair value of company's plan assets	208	150
U.S. Based Pension Plans [Member] | Other Asset [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Other Asset [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	208	150
U.S. Based Pension Plans [Member] | Other Asset [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member]
Equity securities:
Fair value of company's plan assets	2,280	2,114
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	1,655	1,558
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	625	556
U.S. Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
U.S. Based Pension Plans [Member] | Liabilities for Unsettled Trades, Net [Member]
Equity securities:
Fair value of company's plan assets	-13	-11
Canadian Based Pension Plans [Member]
Equity securities:
Fair value of company's plan assets	303	300
Canadian Based Pension Plans [Member] | U.S. Equity [Member]
Equity securities:
Fair value of company's plan assets	91	72
Canadian Based Pension Plans [Member] | U.S. Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	58	54
Canadian Based Pension Plans [Member] | U.S. Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	33	18
Canadian Based Pension Plans [Member] | U.S. Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | International Equity [Member]
Equity securities:
Fair value of company's plan assets	120	135
Canadian Based Pension Plans [Member] | International Equity [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	107	117
Canadian Based Pension Plans [Member] | International Equity [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	13	18
Canadian Based Pension Plans [Member] | International Equity [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member]
Equity securities:
Fair value of company's plan assets	62	82
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	62	82
Canadian Based Pension Plans [Member] | Fixed Income - Investment Grade [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Fixed Income - High Yield [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Real Estate Investment Trusts [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Other Asset [Member]
Equity securities:
Fair value of company's plan assets	30	11
Canadian Based Pension Plans [Member] | Other Asset [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	4	6
Canadian Based Pension Plans [Member] | Other Asset [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	26	5
Canadian Based Pension Plans [Member] | Other Asset [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member]
Equity securities:
Fair value of company's plan assets	303	300
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 1 [Member]
Equity securities:
Fair value of company's plan assets	169	177
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 2 [Member]
Equity securities:
Fair value of company's plan assets	134	123
Canadian Based Pension Plans [Member] | Total Assets at Fair Value [Member] | Level 3 [Member]
Equity securities:
Fair value of company's plan assets
Canadian Based Pension Plans [Member] | Liabilities for Unsettled Trades, Net [Member]
Equity securities:
Fair value of company's plan assets

Recovered_Sheet8

Pensions and Other Employee Benefits - Fair Value of the Company's Pension Plans' and Postretirement Benefit Plans' Assets (Parenthetical) (Detail)	Dec. 31, 2014	Dec. 31, 2013
U.S. Based Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of mutual fund in total investment in fixed income - investment grade securities	60.00%	59.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities	40.00%	41.00%
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of mutual fund in total investment in fixed income - investment grade securities	83.00%	78.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities	17.00%	22.00%

Recovered_Sheet9

Pensions and Other Employee Benefits - Estimated Future Benefit Payments (Detail) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
Pension Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2015	$131
2016	138
2017	151
2018	159
2019	164
Years 2020-2024	991
Postretirement Benefit Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2015	13
2016	13
2017	14
2018	15
2019	15
Years 2020-2024	73
Subsidy Receipts, 2015
Subsidy Receipts, 2016
Subsidy Receipts, 2017
Subsidy Receipts, 2018
Subsidy Receipts, 2019
Subsidy Receipts, Years 2020-2024	$1

Recovered_Sheet10

Pensions and Other Employee Benefits - Cash Contributions and Expenses under Multi-Employer Benefit Plans (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Multiemployer Plans [Line Items]
Contributions by L-3 Communications	$19	$21	$20
IAM National Pension Fund [Member]
Multiemployer Plans [Line Items]
Contributions by L-3 Communications	19	21	20
EIN/Pension Plan Number	51-6031295/002
Pension Protection Act Zone Status	Green	Green
FIP/RP Status Pending/Implemented	No
Surcharge Imposed	No
Expiration Date of Collective-Bargaining Agreement, First	4-Feb-15
Expiration Date of Collective-Bargaining Agreement, Last	28-Apr-19
Other Pension Funds [Member]
Multiemployer Plans [Line Items]
Contributions by L-3 Communications

Recovered_Sheet11

Pensions and Other Employee Benefits - Cash Contributions and Expenses under Multi-Employer Benefit Plans (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Funds
Compensation and Retirement Disclosure [Abstract]
Minimum percentage funded to have green zone status rating	80.00%
Period of amortization of pension fund	5 years
Percentage of total plan contributions		6.00%	6.00%
Percentage of contributions from reportable segment	67.00%
Expiration date of multiple bargaining agreements	28-Apr-19
Number of pension funds included in Other Pension Funds	3

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information - Supplemental Cash Flow Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Interest paid on outstanding debt	$176	$171	$198
Income tax payments	129	245	332
Income tax refunds	$9	$23	$22

Segment_Information_Additional

Segment Information - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2012
	Segment
Segment Reporting [Abstract]
Number of segments	4
Corporate expenses		$10

Segment_Information_Summary_of

Segment Information - Summary of Segment Information (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Sales
Net products sales									$6,909	$7,189	$7,586
Net services sales									5,215	5,433	5,521
Consolidated total	3,208	2,940	3,019	2,957	3,234	3,002	3,189	3,197	12,124	12,622	13,107
Operating Income
Operating income	303	257	239	286	306	306	290	310	1,085	1,212	1,308
Depreciation and amortization
Depreciation and amortization									225	214	228
Capital Expenditures
Capital Expenditures									183	209	210
Total Assets
Assets held for sale	547								547
Total Assets	13,836				14,007				13,836	14,007	13,800
Operating Segments [Member] | Electronic Systems [Member]
Net Sales
Net products sales									3,685	3,661	3,754
Net services sales									1,029	1,054	1,011
Operating Income
Operating income									537	533	569
Depreciation and amortization
Depreciation and amortization									123	117	121
Capital Expenditures
Capital Expenditures									80	71	77
Total Assets
Total Assets	6,287				6,928				6,287	6,928	6,792
Operating Segments [Member] | Aerospace Systems [Member]
Net Sales
Net products sales									1,722	1,827	1,755
Net services sales									2,604	2,730	2,844
Operating Income
Operating income									288	426	437
Depreciation and amortization
Depreciation and amortization									40	38	46
Capital Expenditures
Capital Expenditures									59	54	42
Total Assets
Total Assets	3,011				3,106				3,011	3,106	3,074
Operating Segments [Member] | Communication Systems [Member]
Net Sales
Net products sales									1,541	1,755	2,083
Net services sales									499	471	445
Operating Income
Operating income									196	168	223
Depreciation and amortization
Depreciation and amortization									51	48	47
Capital Expenditures
Capital Expenditures									29	59	84
Total Assets
Total Assets	1,997				2,130				1,997	2,130	2,179
Operating Segments [Member] | NSS [Member]
Net Sales
Net products sales									75	71	98
Net services sales									1,140	1,228	1,292
Operating Income
Operating income									64	85	79
Depreciation and amortization
Depreciation and amortization									11	11	14
Capital Expenditures
Capital Expenditures									9	5	5
Total Assets
Total Assets	1,287				1,247				1,287	1,247	1,228
Corporate [Member]
Capital Expenditures
Capital Expenditures									6	20	2
Total Assets
Total Assets	707				596				707	596	527
Elimination of Intercompany Sales [Member]
Net Sales
Net products sales									-114	-125	-104
Net services sales									($57)	($50)	($71)

Segment_Information_Companys_S

Segment Information - Company's Sales Attributable to U.S. Customers and International Customers (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$3,208	$2,940	$3,019	$2,957	$3,234	$3,002	$3,189	$3,197	$12,124	$12,622	$13,107
Operating Segments [Member] | U.S. [Member]
Segment Reporting Information [Line Items]
Net sales									9,172	9,808	10,658
Operating Segments [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Net sales									342	449	360
Operating Segments [Member] | Canada [Member]
Segment Reporting Information [Line Items]
Net sales									289	357	314
Operating Segments [Member] | Australia [Member]
Segment Reporting Information [Line Items]
Net sales									254	218	222
Operating Segments [Member] | Germany [Member]
Segment Reporting Information [Line Items]
Net sales									243	272	263
Operating Segments [Member] | South Korea [Member]
Segment Reporting Information [Line Items]
Net sales									226	178	125
Operating Segments [Member] | Saudi Arabia (Member)
Segment Reporting Information [Line Items]
Net sales									160	132	76
Operating Segments [Member] | JAPAN
Segment Reporting Information [Line Items]
Net sales									124	67	78
Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Net sales									1,314	1,141	1,011
Operating Segments [Member] | Total International [Member]
Segment Reporting Information [Line Items]
Net sales									$2,952	$2,814	$2,449

Segment_Information_Net_Sales_

Segment Information - Net Sales to Principal Customers (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net sales	$3,208	$2,940	$3,019	$2,957	$3,234	$3,002	$3,189	$3,197	$12,124	$12,622	$13,107
Operating Segments [Member] | U.S. Government Agencies [Member]
Segment Reporting Information [Line Items]
Net sales									8,584	9,186	9,986
Operating Segments [Member] | Commercial [Member]
Segment Reporting Information [Line Items]
Net sales									1,693	1,689	1,658
Operating Segments [Member] | Foreign Governments [Member]
Segment Reporting Information [Line Items]
Net sales									$1,847	$1,747	$1,463

Employee_Severance_and_Termina2

Employee Severance and Termination Costs - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	Employees	Employees	Employees
Restructuring Cost and Reserve [Line Items]
Employee severance and other termination costs	$30	$29	$23
Number of employees terminated	2,000	2,000	1,600
Remaining balance of employee termination costs	11
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Payments for employee termination costs	$11

Employee_Severance_and_Termina3

Employee Severance and Termination Costs - Employee Severance and Other Termination Costs Incurred by Reportable Segment (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Employee severance and other termination costs	$30	$29	$23
Electronic Systems [Member]
Restructuring Cost and Reserve [Line Items]
Employee severance and other termination costs	16	16	13
Aerospace Systems [Member]
Restructuring Cost and Reserve [Line Items]
Employee severance and other termination costs	5	2	1
Communication Systems [Member]
Restructuring Cost and Reserve [Line Items]
Employee severance and other termination costs	8	11	8
NSS [Member]
Restructuring Cost and Reserve [Line Items]
Employee severance and other termination costs	$1		$1

Unaudited_Quarterly_Financial_2

Unaudited Quarterly Financial Data - Company's Unaudited Quarterly Results of Operations (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Sales	$3,208	$2,940	$3,019	$2,957	$3,234	$3,002	$3,189	$3,197	$12,124	$12,622	$13,107
Operating income	303	257	239	286	306	306	290	310	1,085	1,212	1,308
Net income	207	157	141	172	188	204	176	192	677	760	794
Net income attributable to L-3	$203	$154	$137	$170	$185	$200	$175	$191	$664	$751	$784
Basic EPS	$2.41	$1.81	$1.59	$1.97	$2.10	$2.23	$1.95	$2.12	$7.78	$8.40	$8.14
Diluted EPS	$2.36	$1.78	$1.53	$1.90	$2.04	$2.19	$1.92	$2.09	$7.56	$8.24	$8.03

Financial_Information_of_L3_Co2

Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Equity (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				$6,056				$5,527	$6,056	$5,527	$6,733
Net income attributable to L-3	203	154	137	170	185	200	175	191	664	751	784
Comprehensive income (loss)									-474	440	-96
Other									-19	-4	-9
Ending Balance	5,360				6,056				5,360	6,056	5,527
Common Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance												1
Beginning Balance, Shares												99,000,000
Ending Balance	1				1				1	1	1	1
Ending Balance, Shares	82,000,000				85,800,000				82,000,000	85,800,000	90,400,000	99,000,000
Additional Paid-in Capital [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				5,652				5,313	5,652	5,313	5,063
Other									-19	-5	-9
Ending Balance	5,798				5,652				5,798	5,652	5,313
Treasury Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance												-3,616
Ending Balance	-6,111				-5,288				-6,111	-5,288	-4,488	-3,616
Retained Earnings [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance								5,175		5,175		5,650
Other										1
Ending Balance	6,181				5,726				6,181	5,726		5,650
Accumulated Other Comprehensive (Loss) Income [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance												-454
Ending Balance	-584				-110				-584	-110	-550	-454
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				5,981				5,451	5,981	5,451	6,644
Net income attributable to L-3									664	751	784
Contributions from L-3 Holdings									146	339	250
Dividends to L-3 Holdings									-1,032	-1,001	-1,068
Comprehensive income (loss)									-474	440	-96
Net change of equity due to spin-off of Engility											-1,063
Other										1
Ending Balance	5,285				5,981				5,285	5,981	5,451
L-3 Communications Corporation [Member] | Common Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance
Beginning Balance, Shares				100,000,000				100,000,000	100,000,000	100,000,000	100,000,000
Net income attributable to L-3
Contributions from L-3 Holdings
Dividends to L-3 Holdings
Comprehensive income (loss)
Net change of equity due to spin-off of Engility
Other
Ending Balance
Ending Balance, Shares	100,000,000				100,000,000				100,000,000	100,000,000	100,000,000
L-3 Communications Corporation [Member] | Additional Paid-in Capital [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				5,653				5,314	5,653	5,314	5,064
Net income attributable to L-3
Contributions from L-3 Holdings									146	339	250
Dividends to L-3 Holdings
Comprehensive income (loss)
Net change of equity due to spin-off of Engility
Other
Ending Balance	5,799				5,653				5,799	5,653	5,314
L-3 Communications Corporation [Member] | Treasury Stock [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance
Net income attributable to L-3
Contributions from L-3 Holdings
Dividends to L-3 Holdings
Comprehensive income (loss)
Net change of equity due to spin-off of Engility
Other
Ending Balance
L-3 Communications Corporation [Member] | Retained Earnings [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				438				687	438	687	2,034
Net income attributable to L-3									664	751	784
Contributions from L-3 Holdings
Dividends to L-3 Holdings									-1,032	-1,001	-1,068
Comprehensive income (loss)
Net change of equity due to spin-off of Engility											-1,063
Other										1
Ending Balance	70				438				70	438	687
L-3 Communications Corporation [Member] | Accumulated Other Comprehensive (Loss) Income [Member]
Condensed Financial Statements, Captions [Line Items]
Beginning Balance				-110				-550	-110	-550	-454
Net income attributable to L-3
Contributions from L-3 Holdings
Dividends to L-3 Holdings
Comprehensive income (loss)									-474	440	-96
Net change of equity due to spin-off of Engility
Other
Ending Balance	($584)				($110)				($584)	($110)	($550)

Financial_Information_of_L3_Co3

Financial Information of L-3 Communications and Its Subsidiaries - Additional Information (Detail)	Dec. 31, 2014
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Ownership percentage held in subsidiary	100.00%

Financial_Information_of_L3_Co4

Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Balance Sheets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$442	$500	$349	$764
Billed receivables, net	852	991
Contracts in process	2,295	2,442
Other current assets	601	680
Assets held for sale	547
Total current assets	4,737	4,613
Goodwill	7,501	7,796	7,776
Other assets	1,598	1,598
Investment in and amounts due from consolidated subsidiaries
Total assets	13,836	14,007	13,800
Current liabilities	2,288	2,553
Liabilities held for sale	237
Amounts due to consolidated subsidiaries
Other long-term liabilities	2,012	1,768
Long-term debt	3,939	3,630
Total liabilities	8,476	7,951
L-3 shareholders' equity	5,285	5,981
Noncontrolling interests	75	75
Total equity	5,360	6,056	5,527	6,733
Total liabilities and equity	13,836	14,007
L-3 Communications Holdings, Inc. [Member]
Current assets:
Cash and cash equivalents
Billed receivables, net
Contracts in process
Other current assets
Assets held for sale
Total current assets
Goodwill
Other assets
Investment in and amounts due from consolidated subsidiaries	5,285	6,670
Total assets	5,285	6,670
Current liabilities
Liabilities held for sale
Amounts due to consolidated subsidiaries
Other long-term liabilities
Long-term debt		689
Total liabilities		689
L-3 shareholders' equity	5,285	5,981
Noncontrolling interests
Total equity	5,285	5,981
Total liabilities and equity	5,285	6,670
L-3 Communications Corporation [Member]
Current assets:
Cash and cash equivalents	361	258	246	644
Billed receivables, net	320	364
Contracts in process	867	919
Other current assets	365	350
Assets held for sale
Total current assets	1,913	1,891
Goodwill	2,350	2,350
Other assets	817	838
Investment in and amounts due from consolidated subsidiaries	6,813	6,897
Total assets	11,893	11,976
Current liabilities	878	914
Liabilities held for sale
Amounts due to consolidated subsidiaries
Other long-term liabilities	1,791	1,451
Long-term debt	3,939	3,630
Total liabilities	6,608	5,995
L-3 shareholders' equity	5,285	5,981
Noncontrolling interests
Total equity	5,285	5,981	5,451	6,644
Total liabilities and equity	11,893	11,976
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	1
Billed receivables, net	329	401
Contracts in process	1,144	1,169
Other current assets	141	162
Assets held for sale	52
Total current assets	1,667	1,732
Goodwill	4,246	4,247
Other assets	576	532
Investment in and amounts due from consolidated subsidiaries	4,191	3,822
Total assets	10,680	10,333
Current liabilities	1,017	1,030
Liabilities held for sale	10
Amounts due to consolidated subsidiaries
Other long-term liabilities	190	193
Long-term debt
Total liabilities	1,217	1,223
L-3 shareholders' equity	9,463	9,110
Noncontrolling interests
Total equity	9,463	9,110
Total liabilities and equity	10,680	10,333
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	142	261	242	222
Billed receivables, net	203	226
Contracts in process	284	354
Other current assets	95	168
Assets held for sale	495
Total current assets	1,219	1,009
Goodwill	905	1,199
Other assets	205	228
Investment in and amounts due from consolidated subsidiaries
Total assets	2,329	2,436
Current liabilities	455	628
Liabilities held for sale	227
Amounts due to consolidated subsidiaries	325	305
Other long-term liabilities	31	124
Long-term debt
Total liabilities	1,038	1,057
L-3 shareholders' equity	1,291	1,379
Noncontrolling interests
Total equity	1,291	1,379
Total liabilities and equity	2,329	2,436
Eliminations [Member]
Current assets:
Cash and cash equivalents	-62	-19	-139	-102
Billed receivables, net
Contracts in process
Other current assets
Assets held for sale
Total current assets	-62	-19
Goodwill
Other assets
Investment in and amounts due from consolidated subsidiaries	-16,289	-17,389
Total assets	-16,351	-17,408
Current liabilities	-62	-19
Liabilities held for sale
Amounts due to consolidated subsidiaries	-325	-305
Other long-term liabilities
Long-term debt		-689
Total liabilities	-387	-1,013
L-3 shareholders' equity	-16,039	-16,470
Noncontrolling interests	75	75
Total equity	-15,964	-16,395
Total liabilities and equity	($16,351)	($17,408)

Financial_Information_of_L3_Co5

Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Operations (Detail) (USD $)	3 Months Ended								12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net sales	$3,208	$2,940	$3,019	$2,957	$3,234	$3,002	$3,189	$3,197	$12,124	$12,622	$13,107
Cost of sales									-11,039	-11,410	-11,799
Operating (loss) income	303	257	239	286	306	306	290	310	1,085	1,212	1,308
Interest expense									-178	-177	-184
Interest and other income (expense), net									18	20	11
Debt Retirement Charge											-13
(Loss) income from continuing operations before income taxes									925	1,055	1,122
Benefit (provision) for income taxes									-248	-295	-360
Equity in net income of consolidated subsidiaries
Income from continuing operations									677	760	762
Income from discontinued operations, net of income tax											32
Net income	207	157	141	172	188	204	176	192	677	760	794
Net income attributable to noncontrolling interests									-13	-9	-10
Net income attributable to L-3	203	154	137	170	185	200	175	191	664	751	784
Comprehensive income attributable to L-3									190	1,191	688
L-3 Communications Holdings, Inc. [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales
Cost of sales									-52	-59	-59
Operating (loss) income									-52	-59	-59
Interest expense									-2	-21	-21
Interest and other income (expense), net
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									-54	-80	-80
Benefit (provision) for income taxes									14	22	26
Equity in net income of consolidated subsidiaries									704	809	838
Income from continuing operations											784
Income from discontinued operations, net of income tax
Net income									664	751	784
Net income attributable to noncontrolling interests
Net income attributable to L-3									664	751	784
Comprehensive income attributable to L-3									190	1,191	688
L-3 Communications Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									3,556	3,842	3,737
Cost of sales									-3,211	-3,549	-3,434
Operating (loss) income									345	293	303
Interest expense									-176	-176	-183
Interest and other income (expense), net									15	15	14
Debt Retirement Charge											-13
(Loss) income from continuing operations before income taxes									184	132	121
Benefit (provision) for income taxes									-49	-38	-37
Equity in net income of consolidated subsidiaries									529	657	668
Income from continuing operations											752
Income from discontinued operations, net of income tax											32
Net income									664	751	784
Net income attributable to noncontrolling interests
Net income attributable to L-3									664	751	784
Comprehensive income attributable to L-3									190	1,191	688
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									6,618	6,804	7,475
Cost of sales									-6,117	-6,139	-6,749
Operating (loss) income									501	665	726
Interest expense									-2
Interest and other income (expense), net											-5
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									499	665	721
Benefit (provision) for income taxes									-134	-184	-230
Equity in net income of consolidated subsidiaries
Income from continuing operations											491
Income from discontinued operations, net of income tax
Net income									365	481	491
Net income attributable to noncontrolling interests
Net income attributable to L-3									365	481	491
Comprehensive income attributable to L-3									363	480	493
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									2,256	2,363	2,278
Cost of sales									-2,017	-2,109	-1,999
Operating (loss) income									239	254	279
Interest expense										-1	-1
Interest and other income (expense), net									3	5	2
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									242	258	280
Benefit (provision) for income taxes									-65	-73	-93
Equity in net income of consolidated subsidiaries
Income from continuing operations											187
Income from discontinued operations, net of income tax
Net income									177	185	187
Net income attributable to noncontrolling interests
Net income attributable to L-3									177	185	187
Comprehensive income attributable to L-3									46	159	215
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales									-306	-387	-383
Cost of sales									358	446	442
Operating (loss) income									52	59	59
Interest expense									2	21	21
Interest and other income (expense), net
Debt Retirement Charge
(Loss) income from continuing operations before income taxes									54	80	80
Benefit (provision) for income taxes									-14	-22	-26
Equity in net income of consolidated subsidiaries									-1,233	-1,466	-1,506
Income from continuing operations											-1,452
Income from discontinued operations, net of income tax
Net income									-1,193	-1,408	-1,452
Net income attributable to noncontrolling interests									-13	-9	-10
Net income attributable to L-3									-1,206	-1,417	-1,462
Comprehensive income attributable to L-3									($599)	($1,830)	($1,396)

Financial_Information_of_L3_Co6

Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Cash Flows (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net cash from operating activities from continuing operations	$1,125	$1,263	$1,231
Investing activities:
Business acquisitions, net of cash acquired	-57	-62	-348
Investments in L-3 Communications
Other investing activities	-172	-199	148
Net cash used in investing activities from continuing operations	-229	-261	-200
Financing activities:
Proceeds from sale of senior notes	996
Redemption of senior subordinated notes			-500
Redemption of CODES	-935
Common stock repurchased	-823	-800	-872
Dividends paid on L-3 Holdings' common stock	-208	-199	-195
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	94	150	40
Net cash used in financing activities from continuing operations	-876	-849	-1,527
Effect of foreign currency exchange rate changes on cash	-17	-2	7
Change in cash balance in assets held for sale	-61
Net increase in cash and cash equivalents of discontinued operations			74
Net increase (decrease) in cash	-58	151	-415
Cash and cash equivalents, beginning of the year	500	349	764
Cash and cash equivalents, end of the year	442	500	349
L-3 Communications Holdings, Inc. [Member]
Operating activities:
Net cash from operating activities from continuing operations	1,966	999	1,067
Investing activities:
Business acquisitions, net of cash acquired
Investments in L-3 Communications	-102	-149	-42
Other investing activities
Net cash used in investing activities from continuing operations	-102	-149	-42
Financing activities:
Proceeds from sale of senior notes
Redemption of senior subordinated notes
Redemption of CODES	-935
Common stock repurchased	-823	-800	-872
Dividends paid on L-3 Holdings' common stock	-208	-199	-195
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	102	149	42
Net cash used in financing activities from continuing operations	-1,864	-850	-1,025
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale
Net increase in cash and cash equivalents of discontinued operations
Net increase (decrease) in cash
Cash and cash equivalents, beginning of the year
Cash and cash equivalents, end of the year
L-3 Communications Corporation [Member]
Operating activities:
Net cash from operating activities from continuing operations	478	437	252
Investing activities:
Business acquisitions, net of cash acquired	-57	-62	-348
Investments in L-3 Communications
Other investing activities	-57	-88	225
Net cash used in investing activities from continuing operations	-114	-150	-123
Financing activities:
Proceeds from sale of senior notes	996
Redemption of senior subordinated notes			-500
Redemption of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings	-1,966	-999	-1,067
Investments from L-3 Holdings	102	149	42
Other financing activities	607	575	924
Net cash used in financing activities from continuing operations	-261	-275	-601
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale
Net increase in cash and cash equivalents of discontinued operations			74
Net increase (decrease) in cash	103	12	-398
Cash and cash equivalents, beginning of the year	258	246	644
Cash and cash equivalents, end of the year	361	258	246
Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities from continuing operations	599	776	858
Investing activities:
Business acquisitions, net of cash acquired
Investments in L-3 Communications
Other investing activities	-94	-89	-59
Net cash used in investing activities from continuing operations	-94	-89	-59
Financing activities:
Proceeds from sale of senior notes
Redemption of senior subordinated notes
Redemption of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	-503	-687	-799
Net cash used in financing activities from continuing operations	-503	-687	-799
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale	-1
Net increase in cash and cash equivalents of discontinued operations
Net increase (decrease) in cash	1
Cash and cash equivalents, beginning of the year
Cash and cash equivalents, end of the year	1
Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash from operating activities from continuing operations	141	231	265
Investing activities:
Business acquisitions, net of cash acquired
Investments in L-3 Communications
Other investing activities	-21	-22	-18
Net cash used in investing activities from continuing operations	-21	-22	-18
Financing activities:
Proceeds from sale of senior notes
Redemption of senior subordinated notes
Redemption of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings
Investments from L-3 Holdings
Other financing activities	-162	-188	-234
Net cash used in financing activities from continuing operations	-162	-188	-234
Effect of foreign currency exchange rate changes on cash	-17	-2	7
Change in cash balance in assets held for sale	-60
Net increase in cash and cash equivalents of discontinued operations
Net increase (decrease) in cash	-119	19	20
Cash and cash equivalents, beginning of the year	261	242	222
Cash and cash equivalents, end of the year	142	261	242
Eliminations [Member]
Operating activities:
Net cash from operating activities from continuing operations	-2,059	-1,180	-1,211
Investing activities:
Business acquisitions, net of cash acquired
Investments in L-3 Communications	102	149	42
Other investing activities
Net cash used in investing activities from continuing operations	102	149	42
Financing activities:
Proceeds from sale of senior notes
Redemption of senior subordinated notes
Redemption of CODES
Common stock repurchased
Dividends paid on L-3 Holdings' common stock
Dividends paid to L-3 Holdings	1,966	999	1,067
Investments from L-3 Holdings	-102	-149	-42
Other financing activities	50	301	107
Net cash used in financing activities from continuing operations	1,914	1,151	1,132
Effect of foreign currency exchange rate changes on cash
Change in cash balance in assets held for sale
Net increase in cash and cash equivalents of discontinued operations
Net increase (decrease) in cash	-43	120	-37
Cash and cash equivalents, beginning of the year	-19	-139	-102
Cash and cash equivalents, end of the year	($62)	($19)	($139)