L3 10-Q 30 Oct 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Sep. 26, 2014	Oct. 24, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	26-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'LLL	'
Entity Registrant Name	'L 3 COMMUNICATIONS HOLDINGS INC	'
Entity Central Index Key	'0001056239	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	85,133,193

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$508	$500
Billed receivables, net of allowances of $24 in 2014 and $26 in 2013	871	991
Contracts in process	2,546	2,431
Inventories	371	359
Deferred income taxes	145	147
Other current assets	215	166
Total current assets	4,656	4,594
Property, plant and equipment, net	1,072	1,042
Goodwill	7,784	7,796
Identifiable intangible assets	263	285
Deferred debt issue costs	28	24
Other assets	238	247
Total assets	14,041	13,988
Current liabilities:	'	'
Accounts payable, trade	415	541
Accrued employment costs	577	545
Accrued expenses	400	458
Advance payments and billings in excess of costs incurred	609	576
Income taxes	25	31
Other current liabilities	366	383
Total current liabilities	2,392	2,534
Pension and postretirement benefits	684	727
Deferred income taxes	649	635
Other liabilities	399	406
Long-term debt	3,938	3,630
Total liabilities	8,062	7,932
Commitments and contingencies (see Note 18)	'	'
L-3 shareholders' equity:	'	'
L-3 Communications Holdings, Inc.'s common stock: $.01 par value; 300,000,000 shares authorized, 85,053,114 shares outstanding at September 26, 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)	5,736	5,653
L-3 Communications Holdings, Inc.'s treasury stock (at cost), 69,683,610 shares at September 26, 2014 and 66,118,406 shares at December 31, 2013	-5,701	-5,288
Retained earnings	6,028	5,726
Accumulated other comprehensive loss	-160	-110
Total L-3 shareholders' equity	5,903	5,981
Noncontrolling interests	76	75
Total equity	5,979	6,056
Total liabilities and equity	$14,041	$13,988

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Class of Stock [Line Items]	'	'
Net allowances for billed receivables	$24	$26
Treasury stock (at cost), shares	69,683,610	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	85,053,114	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

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Net sales:	'	'	'	'
Products	$1,644	$1,697	$4,991	$5,321
Services	1,296	1,305	3,925	4,067
Total net sales	2,940	3,002	8,916	9,388
Cost of sales:	'	'	'	'
Products	-1,480	-1,487	-4,498	-4,732
Services	-1,203	-1,209	-3,636	-3,750
Total cost of sales	-2,683	-2,696	-8,134	-8,482
Operating income	257	306	782	906
Interest expense	-47	-44	-129	-131
Interest and other income, net	5	4	14	14
Income before income taxes	215	266	667	789
Provision for income taxes	-58	-62	-197	-217
Net income	157	204	470	572
Net income attributable to noncontrolling interests	-3	-4	-9	-6
Net income attributable to L-3	$154	$200	$461	$566
Earnings per share attributable to L-3 Holdings' common shareholders:	'	'	'	'
Basic	$1.81	$2.23	$5.38	$6.30
Diluted	$1.78	$2.19	$5.21	$6.20
Cash dividends paid per common share	$0.60	$0.55	$1.80	$1.65
L-3 Holdings' weighted average common shares outstanding:	'	'	'	'
Basic	85.1	89.6	85.7	89.9
Diluted	86.6	91.3	88.4	91.3

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014		Sep. 27, 2013		Sep. 26, 2014		Sep. 27, 2013
Statement of Comprehensive Income [Abstract]	'		'		'		'
Net income	$157		$204		$470		$572
Other comprehensive (loss) income:	'		'		'		'
Foreign currency translation adjustments	-63		34		-57		-18
Unrealized (losses) gains on hedging instruments	-3	[1]	3	[1]	'		-1	[1]
Pension and postretirement benefit plans:	'		'		'		'
Amortization of net loss and prior service cost previously recognized	2	[2]	13	[2]	7	[2]	40	[2]
Total other comprehensive (loss) income	-64		50		-50		21
Comprehensive income	93		254		420		593
Comprehensive income attributable to noncontrolling interests	-3		-4		-9		-6
Comprehensive income attributable to L-3	$90		$250		$411		$587
[1]	Amounts are net of income tax benefits of $3 million and income taxes of $2 million for the quarterly periods ended September 26, 2014 and September 27, 2013, respectively, and an income tax benefit of $2 million for the year-to-date period ended September 27, 2013.
[2]	Amounts are net of income taxes of $1 million and $7 million for the quarterly periods ended September 26, 2014 and September 27, 2013, respectively, and income taxes of $4 million and $23 million for the year-to-date periods ended September 26, 2014 and September 27, 2013, respectively.

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Income tax expense (benefit) on unrealized gains (losses) on hedging instruments	($1)	$1	'	($1)
Income taxes on amortization of net loss and prior service cost previously recognized	$1	$7	$4	$23

Condensed_Consolidated_Stateme3

Condensed 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, unless otherwise specified
Beginning Balance at Dec. 31, 2012	$5,527	$1	$5,313	($4,488)	$5,175	($550)	$76
Beginning Balance, Shares at Dec. 31, 2012	'	90.4	'	'	'	'	'
Class of Stock [Line Items]	'	'	'	'	'	'	'
Net income	572	'	'	'	566	'	6
Other comprehensive income (loss)	21	'	'	'	'	21	'
Distributions to noncontrolling interests	-7	'	'	'	'	'	-7
Cash dividends paid on common stock	-149	'	'	'	-149	'	'
Shares issued:	'	'	'	'	'	'	'
Employee savings plans	97	'	97	'	'	'	'
Employee savings plans, Shares	'	1.3	'	'	'	'	'
Exercise of stock options	90	'	90	'	'	'	'
Exercise of stock options, Shares	'	1.3	'	'	'	'	'
Employee stock purchase plan	18	'	18	'	'	'	'
Employee stock purchase plan, Shares	'	0.5	'	'	'	'	'
Stock-based compensation expense	42	'	42	'	'	'	'
Treasury stock purchased	-404	'	'	-404	'	'	'
Treasury stock purchased, Shares	'	-4.8	'	'	'	'	'
Other	-9	'	-6	'	-3	'	'
Other, Shares	'	0.3	'	'	'	'	'
Ending Balance at Sep. 27, 2013	5,798	1	5,554	-4,892	5,589	-529	75
Ending Balance, Shares at Sep. 27, 2013	'	89	'	'	'	'	'
Beginning Balance at Dec. 31, 2013	6,056	1	5,652	-5,288	5,726	-110	75
Beginning Balance, Shares at Dec. 31, 2013	'	85.8	'	'	'	'	'
Class of Stock [Line Items]	'	'	'	'	'	'	'
Net income	470	'	'	'	461	'	9
Other comprehensive income (loss)	-50	'	'	'	'	-50	'
Distributions to noncontrolling interests	-8	'	'	'	'	'	-8
Cash dividends paid on common stock	-155	'	'	'	-155	'	'
Shares issued:	'	'	'	'	'	'	'
Employee savings plans	105	'	105	'	'	'	'
Employee savings plans, Shares	'	1	'	'	'	'	'
Exercise of stock options	102	'	102	'	'	'	'
Exercise of stock options, Shares	'	1.1	'	'	'	'	'
Employee stock purchase plan	18	'	18	'	'	'	'
Employee stock purchase plan, Shares	'	0.3	'	'	'	'	'
Stock-based compensation expense	39	'	39	'	'	'	'
Treasury stock purchased	-413	'	'	-413	'	'	'
Treasury stock purchased, Shares	'	-3.6	'	'	'	'	'
Retirement of Convertible Contingent Debt Securities	-160	'	-160	'	'	'	'
Other	-25	'	-21	'	-4	'	'
Other, Shares	'	0.5	'	'	'	'	'
Ending Balance at Sep. 26, 2014	$5,979	$1	$5,735	($5,701)	$6,028	($160)	$76
Ending Balance, Shares at Sep. 26, 2014	'	85.1	'	'	'	'	'

Condensed_Consolidated_Stateme4

Condensed Consolidated Statements of Equity (Parenthetical) (USD $)	9 Months Ended
	Sep. 26, 2014	Sep. 27, 2013
Class of Stock [Line Items]	'	'
Cash dividends paid on common stock, per share	$1.80	$1.65
Retained Earnings [Member]	'	'
Class of Stock [Line Items]	'	'
Cash dividends paid on common stock, per share	$1.80	$1.65

Condensed_Consolidated_Stateme5

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Operating activities:	'	'
Net income	$470	$572
Depreciation of property, plant and equipment	127	122
Amortization of intangibles and other assets	38	36
Deferred income tax provision	91	38
Stock-based employee compensation expense	39	42
Contributions to employee savings plans in L-3 Holdings' common stock	105	90
Amortization of pension and postretirement benefit plans net loss and prior service cost	11	63
Amortization of bond discounts and deferred debt issue costs (included in interest expense)	5	5
Other non-cash items	-5	1
Changes in operating assets and liabilities, excluding amounts from acquisitions and divestitures:	'	'
Billed receivables	118	-117
Contracts in process	-157	-70
Inventories	-17	-60
Other assets	'	-48
Accounts payable, trade	-125	54
Accrued employment costs	26	37
Accrued expenses	-51	-45
Advance payments and billings in excess of costs incurred	39	-61
Income taxes	-4	31
Excess income tax benefits related to share-based payment arrangements	-16	-3
Other current liabilities	-21	-5
Pension and postretirement benefits	-40	-23
All other operating activities	-28	-42
Net cash from operating activities	605	617
Investing activities:	'	'
Business acquisitions, net of cash acquired	-57	-2
Proceeds from the sale of a business and product line	5	4
Capital expenditures	-115	-147
Dispositions of property, plant and equipment	4	10
Other investing activities	1	-6
Net cash used in investing activities	-162	-141
Financing activities:	'	'
Proceeds from sale of senior notes	996	'
Retirement of CODES	-935	'
Borrowings under revolving credit facility	1,367	1,382
Repayment of borrowings under revolving credit facility	-1,367	-1,382
Common stock repurchased	-413	-404
Dividends paid on L-3 Holdings' common stock	-158	-151
Proceeds from exercises of stock options	87	91
Proceeds from employee stock purchase plan	27	28
Excess income tax benefits related to share-based payment arrangements	16	3
Debt issue costs	-8	'
Other financing activities	-38	-13
Net cash used in financing activities	-426	-446
Effect of foreign currency exchange rate changes on cash and cash equivalents	-9	-2
Net increase in cash and cash equivalents	8	28
Cash and cash equivalents, beginning of the period	500	349
Cash and cash equivalents, end of the period	$508	$377

Description_of_Business

Description of Business	9 Months Ended
	Sep. 26, 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 aerospace systems and national security solutions. 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), U.S. Department of State (DoS), allied international governments, and domestic and international commercial customers.
	In the first quarter of 2014, the Company completed a realignment of its segments to better align its organizational structure with customer priorities and increase operational efficiencies. As a result of the realignment, L-3’s structure consists of four 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 international, aviation products, warrior systems and security & detection systems. Aerospace Systems delivers integrated solutions for the global Intelligence, Surveillance and Reconnaissance (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 information technology (IT) services, analytics and intelligence analysis to the DoD, U.S. Government intelligence agencies, federal civilian agencies and allied international governments.
	Financial information with respect to the Company’s segments is included in Note 22 to the unaudited condensed consolidated financial statements and Note 23 to the audited consolidated financial statements included in its Form 10-K/A. Financial information for the quarterly and year-to-date periods ended September 27, 2013 in these unaudited condensed consolidated financial statements has been revised for the segment realignment discussed above and the revision to previously issued financial statements discussed in Note 3 to the unaudited condensed consolidated financial statements.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Sep. 26, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	2.  Basis of Presentation
	These unaudited condensed consolidated financial statements for the quarterly and year-to-date periods ended September 26, 2014 should be read in conjunction with the audited consolidated financial statements of L-3 Holdings and L-3 Communications included in their Form 10-K/A filed on October 10, 2014.
	Principles of Consolidation and Reporting
	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 of L-3 Communications and (2) its guarantee of other contractual obligations of L-3 Communications and its subsidiaries. As of the date of this report, 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. See Note 10 to these unaudited financial statements. 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, 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 24 for additional information regarding the unaudited financial information of L-3 Communications and its subsidiaries.
	The unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the disclosures required by U.S. GAAP for a complete set of annual audited financial statements. The December 31, 2013 condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. In the opinion of management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair presentation of the results for the interim periods presented have been included. The results of operations for the interim periods are not necessarily indicative of results for the full year.
	It is the Company’s established practice to close its books for the quarters ending March, June and September on the Friday nearest to the end of the calendar quarter. The interim unaudited condensed consolidated financial statements included herein have been prepared and are labeled based on that convention. The Company closes its books for annual periods on December 31 regardless of what day it falls on.
	Accounting Estimates
	The preparation of financial statements in conformity with 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 for L-3 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 valuation 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.
	Sales and profits on contracts that are covered by accounting standards for construction-type and production-type contracts and federal government contractors are recognized using percentage-of-completion (POC) methods of accounting. Approximately 47% of the Company’s net sales in 2013 were accounted for under contract accounting standards, of which approximately 38% were fixed-price type contracts and approximately 9% were cost-plus type contracts. For contracts accounted for under contract accounting standards, sales and profits are recognized based on: (1) a 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). 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 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.
	Accounting for the sales and profit on these fixed-price type contracts requires the preparation of estimates of: (1) the total contract revenue, (2) the total costs at completion, which is equal to the sum of the actual incurred costs to date on the contract and the estimated costs to complete the contract’s statement of work, and (3) the measurement of progress towards completion. The estimated profit or loss at completion on a contract is equal to the difference between the total estimated contract revenue and the total estimated cost at completion. The profit recorded on a contract in any period using either the units-of-delivery method or cost-to-cost method is equal to the current estimated total profit margin multiplied by the cumulative sales recognized, less the amount of cumulative profit previously recorded for the contract.
	Sales and profits on cost-plus type contracts that are covered by contract accounting standards are recognized as allowable costs are incurred on the contract, at an amount equal to the allowable costs plus the estimated profit on those costs. The estimated profit on a cost-plus type contract is fixed or variable based on the contractual fee arrangement. Incentive and award fees are the primary variable fee contractual arrangement types for the Company. Incentive and award fees on cost-plus type contracts are included as an element of total estimated contract revenues and are recorded to 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.
	Revisions or adjustments to estimates for a contract’s revenue, estimated costs at completion and estimated profit or loss are often required as work progresses under a contract, as experience is gained, as facts and circumstances change and as new information is obtained, even though the scope of work required under the contract may not change. Revisions or adjustments may also be required if contract modifications occur. The impact of revisions in profit (loss) estimates for all types of contracts subject to POC accounting are recognized on a cumulative catch-up basis in the period in which the revisions are made. The revisions in contract estimates, if significant, can materially affect the Company’s results of operations and cash flows, as well as reduce the valuations of receivables and inventories, and in some cases result in liabilities to complete contracts in a loss position. Aggregate net changes in contract estimates increased consolidated operating income by $62 million, or 8%, for the year-to-date period ended September 26, 2014 and $92 million, or 10%, for the year-to-date period ended September 27, 2013.
	For a more complete discussion of these estimates and assumptions, see the Form 10-K/A filed on October 10, 2014.

Revisions_to_Previously_Issued

Revisions to Previously Issued Financial Statements	9 Months Ended
	Sep. 26, 2014
Accounting Changes and Error Corrections [Abstract]	'
Revisions to Previously Issued Financial Statements	'
	3.  Revisions to Previously Issued Financial Statements
	As disclosed on October 10, 2014, the Company is revising its previously issued financial statements for the quarterly and year-to-date periods ended September 27, 2013 to update for: (1) accounting adjustments due to the internal review at its Aerospace Systems segment, (2) accounting related to a sales-type lease transaction for flight simulator systems within its Electronic Systems segment, and (3) previously identified immaterial errors already recognized in its financial statements but not recorded in the appropriate periods. The accounting errors related to the sales-type lease transaction and immaterial out of period amounts are not related to the internal review at its Aerospace Systems segment.
	Internal Review of Aerospace Systems Segment: The Company conducted an internal review related to instances of misconduct and accounting errors at its Aerospace Systems segment. This review was conducted with the assistance of outside legal and accounting advisors, and has been completed. As a result of the internal review, the Company identified and recorded aggregate pre-tax charges as follows: (1) $75 million for the six months ended June 27, 2014, (2) $60 million for 2013, (3) $25 million for 2012, (4) $5 million for 2011, and (5) $4 million for periods prior to 2011. The pre-tax charges related to the quarterly and year-to-date periods ended September 27, 2013 were approximately $7 million and $36 million, respectively.
	The adjustments related to the internal review only affected the Logistics Solutions and Platform Systems sectors of the Aerospace Systems segment. The cumulative aggregate adjustments attributable to the Logistics Solutions sector are approximately $117 million, and at the Platform Systems sector are approximately $52 million through June 27, 2014. The Logistics Solutions sector adjustments relate to: (1) losses of $69 million with respect to the U.S. Army C-12 fixed-price maintenance and logistics support contract due to cost overruns inappropriately deferred, sales invoices inappropriately prepared, and the failure to timely and accurately perform contract estimates at completion and valuation assessments of inventories and receivables, at the Army Sustainment Division, and (2) accounting errors of $48 million in connection with the valuation of inventories and receivables as well as the correction for certain accruals on other logistics support contracts. The Platform Systems sector adjustments are primarily due to: (1) losses of $37 million on two aircraft modification contracts and two contracts for rotary wing sub-assemblies and parts, and (2) write-offs of deferred costs of $15 million to design and test aerostructures for a new commercial aircraft.
	Sales-Type Lease Transaction: The Company routinely performs on-site accounting and internal control review procedures on a rotational basis. As part of a previously planned review of the Simulation & Training business in its Electronic Systems segment and unrelated to the internal review at its Aerospace Systems segment, the Company evaluated the accounting treatment related to a sales-type lease transaction with the U.S. Army for rotary wing flight simulator systems. The period of performance under this contract began in 2004 and ends in 2023. Based on the results of this evaluation, the Company has adjusted its previously issued financial statements to: (1) increase interest income accretion on the net investment related to this sales-type lease transaction by an estimated aggregate amount of approximately $5 million for 2013, $3 million for each of 2012 and 2011, and $12 million for periods prior to 2011 and (2) decrease sales by approximately $8 million for 2014 and $7 million for 2013 and a related decrease in cost of sales by approximately $7 million for each of 2014 and 2013 and $5 million for periods prior to 2011.
	Out of Period Amounts: The Company identified various out of period amounts included in its previously issued financial statements that were deemed to be immaterial individually and in the aggregate. In prior periods, in accordance with Accounting Standards Codification (“ASC”) 250-10-S99 and S55 (formerly Staff Accounting Bulletins (“SAB”) No. 99 and No. 108), Accounting Changes and Error Corrections, the Company concluded that these errors were, individually, and in the aggregate, not material, quantitatively or qualitatively, to the financial statements in the period recorded or to the relevant prior periods. Accordingly, the Company recorded these errors in the financial statements in the period that the error was identified. The Company, on a voluntary basis, is revising its previously issued financial statements to correct for these errors already recognized in its financial statements but not recorded in the appropriate periods to reflect them in the appropriate period. These out of period amounts were not discovered as part of the internal review of the Aerospace Systems segment discussed above, but rather represent previously identified errors “resulting from mathematical mistakes, mistakes in application of generally accepted accounting principles, or oversight or misuse of facts that existed at the time the financial statements were prepared,” as defined in ASC 250-10-20 Accounting Changes and Error Corrections. The Company, therefore, is not treating these amounts as changes in estimates. These errors consist of: (1) increases in development and material costs related to Broadband Communication Systems that were recorded in the first quarter of 2013 but should have been recorded in the fourth quarter of 2012, (2) a sub-contractor subscription deposit that was recorded as sales and income in the fourth quarter of 2012 but should have been amortized to sales and income during 2013, (3) costs accrued in the fourth quarter of 2012 for goods or services received in the first quarter of 2013, (4) several unrecorded liabilities that were recorded in the first quarter of 2013 but should have been recorded in the fourth quarter of 2012, (5) a correction of accrued vacation that was recorded in the fourth quarter of 2013 but should have been recorded in the fourth quarter of 2012 and the first, second and third quarters of 2013, and (6) a warranty reserve reduction recorded in the third quarter of 2012 that should have been recorded in the fourth quarter of 2011.
	With respect to each of these immaterial out of period amounts included in the Company’s previously issued financial statements, the table below presents the: (1) nature of the adjustments, (2) applicable segment and (3) amount of increase (or decrease) to sales and operating income for the quarters ended December 31, September 27, June 28, and March 29, 2013.
					December 31,								September 27,								June 28,								March 29,
					2013								2013								2013								2013
	Nature of Adjustment		Applicable		Sales				Operating				Sales				Operating				Sales				Operating				Sales				Operating
			Segment						Income								Income								Income								Income
					($ in millions)
	Higher development and material costs for networked communications systems		Communication Systems		$	—			$	—			$	—			$	—			$	—			$	—			$	10			$	10
	Sub-contractor subscription deposit		Aerospace Systems			5				—				7				1				7				1				7				1
	Costs accruals for goods/services received		Aerospace Systems			—				—				—				—				—				—				5				1
	Unrecorded liabilities		Aerospace Systems			—				—				—				—				—				—				(2	)			—
	Accrued vacation		Aerospace Systems			—				6				—				(2	)			—				(2	)			—				(2	)
	Overstated revenue		Aerospace Systems			4				—				(4	)			—				—				—				—				—
	Total				$	9			$	6			$	3			$	(1	)		$	7			$	(1	)		$	20			$	10
	The table below presents the impact of the matters discussed above on sales and pre-tax income in total, for the six month period ended June 27, 2014, years ended December 31, 2013, 2012, and 2011, and for the years ended prior to December 31, 2011.
			Total								Six Months								2013								2012								2011						Prior to 2011
											2014
			Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales			Pre-tax			Sales			Pre-tax
							Income								Income								Income								Income							Income						Income
			(in millions)
	Army C-12 Contract		$	(32	)		$	(69	)		$	(3	)		$	(15	)		$	(25	)		$	(35	)		$	(3	)		$	(16	)		$	(1	)	$	(3	)	$	—		$	—
	Other Logistics Support Contracts			(5	)			(48	)			—				(20	)			(2	)			(11	)			(2	)			(11	)			—			(2	)		(1	)		(4	)
	Logistics Solutions			(37	)			(117	)			(3	)			(35	)			(27	)			(46	)			(5	)			(27	)			(1	)		(5	)		(1	)		(4	)
	Platform Systems			(21	)			(52	)			(12	)			(40	)			(12	)			(14	)			3				2				—			—			—			—
	Total Internal Review of Aerospace Systems Segment			(58	)			(169	)			(15	)			(75	)			(39	)			(60	)			(2	)			(25	)			(1	)		(5	)		(1	)		(4	)
	Sales-Type Lease Transaction			(15	)			29				(8	)			1				(7	)			5				—				3				—			3			—			17
	Out of Period Amounts			—				—				—				—				39				14				(36	)			(18	)			(3	)		4			—			—
	Total Revisions		$	(73	)		$	(140	)		$	(23	)		$	(74	)		$	(7	)		$	(41	)		$	(38	)		$	(40	)		$	(4	)	$	2		$	(1	)	$	13
	The table below presents the impact of the matters discussed above on sales and pre-tax income for the quarters ended June 27 and March 28, 2014, December 31, September 27, June 28, 2013 and March 29, 2013.
			June 27,								March 28,								December 31,								September 27,								June 28,						March 29,
			2014								2014								2013								2013								2013						2013
			Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales			Pre-tax			Sales			Pre-tax
							Income								Income								Income								Income							Income						Income
			(in millions)
	Army C-12 Contract		$	(1	)		$	(11	)		$	(2	)		$	(4	)		$	(24	)		$	(20	)		$	3			$	(2	)		$	(3	)	$	(7	)	$	(1	)	$	(6	)
	Other Logistics Support Contracts			—				(15	)			—				(5	)			(1	)			(2	)			(1	)			(5	)			—			(2	)		—			(2	)
	Logistics Solutions			(1	)			(26	)			(2	)			(9	)			(25	)			(22	)			2				(7	)			(3	)		(9	)		(1	)		(8	)
	Platform Systems			(6	)			(29	)			(6	)			(11	)			(2	)			(2	)			1				—				(6	)		(6	)		(5	)		(6	)
	Total Internal Review of Aerospace Systems Segment			(7	)			(55	)			(8	)			(20	)			(27	)			(24	)			3				(7	)			(9	)		(15	)		(6	)		(14	)
	Sales-Type Lease Transaction			(3	)			1				(5	)			—				(3	)			1				(1	)			2				(1	)		1			(2	)		1
	Out of Period Amounts			—				—				—				—				9				6				3				(1	)			7			(1	)		20			10
	Total Revisions		$	(10	)		$	(54	)		$	(13	)		$	(20	)		$	(21	)		$	(17	)		$	5			$	(6	)		$	(3	)	$	(15	)	$	12		$	(3	)
	In accordance with ASC 250-10-S99 and S55, the Company performed an analysis to determine if the impact of the amounts disclosed above were material to its previously issued financial statements. Based on that analysis, the Company believes that its previously issued financial statements are not materially misstated on either a quantitative or qualitative basis. However, as a result of completing the review, the Company believed that correcting these errors in the quarterly report on Form 10-Q for the quarter ended June 27, 2014 would, in the aggregate, have caused a material misstatement to forecasted pre-tax income and net income for the fiscal year ending December 31, 2014. Accordingly, the Company is correcting these errors by revising its previously issued financial statements for the quarterly and year-to-date periods ended September 27, 2013 on this Form 10-Q to record all the adjustments in the tables above in the appropriate period. In addition, the Company revised its previously issued financial statements for the quarterly and first half periods ended June 28, 2013 on its Quarterly Report on Form 10-Q filed on October 10, 2014 for the quarterly and first half periods ended June 27, 2014, for the quarterly periods ended March 28, 2014 and March 29, 2013 on its Quarterly Report on Form 10-Q/A filed on October 10, 2014 for the quarterly period ended March 28, 2014, and its Annual Report on Form 10-K/A filed on October 10, 2014 for the years ended December 31, 2013, 2012 and 2011 to record all the adjustments in the tables above in the appropriate period.
	The tables below present the Company’s: (1) As Previously Reported, (2) Adjustments, and (3) As Revised Condensed Consolidated Statements of Operations for the quarterly and year-to-date periods ended September 27, 2013 and the Operating Activities for the Statement of Cash Flows for the year-to-date period ended September 27, 2013. The Adjustments correct for: (1) the results of the Aerospace Systems internal review, (2) the accounting related to a sales-type lease transaction within the Company’s Electronic Systems segment and (3) immaterial out of period amounts previously recorded in the Company’s financial statements but not recorded in the appropriate period to reflect them in the appropriate period.
							Adjustments for:
			As				Aerospace				Sales-Type				Out of Period				As
			Previously				Systems				Lease				Amounts				Revised
			Reported				Segment				Transaction
							Internal
							Review
			(in millions, except per share data)
	Unaudited Condensed Consolidated Statement of Operations, for the third quarter ended September 27, 2013:
	Net sales:
	Products		$	1,696			$	2			$	(1	)		$	—			$	1,697
	Services			1,300				2				—				3				1,305
	Total net sales			2,996				4	(1)			(1	)			3				3,002
	Cost of sales:
	Products			(1,486	)			(2	)			1				—				(1,487	)
Services			(1,196	)			(9	)			—				(4	)			(1,209	)
Total cost of sales			(2,682	)			(11	)			1				(4	)			(2,696	)
Operating income			314				(7	)			—				(1	)			306
Interest expense			(44	)			—				—				—				(44	)
Interest and other income, net			3				—				1				—				4
Income before income taxes			273				(7	)			1	(1)			(1	)			266
Provision for income taxes			(65	)			3				—				—				(62	)
Net income		$	208			$	(4	)		$	1			$	(1	)		$	204
Net income attributable to noncontrolling interests			(4	)			—				—				—				(4	)
Net income attributable to L-3		$	204			$	(4	)		$	1			$	(1	)		$	200
Earnings per share attributable to L-3 Holdings’ common shareholders:
Basic		$	2.28			$	(0.05	)		$	0.01			$	(0.01	)		$	2.23
Diluted		$	2.23			$	(0.04	)		$	0.01			$	(0.01	)		$	2.19
Cash dividends paid per common share		$	0.55			$	—			$	—			$	—			$	0.55
L-3 Holdings’ weighted average common shares outstanding:
Basic			89.6				—				—				—				89.6
Diluted			91.3				—				—				—				91.3
(1)	Includes rounding of $1 million.
						Adjustments for:
		As				Aerospace				Sales-Type				Out of Period				As
		Previously				Systems				Lease				Amounts				Revised
		Reported				Segment				Transaction
						Internal
						Review
		(in millions, except per share data)
Unaudited Condensed Consolidated Statement of Operations, for the Year-to-Date Period Ended September 27, 2013:
Net sales:
Products		$	5,319			$	(9	)		$	(4	)		$	15			$	5,321
Services			4,054				(2	)			—				15				4,067
Total net sales			9,373				(11	)(1)			(4	)			30				9,388
Cost of sales:
Products			(4,729	)			(3	)			5				(5	)			(4,732	)
Services			(3,710	)			(22	)			—				(18	)			(3,750	)
Total cost of sales			(8,439	)			(25	)			5				(23	)			(8,482	)
Operating income			934				(36	)			1				7	-1			906
Interest expense			(131	)			—				—				—				(131	)
Interest and other income, net			11				—				3				—				14
Income before income taxes			814				(36	)			4				7				789
Provision for income taxes			(226	)			13				(1	)			(3	)			(217	)
Net income		$	588			$	(23	)		$	3			$	4			$	572
Net income attributable to noncontrolling interests			(6	)			—				—				—				(6	)
Net income attributable to L-3		$	582			$	(23	)		$	3			$	4			$	566
Earnings per share attributable to L-3 Holdings’ common shareholders:
Basic		$	6.47			$	(0.25	)		$	0.04			$	0.04			$	6.3
Diluted		$	6.37			$	(0.25	)		$	0.04			$	0.04			$	6.2
Cash dividends paid per common share		$	1.65			$	—			$	—			$	—			$	1.65
L-3 Holdings’ weighted average common shares outstanding:
Basic			89.9				—				—				—				89.9
Diluted			91.3				—				—				—				91.3
(1)	Includes rounding of $1 million.
		As				Net				As
		Previously				Adjustments				Revised
		Reported
		(in millions)
Unaudited Consolidated Statement of Cash Flows for the Year-to-Date Period Ended September 27, 2013:
Operating activities:
Net income		$	588			$	(16	)		$	572
Depreciation of property, plant and equipment			122				—				122
Amortization of intangibles and other assets			36				—				36
Deferred income tax provision			45				(7	)			38
Stock-based employee compensation expense			42				—				42
Contributions to employee savings plans in L-3 Holdings’ common stock			90				—				90
Amortization of pension and postretirement benefit plans net loss and prior service cost			63				—				63
Amortization of bond discounts and deferred debt issue costs (included in interest expense)			5				—				5
Other non-cash items			1				—				1
Changes in operating assets and liabilities, excluding amounts from acquisitions and divestitures:
Billed receivables			(117	)			—				(117	)
Contracts in process			(36	)			(34	)			(70	)
Inventories			(55	)			(5	)			(60	)
Other assets			(45	)			(3	)			(48	)
Accounts payable, trade			65				(11	)			54
Accrued employment costs			27				10				37
Accrued expenses			(41	)			(4	)			(45	)
Advance payments and billings in excess of costs incurred			(109	)			48				(61	)
Income taxes			32				(1	)			31
Excess income tax benefits related to share-based payment arrangements			(3	)			—				(3	)
Other current liabilities			(8	)			3				(5	)
Pension and postretirement benefits			(23	)			—				(23	)
All other operating activities			(62	)			20				(42	)
Net cash from operating activities		$	617			$	—			$	617

Recently_Issued_Accounting_Sta

Recently Issued Accounting Standards	9 Months Ended
	Sep. 26, 2014
Accounting Changes and Error Corrections [Abstract]	'
Recently Issued Accounting Standards	'
	4.  Recently Issued Accounting Standards
	Effective January 1, 2014, the Company adopted Financial Accounting Standards Board (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 impact the Company’s financial position, results of operations or cash flows.
	In June 2014, the FASB issued Accounting Standard Update (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 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 Company is currently evaluating the impact of the adoption of this standard, if any, on our consolidated financial statements.
	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, and provide companies with a single revenue recognition model for recognizing revenue from contracts with customers. One of the core principles of the new standard is that a company should recognize revenue based on the satisfaction of performance obligations, which depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. 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 the transition alternatives available.
	In April 2014, the FASB issued an accounting standards update 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 update is effective for the Company for interim and annual periods beginning January 1, 2015. The adoption of this standard is not expected to impact the Company’s financial position, results of operations or cash flows and will only affect the treatment of future discontinued operations.

Acquisitions

Acquisitions	9 Months Ended
	Sep. 26, 2014
Business Combinations [Abstract]	'
Acquisitions	'
	5.  Acquisitions
	The business acquisitions discussed below are included in the Company’s results of operations from their respective dates of acquisition.
	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 is subject to adjustment based on closing date net working capital. 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 preliminary purchase price, the aggregate goodwill recognized for this business was $39 million, most of which is expected to be deductible for income tax purposes. The goodwill was assigned to the NSS reportable segment. The final purchase price allocation, which is expected to be completed in the fourth quarter of 2014, will be based on the final purchase price and final appraisals and other analysis of fair values of acquired assets and liabilities. The Company does not expect that differences between the preliminary and final purchase price allocations will have a material impact on its results of operations or financial position.
	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, most of which is expected to be deductible for income tax purposes. The goodwill was assigned to the Electronic Systems reportable segment.
	Unaudited Pro Forma Statements of Operations Data
	The following unaudited pro forma Statements of Operations data present the combined results of the Company and its business acquisitions completed during the year-to-date period ended September 26, 2014 and the year ended December 31, 2013, in each case assuming that the business acquisitions completed during these periods had occurred on January 1, 2013.
		Third Quarter Ended				Year-to-Date Ended
		September 26,		September 27,		September 26,		September 27,
		2014		2013		2014		2013
		(in millions, except per share data)
	Pro forma net sales	$	2,940	$	3,025	$	8,923	$	9,450
	Pro forma net income attributable to L-3	$	154	$	200	$	460	$	567
	Pro forma diluted earnings per share	$	1.78	$	2.19	$	5.2	$	6.21
	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 January 1, 2013.

Contracts_in_Process

Contracts in Process	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Contracts in Process	'
	6.  Contracts in Process
	The components of contracts in process are presented in the table below.
		September 26,			December 31,
		2014			2013
		(in millions)
	Unbilled contract receivables, gross	$	2,449		$	2,502
	Unliquidated progress payments		(900	)		(1,035	)
	Unbilled contract receivables, net		1,549			1,467
	Inventoried contract costs, gross		1,069			1,044
	Unliquidated progress payments		(72	)		(80	)
	Inventoried contract costs, net		997			964
	Total contracts in process	$	2,546		$	2,431
	Inventoried Contract Costs. In accordance with contract accounting standards, the Company’s U.S. Government contractor businesses account for the portion of their general and administrative (G&A), independent research and development (IRAD) and bids and proposal (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.
		Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
		(in millions)
	Amounts included in inventoried contract costs at beginning of the period:	$	151		$	115		$	138		$	110
	IRAD and B&P costs		70			66			215			219
	Other G&A costs		239			216			658			653
	Total contract costs incurred		309			282			873			872
	Amounts charged to cost of sales		(309	)		(271	)		(860	)		(856	)
	Amounts included in inventoried contract costs at end of the period	$	151		$	126		$	151		$	126
	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 not included in inventoried contract costs.
		Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
		(in millions)
	Selling, general and administrative expenses	$	70		$	70		$	213		$	214
	Research and development expenses		14			17			48			62
	Total	$	84		$	87		$	261		$	276

Inventories

Inventories	9 Months Ended
	Sep. 26, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	7.  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.
		September 26,		December 31,
		2014		2013
		(in millions)
	Raw materials, components and sub-assemblies	$	156	$	160
	Work in process		137		125
	Finished goods		78		74
	Total	$	371	$	359

Goodwill_and_Identifiable_Inta

Goodwill and Identifiable Intangible Assets	9 Months Ended
	Sep. 26, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Identifiable Intangible Assets	'
	8.  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). The table below presents the changes in goodwill by segment for the year-to-date period ended September 26, 2014.
			Electronic			Aerospace			Communication		NSS		Consolidated
			Systems			Systems			Systems				Total
			(in millions)
	Balance at December 31, 2013		$	4,085		$	1,751		$	992	$	968	$	7,796
	Business acquisition(1)			(3	)		—			—		39		36
	Foreign currency translation adjustments(2)			(39	)		(9	)		—		—		(48	)
	Balance at September 26, 2014		$	4,043		$	1,742		$	992	$	1,007	$	7,784
	(1)	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.
	(2)	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 the year-to-date period ended September 26, 2014. The decrease in goodwill presented in the Aerospace Systems segment was due to the strengthening of the U.S. dollar against the Canadian dollar during the year-to-date period ended September 26, 2014.
	The Company’s accumulated goodwill impairment losses were $58 million at September 26, 2014 and December 31, 2013, of which $43 million and $15 million were recorded in the Electronic Systems and Communication Systems segments, respectively.
	Identifiable Intangible Assets. The table below presents information for the Company’s identifiable intangible assets that are subject to amortization.
						September 26, 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			19		$	474		$	275	$	199	$	466		$	253	$	213
	Technology			11			168			115		53		168			108		60
	Other			18			27			16		11		27			15		12
	Total			17		$	669		$	406	$	263	$	661		$	376	$	285
	The table below presents amortization expense recorded by the Company for its identifiable intangible assets.
			Third Quarter Ended						Year-to-Date Ended
			(in millions)
			September 26,			September 27,			September 26,		September 27,
			2014			2013			2014		2013
	Amortization Expense		$	11		$	10		$	32	$	29
	Based on gross carrying amounts at September 26, 2014, the Company’s estimate of amortization expense for identifiable intangible assets for the years ending December 31, 2014 through 2018 is presented in the table below.
			Year Ending December 31,
			2014			2015			2016		2017		2018
			(in millions)
	Estimated amortization expense		$	42		$	41		$	34	$	32	$	26

Other_Current_Liabilities_and_

Other Current Liabilities and Other Liabilities	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Other Current Liabilities and Other Liabilities	'
	9.  Other Current Liabilities and Other Liabilities
	The table below presents the components of other current liabilities.
			September 26,			December 31,
			2014			2013
			(in millions)
	Other Current Liabilities:
	Accruals for pending and threatened litigation (see Note 18)		$	7		$	6
	Accrued product warranty costs			79			75
	Estimated costs in excess of estimated contract value to complete contracts in process in a loss position			71			78
	Accrued interest			52			52
	Deferred revenues			36			35
	Notes payable and capital lease obligation			16			10
	Other			105			127
	Total other current liabilities		$	366		$	383
	The table below presents the components of other liabilities.
			September 26,			December 31,
			2014			2013
			(in millions)
	Other Liabilities:
	Non-current income taxes payable (see Note 11)		$	193		$	177
	Deferred compensation			46			45
	Accrued workers’ compensation			40			46
	Accrued product warranty costs			26			24
	Notes payable and capital lease obligations			2			15
	Other			92			99
	Total other liabilities		$	399		$	406
	The table below presents the changes in the Company’s accrued product warranty costs.
			Year-to-Date Ended
			September 26,			September 27,
			2014			2013
			(in millions)
	Accrued product warranty costs:(1)
	Balance at January 1		$	99		$	99
	Accruals for product warranties issued during the period			53			56
	Settlements made during the period			(46	)		(56	)
	Foreign currency translation adjustments			(1	)		—
	Balance at end of period		$	105		$	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.

Debt

Debt	9 Months Ended
	Sep. 26, 2014
Debt Disclosure [Abstract]	'
Debt	'
	10.  Debt
	The components of debt and a reconciliation to the carrying amount of long-term debt is presented in the table below.
			September 26,			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 (CODES)			—			689
	Principal amount of long-term debt			3,950			3,639
	Unamortized discounts			(12	)		(9	)
	Carrying amount of long-term debt		$	3,938		$	3,630
	(1)	During the year-to-date period ended September 26, 2014, L-3 Communications’ aggregate borrowings and repayments under the Amended and Restated Revolving Credit Facility were $1,367 million. At September 26, 2014, L-3 Communications had the availability of all of its $1 billion Amended and Restated Revolving Credit Facility, which expires on February 3, 2017.
	L-3 Communications
	Senior Notes: On May 28, 2014, L-3 Communications issued two series of Senior Notes, which are unsecured senior obligations of L-3 Communications. The terms of each series of Senior Notes are presented in the table below.
	Note		Date of Issuance			Amount			Bond		Net		Effective			Redemption
						Issued			Discount(1)		Cash		Interest			at Treasury
											Proceeds(2)		Rate			Rate(3)(4)
						(in millions)
	1.50% Senior Notes due May 28, 2017 (2017 Notes)			May 28, 2014		$	350		$	1	$	347		1.55	%		10 bps
	3.95% Senior Notes due May 28, 2024 (2024 Notes)			May 28, 2014		$	650		$	3	$	641		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 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 are available for general corporate purposes.
	(3)	The 2017 Senior Notes may be redeemed at any time prior to their maturity and the 2024 Notes 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 2024 Senior Notes are redeemed at any time on or after February 28, 2024, the redemption price would be equal to 100% of the principal amount.
	(4)	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 a price in cash equal to 101% of the aggregate principal amount plus accrued and unpaid interest, if any, but not including, the date of purchase.
	L-3 Holdings
	On May 13, 2014, the Company called for full the 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 “Redemption Conversion Period”). The conversion value of CODES of $935 million was calculated in accordance with the indenture governing the CODES based on the closing sales price of L-3 Holdings’ common stock and the conversion rate for each trading day in the 20 trading day period as follows: (1) for conversion notices received by May 16, 2014 (5 p.m.), the 20 trading day conversion period began on the third trading day following receipt of the conversion notice and (2) for conversion notices received after that time, the 20 trading day conversion period began on May 2, 2014 and ended on May 30, 2014, the trading day immediately preceding the Redemption Date. The Company settled the entire conversion value with respect to converted CODES in cash. As of June 27, 2014, the CODES were retired. As a result of the conversion, the Company recorded a reduction to shareholders’ equity of $160 million related to the excess conversion value over the fair value of the debt component of the CODES, net of deferred tax liability.
	Interest expense recognized for the CODES was $2 million for the year-to-date period ended September 26, 2014 and $5 million and $15 million for the quarterly and year-to-date periods ended September 27, 2013.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 26, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	11.  Income Taxes
	The Company and its subsidiaries file income tax returns in the U.S. Federal jurisdiction and various state and foreign jurisdictions. As of September 26, 2014, the statutes of limitations for the Company’s U.S. Federal income tax returns for the years ended December 31, 2010 through 2013 were open. The U.S. Internal Revenue Service (IRS) commenced audits of the Company’s U.S. Federal income tax returns for 2011 and 2010. The Company cannot predict the outcome of the audits at this time.
	The effective tax rate for the year-to-date period ended September 26, 2014 increased to 29.5% from 27.5% for the year-to-date period ended September 27, 2013. The increase was primarily due to a tax benefit in the year-to-date period ended September 27, 2013 of $28 million related to the retroactive reinstatement in January 2013 of the U.S. Federal research and experimentation tax credit for 2012 and 2013, which did not recur in 2014 and the reversal of previously accrued amounts of $10 million in the quarterly period ended September 27, 2013 for the expiration of the statutes of limitations for several tax returns.
	As of September 26, 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 of the decrease over the next 12 months could vary significantly depending on the ultimate timing and nature of any settlement.
	Non-current income taxes payable include accrued potential interest of $14 million ($8 million after income taxes) at September 26, 2014 and $11 million ($7 million after income taxes) at December 31, 2013, and potential penalties of $8 million at both September 26, 2014 and December 31, 2013.

Amounts_Reclassified_Out_of_Ac

Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income	'
	12.  Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income
	The amounts reclassified from Accumulated Other Comprehensive (Loss) Income (AOCI) for the year-to-date periods ended September 26, 2014 and September 27, 2013 are presented in the table below.
			Foreign			Unrealized			Unrecognized			Total
			currency			gains			(losses) and			accumulated
			translation			(losses) on			prior service			other
						hedging			cost, net			comprehensive
						instruments						(loss) income
			(in millions)
	Balance at December 31, 2012		$	167		$	3		$	(720	)	$	(550	)
	Other comprehensive loss before reclassifications, net of tax			(18	)		(2	)		—			(20	)
	Amounts reclassified from other comprehensive income, net of tax			—			1			40			41
	Net current period other comprehensive (loss) income		$	(18	)	$	(1	)	$	40		$	21
	Balance at September 27, 2013		$	149		$	2		$	(680	)	$	(529	)
	Balance at December 31, 2013		$	142		$	1		$	(253	)	$	(110	)
	Other comprehensive income before reclassifications, net of tax			(57	)		5			—			(52	)
	Amounts reclassified from other comprehensive (loss) income, net of tax			—			(5	)		7			2
	Net current period other comprehensive income			(57	)		—			7			(50	)
	Balance at September 26, 2014		$	85		$	1		$	(246	)	$	(160	)
	Further details regarding the amounts reclassified from AOCI for the quarterly and year-to-date periods ended September 26, 2014 and September 27, 2013 are presented in the table below.
			Amount Reclassified from AOCI												Affected Line Item in the
			Third Quarter Ended						Year-to-Date Ended						Unaudited Condensed Consolidated
	Details About		September 26,			September 27,			September 26,			September 27,			Statements of Operations
	AOCI Components		2014			2013			2014			2013
			(in millions)
	Gain (loss) on hedging instruments		$	1		$	—		$	(6	)	$	1		Cost of sales-products
				1			—			(6	)		1		Income before income taxes
				(1	)		—			1			—		Benefit (Provision) for income taxes
			$	—		$	—		$	(5	)	$	1		Net income
	Amortization of defined benefit pension items:
	Net loss		$	3		$	20		$	11		$	63		(a)
				3			20			11			63		Income before income taxes
				(1	)		(7	)		(4	)		(23	)	Provision for income taxes
			$	2		$	13		$	7		$	40		Net Income
	Total reclassification for the period		$	2		$	13		$	2		$	41		Net Income
	(a)	Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 19 for additional information).

Equity

Equity	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Equity	'
	13.  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. Repurchases of L-3 Holdings’ common stock under the share repurchase program are made at management’s discretion in accordance with applicable U.S. Federal securities laws in the open market or otherwise. 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 repurchased 3.6 million shares of its common stock at an average price of $115.91 per share for an aggregate amount of $413 million from January 1, 2014 through September 26, 2014. All share repurchases of L-3 Holdings’ common stock have been recorded as treasury shares.
	At September 26, 2014, the remaining dollar value of authorization under the share repurchase program was $455 million.
	On June 24, 2014, L-3 Holdings’ Board of Directors declared a cash dividend of $0.60 per share, which resulted in the Company paying total cash dividends of $51 million on September 15, 2014. Also, on October 20, 2014, L-3 Holdings’ Board of Directors declared a quarterly cash dividend of $0.60 per share, payable on December 15, 2014, to shareholders of record at the close of business on November 17, 2014.

L3_Holdings_Earnings_Per_Commo

L-3 Holdings' Earnings Per Common Share	9 Months Ended
	Sep. 26, 2014
Earnings Per Share [Abstract]	'
L-3 Holdings' Earnings Per Common Share	'
	14.  L-3 Holdings’ Earnings Per Common Share
	A reconciliation of basic and diluted earnings per share (EPS) is presented in the table below.
			Third Quarter Ended						Year-to-Date Ended
			September 26,			September 27,			September 26,			September 27,
			2014			2013			2014			2013
			(in millions, except per share data)
	Reconciliation of net income:
	Net income		$	157		$	204		$	470		$	572
	Net income attributable to noncontrolling interests			(3	)		(4	)		(9	)		(6	)
	Net income attributable to L-3 Holdings’ common shareholders		$	154		$	200		$	461		$	566
	Earnings per share attributable to L-3 Holdings’ common shareholders:
	Basic:
	Weighted average common shares outstanding			85.1			89.6			85.7			89.9
	Basic earnings per share:
	Net income		$	1.81		$	2.23		$	5.38		$	6.3
	Diluted:
	Common and potential common shares:
	Weighted average common shares outstanding			85.1			89.6			85.7			89.9
	Assumed exercise of stock options			2.8			4.7			3			3.9
	Unvested restricted stock awards			1.5			1.8			1.6			1.8
	Employee stock purchase plan contributions			—			0.2			0.1			0.2
	Performance unit awards			0.1			0.1			0.1			0.1
	Assumed purchase of common shares for treasury			(2.9	)		(5.2	)		(3.2	)		(4.7	)
	Assumed conversion of the CODES(1)			—			0.1			1.1			0.1
	Common and potential common shares			86.6			91.3			88.4			91.3
	Diluted earnings per share:
	Net income		$	1.78		$	2.19		$	5.21		$	6.2
	(1)	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. Although the CODES were retired during the year-to-date period ended June 27, 2014, they were dilutive for the year-to-date period ended September 26, 2014 as the average market price of L-3 Holdings’ common stock during the period that the CODES were outstanding was greater than the price at which the CODES would have been convertible into L-3 Holdings’ common stock. See Note 10 regarding the retirement of the CODES.
	The computation of diluted EPS excluded shares for stock options and employee stock purchase plan contributions of 0.6 million and 0.5 million for the quarterly and year-to-date periods ended September 26, 2014, respectively, and shares for stock options of 1.2 million for the year-to-date period ended September 27, 2013, as they were anti-dilutive.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Sep. 26, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	15.  Fair Value Measurements
	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.
			September 26, 2014						December 31, 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		$	359	$	—	$	—	$	299	$	—	$	—
	Derivatives (foreign currency forward contracts)			—		5		—		—		6		—
	Total assets		$	359	$	5	$	—	$	299	$	6	$	—
	Liabilities
	Derivatives (foreign currency forward contracts)		$	—	$	4	$	—	$	—	$	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	9 Months Ended
	Sep. 26, 2014
Investments, All Other Investments [Abstract]	'
Financial Instruments	'
	16.  Financial Instruments
	At September 26, 2014 and December 31, 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 their short-term maturities or the 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.
			September 26, 2014				December 31, 2013
			Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value
			(in millions)
	Senior Notes(1)		$	3,938	$	4,181	$	2,941	$	3,121
	CODES(1)			—		—		689		830
	Foreign currency forward contracts(2)			1		1		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)	See Note 17 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative_Financial_Instrumen

Derivative Financial Instruments	9 Months Ended
	Sep. 26, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Financial Instruments	'
	17.  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, at December 31, 2013, representing the contingent interest payment provision related to the CODES.
	Foreign Currency Forward Contracts. 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 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 condensed consolidated 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 AOCI 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. Notional amounts are used to measure the volume of foreign currency forward contracts and do not represent exposure to foreign currency losses. The table below presents the notional amounts of the Company’s outstanding foreign currency forward contracts by currency at September 26, 2014.
	Currency		Notional Amounts
			(in millions)
	Canadian dollar		$	161
	U.S. dollar			101
	Euro			66
	British pound			9
	Total		$	337
	At September 26, 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 condensed consolidated balance sheets.
			September 26, 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)		$	4	$	1	$	3	$	1	$	5	$	1	$	3	$	2
	Derivatives not designated as hedging instruments:
	Foreign currency forward contracts(1)			—		—		—		—		—		—		—		—
	Embedded derivative related to the CODES(2)			—		—		—		—		—		—		—		—
	Total derivative instruments		$	4	$	1	$	3	$	1	$	5	$	1	$	3	$	2
	(1)	See Note 15 for a description of the fair value hierarchy related to the Company’s foreign currency forward contracts.
	(2)	See Note 10 for a description of the CODES Retirement.
	The effect of gains or losses from foreign currency forward contracts was not material to the unaudited condensed consolidated statements of operations for the quarterly or year-to-date periods ended September 26, 2014 and September 27, 2013. At September 26, 2014, the estimated amount of existing losses that are expected to be reclassified into income within the next 12 months is less than $1 million.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 26, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	18.  Commitments and Contingencies
	Guarantees
	In connection with the spin-off of Engility Holdings, Inc. (Engility), 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.
	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 international 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. 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. International government contracts generally include comparable provisions relating to terminations for convenience or default, as well as other procurement clauses relevant to the international 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 9. Amounts recoverable from insurance contracts or third parties are recorded as assets when deemed probable. At September 26, 2014, the Company did not record any amounts for recoveries from insurance contracts or third parties in connection with the amount of liabilities recorded for pending and threatened litigation. Legal defense costs are expensed as incurred. The Company believes it has recorded adequate provisions for its litigation matters. The Company reviews these provisions 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, Zubair Patel, Alan Nguyen and Carmen Valentino filed separate, putative class action complaints in the United States District Court for the Southern District of New York against the Company and certain of its officers. Each 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. On October 20, 2014, these cases were consolidated into a single, putative class action in the United States District Court for the Southern District of New York. The Company believes the action lacks merit and intends to defend against it vigorously. 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. For a discussion of the Company’s internal review relating to the accounting matters at issue, see Note 3.
	Government Inquiries. On July 30, 2014, the Company voluntarily contacted the 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 because they are in their early stages.
	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 and seek approximately $315 million in damages, including $150 million in punitive damages. The Company’s insurers have accepted defense of this matter and have 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. On July 1, 2013, the Supreme Court agreed to consider the appeal, and the parties are awaiting the Supreme Court’s decision. The Company believes that the ruling and the damages awarded are inconsistent with the law and evidence presented and, accordingly, that it is not probable that the Company has incurred a loss with respect to this matter. As of the date of this filing, 18 out of the 30 plaintiffs have released their claims against ACSS in consideration for payments made by the Company’s insurance carriers.
	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.

Pension_and_Other_Postretireme

Pension and Other Postretirement Benefits	9 Months Ended
	Sep. 26, 2014
Compensation and Retirement Disclosure [Abstract]	'
Pension and Other Postretirement Benefits	'
	19.  Pension and Other Postretirement Benefits
	The following table summarizes the components of net periodic benefit cost for the Company’s pension and other postretirement benefit plans.
		Pension Plans												Postretirement Benefit Plans
		Third Quarter Ended						Year-to-Date Ended						Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,			September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013			2014			2013			2014			2013
		(in millions)
	Components of net periodic benefit cost:
	Service cost	$	26		$	30		$	80		$	95		$	(2	)	$	1		$	—		$	3
	Interest cost		37			33			110			99			4			2			8			5
	Expected return on plan assets		(48	)		(41	)		(145	)		(124	)		(1	)		—			(3	)		(2	)
	Amortization of prior service costs (credits)		—			1			1			1			—			(1	)		(1	)		(2	)
	Amortization of net loss (gain)		4			20			13			63			(1	)		—			(2	)		1
	Curtailment loss		—			2			1			2			(1	)		—			(1	)		—
	Net periodic benefit cost	$	19		$	45		$	60		$	136		$	(1	)	$	2		$	1		$	5
	Contributions. The Company contributed cash of $85 million to its pension plans and $5 million to its other postretirement benefit plans during the year-to-date period ended September 26, 2014. The Company expects to contribute an additional $12 million to its pension plans and $5 million to its other postretirement benefit plans during the remainder of 2014.

StockBased_Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 26, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock-Based Compensation	'
	20.  Stock-Based Compensation
	During the year-to-date period ended September 26, 2014, the Company granted stock-based compensation under the Amended and Restated 2008 Long Term Performance Plan (2008 LTPP) in the form of stock options, restricted stock units and performance units further discussed below.
	Stock Options. The Company granted 472,992 stock options with an exercise price of $113.67 per option, which was equal to the closing price of L-3 Holdings’ common stock on the date of grant. The 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. The options granted to our Chairman, President and Chief Executive Officer are also subject to performance-based vesting conditions. The weighted average grant date fair value for the options of $20.02 per option was estimated using the Black-Scholes option-pricing model. The weighted average assumptions used in the valuation model for this grant are presented in the table below.
	Expected holding period (in years)	5.5
	Expected volatility	24.4	%
	Expected dividend yield	2.7	%
	Risk-free interest rate	1.7	%
	Restricted Stock Units. The Company granted 414,694 restricted stock units with a weighted average grant date fair value of $113.69 per share. Restricted stock units automatically convert into shares of L-3 Holdings’ common stock upon vesting, and 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 non-employee directors, in each case starting on the date of grant.
	Performance Units. The Company granted 47,467 performance units with a weighted average grant date fair value per unit of $113.67. The final payout for these units is based on the achievement of pre-determined EPS goals established by the compensation committee of the Company’s Board of Directors for the three-year period ending December 31, 2016. The payout can range from zero to 200% of the original number of units awarded, which are converted into shares of L-3 Holdings’ common stock based on the then existing closing price at the end of the performance period.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	9 Months Ended
	Sep. 26, 2014
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
	21.  Supplemental Cash Flow Information
		Year-to-Date Ended
		September 26,		September 27,
		2014		2013
		(in millions)
	Interest paid on outstanding debt	$	123	$	133
	Income tax payments		116		168
	Income tax refunds		8		20

Segment_Information

Segment Information	9 Months Ended
	Sep. 26, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	22.  Segment Information
	The Company has four reportable segments, as 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.
	The tables below present net sales, operating income, depreciation and amortization and total assets by reportable segment.
		Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
		(in millions)
	Net Sales:
	Electronic Systems	$	1,128		$	1,139		$	3,349		$	3,438
	Aerospace Systems		1,037			1,092			3,173			3,416
	Communication Systems		507			486			1,562			1,667
	NSS		307			323			948			987
	Elimination of intercompany sales		(39	)		(38	)		(116	)		(120	)
	Consolidated total	$	2,940		$	3,002		$	8,916		$	9,388
	Operating Income:
	Electronic Systems	$	125		$	144		$	383		$	388
	Aerospace Systems		64			105			196			336
	Communication Systems		49			31			147			116
	NSS		19			26			56			66
	Consolidated total	$	257		$	306		$	782		$	906
	Depreciation and amortization:
	Electronic Systems	$	30		$	28		$	89		$	87
	Aerospace Systems		11			10			30			28
	Communication Systems		13			12			38			35
	NSS		2			2			8			8
	Consolidated total	$	56		$	52		$	165		$	158
		September 26,			December 31,
		2014			2013
		(in millions)
	Total Assets:
	Electronic Systems	$	6,998		$	6,928
	Aerospace Systems		2,961			3,087
	Communication Systems		2,076			2,130
	NSS		1,312			1,247
	Corporate		694			596
	Consolidated total	$	14,041		$	13,988

Employee_Severance_and_Termina

Employee Severance and Termination Costs	9 Months Ended
	Sep. 26, 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 $23 million in employee severance and other termination costs with respect to approximately 1,500 employees during the year-to-date period ended September 26, 2014. During the year ended December 31, 2013, the Company recorded a total of $29 million in employee severance and other termination costs with respect to approximately 2,000 employees. Employee severance and other termination costs are reported within cost of sales on the unaudited condensed consolidated statement of operations. The remaining balance to be paid in connection with these initiatives was $11 million at September 26, 2014 and December 31, 2013. Employee severance and other termination costs incurred by reportable segment for the year-to-date periods ended September 26, 2014 and September 27, 2013 are presented in the table below.
		Year-to-Date Ended
		September 26,		September 27,
		2014		2013
		(in millions)
	Reportable Segment
	Electronic Systems	$	14	$	11
	Aerospace Systems		3		1
	Communication Systems		5		6
	NSS		1		1
	Consolidated	$	23	$	19

Condensed_Combining_Financial_

Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries	'
	24.  Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries
	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 Amended and Restated Revolving Credit Facility is 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 Amended and Restated Revolving 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 11 to the audited consolidated financial statements for the year ended December 31, 2013, included in the Company’s Form 10-K/A. 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.
	The following unaudited 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.
	As discussed in Note 3, the Company is revising its previously issued financial statements. As part of that revision, the Company has revised the accompanying condensed combining financial statements contained herein. The adjustments related to the internal review of the Aerospace Systems segment, excluding certain adjustments related to the Platform Systems segment, were recorded as adjustments to the Guarantor Subsidiaries financial statement amounts. Adjustments from the internal review that related to a foreign subsidiary of the Platform Systems segment, with a cumulative operating impact through September 26, 2014 of $28 million, were recorded to the Non-Guarantor Subsidiaries financial statement amounts. The adjustments for the accounting related to a sales-type lease transaction for flight simulator systems within its Electronic Systems segment have been recorded as adjustments to the L-3 Communications financial statement amounts. The adjustments for the previously identified immaterial errors were recorded as adjustments to the Guarantor Subsidiaries financial statement amounts.
		L-3			L-3			Guarantor			Non-			Eliminations			Consolidated
		Holdings			Communications			Subsidiaries			Guarantor						L-3
		(Parent)									Subsidiaries
		(in millions)
	Condensed Combining Balance Sheets:
	At September 26, 2014:
	Current assets:
	Cash and cash equivalents	$	—		$	330		$	1		$	239		$	(62	)	$	508
	Billed receivables, net		—			296			348			227			—			871
	Contracts in process		—			994			1,165			387			—			2,546
	Other current assets		—			410			145			176			—			731
	Total current assets		—			2,030			1,659			1,029			(62	)		4,656
	Goodwill		—			2,324			4,320			1,140			—			7,784
	Other assets		—			800			568			233			—			1,601
	Investment in and amounts due from consolidated subsidiaries		5,903			6,993			4,049			—			(16,945	)		—
	Total assets	$	5,903		$	12,147		$	10,596		$	2,402		$	(17,007	)	$	14,041
	Current liabilities	$	—		$	872		$	999		$	583		$	(62	)	$	2,392
	Amounts due to consolidated subsidiaries		—			—			—			366			(366	)		—
	Other long-term liabilities		—			1,434			187			111			—			1,732
	Long-term debt		—			3,938			—			—			—			3,938
	Total liabilities		—			6,244			1,186			1,060			(428	)		8,062
	L-3 shareholders’ equity		5,903			5,903			9,410			1,342			(16,655	)		5,903
	Noncontrolling interests		—			—			—			—			76			76
	Total equity		5,903			5,903			9,410			1,342			(16,579	)		5,979
	Total liabilities and equity	$	5,903		$	12,147		$	10,596		$	2,402		$	(17,007	)	$	14,041
	At December 31, 2013:
	Current assets:
	Cash and cash equivalents	$	—		$	258		$	—		$	261		$	(19	)	$	500
	Billed receivables, net		—			364			401			226			—			991
	Contracts in process		—			925			1,152			354			—			2,431
	Other current assets		—			344			159			169			—			672
	Total current assets		—			1,891			1,712			1,010			(19	)		4,594
	Goodwill		—			2,324			4,320			1,152			—			7,796
	Other assets		—			838			532			228			—			1,598
	Investment in and amounts due from consolidated subsidiaries		6,670			6,923			3,750			—			(17,343	)		—
	Total assets	$	6,670		$	11,976		$	10,314		$	2,390		$	(17,362	)	$	13,988
	Current liabilities	$	—		$	914		$	1,011		$	628		$	(19	)	$	2,534
	Amounts due to consolidated subsidiaries		—			—			—			259			(259	)		—
	Other long-term liabilities		—			1,451			193			124			—			1,768
	Long-term debt		689			3,630			—			—			(689	)		3,630
	Total liabilities		689			5,995			1,204			1,011			(967	)		7,932
	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		$	10,314		$	2,390		$	(17,362	)	$	13,988
	Condensed Combining Statements of Operations:
	For the quarter ended September 26, 2014:
	Total net sales	$	—		$	860		$	1,628		$	525		$	(73	)	$	2,940
	Total cost of sales		(10	)		(787	)		(1,500	)		(469	)		83			(2,683	)
	Operating (loss) income		(10	)		73			128			56			10			257
	Interest expense		—			(46	)		(2	)		1			—			(47	)
	Interest and other income, net		—			4			—			1			—			5
	(Loss) income before income taxes		(10	)		31			126			58			10			215
	Benefit (provision) for income taxes		3			(8	)		(34	)		(16	)		(3	)		(58	)
	Equity in net income of consolidated subsidiaries		161			131			—			—			(292	)		—
	Net income		154			154			92			42			(285	)		157
	Net income attributable to noncontrolling interests		—			—			—			—			(3	)		(3	)
	Net income attributable to L-3	$	154		$	154		$	92		$	42		$	(288	)	$	154
Comprehensive income attributable to L-3	$	90		$	90		$	89		$	(22	)	$	(157	)	$	90
For the quarter ended September 27, 2013:
Total net sales	$	—		$	912		$	1,646		$	543		$	(99	)	$	3,002
Total cost of sales		(14	)		(854	)		(1,458	)		(483	)		113			(2,696	)
Operating (loss) income		(14	)		58			188			60			14			306
Interest expense		(5	)		(43	)		—			(1	)		5			(44	)
Interest and other income, net		—			3			1			—			—			4
(Loss) income before income taxes		(19	)		18			189			59			19			266
Benefit (provision) for income taxes		5			(3	)		(45	)		(14	)		(5	)		(62	)
Equity in net income of consolidated subsidiaries		214			185			—			—			(399	)		—
Net income		200			200			144			45			(385	)		204
Net income attributable to noncontrolling interests		—			—			—			—			(4	)		(4	)
Net income attributable to L-3	$	200		$	200		$	144		$	45		$	(389	)	$	200
Comprehensive income attributable to L-3	$	250		$	250		$	145		$	77		$	(472	)	$	250
Condensed Combining Statements of Operations:
For the Year-to-Date Period Ended September 26, 2014:
Total net sales	$	—		$	2,606		$	4,908		$	1,623		$	(221	)	$	8,916
Total cost of sales		(39	)		(2,354	)		(4,533	)		(1,468	)		260			(8,134	)
Operating (loss) income		(39	)		252			375			155			39			782
Interest expense		(2	)		(127	)		(2	)		—			2			(129	)
Interest and other income, net		—			12			—			2			—			14
(Loss) income before income taxes		(41	)		137			373			157			41			667
Benefit (provision) for income taxes		12			(41	)		(110	)		(46	)		(12	)		(197	)
Equity in net income of consolidated subsidiaries		490			365			—			—			(855	)		—
Net income		461			461			263			111			(826	)		470
Net income attributable to noncontrolling interests		—			—			—			—			(9	)		(9	)
Net income attributable to L-3	$	461		$	461		$	263		$	111		$	(835	)	$	461
Comprehensive income attributable to L-3	$	411		$	411		$	264		$	53		$	(728	)	$	411
For the Year-to-Date Period Ended September 27, 2013:
Total net sales	$	—		$	2,847		$	5,104		$	1,705		$	(268	)	$	9,388
Total cost of sales		(42	)		(2,625	)		(4,598	)		(1,527	)		310			(8,482	)
Operating (loss) income		(42	)		222			506			178			42			906
Interest expense		(15	)		(130	)		—			(1	)		15			(131	)
Interest and other income, net		—			9			1			4			—			14
(Loss) income before income taxes		(57	)		101			507			181			57			789
Benefit (provision) for income taxes		16			(28	)		(139	)		(50	)		(16	)		(217	)
Equity in net income of consolidated subsidiaries		607			493			—			—			(1,100	)		—
Net income		566			566			368			131			(1,059	)		572
Net income attributable to noncontrolling interests		—			—			—			—			(6	)		(6	)
Net income attributable to L-3	$	566		$	566		$	368		$	131		$	(1,065	)	$	566
Comprehensive income attributable to L-3	$	587		$	587		$	369		$	108		$	(1,064	)	$	587
Condensed Combining Statements of Cash Flows:
For the Year-to-Date Period Ended September 26, 2014:
Operating activities:
Net cash from operating activities	$	1,506		$	201		$	382		$	69		$	(1,553	)	$	605
Investing activities:
Business acquisitions, net of cash acquired		—			(57	)		—			—			—			(57	)
Investments in L-3 Communications		(87	)		—			—			—			87			—
Other investing activities		—			(37	)		(52	)		(16	)		—			(105	)
Net cash used in investing activities		(87	)		(94	)		(52	)		(16	)		87			(162	)
Financing activities:
Proceeds from sale of senior notes		—			996			—			—			—			996
Retirement of CODES		(935	)		—			—			—			—			(935	)
Common stock repurchased		(413	)		—			—			—			—			(413	)
Dividends paid on L-3 Holdings common stock		(158	)		—			—			—			—			(158	)
Dividends paid to L-3 Holdings		—			(1,506	)		—			—			1,506			—
Investments from L-3 Holdings		—			87			—			—			(87	)		—
Other financing activities		87			388			(329	)		(66	)		4			84
Net cash used in financing activities		(1,419	)		(35	)		(329	)		(66	)		1,423			(426	)
Effect of foreign currency exchange rate changes on cash		—			—			—			(9	)		—			(9	)
Net increase (decrease) in cash		—			72			1			(22	)		(43	)		8
Cash and cash equivalents, beginning of the period		—			258			—			261			(19	)		500
Cash and cash equivalents, end of the period	$	—		$	330		$	1		$	239		$	(62	)	$	508
For the Year-to-Date Period Ended September 27, 2013:
Net cash from operating activities	$	555		$	86		$	523		$	101		$	(648	)	$	617
Investing activities:
Business acquisitions, net of cash acquired		—			(2	)		—			—			—			(2	)
Investments in L-3 Communications		(104	)		—			—			—			104			—
Other investing activities		—			(70	)		(53	)		(16	)		—			(139	)
Net cash used in investing activities		(104	)		(72	)		(53	)		(16	)		104			(141	)
Financing activities:
Common stock repurchased		(404	)		—			—			—			—			(404	)
Dividends paid on L-3 Holdings common stock		(151	)		—			—			—			—			(151	)
Dividends paid to L-3 Holdings		—			(555	)		—			—			555			—
Investments from L-3 Holdings		—			104			—			—			(104	)		—
Other financing activities		104			345			(469	)		(81	)		210			109
Net cash used in financing activities		(451	)		(106	)		(469	)		(81	)		661			(446	)
Effect of foreign currency exchange rate changes on cash		—			—			—			(2	)		—			(2	)
Net (decrease) increase in cash		—			(92	)		1			2			117			28
Cash and cash equivalents, beginning of the period		—			246			—			242			(139	)		349
Cash and cash equivalents, end of the period	$	—		$	154		$	1		$	244		$	(22	)	$	377

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 26, 2014
Accounting Changes and Error Corrections [Abstract]	'
Principles of Consolidation and Reporting	'
	Principles of Consolidation and Reporting
	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 of L-3 Communications and (2) its guarantee of other contractual obligations of L-3 Communications and its subsidiaries. As of the date of this report, 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. See Note 10 to these unaudited financial statements. 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, 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 24 for additional information regarding the unaudited financial information of L-3 Communications and its subsidiaries.
	The unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and in accordance with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the disclosures required by U.S. GAAP for a complete set of annual audited financial statements. The December 31, 2013 condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. In the opinion of management, all adjustments (consisting of normal and recurring adjustments) considered necessary for a fair presentation of the results for the interim periods presented have been included. The results of operations for the interim periods are not necessarily indicative of results for the full year.
	It is the Company’s established practice to close its books for the quarters ending March, June and September on the Friday nearest to the end of the calendar quarter. The interim unaudited condensed consolidated financial statements included herein have been prepared and are labeled based on that convention. The Company closes its books for annual periods on December 31 regardless of what day it falls on.
Accounting Estimates	'
	Accounting Estimates
	The preparation of financial statements in conformity with 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 for L-3 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 valuation 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.
	Sales and profits on contracts that are covered by accounting standards for construction-type and production-type contracts and federal government contractors are recognized using percentage-of-completion (POC) methods of accounting. Approximately 47% of the Company’s net sales in 2013 were accounted for under contract accounting standards, of which approximately 38% were fixed-price type contracts and approximately 9% were cost-plus type contracts. For contracts accounted for under contract accounting standards, sales and profits are recognized based on: (1) a 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). 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 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.
	Accounting for the sales and profit on these fixed-price type contracts requires the preparation of estimates of: (1) the total contract revenue, (2) the total costs at completion, which is equal to the sum of the actual incurred costs to date on the contract and the estimated costs to complete the contract’s statement of work, and (3) the measurement of progress towards completion. The estimated profit or loss at completion on a contract is equal to the difference between the total estimated contract revenue and the total estimated cost at completion. The profit recorded on a contract in any period using either the units-of-delivery method or cost-to-cost method is equal to the current estimated total profit margin multiplied by the cumulative sales recognized, less the amount of cumulative profit previously recorded for the contract.
	Sales and profits on cost-plus type contracts that are covered by contract accounting standards are recognized as allowable costs are incurred on the contract, at an amount equal to the allowable costs plus the estimated profit on those costs. The estimated profit on a cost-plus type contract is fixed or variable based on the contractual fee arrangement. Incentive and award fees are the primary variable fee contractual arrangement types for the Company. Incentive and award fees on cost-plus type contracts are included as an element of total estimated contract revenues and are recorded to 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.
	Revisions or adjustments to estimates for a contract’s revenue, estimated costs at completion and estimated profit or loss are often required as work progresses under a contract, as experience is gained, as facts and circumstances change and as new information is obtained, even though the scope of work required under the contract may not change. Revisions or adjustments may also be required if contract modifications occur. The impact of revisions in profit (loss) estimates for all types of contracts subject to POC accounting are recognized on a cumulative catch-up basis in the period in which the revisions are made. The revisions in contract estimates, if significant, can materially affect the Company’s results of operations and cash flows, as well as reduce the valuations of receivables and inventories, and in some cases result in liabilities to complete contracts in a loss position. Aggregate net changes in contract estimates increased consolidated operating income by $62 million, or 8%, for the year-to-date period ended September 26, 2014 and $92 million, or 10%, for the year-to-date period ended September 27, 2013.
	For a more complete discussion of these estimates and assumptions, see the Form 10-K/A filed on October 10, 2014.
Adoption of New Accounting Standards	'
	Effective January 1, 2014, the Company adopted Financial Accounting Standards Board (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 impact the Company’s financial position, results of operations or cash flows.
	In June 2014, the FASB issued Accounting Standard Update (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 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 Company is currently evaluating the impact of the adoption of this standard, if any, on our consolidated financial statements.
	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, and provide companies with a single revenue recognition model for recognizing revenue from contracts with customers. One of the core principles of the new standard is that a company should recognize revenue based on the satisfaction of performance obligations, which depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. 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 the transition alternatives available.
	In April 2014, the FASB issued an accounting standards update 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 update is effective for the Company for interim and annual periods beginning January 1, 2015. The adoption of this standard is not expected to impact the Company’s financial position, results of operations or cash flows and will only affect the treatment of future discontinued operations.

Revisions_to_Previously_Issued1

Revisions to Previously Issued Financial Statements (Tables)	9 Months Ended
	Sep. 26, 2014
Accounting Changes and Error Corrections [Abstract]	'
Schedule of Nature of Adjustments, Applicable Segment, Amount of Increase (or Decrease) to Sales and Operating Income, Period Recorded and Correct Period	'
	With respect to each of these immaterial out of period amounts included in the Company’s previously issued financial statements, the table below presents the: (1) nature of the adjustments, (2) applicable segment and (3) amount of increase (or decrease) to sales and operating income for the quarters ended December 31, September 27, June 28, and March 29, 2013.
					December 31,								September 27,								June 28,								March 29,
					2013								2013								2013								2013
	Nature of Adjustment		Applicable		Sales				Operating				Sales				Operating				Sales				Operating				Sales				Operating
			Segment						Income								Income								Income								Income
					($ in millions)
	Higher development and material costs for networked communications systems		Communication Systems		$	—			$	—			$	—			$	—			$	—			$	—			$	10			$	10
	Sub-contractor subscription deposit		Aerospace Systems			5				—				7				1				7				1				7				1
	Costs accruals for goods/services received		Aerospace Systems			—				—				—				—				—				—				5				1
	Unrecorded liabilities		Aerospace Systems			—				—				—				—				—				—				(2	)			—
	Accrued vacation		Aerospace Systems			—				6				—				(2	)			—				(2	)			—				(2	)
	Overstated revenue		Aerospace Systems			4				—				(4	)			—				—				—				—				—
	Total				$	9			$	6			$	3			$	(1	)		$	7			$	(1	)		$	20			$	10
Schedule of Impact on Sales and Pre-tax Income	'
	The table below presents the impact of the matters discussed above on sales and pre-tax income in total, for the six month period ended June 27, 2014, years ended December 31, 2013, 2012, and 2011, and for the years ended prior to December 31, 2011.
			Total								Six Months								2013								2012								2011						Prior to 2011
											2014
			Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales			Pre-tax			Sales			Pre-tax
							Income								Income								Income								Income							Income						Income
			(in millions)
	Army C-12 Contract		$	(32	)		$	(69	)		$	(3	)		$	(15	)		$	(25	)		$	(35	)		$	(3	)		$	(16	)		$	(1	)	$	(3	)	$	—		$	—
	Other Logistics Support Contracts			(5	)			(48	)			—				(20	)			(2	)			(11	)			(2	)			(11	)			—			(2	)		(1	)		(4	)
	Logistics Solutions			(37	)			(117	)			(3	)			(35	)			(27	)			(46	)			(5	)			(27	)			(1	)		(5	)		(1	)		(4	)
	Platform Systems			(21	)			(52	)			(12	)			(40	)			(12	)			(14	)			3				2				—			—			—			—
	Total Internal Review of Aerospace Systems Segment			(58	)			(169	)			(15	)			(75	)			(39	)			(60	)			(2	)			(25	)			(1	)		(5	)		(1	)		(4	)
	Sales-Type Lease Transaction			(15	)			29				(8	)			1				(7	)			5				—				3				—			3			—			17
	Out of Period Amounts			—				—				—				—				39				14				(36	)			(18	)			(3	)		4			—			—
	Total Revisions		$	(73	)		$	(140	)		$	(23	)		$	(74	)		$	(7	)		$	(41	)		$	(38	)		$	(40	)		$	(4	)	$	2		$	(1	)	$	13
	The table below presents the impact of the matters discussed above on sales and pre-tax income for the quarters ended June 27 and March 28, 2014, December 31, September 27, June 28, 2013 and March 29, 2013.
			June 27,								March 28,								December 31,								September 27,								June 28,						March 29,
			2014								2014								2013								2013								2013						2013
			Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales				Pre-tax				Sales			Pre-tax			Sales			Pre-tax
							Income								Income								Income								Income							Income						Income
			(in millions)
	Army C-12 Contract		$	(1	)		$	(11	)		$	(2	)		$	(4	)		$	(24	)		$	(20	)		$	3			$	(2	)		$	(3	)	$	(7	)	$	(1	)	$	(6	)
	Other Logistics Support Contracts			—				(15	)			—				(5	)			(1	)			(2	)			(1	)			(5	)			—			(2	)		—			(2	)
	Logistics Solutions			(1	)			(26	)			(2	)			(9	)			(25	)			(22	)			2				(7	)			(3	)		(9	)		(1	)		(8	)
	Platform Systems			(6	)			(29	)			(6	)			(11	)			(2	)			(2	)			1				—				(6	)		(6	)		(5	)		(6	)
	Total Internal Review of Aerospace Systems Segment			(7	)			(55	)			(8	)			(20	)			(27	)			(24	)			3				(7	)			(9	)		(15	)		(6	)		(14	)
	Sales-Type Lease Transaction			(3	)			1				(5	)			—				(3	)			1				(1	)			2				(1	)		1			(2	)		1
	Out of Period Amounts			—				—				—				—				9				6				3				(1	)			7			(1	)		20			10
	Total Revisions		$	(10	)		$	(54	)		$	(13	)		$	(20	)		$	(21	)		$	(17	)		$	5			$	(6	)		$	(3	)	$	(15	)	$	12		$	(3	)
Schedule of As Previously Reported, Adjustments and As Revised Financial Statements	'
	The tables below present the Company’s: (1) As Previously Reported, (2) Adjustments, and (3) As Revised Condensed Consolidated Statements of Operations for the quarterly and year-to-date periods ended September 27, 2013 and the Operating Activities for the Statement of Cash Flows for the year-to-date period ended September 27, 2013. The Adjustments correct for: (1) the results of the Aerospace Systems internal review, (2) the accounting related to a sales-type lease transaction within the Company’s Electronic Systems segment and (3) immaterial out of period amounts previously recorded in the Company’s financial statements but not recorded in the appropriate period to reflect them in the appropriate period.
							Adjustments for:
			As				Aerospace				Sales-Type				Out of Period				As
			Previously				Systems				Lease				Amounts				Revised
			Reported				Segment				Transaction
							Internal
							Review
			(in millions, except per share data)
	Unaudited Condensed Consolidated Statement of Operations, for the third quarter ended September 27, 2013:
	Net sales:
	Products		$	1,696			$	2			$	(1	)		$	—			$	1,697
	Services			1,300				2				—				3				1,305
	Total net sales			2,996				4	(1)			(1	)			3				3,002
	Cost of sales:
	Products			(1,486	)			(2	)			1				—				(1,487	)
	Services			(1,196	)			(9	)			—				(4	)			(1,209	)
	Total cost of sales			(2,682	)			(11	)			1				(4	)			(2,696	)
	Operating income			314				(7	)			—				(1	)			306
	Interest expense			(44	)			—				—				—				(44	)
	Interest and other income, net			3				—				1				—				4
	Income before income taxes			273				(7	)			1	(1)			(1	)			266
	Provision for income taxes			(65	)			3				—				—				(62	)
	Net income		$	208			$	(4	)		$	1			$	(1	)		$	204
	Net income attributable to noncontrolling interests			(4	)			—				—				—				(4	)
	Net income attributable to L-3		$	204			$	(4	)		$	1			$	(1	)		$	200
	Earnings per share attributable to L-3 Holdings’ common shareholders:
	Basic		$	2.28			$	(0.05	)		$	0.01			$	(0.01	)		$	2.23
	Diluted		$	2.23			$	(0.04	)		$	0.01			$	(0.01	)		$	2.19
	Cash dividends paid per common share		$	0.55			$	—			$	—			$	—			$	0.55
	L-3 Holdings’ weighted average common shares outstanding:
	Basic			89.6				—				—				—				89.6
	Diluted			91.3				—				—				—				91.3
	(1)	Includes rounding of $1 million.
							Adjustments for:
			As				Aerospace				Sales-Type				Out of Period				As
			Previously				Systems				Lease				Amounts				Revised
			Reported				Segment				Transaction
							Internal
							Review
			(in millions, except per share data)
	Unaudited Condensed Consolidated Statement of Operations, for the Year-to-Date Period Ended September 27, 2013:
	Net sales:
	Products		$	5,319			$	(9	)		$	(4	)		$	15			$	5,321
	Services			4,054				(2	)			—				15				4,067
	Total net sales			9,373				(11	)(1)			(4	)			30				9,388
	Cost of sales:
	Products			(4,729	)			(3	)			5				(5	)			(4,732	)
	Services			(3,710	)			(22	)			—				(18	)			(3,750	)
	Total cost of sales			(8,439	)			(25	)			5				(23	)			(8,482	)
	Operating income			934				(36	)			1				7	-1			906
	Interest expense			(131	)			—				—				—				(131	)
	Interest and other income, net			11				—				3				—				14
	Income before income taxes			814				(36	)			4				7				789
	Provision for income taxes			(226	)			13				(1	)			(3	)			(217	)
	Net income		$	588			$	(23	)		$	3			$	4			$	572
	Net income attributable to noncontrolling interests			(6	)			—				—				—				(6	)
	Net income attributable to L-3		$	582			$	(23	)		$	3			$	4			$	566
	Earnings per share attributable to L-3 Holdings’ common shareholders:
	Basic		$	6.47			$	(0.25	)		$	0.04			$	0.04			$	6.3
	Diluted		$	6.37			$	(0.25	)		$	0.04			$	0.04			$	6.2
	Cash dividends paid per common share		$	1.65			$	—			$	—			$	—			$	1.65
	L-3 Holdings’ weighted average common shares outstanding:
	Basic			89.9				—				—				—				89.9
Diluted			91.3				—				—				—				91.3
(1)	Includes rounding of $1 million.
		As				Net				As
		Previously				Adjustments				Revised
		Reported
		(in millions)
Unaudited Consolidated Statement of Cash Flows for the Year-to-Date Period Ended September 27, 2013:
Operating activities:
Net income		$	588			$	(16	)		$	572
Depreciation of property, plant and equipment			122				—				122
Amortization of intangibles and other assets			36				—				36
Deferred income tax provision			45				(7	)			38
Stock-based employee compensation expense			42				—				42
Contributions to employee savings plans in L-3 Holdings’ common stock			90				—				90
Amortization of pension and postretirement benefit plans net loss and prior service cost			63				—				63
Amortization of bond discounts and deferred debt issue costs (included in interest expense)			5				—				5
Other non-cash items			1				—				1
Changes in operating assets and liabilities, excluding amounts from acquisitions and divestitures:
Billed receivables			(117	)			—				(117	)
Contracts in process			(36	)			(34	)			(70	)
Inventories			(55	)			(5	)			(60	)
Other assets			(45	)			(3	)			(48	)
Accounts payable, trade			65				(11	)			54
Accrued employment costs			27				10				37
Accrued expenses			(41	)			(4	)			(45	)
Advance payments and billings in excess of costs incurred			(109	)			48				(61	)
Income taxes			32				(1	)			31
Excess income tax benefits related to share-based payment arrangements			(3	)			—				(3	)
Other current liabilities			(8	)			3				(5	)
Pension and postretirement benefits			(23	)			—				(23	)
All other operating activities			(62	)			20				(42	)
Net cash from operating activities		$	617			$	—			$	617

Acquisitions_Tables

Acquisitions (Tables)	9 Months Ended
	Sep. 26, 2014
Business Combinations [Abstract]	'
Unaudited Pro Forma Statements of Operations Data	'
	The following unaudited pro forma Statements of Operations data present the combined results of the Company and its business acquisitions completed during the year-to-date period ended September 26, 2014 and the year ended December 31, 2013, in each case assuming that the business acquisitions completed during these periods had occurred on January 1, 2013.
		Third Quarter Ended				Year-to-Date Ended
		September 26,		September 27,		September 26,		September 27,
		2014		2013		2014		2013
		(in millions, except per share data)
	Pro forma net sales	$	2,940	$	3,025	$	8,923	$	9,450
	Pro forma net income attributable to L-3	$	154	$	200	$	460	$	567
	Pro forma diluted earnings per share	$	1.78	$	2.19	$	5.2	$	6.21

Contracts_in_Process_Tables

Contracts in Process (Tables)	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Components of Contracts in Process	'
	The components of contracts in process are presented in the table below.
		September 26,			December 31,
		2014			2013
		(in millions)
	Unbilled contract receivables, gross	$	2,449		$	2,502
	Unliquidated progress payments		(900	)		(1,035	)
	Unbilled contract receivables, net		1,549			1,467
	Inventoried contract costs, gross		1,069			1,044
	Unliquidated progress payments		(72	)		(80	)
	Inventoried contract costs, net		997			964
	Total contracts in process	$	2,546		$	2,431
General and Administrative, Independent Research and Development and Bids 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.
		Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
		(in millions)
	Amounts included in inventoried contract costs at beginning of the period:	$	151		$	115		$	138		$	110
	IRAD and B&P costs		70			66			215			219
	Other G&A costs		239			216			658			653
	Total contract costs incurred		309			282			873			872
	Amounts charged to cost of sales		(309	)		(271	)		(860	)		(856	)
	Amounts included in inventoried contract costs at end of the period	$	151		$	126		$	151		$	126
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 not included in inventoried contract costs.
		Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
		(in millions)
	Selling, general and administrative expenses	$	70		$	70		$	213		$	214
	Research and development expenses		14			17			48			62
	Total	$	84		$	87		$	261		$	276

Inventories_Tables

Inventories (Tables)	9 Months Ended
	Sep. 26, 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.
		September 26,		December 31,
		2014		2013
		(in millions)
	Raw materials, components and sub-assemblies	$	156	$	160
	Work in process		137		125
	Finished goods		78		74
	Total	$	371	$	359

Goodwill_and_Identifiable_Inta1

Goodwill and Identifiable Intangible Assets (Tables)	9 Months Ended
	Sep. 26, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Changes in Goodwill by Segment	'
	The table below presents the changes in goodwill by segment for the year-to-date period ended September 26, 2014.
			Electronic			Aerospace			Communication		NSS		Consolidated
			Systems			Systems			Systems				Total
			(in millions)
	Balance at December 31, 2013		$	4,085		$	1,751		$	992	$	968	$	7,796
	Business acquisition(1)			(3	)		—			—		39		36
	Foreign currency translation adjustments(2)			(39	)		(9	)		—		—		(48	)
	Balance at September 26, 2014		$	4,043		$	1,742		$	992	$	1,007	$	7,784
	(1)	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.
	(2)	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 the year-to-date period ended September 26, 2014. The decrease in goodwill presented in the Aerospace Systems segment was due to the strengthening of the U.S. dollar against the Canadian dollar during the year-to-date period ended September 26, 2014.
Identifiable Intangible Assets	'
	The table below presents information for the Company’s identifiable intangible assets that are subject to amortization.
						September 26, 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			19		$	474		$	275	$	199	$	466		$	253	$	213
	Technology			11			168			115		53		168			108		60
	Other			18			27			16		11		27			15		12
	Total			17		$	669		$	406	$	263	$	661		$	376	$	285
Amortization Expense	'
	The table below presents amortization expense recorded by the Company for its identifiable intangible assets.
			Third Quarter Ended						Year-to-Date Ended
			(in millions)
			September 26,			September 27,			September 26,		September 27,
			2014			2013			2014		2013
	Amortization Expense		$	11		$	10		$	32	$	29
Estimated Amortization Expense	'
	Based on gross carrying amounts at September 26, 2014, the Company’s estimate of amortization expense for identifiable intangible assets for the years ending December 31, 2014 through 2018 is presented in the table below.
			Year Ending December 31,
			2014			2015			2016		2017		2018
			(in millions)
	Estimated amortization expense		$	42		$	41		$	34	$	32	$	26

Other_Current_Liabilities_and_1

Other Current Liabilities and Other Liabilities (Tables)	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Other Current Liabilities	'
	The table below presents the components of other current liabilities.
			September 26,			December 31,
			2014			2013
			(in millions)
	Other Current Liabilities:
	Accruals for pending and threatened litigation (see Note 18)		$	7		$	6
	Accrued product warranty costs			79			75
	Estimated costs in excess of estimated contract value to complete contracts in process in a loss position			71			78
	Accrued interest			52			52
	Deferred revenues			36			35
	Notes payable and capital lease obligation			16			10
	Other			105			127
	Total other current liabilities		$	366		$	383
Other Liabilities	'
	The table below presents the components of other liabilities.
			September 26,			December 31,
			2014			2013
			(in millions)
	Other Liabilities:
	Non-current income taxes payable (see Note 11)		$	193		$	177
	Deferred compensation			46			45
	Accrued workers’ compensation			40			46
	Accrued product warranty costs			26			24
	Notes payable and capital lease obligations			2			15
	Other			92			99
	Total other liabilities		$	399		$	406
Changes in Company's Accrued Product Warranty Costs	'
	The table below presents the changes in the Company’s accrued product warranty costs.
			Year-to-Date Ended
			September 26,			September 27,
			2014			2013
			(in millions)
	Accrued product warranty costs:(1)
	Balance at January 1		$	99		$	99
	Accruals for product warranties issued during the period			53			56
	Settlements made during the period			(46	)		(56	)
	Foreign currency translation adjustments			(1	)		—
	Balance at end of period		$	105		$	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.

Debt_Tables

Debt (Tables)	9 Months Ended
	Sep. 26, 2014
Debt Disclosure [Abstract]	'
Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt	'
	The components of debt and a reconciliation to the carrying amount of long-term debt is presented in the table below.
			September 26,			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 (CODES)			—			689
	Principal amount of long-term debt			3,950			3,639
	Unamortized discounts			(12	)		(9	)
	Carrying amount of long-term debt		$	3,938		$	3,630
	(1)	During the year-to-date period ended September 26, 2014, L-3 Communications’ aggregate borrowings and repayments under the Amended and Restated Revolving Credit Facility were $1,367 million. At September 26, 2014, L-3 Communications had the availability of all of its $1 billion Amended and Restated Revolving Credit Facility, which expires on February 3, 2017.
Information Regarding Outstanding Series of Senior Subordinated Note	'
	The terms of each series of Senior Notes are presented in the table below.
	Note		Date of Issuance			Amount			Bond		Net		Effective			Redemption
						Issued			Discount(1)		Cash		Interest			at Treasury
											Proceeds(2)		Rate			Rate(3)(4)
						(in millions)
	1.50% Senior Notes due May 28, 2017 (2017 Notes)			May 28, 2014		$	350		$	1	$	347		1.55	%		10 bps
	3.95% Senior Notes due May 28, 2024 (2024 Notes)			May 28, 2014		$	650		$	3	$	641		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 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 are available for general corporate purposes.
	(3)	The 2017 Senior Notes may be redeemed at any time prior to their maturity and the 2024 Notes 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 2024 Senior Notes are redeemed at any time on or after February 28, 2024, the redemption price would be equal to 100% of the principal amount.
	(4)	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 a price in cash equal to 101% of the aggregate principal amount plus accrued and unpaid interest, if any, but not including, the date of purchase.

Amounts_Reclassified_Out_of_Ac1

Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income (Tables)	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Summary of Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income	'
	The amounts reclassified from Accumulated Other Comprehensive (Loss) Income (AOCI) for the year-to-date periods ended September 26, 2014 and September 27, 2013 are presented in the table below.
			Foreign			Unrealized			Unrecognized			Total
			currency			gains			(losses) and			accumulated
			translation			(losses) on			prior service			other
						hedging			cost, net			comprehensive
						instruments						(loss) income
			(in millions)
	Balance at December 31, 2012		$	167		$	3		$	(720	)	$	(550	)
	Other comprehensive loss before reclassifications, net of tax			(18	)		(2	)		—			(20	)
	Amounts reclassified from other comprehensive income, net of tax			—			1			40			41
	Net current period other comprehensive (loss) income		$	(18	)	$	(1	)	$	40		$	21
	Balance at September 27, 2013		$	149		$	2		$	(680	)	$	(529	)
	Balance at December 31, 2013		$	142		$	1		$	(253	)	$	(110	)
	Other comprehensive income before reclassifications, net of tax			(57	)		5			—			(52	)
	Amounts reclassified from other comprehensive (loss) income, net of tax			—			(5	)		7			2
	Net current period other comprehensive income			(57	)		—			7			(50	)
	Balance at September 26, 2014		$	85		$	1		$	(246	)	$	(160	)
	Further details regarding the amounts reclassified from AOCI for the quarterly and year-to-date periods ended September 26, 2014 and September 27, 2013 are presented in the table below.
			Amount Reclassified from AOCI												Affected Line Item in the
			Third Quarter Ended						Year-to-Date Ended						Unaudited Condensed Consolidated
	Details About		September 26,			September 27,			September 26,			September 27,			Statements of Operations
	AOCI Components		2014			2013			2014			2013
			(in millions)
	Gain (loss) on hedging instruments		$	1		$	—		$	(6	)	$	1		Cost of sales-products
				1			—			(6	)		1		Income before income taxes
				(1	)		—			1			—		Benefit (Provision) for income taxes
			$	—		$	—		$	(5	)	$	1		Net income
	Amortization of defined benefit pension items:
	Net loss		$	3		$	20		$	11		$	63		(a)
				3			20			11			63		Income before income taxes
				(1	)		(7	)		(4	)		(23	)	Provision for income taxes
			$	2		$	13		$	7		$	40		Net Income
	Total reclassification for the period		$	2		$	13		$	2		$	41		Net Income
	(a)	Amounts related to pension and postretirement benefit plans were reclassified from AOCI and recorded as a component of net periodic benefit cost (see Note 19 for additional information).

L3_Holdings_Earnings_Per_Commo1

L-3 Holdings' Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 26, 2014
Earnings Per Share [Abstract]	'
Reconciliation of Basic and Diluted Earnings Per Share	'
	A reconciliation of basic and diluted earnings per share (EPS) is presented in the table below.
			Third Quarter Ended						Year-to-Date Ended
			September 26,			September 27,			September 26,			September 27,
			2014			2013			2014			2013
			(in millions, except per share data)
	Reconciliation of net income:
	Net income		$	157		$	204		$	470		$	572
	Net income attributable to noncontrolling interests			(3	)		(4	)		(9	)		(6	)
	Net income attributable to L-3 Holdings’ common shareholders		$	154		$	200		$	461		$	566
	Earnings per share attributable to L-3 Holdings’ common shareholders:
	Basic:
	Weighted average common shares outstanding			85.1			89.6			85.7			89.9
	Basic earnings per share:
	Net income		$	1.81		$	2.23		$	5.38		$	6.3
	Diluted:
	Common and potential common shares:
	Weighted average common shares outstanding			85.1			89.6			85.7			89.9
	Assumed exercise of stock options			2.8			4.7			3			3.9
	Unvested restricted stock awards			1.5			1.8			1.6			1.8
	Employee stock purchase plan contributions			—			0.2			0.1			0.2
	Performance unit awards			0.1			0.1			0.1			0.1
	Assumed purchase of common shares for treasury			(2.9	)		(5.2	)		(3.2	)		(4.7	)
	Assumed conversion of the CODES(1)			—			0.1			1.1			0.1
	Common and potential common shares			86.6			91.3			88.4			91.3
	Diluted earnings per share:
	Net income		$	1.78		$	2.19		$	5.21		$	6.2
	(1)	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. Although the CODES were retired during the year-to-date period ended June 27, 2014, they were dilutive for the year-to-date period ended September 26, 2014 as the average market price of L-3 Holdings’ common stock during the period that the CODES were outstanding was greater than the price at which the CODES would have been convertible into L-3 Holdings’ common stock. See Note 10 regarding the retirement of the CODES.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 26, 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.
			September 26, 2014						December 31, 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		$	359	$	—	$	—	$	299	$	—	$	—
	Derivatives (foreign currency forward contracts)			—		5		—		—		6		—
	Total assets		$	359	$	5	$	—	$	299	$	6	$	—
	Liabilities
	Derivatives (foreign currency forward contracts)		$	—	$	4	$	—	$	—	$	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)	9 Months Ended
	Sep. 26, 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.
			September 26, 2014				December 31, 2013
			Carrying		Estimated		Carrying		Estimated
			Amount		Fair Value		Amount		Fair Value
			(in millions)
	Senior Notes(1)		$	3,938	$	4,181	$	2,941	$	3,121
	CODES(1)			—		—		689		830
	Foreign currency forward contracts(2)			1		1		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)	See Note 17 for additional disclosures regarding the notional amounts and fair values of foreign currency forward contracts.

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 26, 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 at September 26, 2014.
	Currency		Notional Amounts
			(in millions)
	Canadian dollar		$	161
	U.S. dollar			101
	Euro			66
	British pound			9
	Total		$	337
Location of Company's Derivative Instruments Recorded at Fair Value on Condensed Consolidated Balance Sheets	'
	The table below presents the location of the Company’s derivative instruments recorded at fair value on the condensed consolidated balance sheets.
			September 26, 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)		$	4	$	1	$	3	$	1	$	5	$	1	$	3	$	2
	Derivatives not designated as hedging instruments:
	Foreign currency forward contracts(1)			—		—		—		—		—		—		—		—
	Embedded derivative related to the CODES(2)			—		—		—		—		—		—		—		—
	Total derivative instruments		$	4	$	1	$	3	$	1	$	5	$	1	$	3	$	2
	(1)	See Note 15 for a description of the fair value hierarchy related to the Company’s foreign currency forward contracts.
	(2)	See Note 10 for a description of the CODES Retirement.

Pension_and_Other_Postretireme1

Pension and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 26, 2014
Compensation and Retirement Disclosure [Abstract]	'
Components of Net Periodic Benefit Cost	'
	The following table summarizes the components of net periodic benefit cost for the Company’s pension and other postretirement benefit plans.
		Pension Plans												Postretirement Benefit Plans
		Third Quarter Ended						Year-to-Date Ended						Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,			September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013			2014			2013			2014			2013
		(in millions)
	Components of net periodic benefit cost:
	Service cost	$	26		$	30		$	80		$	95		$	(2	)	$	1		$	—		$	3
	Interest cost		37			33			110			99			4			2			8			5
	Expected return on plan assets		(48	)		(41	)		(145	)		(124	)		(1	)		—			(3	)		(2	)
	Amortization of prior service costs (credits)		—			1			1			1			—			(1	)		(1	)		(2	)
	Amortization of net loss (gain)		4			20			13			63			(1	)		—			(2	)		1
	Curtailment loss		—			2			1			2			(1	)		—			(1	)		—
	Net periodic benefit cost	$	19		$	45		$	60		$	136		$	(1	)	$	2		$	1		$	5

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 26, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Weighted Average Assumptions used in Valuation Model	'
	The weighted average assumptions used in the valuation model for this grant are presented in the table below.
	Expected holding period (in years)	5.5
	Expected volatility	24.4	%
	Expected dividend yield	2.7	%
	Risk-free interest rate	1.7	%

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 26, 2014
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Cash Flow Information	'
		Year-to-Date Ended
		September 26,		September 27,
		2014		2013
		(in millions)
	Interest paid on outstanding debt	$	123	$	133
	Income tax payments		116		168
	Income tax refunds		8		20

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 26, 2014
Segment Reporting [Abstract]	'
Summary of Segment Information	'
	The tables below present net sales, operating income, depreciation and amortization and total assets by reportable segment.
		Third Quarter Ended						Year-to-Date Ended
		September 26,			September 27,			September 26,			September 27,
		2014			2013			2014			2013
		(in millions)
	Net Sales:
	Electronic Systems	$	1,128		$	1,139		$	3,349		$	3,438
	Aerospace Systems		1,037			1,092			3,173			3,416
	Communication Systems		507			486			1,562			1,667
	NSS		307			323			948			987
	Elimination of intercompany sales		(39	)		(38	)		(116	)		(120	)
	Consolidated total	$	2,940		$	3,002		$	8,916		$	9,388
	Operating Income:
	Electronic Systems	$	125		$	144		$	383		$	388
	Aerospace Systems		64			105			196			336
	Communication Systems		49			31			147			116
	NSS		19			26			56			66
	Consolidated total	$	257		$	306		$	782		$	906
	Depreciation and amortization:
	Electronic Systems	$	30		$	28		$	89		$	87
	Aerospace Systems		11			10			30			28
	Communication Systems		13			12			38			35
	NSS		2			2			8			8
	Consolidated total	$	56		$	52		$	165		$	158
		September 26,			December 31,
		2014			2013
		(in millions)
	Total Assets:
	Electronic Systems	$	6,998		$	6,928
	Aerospace Systems		2,961			3,087
	Communication Systems		2,076			2,130
	NSS		1,312			1,247
	Corporate		694			596
	Consolidated total	$	14,041		$	13,988

Employee_Severance_and_Termina1

Employee Severance and Termination Costs (Tables)	9 Months Ended
	Sep. 26, 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 for the year-to-date periods ended September 26, 2014 and September 27, 2013 are presented in the table below.
		Year-to-Date Ended
		September 26,		September 27,
		2014		2013
		(in millions)
	Reportable Segment
	Electronic Systems	$	14	$	11
	Aerospace Systems		3		1
	Communication Systems		5		6
	NSS		1		1
	Consolidated	$	23	$	19

Condensed_Combining_Financial_1

Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries (Tables)	9 Months Ended
	Sep. 26, 2014
Text Block [Abstract]	'
Condensed Combining Balance Sheets	'
	The following unaudited 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.
	As discussed in Note 3, the Company is revising its previously issued financial statements. As part of that revision, the Company has revised the accompanying condensed combining financial statements contained herein. The adjustments related to the internal review of the Aerospace Systems segment, excluding certain adjustments related to the Platform Systems segment, were recorded as adjustments to the Guarantor Subsidiaries financial statement amounts. Adjustments from the internal review that related to a foreign subsidiary of the Platform Systems segment, with a cumulative operating impact through September 26, 2014 of $28 million, were recorded to the Non-Guarantor Subsidiaries financial statement amounts. The adjustments for the accounting related to a sales-type lease transaction for flight simulator systems within its Electronic Systems segment have been recorded as adjustments to the L-3 Communications financial statement amounts. The adjustments for the previously identified immaterial errors were recorded as adjustments to the Guarantor Subsidiaries financial statement amounts.
		L-3			L-3			Guarantor			Non-			Eliminations			Consolidated
		Holdings			Communications			Subsidiaries			Guarantor						L-3
		(Parent)									Subsidiaries
		(in millions)
	Condensed Combining Balance Sheets:
	At September 26, 2014:
	Current assets:
	Cash and cash equivalents	$	—		$	330		$	1		$	239		$	(62	)	$	508
	Billed receivables, net		—			296			348			227			—			871
	Contracts in process		—			994			1,165			387			—			2,546
	Other current assets		—			410			145			176			—			731
	Total current assets		—			2,030			1,659			1,029			(62	)		4,656
	Goodwill		—			2,324			4,320			1,140			—			7,784
	Other assets		—			800			568			233			—			1,601
	Investment in and amounts due from consolidated subsidiaries		5,903			6,993			4,049			—			(16,945	)		—
	Total assets	$	5,903		$	12,147		$	10,596		$	2,402		$	(17,007	)	$	14,041
	Current liabilities	$	—		$	872		$	999		$	583		$	(62	)	$	2,392
	Amounts due to consolidated subsidiaries		—			—			—			366			(366	)		—
	Other long-term liabilities		—			1,434			187			111			—			1,732
	Long-term debt		—			3,938			—			—			—			3,938
	Total liabilities		—			6,244			1,186			1,060			(428	)		8,062
	L-3 shareholders’ equity		5,903			5,903			9,410			1,342			(16,655	)		5,903
	Noncontrolling interests		—			—			—			—			76			76
	Total equity		5,903			5,903			9,410			1,342			(16,579	)		5,979
	Total liabilities and equity	$	5,903		$	12,147		$	10,596		$	2,402		$	(17,007	)	$	14,041
	At December 31, 2013:
	Current assets:
	Cash and cash equivalents	$	—		$	258		$	—		$	261		$	(19	)	$	500
	Billed receivables, net		—			364			401			226			—			991
	Contracts in process		—			925			1,152			354			—			2,431
	Other current assets		—			344			159			169			—			672
	Total current assets		—			1,891			1,712			1,010			(19	)		4,594
	Goodwill		—			2,324			4,320			1,152			—			7,796
	Other assets		—			838			532			228			—			1,598
	Investment in and amounts due from consolidated subsidiaries		6,670			6,923			3,750			—			(17,343	)		—
	Total assets	$	6,670		$	11,976		$	10,314		$	2,390		$	(17,362	)	$	13,988
	Current liabilities	$	—		$	914		$	1,011		$	628		$	(19	)	$	2,534
	Amounts due to consolidated subsidiaries		—			—			—			259			(259	)		—
	Other long-term liabilities		—			1,451			193			124			—			1,768
	Long-term debt		689			3,630			—			—			(689	)		3,630
	Total liabilities		689			5,995			1,204			1,011			(967	)		7,932
	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		$	10,314		$	2,390		$	(17,362	)	$	13,988
Condensed Combining Statements of Operations	'
	Condensed Combining Statements of Operations:
	For the quarter ended September 26, 2014:
	Total net sales	$	—		$	860		$	1,628		$	525		$	(73	)	$	2,940
	Total cost of sales		(10	)		(787	)		(1,500	)		(469	)		83			(2,683	)
	Operating (loss) income		(10	)		73			128			56			10			257
	Interest expense		—			(46	)		(2	)		1			—			(47	)
	Interest and other income, net		—			4			—			1			—			5
	(Loss) income before income taxes		(10	)		31			126			58			10			215
	Benefit (provision) for income taxes		3			(8	)		(34	)		(16	)		(3	)		(58	)
	Equity in net income of consolidated subsidiaries		161			131			—			—			(292	)		—
	Net income		154			154			92			42			(285	)		157
	Net income attributable to noncontrolling interests		—			—			—			—			(3	)		(3	)
	Net income attributable to L-3	$	154		$	154		$	92		$	42		$	(288	)	$	154
	Comprehensive income attributable to L-3	$	90		$	90		$	89		$	(22	)	$	(157	)	$	90
	For the quarter ended September 27, 2013:
	Total net sales	$	—		$	912		$	1,646		$	543		$	(99	)	$	3,002
	Total cost of sales		(14	)		(854	)		(1,458	)		(483	)		113			(2,696	)
	Operating (loss) income		(14	)		58			188			60			14			306
	Interest expense		(5	)		(43	)		—			(1	)		5			(44	)
	Interest and other income, net		—			3			1			—			—			4
	(Loss) income before income taxes		(19	)		18			189			59			19			266
	Benefit (provision) for income taxes		5			(3	)		(45	)		(14	)		(5	)		(62	)
	Equity in net income of consolidated subsidiaries		214			185			—			—			(399	)		—
	Net income		200			200			144			45			(385	)		204
	Net income attributable to noncontrolling interests		—			—			—			—			(4	)		(4	)
	Net income attributable to L-3	$	200		$	200		$	144		$	45		$	(389	)	$	200
	Comprehensive income attributable to L-3	$	250		$	250		$	145		$	77		$	(472	)	$	250
	Condensed Combining Statements of Operations:
	For the Year-to-Date Period Ended September 26, 2014:
	Total net sales	$	—		$	2,606		$	4,908		$	1,623		$	(221	)	$	8,916
	Total cost of sales		(39	)		(2,354	)		(4,533	)		(1,468	)		260			(8,134	)
	Operating (loss) income		(39	)		252			375			155			39			782
	Interest expense		(2	)		(127	)		(2	)		—			2			(129	)
	Interest and other income, net		—			12			—			2			—			14
	(Loss) income before income taxes		(41	)		137			373			157			41			667
	Benefit (provision) for income taxes		12			(41	)		(110	)		(46	)		(12	)		(197	)
	Equity in net income of consolidated subsidiaries		490			365			—			—			(855	)		—
	Net income		461			461			263			111			(826	)		470
	Net income attributable to noncontrolling interests		—			—			—			—			(9	)		(9	)
	Net income attributable to L-3	$	461		$	461		$	263		$	111		$	(835	)	$	461
	Comprehensive income attributable to L-3	$	411		$	411		$	264		$	53		$	(728	)	$	411
	For the Year-to-Date Period Ended September 27, 2013:
	Total net sales	$	—		$	2,847		$	5,104		$	1,705		$	(268	)	$	9,388
	Total cost of sales		(42	)		(2,625	)		(4,598	)		(1,527	)		310			(8,482	)
	Operating (loss) income		(42	)		222			506			178			42			906
	Interest expense		(15	)		(130	)		—			(1	)		15			(131	)
	Interest and other income, net		—			9			1			4			—			14
	(Loss) income before income taxes		(57	)		101			507			181			57			789
	Benefit (provision) for income taxes		16			(28	)		(139	)		(50	)		(16	)		(217	)
	Equity in net income of consolidated subsidiaries		607			493			—			—			(1,100	)		—
	Net income		566			566			368			131			(1,059	)		572
	Net income attributable to noncontrolling interests		—			—			—			—			(6	)		(6	)
	Net income attributable to L-3	$	566		$	566		$	368		$	131		$	(1,065	)	$	566
	Comprehensive income attributable to L-3	$	587		$	587		$	369		$	108		$	(1,064	)	$	587
Condensed Combining Statements of Cash Flows	'
	Condensed Combining Statements of Cash Flows:
	For the Year-to-Date Period Ended September 26, 2014:
	Operating activities:
	Net cash from operating activities	$	1,506		$	201		$	382		$	69		$	(1,553	)	$	605
	Investing activities:
	Business acquisitions, net of cash acquired		—			(57	)		—			—			—			(57	)
	Investments in L-3 Communications		(87	)		—			—			—			87			—
	Other investing activities		—			(37	)		(52	)		(16	)		—			(105	)
	Net cash used in investing activities		(87	)		(94	)		(52	)		(16	)		87			(162	)
	Financing activities:
	Proceeds from sale of senior notes		—			996			—			—			—			996
	Retirement of CODES		(935	)		—			—			—			—			(935	)
	Common stock repurchased		(413	)		—			—			—			—			(413	)
	Dividends paid on L-3 Holdings common stock		(158	)		—			—			—			—			(158	)
	Dividends paid to L-3 Holdings		—			(1,506	)		—			—			1,506			—
	Investments from L-3 Holdings		—			87			—			—			(87	)		—
	Other financing activities		87			388			(329	)		(66	)		4			84
	Net cash used in financing activities		(1,419	)		(35	)		(329	)		(66	)		1,423			(426	)
	Effect of foreign currency exchange rate changes on cash		—			—			—			(9	)		—			(9	)
	Net increase (decrease) in cash		—			72			1			(22	)		(43	)		8
	Cash and cash equivalents, beginning of the period		—			258			—			261			(19	)		500
	Cash and cash equivalents, end of the period	$	—		$	330		$	1		$	239		$	(62	)	$	508
	For the Year-to-Date Period Ended September 27, 2013:
	Net cash from operating activities	$	555		$	86		$	523		$	101		$	(648	)	$	617
	Investing activities:
	Business acquisitions, net of cash acquired		—			(2	)		—			—			—			(2	)
	Investments in L-3 Communications		(104	)		—			—			—			104			—
	Other investing activities		—			(70	)		(53	)		(16	)		—			(139	)
	Net cash used in investing activities		(104	)		(72	)		(53	)		(16	)		104			(141	)
	Financing activities:
	Common stock repurchased		(404	)		—			—			—			—			(404	)
	Dividends paid on L-3 Holdings common stock		(151	)		—			—			—			—			(151	)
	Dividends paid to L-3 Holdings		—			(555	)		—			—			555			—
	Investments from L-3 Holdings		—			104			—			—			(104	)		—
	Other financing activities		104			345			(469	)		(81	)		210			109
	Net cash used in financing activities		(451	)		(106	)		(469	)		(81	)		661			(446	)
	Effect of foreign currency exchange rate changes on cash		—			—			—			(2	)		—			(2	)
	Net (decrease) increase in cash		—			(92	)		1			2			117			28
	Cash and cash equivalents, beginning of the period		—			246			—			242			(139	)		349
	Cash and cash equivalents, end of the period	$	—		$	154		$	1		$	244		$	(22	)	$	377

Description_of_Business_Additi

Description of Business - Additional Information (Detail)	9 Months Ended
	Sep. 26, 2014
	Segment
Disclosure Description Of Business Additional Information [Abstract]	'
Number of segments	4

Basis_of_Presentation_Addition

Basis of Presentation - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Summary Of Significant Accounting Policies [Line Items]	'	'
Percentage of sales accounted for under contract accounting standards	47.00%	'
Percentage of fixed-price type contracts	38.00%	'
Percentage of cost-plus type contracts	9.00%	'
Period of performance for contracts accounted for under the percentage-of-completion method of accounting, minimum	'1 year	'
Increase in operating income due to changes in contract estimates	$62	$92
Percentage of increase in operating income due to changes in contract estimates	8.00%	10.00%
CODES Due 2035 [Member]	'	'
Summary Of Significant Accounting Policies [Line Items]	'	'
Interest rate on debt instruments	3.00%	'
Debt instruments, maturity year	'2035	'

Revisions_to_Previously_Issued2

Revisions to Previously Issued Financial Statements - Additional Information (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

9 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Sep. 26, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Dec. 31, 2010

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Sep. 27, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Sep. 26, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Sep. 26, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Sep. 26, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Sep. 26, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Change in Accounting Estimate [Line Items]

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Aggregate pre-tax charges as a result of internal review

$215

$266

$667

$789

($54)

($20)

($17)

($6)

($15)

($3)

($74)

($41)

($40)

$2

($140)

$13

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$1

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$1

$2

$1

$1

$1

$5

$3

$3

$29

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$17

($55)

($20)

($24)

($7)

($15)

($14)

($75)

($36)

($60)

($25)

($5)

($169)

($4)

($26)

($9)

($22)

($7)

($9)

($8)

($35)

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($46)

($27)

($5)

($117)

($4)

($29)

($11)

($2)

($6)

($6)

($40)

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($14)

$2

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($52)

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($11)

($4)

($20)

($2)

($7)

($6)

($15)

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($35)

($16)

($3)

($69)

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($15)

($5)

($2)

($5)

($2)

($2)

($20)

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($11)

($11)

($2)

($48)

($4)

Cumulative aggregate adjustments, net

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-117

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Cumulative aggregate adjustments losses

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Adjustment description

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'The Platform Systems sector adjustments are primarily due to: (1) losses of $37 million on two aircraft modification contracts and two contracts for rotary wing sub-assemblies and parts, and (2) write-offs of deferred costs of $15 million to design and test aerostructures for a new commercial aircraft.

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Write-offs of deferred costs

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Lease period

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'The period of performance under this contract began in 2004 and ends in 2023.

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Increase in interest income

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5

3

3

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12

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Decrease in sales

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-8

-7

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Decrease in cost of sales

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($7)

($7)

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($5)

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Revisions_to_Previously_Issued3

Revisions to Previously Issued Financial Statements - Schedule of Nature of Adjustments, Applicable Segment, Amount of Increase (or Decrease) to Sales and Operating Income, Period Recorded and Correct Period (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

In Millions, unless otherwise specified

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Communication Systems [Member]

Communication Systems [Member]

Communication Systems [Member]

Communication Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Higher Development and Material Costs for Networked Communications Systems [Member]

Higher Development and Material Costs for Networked Communications Systems [Member]

Higher Development and Material Costs for Networked Communications Systems [Member]

Higher Development and Material Costs for Networked Communications Systems [Member]

Sub-Contractor Subscription Deposit [Member]

Sub-Contractor Subscription Deposit [Member]

Sub-Contractor Subscription Deposit [Member]

Sub-Contractor Subscription Deposit [Member]

Costs Accruals for Goods/Services Received [Member]

Costs Accruals for Goods/Services Received [Member]

Costs Accruals for Goods/Services Received [Member]

Costs Accruals for Goods/Services Received [Member]

Unrecorded Liabilities [Member]

Unrecorded Liabilities [Member]

Unrecorded Liabilities [Member]

Unrecorded Liabilities [Member]

Accrued Vacation [Member]

Accrued Vacation [Member]

Accrued Vacation [Member]

Accrued Vacation [Member]

Overstated Revenue [Member]

Overstated Revenue [Member]

Overstated Revenue [Member]

Overstated Revenue [Member]

Quantifying Misstatement in Current Year Financial Statements [Line Items]

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Sales

$2,940

$3,002

$8,916

$9,388

($10)

($13)

($21)

$5

($3)

$12

($23)

($7)

($38)

($4)

($73)

$9

$3

$7

$20

'

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$10

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$9

$3

$7

$20

'

$39

($36)

($3)

'

$5

$7

$7

$7

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$5

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($2)

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$4

($4)

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Operating income

$257

$306

$782

$906

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$6

($1)

($1)

$10

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$10

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$1

$1

$1

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$1

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$6

($2)

($2)

($2)

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Revisions_to_Previously_Issued4

Revisions to Previously Issued Financial Statements - Schedule of Impact on Sales and Pre-tax Income (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

9 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

12 Months Ended

In Millions, unless otherwise specified

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Sep. 27, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Prior to 2011 [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Army C-12 Contract [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Other Logistics Support Contracts [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Logistics Solutions [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Platform Systems [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Sales-Type Lease Transaction [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Out of Period Amounts [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Army C-12 Contract [Member]

Other Logistics Support Contracts [Member]

Logistics Solutions [Member]

Platform Systems [Member]

Total Internal Review of Aerospace Systems Segment [Member]

Sales-Type Lease Transaction [Member]

Out of Period Amounts [Member]

Quantifying Misstatement in Current Year Financial Statements [Line Items]

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Sales

$2,940

$3,002

$8,916

$9,388

$9

$3

$7

$20

($10)

($13)

($21)

$5

($3)

$12

($23)

($7)

($38)

($4)

($73)

($1)

($2)

($24)

$3

($3)

($1)

($3)

($25)

($3)

($1)

($32)

'

'

($1)

($1)

'

'

'

($2)

($2)

'

($5)

($1)

($2)

($25)

$2

($3)

($1)

($3)

($27)

($5)

($1)

($37)

($6)

($6)

($2)

$1

($6)

($5)

($12)

($12)

$3

'

($21)

($7)

($8)

($27)

$3

($9)

($6)

($15)

'

($39)

($2)

($1)

($58)

($3)

($5)

($3)

($1)

($1)

($2)

($8)

($7)

'

'

($15)

'

'

$9

$3

$7

$20

'

$39

($36)

($3)

'

($1)

'

($1)

($1)

'

($1)

'

'

Pre-tax Income

$215

$266

$667

$789

'

'

'

'

($54)

($20)

($17)

($6)

($15)

($3)

($74)

($41)

($40)

$2

($140)

($11)

($4)

($20)

($2)

($7)

($6)

($15)

($35)

($16)

($3)

($69)

($15)

($5)

($2)

($5)

($2)

($2)

($20)

($11)

($11)

($2)

($48)

($26)

($9)

($22)

($7)

($9)

($8)

($35)

($46)

($27)

($5)

($117)

($29)

($11)

($2)

'

($6)

($6)

($40)

($14)

$2

'

($52)

($55)

($20)

($24)

($7)

($15)

($14)

($75)

($36)

($60)

($25)

($5)

($169)

$1

'

$1

$2

$1

$1

$1

$5

$3

$3

$29

'

'

$6

($1)

($1)

$10

'

$14

($18)

$4

'

$13

'

($4)

($4)

'

($4)

$17

'

Revisions_to_Previously_Issued5

Revisions to Previously Issued Financial Statements - Schedule of Condensed Consolidated Statement of Operations (Detail) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended					9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	Dec. 31, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013	Sep. 27, 2013
					Out of Period Amounts [Member]	Out of Period Amounts [Member]	Out of Period Amounts [Member]	Out of Period Amounts [Member]	As Previously Reported [Member]	As Previously Reported [Member]	Restatement Adjustments [Member]	Restatement Adjustments [Member]	Restatement Adjustments [Member]	Restatement Adjustments [Member]	Restatement Adjustments [Member]	Restatement Adjustments [Member]	Restatement Adjustments [Member]
												Aerospace Systems Segment Internal Review [Member ]	Aerospace Systems Segment Internal Review [Member ]	Sales-Type Lease Transaction [Member]	Sales-Type Lease Transaction [Member]	Out of Period Amounts [Member]	Out of Period Amounts [Member]
Net sales:	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Products	$1,644	$1,697	$4,991	$5,321	'	'	'	'	$1,696	$5,319	'	$2	($9)	($1)	($4)	'	$15
Services	1,296	1,305	3,925	4,067	'	'	'	'	1,300	4,054	'	2	-2	'	'	3	15
Total net sales	2,940	3,002	8,916	9,388	9	3	7	20	2,996	9,373	'	4	-11	-1	-4	3	30
Cost of sales:	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Products	-1,480	-1,487	-4,498	-4,732	'	'	'	'	-1,486	-4,729	'	-2	-3	1	5	'	-5
Services	-1,203	-1,209	-3,636	-3,750	'	'	'	'	-1,196	-3,710	'	-9	-22	'	'	-4	-18
Total cost of sales	-2,683	-2,696	-8,134	-8,482	'	'	'	'	-2,682	-8,439	'	-11	-25	1	5	-4	-23
Operating income	257	306	782	906	6	-1	-1	10	314	934	'	-7	-36	'	1	-1	7
Interest expense	-47	-44	-129	-131	'	'	'	'	-44	-131	'	'	'	'	'	'	'
Interest and other income, net	5	4	14	14	'	'	'	'	3	11	'	'	'	1	3	'	'
Income before income taxes	215	266	667	789	'	'	'	'	273	814	'	-7	-36	1	4	-1	7
Provision for income taxes	-58	-62	-197	-217	'	'	'	'	-65	-226	'	3	13	'	-1	'	-3
Net income	157	204	470	572	'	'	'	'	208	588	-16	-4	-23	1	3	-1	4
Net income attributable to noncontrolling interests	-3	-4	-9	-6	'	'	'	'	-4	-6	'	'	'	'	'	'	'
Net income attributable to L-3	$154	$200	$461	$566	'	'	'	'	$204	$582	'	($4)	($23)	$1	$3	($1)	$4
Earnings per share attributable to L-3 Holdings' common shareholders:	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Basic	$1.81	$2.23	$5.38	$6.30	'	'	'	'	$2.28	$6.47	'	($0.05)	($0.25)	$0.01	$0.04	($0.01)	$0.04
Diluted	$1.78	$2.19	$5.21	$6.20	'	'	'	'	$2.23	$6.37	'	($0.04)	($0.25)	$0.01	$0.04	($0.01)	$0.04
Cash dividends paid per common share	$0.60	$0.55	$1.80	$1.65	'	'	'	'	$0.55	$1.65	'	'	'	'	'	'	'
L-3 Holdings' weighted average common shares outstanding:	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'	'
Basic	85.1	89.6	85.7	89.9	'	'	'	'	89.6	89.9	'	'	'	'	'	'	'
Diluted	86.6	91.3	88.4	91.3	'	'	'	'	91.3	91.3	'	'	'	'	'	'	'

Revisions_to_Previously_Issued6

Revisions to Previously Issued Financial Statements - Schedule of Condensed Consolidated Statement of Cash Flows (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Operating activities:	'	'
Net income	$470	$572
Depreciation of property, plant and equipment	127	122
Amortization of intangibles and other assets	38	36
Deferred income tax provision	91	38
Stock-based employee compensation expense	39	42
Contributions to employee savings plans in L-3 Holdings' common stock	105	90
Amortization of pension and postretirement benefit plans net loss and prior service cost	11	63
Amortization of bond discounts and deferred debt issue costs (included in interest expense)	5	5
Other non-cash items	-5	1
Changes in operating assets and liabilities, excluding amounts from acquisitions and divestitures:	'	'
Billed receivables	118	-117
Contracts in process	-157	-70
Inventories	-17	-60
Other assets	'	-48
Accounts payable, trade	-125	54
Accrued employment costs	26	37
Accrued expenses	-51	-45
Advance payments and billings in excess of costs incurred	39	-61
Income taxes	-4	31
Excess income tax benefits related to share-based payment arrangements	-16	-3
Other current liabilities	-21	-5
Pension and postretirement benefits	-40	-23
All other operating activities	-28	-42
Net cash from operating activities	605	617
As Previously Reported [Member]	'	'
Operating activities:	'	'
Net income	'	588
Depreciation of property, plant and equipment	'	122
Amortization of intangibles and other assets	'	36
Deferred income tax provision	'	45
Stock-based employee compensation expense	'	42
Contributions to employee savings plans in L-3 Holdings' common stock	'	90
Amortization of pension and postretirement benefit plans net loss and prior service cost	'	63
Amortization of bond discounts and deferred debt issue costs (included in interest expense)	'	5
Other non-cash items	'	1
Changes in operating assets and liabilities, excluding amounts from acquisitions and divestitures:	'	'
Billed receivables	'	-117
Contracts in process	'	-36
Inventories	'	-55
Other assets	'	-45
Accounts payable, trade	'	65
Accrued employment costs	'	27
Accrued expenses	'	-41
Advance payments and billings in excess of costs incurred	'	-109
Income taxes	'	32
Excess income tax benefits related to share-based payment arrangements	'	-3
Other current liabilities	'	-8
Pension and postretirement benefits	'	-23
All other operating activities	'	-62
Net cash from operating activities	'	617
Restatement Adjustments [Member]	'	'
Operating activities:	'	'
Net income	'	-16
Depreciation of property, plant and equipment	'	'
Amortization of intangibles and other assets	'	'
Deferred income tax provision	'	-7
Stock-based employee compensation expense	'	'
Contributions to employee savings plans in L-3 Holdings' common stock	'	'
Amortization of pension and postretirement benefit plans net loss and prior service cost	'	'
Amortization of bond discounts and deferred debt issue costs (included in interest expense)	'	'
Other non-cash items	'	'
Changes in operating assets and liabilities, excluding amounts from acquisitions and divestitures:	'	'
Billed receivables	'	'
Contracts in process	'	-34
Inventories	'	-5
Other assets	'	-3
Accounts payable, trade	'	-11
Accrued employment costs	'	10
Accrued expenses	'	-4
Advance payments and billings in excess of costs incurred	'	48
Income taxes	'	-1
Excess income tax benefits related to share-based payment arrangements	'	'
Other current liabilities	'	3
Pension and postretirement benefits	'	'
All other operating activities	'	20
Net cash from operating activities	'	'

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013	Mar. 04, 2014	Jun. 27, 2014	Dec. 19, 2013
In Millions, unless otherwise specified			2014 Business Acquisition [Member]	2013 Business Acquisition [Member]	2013 Business Acquisition [Member]
Business Acquisition [Line Items]	'	'	'	'	'
Purchase price of acquisition	'	'	$57	'	$54
Amount of goodwill recognized	7,784	7,796	39	41	'
Goodwill deductible for income tax purposes	'	'	$39	$41	'

Acquisitions_Unaudited_Pro_For

Acquisitions - Unaudited Pro Forma Statements of Operations Data (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Business Combinations [Abstract]	'	'	'	'
Pro forma net sales	$2,940	$3,025	$8,923	$9,450
Pro forma net income attributable to L-3	$154	$200	$460	$567
Pro forma diluted earnings per share	$1.78	$2.19	$5.20	$6.21

Contracts_in_Process_Component

Contracts in Process - Components of Contracts in Process (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Components of contracts in process	'	'
Unbilled contract receivables, gross	$2,449	$2,502
Unliquidated progress payments	-900	-1,035
Unbilled contract receivables, net	1,549	1,467
Inventoried contract costs, gross	1,069	1,044
Unliquidated progress payments	-72	-80
Inventoried contract costs, net	997	964
Total contracts in process	$2,546	$2,431

Contracts_in_Process_General_a

Contracts in Process - General and Administrative, Independent Research and Development and Bids and Proposal Costs (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Inventory Disclosure [Abstract]	'	'	'	'
Amounts included in inventoried contract costs at beginning of the period:	$151	$115	$138	$110
IRAD and B&P costs	70	66	215	219
Other G&A costs	239	216	658	653
Total contract costs incurred	309	282	873	872
Amounts charged to cost of sales	-309	-271	-860	-856
Amounts included in inventoried contract costs at end of the period	$151	$126	$151	$126

Contracts_in_Process_Selling_G

Contracts in Process - Selling, General and Administrative Expenses and Research and Development Expenses (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Inventory Disclosure [Abstract]	'	'	'	'
Selling, general and administrative expenses	$70	$70	$213	$214
Research and development expenses	14	17	48	62
Total	$84	$87	$261	$276

Inventories_Inventories_at_Low

Inventories - Inventories at Lower of Cost or Market (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Raw materials, components and sub-assemblies	$156	$160
Work in process	137	125
Finished goods	78	74
Total	$371	$359

Goodwill_and_Identifiable_Inta2

Goodwill and Identifiable Intangible Assets - Changes in Goodwill by Segment (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014
Goodwill [Line Items]	'
Balance, Beginning	$7,796
Business acquisition	36
Foreign currency translation adjustments	-48
Balance, Ending	7,784
Electronic Systems [Member]	'
Goodwill [Line Items]	'
Balance, Beginning	4,085
Business acquisition	-3
Foreign currency translation adjustments	-39
Balance, Ending	4,043
Aerospace Systems [Member]	'
Goodwill [Line Items]	'
Balance, Beginning	1,751
Business acquisition	'
Foreign currency translation adjustments	-9
Balance, Ending	1,742
Communication Systems [Member]	'
Goodwill [Line Items]	'
Balance, Beginning	992
Business acquisition	'
Foreign currency translation adjustments	'
Balance, Ending	992
NSS [Member]	'
Goodwill [Line Items]	'
Balance, Beginning	968
Business acquisition	39
Foreign currency translation adjustments	'
Balance, Ending	$1,007

Goodwill_and_Identifiable_Inta3

Goodwill and Identifiable Intangible Assets - Additional Information (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Goodwill [Line Items]	'	'
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_Inta4

Goodwill and Identifiable Intangible Assets - Identifiable Intangible Assets (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]	'	'
Weighted Average Amortization Period (in years)	'17 years	'
Gross Carrying Amount	$669	$661
Accumulated Amortization	406	376
Net Carrying Amount	263	285
Customer Contractual Relationships [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Weighted Average Amortization Period (in years)	'19 years	'
Gross Carrying Amount	474	466
Accumulated Amortization	275	253
Net Carrying Amount	199	213
Technology [Member]	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Weighted Average Amortization Period (in years)	'11 years	'
Gross Carrying Amount	168	168
Accumulated Amortization	115	108
Net Carrying Amount	53	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 - Amortization Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Goodwill and Intangible Assets Disclosure [Abstract]	'	'	'	'
Amortization Expense	$11	$10	$32	$29

Goodwill_and_Identifiable_Inta6

Goodwill and Identifiable Intangible Assets - Estimated Amortization Expense (Detail) (USD $)	Sep. 26, 2014
In Millions, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]	'
Estimated amortization expense, 2014	$42
Estimated amortization expense, 2015	41
Estimated amortization expense, 2016	34
Estimated amortization expense, 2017	32
Estimated amortization expense, 2018	$26

Other_Current_Liabilities_and_2

Other Current Liabilities and Other Liabilities - Other Current Liabilities (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Current Liabilities:	'	'
Accruals for pending and threatened litigation (see Note 18)	$7	$6
Accrued product warranty costs	79	75
Estimated costs in excess of estimated contract value to complete contracts in process in a loss position	71	78
Accrued interest	52	52
Deferred revenues	36	35
Notes payable and capital lease obligation	16	10
Other	105	127
Total other current liabilities	$366	$383

Other_Current_Liabilities_and_3

Other Current Liabilities and Other Liabilities - Other Liabilities (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Other Liabilities:	'	'
Non-current income taxes payable (see Note 11)	$193	$177
Deferred compensation	46	45
Accrued workers' compensation	40	46
Accrued product warranty costs	26	24
Notes payable and capital lease obligations	2	15
Other	92	99
Total other liabilities	$399	$406

Other_Current_Liabilities_and_4

Other Current Liabilities and Other Liabilities - Changes in Company's Accrued Product Warranty Costs (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Accrued product warranty costs:	'	'
Balance at January 1	$99	$99
Accruals for product warranties issued during the period	53	56
Settlements made during the period	-46	-56
Foreign currency translation adjustments	-1	'
Balance at end of period	$105	$99

Debt_Components_of_Debt_and_Re

Debt - Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'	'
3% Convertible Contingent Debt Securities due 2035 (CODES)	'	$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 (CODES)	'	689
Principal amount of long-term debt	3,950	3,639
Unamortized discounts	-12	-9
Carrying amount of long-term debt	$3,938	$3,630

Debt_Components_of_Debt_and_Re1

Debt - Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt (Parenthetical) (Detail) (USD $)

9 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

0 Months Ended

Sep. 26, 2014

Sep. 26, 2014

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

CODES Due 2035 [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Corporation [Member]

L-3 Communications Holdings, Inc. [Member]

L-3 Communications Holdings, Inc. [Member]

L-3 Communications Holdings, Inc. [Member]

L-3 Communications Holdings, Inc. [Member]

3.95% Senior Notes due 2016 [Member]

3.95% Senior Notes due 2016 [Member]

3.95% Senior Notes due 2016 [Member]

3.95% Senior Notes due 2016 [Member]

1.50% Senior Notes due 2017 [Member]

1.50% Senior Notes due 2017 [Member]

1.50% Senior Notes due 2017 [Member]

1.50% Senior Notes due 2017 [Member]

5.20% Senior Notes due 2019 [Member]

5.20% Senior Notes due 2019 [Member]

5.20% Senior Notes due 2019 [Member]

5.20% Senior Notes due 2019 [Member]

4.75% Senior Notes due 2020 [Member]

4.75% Senior Notes due 2020 [Member]

4.75% Senior Notes due 2020 [Member]

4.75% Senior Notes due 2020 [Member]

4.95% Senior Notes due 2021 [Member]

4.95% Senior Notes due 2021 [Member]

4.95% Senior Notes due 2021 [Member]

4.95% Senior Notes due 2021 [Member]

3.95% Senior Notes due 2024 [Member]

3.95% Senior Notes due 2024 [Member]

3.95% Senior Notes due 2024 [Member]

3.95% Senior Notes due 2024 [Member]

CODES Due 2035 [Member]

CODES Due 2035 [Member]

CODES Due 2035 [Member]

CODES Due 2035 [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate on Senior Notes

'

3.00%

'

'

3.95%

3.95%

'

'

1.50%

1.50%

'

'

5.20%

5.20%

'

'

4.75%

4.75%

'

'

4.95%

4.95%

'

'

3.95%

3.95%

'

'

3.00%

3.00%

Debt instrument maturity period

'

'

'2016

'2016

'

'

'2017

'2017

'

'

'2019

'2019

'

'

'2020

'2020

'

'

'2021

'2021

'

'

'2024

'2024

'

'

'2035

'2035

'

'

Aggregate borrowings and repayments under the Amended and Restated Revolving Credit Facility

$1,367,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Borrowings under Amended and Restated Revolving Credit Facility

$1,000,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revolving credit facility expiration date

3-Feb-17

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt_Additional_Information_De

Debt - Additional Information (Detail) (USD $)	0 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended		0 Months Ended
	13-May-14	Sep. 26, 2014	13-May-14	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013	28-May-14
				L-3 Communications Holdings, Inc. [Member]	L-3 Communications Holdings, Inc. [Member]	L-3 Communications Holdings, Inc. [Member]	L-3 Communications Corporation [Member]
							Instruments
Debt Instrument [Line Items]	'	'	'	'	'	'	'
Senior Notes issued	'	'	'	'	'	'	2
Principal amount of CODES	'	'	$1,000	'	'	'	'
Redemption price for CODES	'	'	1,000	'	'	'	'
Redemption date	'	2-Jun-14	'	'	'	'	'
Conversion of converted securities	935,000,000	-160,000,000	'	'	'	'	'
Number of trading days in the conversion period	'	'20 days	'	'	'	'	'
Trading day conversion description	'	'(1) for conversion notices received by May 16, 2014 (5 p.m.), the 20 trading day conversion period began on the third trading day following receipt of the conversion notice and (2) for conversion notices received	'	'	'	'	'
Excess of conversion value over fair value of the debt component	'	'	160,000,000	'	'	'	'
Interest expense recognized	'	'	'	$5,000,000	$2,000,000	$15,000,000	'

Debt_Information_Regarding_Out

Debt - Information Regarding Outstanding Series of Senior Subordinated Note (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014
Debt Instrument [Line Items]	'
Net Cash Proceeds	$996
L-3 Communications Corporation [Member]	'
Debt Instrument [Line Items]	'
Net Cash Proceeds	988
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
Bond Discount	1
Net Cash Proceeds	347
Effective Interest Rate	1.55%
Redemption at Treasury Rate	0.10%
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
Bond Discount	3
Net Cash Proceeds	$641
Effective Interest Rate	4.02%
Redemption at Treasury Rate	0.20%

Debt_Information_Regarding_Out1

Debt - Information Regarding Outstanding Series of Senior Subordinated Note (Parenthetical) (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Dec. 31, 2013
Debt Instrument [Line Items]	'	'
Net Cash Proceeds	$996	'
L-3 Communications Corporation [Member]	'	'
Debt Instrument [Line Items]	'	'
Net Cash Proceeds	988	'
Redemption price as percentage of principal amount	100.00%	'
Senior notes redemption price	101.00%	'
L-3 Communications Corporation [Member] | 1.50% Senior Notes due 2017 [Member]	'	'
Debt Instrument [Line Items]	'	'
Interest rate on Senior Notes	1.50%	1.50%
Senior Notes due	28-May-17	'
Net Cash Proceeds	347	'
L-3 Communications Corporation [Member] | 3.95% Senior Notes due 2024 [Member]	'	'
Debt Instrument [Line Items]	'	'
Interest rate on Senior Notes	3.95%	3.95%
Senior Notes due	28-May-24	'
Net Cash Proceeds	$641	'
L-3 Communications Corporation [Member] | Minimum [Member] | 3.95% Senior Notes due 2024 [Member]	'	'
Debt Instrument [Line Items]	'	'
Senior Notes due	28-Feb-24	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Dec. 31, 2013
Tax Credit Carryforward [Line Items]	'	'	'
Effective tax rate	29.50%	27.50%	'
Previously accrued income tax due to the expiration of the statue of limitations	'	$10	'
Anticipated decrease in unrecognized tax benefits over the next 12 months	20	'	'
Accrued potential interest included within non-current income taxes payable	14	'	11
Accrued potential interest included within non-current income taxes payable, after income taxes	8	'	7
Potential penalties	8	'	8
U.S. Federal Research and Experimentation Tax Credit [Member]	'	'	'
Tax Credit Carryforward [Line Items]	'	'	'
Tax benefit	'	$28	'

Amounts_Reclassified_Out_of_Ac2

Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income - Summary of Amounts Reclassified Out of Accumulated Other Comprehensive (Loss) Income (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Beginning Balance	'	'	($110)	($550)
Other comprehensive (loss) income before reclassifications, net of tax	'	'	-52	-20
Amounts reclassified from other comprehensive (loss) income, net of tax	'	'	2	41
Net current period other comprehensive (loss) income	'	'	-50	21
Ending Balance	-160	-529	-160	-529
Cost of sales-products	1,480	1,487	4,498	4,732
Income before income taxes	215	266	667	789
Benefit (Provision) for income taxes	-58	-62	-197	-217
Reclassification out of Accumulated Other Comprehensive Income [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net income	2	13	2	41
Foreign Currency Translation [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Beginning Balance	'	'	142	167
Other comprehensive (loss) income before reclassifications, net of tax	'	'	-57	-18
Amounts reclassified from other comprehensive (loss) income, net of tax	'	'	'	'
Net current period other comprehensive (loss) income	'	'	-57	-18
Ending Balance	85	149	85	149
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	'	'	5	-2
Amounts reclassified from other comprehensive (loss) income, net of tax	'	'	-5	1
Net current period other comprehensive (loss) income	'	'	'	-1
Ending Balance	1	2	1	2
Unrealized Gains (Losses) on Hedging Instruments [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Cost of sales-products	1	'	-6	1
Income before income taxes	1	'	-6	1
Benefit (Provision) for income taxes	-1	'	1	'
Net income	'	'	-5	1
Unrecognized (Losses) and Prior Service Cost, Net [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Beginning Balance	'	'	-253	-720
Other comprehensive (loss) income before reclassifications, net of tax	'	'	'	'
Amounts reclassified from other comprehensive (loss) income, net of tax	'	'	7	40
Net current period other comprehensive (loss) income	'	'	7	40
Ending Balance	-246	-680	-246	-680
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]	'	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Net loss	3	20	11	63
Income before income taxes	3	20	11	63
Benefit (Provision) for income taxes	-1	-7	-4	-23
Net income	$2	$13	$7	$40

Equity_Additional_Information_

Equity - Additional Information (Detail) (USD $)	0 Months Ended			9 Months Ended		0 Months Ended	9 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Sep. 15, 2014	Jun. 24, 2014	Feb. 05, 2013	Sep. 26, 2014	Sep. 27, 2013	Oct. 20, 2014	Sep. 26, 2014	Sep. 27, 2013
						Subsequent Event [Member]	Common Stock [Member]	Common Stock [Member]
Class of Stock [Line Items]	'	'	'	'	'	'	'	'
Amount of shares authorized to be repurchased	'	'	$1,500,000,000	'	'	'	'	'
Average price per share of repurchased shares	'	'	'	$115.91	'	'	'	'
Number of common shares repurchased	'	'	'	'	'	'	3.6	4.8
Aggregate amount of repurchased shares	'	'	'	413,000,000	404,000,000	'	'	'
Remaining value under share repurchase program	'	'	'	455,000,000	'	'	'	'
Cash dividend, declared per share	'	$0.60	'	'	'	$0.60	'	'
Total cash dividends	$51,000,000	'	'	$155,000,000	$149,000,000	'	'	'
Dividend declared date	'	'	'	20-Oct-14	'	'	'	'
Dividend payable date	'	'	'	15-Dec-14	'	'	'	'
Dividend payable, record date	'	'	'	17-Nov-14	'	'	'	'

L3_Holdings_Earnings_Per_Commo2

L-3 Holdings' Earnings Per Common Share - Reconciliation of Basic and Diluted Earnings Per Share (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Reconciliation of net income:	'	'	'	'
Net income	$157	$204	$470	$572
Net income attributable to noncontrolling interests	-3	-4	-9	-6
Net income attributable to L-3 Holdings' common shareholders	$154	$200	$461	$566
Basic:	'	'	'	'
Weighted average common shares outstanding	85.1	89.6	85.7	89.9
Basic earnings per share:	'	'	'	'
Net income	$1.81	$2.23	$5.38	$6.30
Common and potential common shares:	'	'	'	'
Weighted average common shares outstanding	85.1	89.6	85.7	89.9
Assumed purchase of common shares for treasury	-2.9	-5.2	-3.2	-4.7
Assumed conversion of the CODES	'	0.1	1.1	0.1
Common and potential common shares	86.6	91.3	88.4	91.3
Diluted earnings per share:	'	'	'	'
Net income	$1.78	$2.19	$5.21	$6.20
Stock Options [Member]	'	'	'	'
Common and potential common shares:	'	'	'	'
Common and potential common shares	2.8	4.7	3	3.9
Unvested Restricted Stock Awards [Member]	'	'	'	'
Common and potential common shares:	'	'	'	'
Common and potential common shares	1.5	1.8	1.6	1.8
Employee Stock Purchase Plan Contributions [Member]	'	'	'	'
Common and potential common shares:	'	'	'	'
Common and potential common shares	'	0.2	0.1	0.2
Performance Unit Awards [Member]	'	'	'	'
Common and potential common shares:	'	'	'	'
Common and potential common shares	0.1	0.1	0.1	0.1

L3_Holdings_Earnings_Per_Commo3

L-3 Holdings' Earnings Per Common Share - Reconciliation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) (USD $)	Jun. 27, 2014
Earnings Per Share [Abstract]	'
Conversion price of L-3 Holdings' CODES	$88.71

L3_Holdings_Earnings_Per_Commo4

L-3 Holdings' Earnings Per Common Share - Additional Information (Detail)	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 26, 2014	Sep. 27, 2013
Earnings Per Share [Abstract]	'	'	'
Shares excluded from computation of diluted earnings per share and employee stock purchase plan contributions	0.6	0.5	1.2

Fair_Value_Measurements_Compan

Fair Value Measurements - Company's Assets and Liabilities at Fair Value on Recurring Basis (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Level 1 [Member]	'	'
Assets	'	'
Cash equivalents	$359	$299
Derivatives (foreign currency forward contracts)	'	'
Total assets	359	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)	4	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 $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Senior Notes, Carrying Amount	$3,938	$2,941
CODES, Carrying Amount	'	689
Senior Notes, Estimated Fair Value	4,181	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	1	1
Carrying Amount [Member]	'	'
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]	'	'
Foreign currency forward contracts	$1	$1

Derivative_Financial_Instrumen2

Derivative Financial Instruments - Notional Amounts of Company's Outstanding Foreign Currency Forward Contracts by Currency (Detail) (USD $)	Sep. 26, 2014
In Millions, unless otherwise specified
Derivative [Line Items]	'
Notional amounts of foreign currency forward contracts	$337
Canadian Dollar [Member]	'
Derivative [Line Items]	'
Notional amounts of foreign currency forward contracts	161
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	66
British Pound [Member]	'
Derivative [Line Items]	'
Notional amounts of foreign currency forward contracts	$9

Derivative_Financial_Instrumen3

Derivative Financial Instruments - Additional Information (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
	Maximum [Member]	CODES Due 2035 [Member]
Derivative [Line Items]	'	'
Fair value of embedded derivative related to the issuance of the CODES	'	$0
Estimated amount of existing losses expected to be reclassified into income within the next 12 months	($1,000,000)	'

Derivative_Financial_Instrumen4

Derivative Financial Instruments - Location of Company's Derivative Instruments Recorded at Fair Value on Condensed Consolidated Balance Sheets (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
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 Current Assets [Member] | Foreign Currency Forward Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, assets	'	'
Other Current Assets [Member] | CODES Due 2035 [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, assets	'	'
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
Other Assets [Member] | Foreign Currency Forward Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, assets	'	'
Other Assets [Member] | CODES Due 2035 [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, assets	'	'
Other Current Liabilities [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, liabilities	3	3
Other Current Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, liabilities	3	3
Other Current Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, liabilities	'	'
Other Current Liabilities [Member] | CODES Due 2035 [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, liabilities	'	'
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 Liabilities [Member] | Foreign Currency Forward Contracts [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, liabilities	'	'
Other Liabilities [Member] | CODES Due 2035 [Member] | Not Designated as Hedging Instruments [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Total derivative instruments, liabilities	'	'

Commitments_and_Contingencies_

Commitments and Contingencies - Additional Information (Detail)	0 Months Ended					0 Months Ended
In Millions, unless otherwise specified	Jul. 01, 2013	Apr. 23, 2007	31-May-12	Mar. 09, 2010	Jul. 01, 2004	Jul. 23, 2014	Jul. 23, 2014
	Plaintiff	Plaintiff	USD ($)	USD ($)	USD ($)	Property Damages [Member]	Business Interruption [Member]
						EUR (€)	EUR (€)
Contingencies And Commitments [Line Items]	'	'	'	'	'	'	'
Total damages sought	'	'	'	'	$315	'	'
Punitive damages sought	'	'	'	'	150	'	'
Number of plaintiffs re-filed their complaint against ACSS	'	30	'	'	'	'	'
Compensatory damages	'	'	48	6.7	'	'	'
Number of plaintiffs released their claims against ACSS	18	'	'	'	'	'	'
Claims for estimated damages	'	'	'	'	'	€ 11	€ 35

Pension_and_Other_Postretireme2

Pension and Other Postretirement Benefits - Components of Net Periodic Benefit Cost (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Pension Plans [Member]	'	'	'	'
Components of net periodic benefit cost:	'	'	'	'
Service cost	$26	$30	$80	$95
Interest cost	37	33	110	99
Expected return on plan assets	-48	-41	-145	-124
Amortization of prior service costs (credits)	'	1	1	1
Amortization of net loss (gain)	4	20	13	63
Curtailment loss	'	2	1	2
Net periodic benefit cost	19	45	60	136
Postretirement Benefit Plans [Member]	'	'	'	'
Components of net periodic benefit cost:	'	'	'	'
Service cost	-2	1	'	3
Interest cost	4	2	8	5
Expected return on plan assets	-1	'	-3	-2
Amortization of prior service costs (credits)	'	-1	-1	-2
Amortization of net loss (gain)	-1	'	-2	1
Curtailment loss	-1	'	-1	'
Net periodic benefit cost	($1)	$2	$1	$5

Pension_and_Other_Postretireme3

Pension and Other Postretirement Benefits - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014
Pension Plans [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Contribution to pension plans	$85
Expected contributions to plans	12
Postretirement Benefit Plans [Member]	'
Defined Benefit Plan Disclosure [Line Items]	'
Contribution to other postretirement benefit plans	5
Expected contributions to plans	$5

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 26, 2014
Employee Restricted Equity Awards And Performance Stock Awards Vesting Activity [Line Items]	'
Exercise price	$113.67
Stock options granted	472,992
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
Restricted Stock Units [Member]	'
Employee Restricted Equity Awards And Performance Stock Awards Vesting Activity [Line Items]	'
Vesting period	'3 years
Units granted	414,694
Weighted average grant date fair value	$113.69
Vesting period of units granted for non-employee directors	'1 year
Performance Units [Member]	'
Employee Restricted Equity Awards And Performance Stock Awards Vesting Activity [Line Items]	'
Units granted	47,467
Weighted average grant date fair value	$113.67
Length of service after grant date	'3 years
Minimum payout range	0.00%
Maximum payout range	200.00%

StockBased_Compensation_Weight

Stock-Based Compensation - Weighted Average Assumptions used in Valuation Model (Detail)	9 Months Ended
	Sep. 26, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Expected holding period (in years)	'5 years 6 months
Expected volatility	24.40%
Expected dividend yield	2.70%
Risk-free interest rate	1.70%

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information - Supplemental Cash Flow Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]	'	'
Interest paid on outstanding debt	$123	$133
Income tax payments	116	168
Income tax refunds	$8	$20

Segment_Information_Additional

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 26, 2014
	Segment
Segment Reporting [Abstract]	'
Number of segments	4

Segment_Information_Summary_of

Segment Information - Summary of Segment Information (Detail) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

42 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

In Millions, unless otherwise specified

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Jun. 27, 2014

Mar. 28, 2014

Dec. 31, 2013

Sep. 27, 2013

Jun. 28, 2013

Mar. 29, 2013

Jun. 27, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Jun. 27, 2014

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Dec. 31, 2013

Sep. 26, 2014

Dec. 31, 2013

Sep. 26, 2014

Sep. 27, 2013

Sep. 26, 2014

Sep. 27, 2013

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Operating Segments [Member]

Corporate [Member]

Corporate [Member]

Elimination of Intercompany Sales [Member]

Elimination of Intercompany Sales [Member]

Elimination of Intercompany Sales [Member]

Elimination of Intercompany Sales [Member]

Electronic Systems [Member]

Electronic Systems [Member]

Electronic Systems [Member]

Electronic Systems [Member]

Electronic Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Aerospace Systems [Member]

Communication Systems [Member]

Communication Systems [Member]

Communication Systems [Member]

Communication Systems [Member]

Communication Systems [Member]

NSS [Member]

NSS [Member]

NSS [Member]

NSS [Member]

NSS [Member]

Net Sales:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net Sales

$2,940

$3,002

$8,916

$9,388

'

($10)

($13)

($21)

$5

($3)

$12

($23)

($7)

($38)

($4)

($73)

$1,128

$1,139

$3,349

$3,438

'

$1,037

$1,092

$3,173

$3,416

'

$507

$486

$1,562

$1,667

'

$307

$323

$948

$987

'

'

'

($39)

($38)

($116)

($120)

Operating Income:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating income

257

306

782

906

'

'

'

'

'

'

'

'

'

'

'

'

125

144

383

388

'

64

105

196

336

'

49

31

147

116

'

19

26

56

66

'

'

'

'

'

'

'

Depreciation and amortization:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Depreciation and amortization

56

52

165

158

'

'

'

'

'

'

'

'

'

'

'

'

30

28

89

87

'

11

10

30

28

'

13

12

38

35

'

2

2

8

8

'

'

'

'

'

'

'

Total Assets:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total Assets

$14,041

'

$14,041

'

$13,988

'

'

'

'

'

'

'

'

'

'

'

$6,998

'

$6,998

'

$6,928

$2,961

'

$2,961

'

$3,087

$2,076

'

$2,076

'

$2,130

$1,312

'

$1,312

'

$1,247

$694

$596

'

'

'

'

Employee_Severance_and_Termina2

Employee Severance and Termination Costs - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Dec. 31, 2013
	Employees		Employees
Restructuring and Related Activities [Abstract]	'	'	'
Employee severance and other termination costs	$23	$19	$29
Number of employees terminated	1,500	'	2,000
Remaining balance of employee termination costs	$11	'	$11

Employee_Severance_and_Termina3

Employee Severance and Termination Costs - Employee Severance and Other Termination Costs Incurred by Reportable Segment (Detail) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]	'	'	'
Employee severance and other termination costs	$23	$19	$29
Electronic Systems [Member]	'	'	'
Restructuring Cost and Reserve [Line Items]	'	'	'
Employee severance and other termination costs	14	11	'
Aerospace Systems [Member]	'	'	'
Restructuring Cost and Reserve [Line Items]	'	'	'
Employee severance and other termination costs	3	1	'
Communication Systems [Member]	'	'	'
Restructuring Cost and Reserve [Line Items]	'	'	'
Employee severance and other termination costs	5	6	'
NSS [Member]	'	'	'
Restructuring Cost and Reserve [Line Items]	'	'	'
Employee severance and other termination costs	$1	$1	'

Condensed_Combining_Financial_2

Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Additional Information (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014
Condensed Financial Statements, Captions [Line Items]	'
Ownership percentage held in subsidiary	100.00%
Non-Guarantor Subsidiaries [Member]	'
Condensed Financial Statements, Captions [Line Items]	'
Cumulative aggregate adjustments, net	$28

Condensed_Combining_Financial_3

Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Balance Sheets (Detail) (USD $)	Sep. 26, 2014	Dec. 31, 2013	Sep. 27, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Current assets:	'	'	'	'
Cash and cash equivalents	$508	$500	$377	$349
Billed receivables, net	871	991	'	'
Contracts in process	2,546	2,431	'	'
Other current assets	731	672	'	'
Total current assets	4,656	4,594	'	'
Goodwill	7,784	7,796	'	'
Other assets	1,601	1,598	'	'
Investment in and amounts due from consolidated subsidiaries	'	'	'	'
Total assets	14,041	13,988	'	'
Current liabilities	2,392	2,534	'	'
Amounts due to consolidated subsidiaries	'	'	'	'
Other long-term liabilities	1,732	1,768	'	'
Long-term debt	3,938	3,630	'	'
Total liabilities	8,062	7,932	'	'
L-3 shareholders' equity	5,903	5,981	'	'
Noncontrolling interests	76	75	'	'
Total equity	5,979	6,056	5,798	5,527
Total liabilities and equity	14,041	13,988	'	'
L-3 Communications Holdings, Inc. [Member]	'	'	'	'
Current assets:	'	'	'	'
Cash and cash equivalents	'	'	'	'
Billed receivables, net	'	'	'	'
Contracts in process	'	'	'	'
Other current assets	'	'	'	'
Total current assets	'	'	'	'
Goodwill	'	'	'	'
Other assets	'	'	'	'
Investment in and amounts due from consolidated subsidiaries	5,903	6,670	'	'
Total assets	5,903	6,670	'	'
Current liabilities	'	'	'	'
Amounts due to consolidated subsidiaries	'	'	'	'
Other long-term liabilities	'	'	'	'
Long-term debt	'	689	'	'
Total liabilities	'	689	'	'
L-3 shareholders' equity	5,903	5,981	'	'
Noncontrolling interests	'	'	'	'
Total equity	5,903	5,981	'	'
Total liabilities and equity	5,903	6,670	'	'
L-3 Communications Corporation [Member]	'	'	'	'
Current assets:	'	'	'	'
Cash and cash equivalents	330	258	154	246
Billed receivables, net	296	364	'	'
Contracts in process	994	925	'	'
Other current assets	410	344	'	'
Total current assets	2,030	1,891	'	'
Goodwill	2,324	2,324	'	'
Other assets	800	838	'	'
Investment in and amounts due from consolidated subsidiaries	6,993	6,923	'	'
Total assets	12,147	11,976	'	'
Current liabilities	872	914	'	'
Amounts due to consolidated subsidiaries	'	'	'	'
Other long-term liabilities	1,434	1,451	'	'
Long-term debt	3,938	3,630	'	'
Total liabilities	6,244	5,995	'	'
L-3 shareholders' equity	5,903	5,981	'	'
Noncontrolling interests	'	'	'	'
Total equity	5,903	5,981	'	'
Total liabilities and equity	12,147	11,976	'	'
Guarantor Subsidiaries [Member]	'	'	'	'
Current assets:	'	'	'	'
Cash and cash equivalents	1	'	1	'
Billed receivables, net	348	401	'	'
Contracts in process	1,165	1,152	'	'
Other current assets	145	159	'	'
Total current assets	1,659	1,712	'	'
Goodwill	4,320	4,320	'	'
Other assets	568	532	'	'
Investment in and amounts due from consolidated subsidiaries	4,049	3,750	'	'
Total assets	10,596	10,314	'	'
Current liabilities	999	1,011	'	'
Amounts due to consolidated subsidiaries	'	'	'	'
Other long-term liabilities	187	193	'	'
Long-term debt	'	'	'	'
Total liabilities	1,186	1,204	'	'
L-3 shareholders' equity	9,410	9,110	'	'
Noncontrolling interests	'	'	'	'
Total equity	9,410	9,110	'	'
Total liabilities and equity	10,596	10,314	'	'
Non-Guarantor Subsidiaries [Member]	'	'	'	'
Current assets:	'	'	'	'
Cash and cash equivalents	239	261	244	242
Billed receivables, net	227	226	'	'
Contracts in process	387	354	'	'
Other current assets	176	169	'	'
Total current assets	1,029	1,010	'	'
Goodwill	1,140	1,152	'	'
Other assets	233	228	'	'
Investment in and amounts due from consolidated subsidiaries	'	'	'	'
Total assets	2,402	2,390	'	'
Current liabilities	583	628	'	'
Amounts due to consolidated subsidiaries	366	259	'	'
Other long-term liabilities	111	124	'	'
Long-term debt	'	'	'	'
Total liabilities	1,060	1,011	'	'
L-3 shareholders' equity	1,342	1,379	'	'
Noncontrolling interests	'	'	'	'
Total equity	1,342	1,379	'	'
Total liabilities and equity	2,402	2,390	'	'
Eliminations [Member]	'	'	'	'
Current assets:	'	'	'	'
Cash and cash equivalents	-62	-19	-22	-139
Billed receivables, net	'	'	'	'
Contracts in process	'	'	'	'
Other current assets	'	'	'	'
Total current assets	-62	-19	'	'
Goodwill	'	'	'	'
Other assets	'	'	'	'
Investment in and amounts due from consolidated subsidiaries	-16,945	-17,343	'	'
Total assets	-17,007	-17,362	'	'
Current liabilities	-62	-19	'	'
Amounts due to consolidated subsidiaries	-366	-259	'	'
Other long-term liabilities	'	'	'	'
Long-term debt	'	-689	'	'
Total liabilities	-428	-967	'	'
L-3 shareholders' equity	-16,655	-16,470	'	'
Noncontrolling interests	76	75	'	'
Total equity	-16,579	-16,395	'	'
Total liabilities and equity	($17,007)	($17,362)	'	'

Condensed_Combining_Financial_4

Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Operations (Detail) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Total net sales	$2,940	$3,002	$8,916	$9,388
Total cost of sales	-2,683	-2,696	-8,134	-8,482
Operating (loss) income	257	306	782	906
Interest expense	-47	-44	-129	-131
Interest and other income, net	5	4	14	14
(Loss) income before income taxes	215	266	667	789
Benefit (Provision) for income taxes	-58	-62	-197	-217
Equity in net income of consolidated subsidiaries	'	'	'	'
Net income	157	204	470	572
Net income attributable to noncontrolling interests	-3	-4	-9	-6
Net income attributable to L-3	154	200	461	566
Comprehensive income attributable to L-3	90	250	411	587
L-3 Communications Holdings, Inc. [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Total net sales	'	'	'	'
Total cost of sales	-10	-14	-39	-42
Operating (loss) income	-10	-14	-39	-42
Interest expense	'	-5	-2	-15
Interest and other income, net	'	'	'	'
(Loss) income before income taxes	-10	-19	-41	-57
Benefit (Provision) for income taxes	3	5	12	16
Equity in net income of consolidated subsidiaries	161	214	490	607
Net income	154	200	461	566
Net income attributable to noncontrolling interests	'	'	'	'
Net income attributable to L-3	154	200	461	566
Comprehensive income attributable to L-3	90	250	411	587
L-3 Communications Corporation [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Total net sales	860	912	2,606	2,847
Total cost of sales	-787	-854	-2,354	-2,625
Operating (loss) income	73	58	252	222
Interest expense	-46	-43	-127	-130
Interest and other income, net	4	3	12	9
(Loss) income before income taxes	31	18	137	101
Benefit (Provision) for income taxes	-8	-3	-41	-28
Equity in net income of consolidated subsidiaries	131	185	365	493
Net income	154	200	461	566
Net income attributable to noncontrolling interests	'	'	'	'
Net income attributable to L-3	154	200	461	566
Comprehensive income attributable to L-3	90	250	411	587
Guarantor Subsidiaries [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Total net sales	1,628	1,646	4,908	5,104
Total cost of sales	-1,500	-1,458	-4,533	-4,598
Operating (loss) income	128	188	375	506
Interest expense	-2	'	-2	'
Interest and other income, net	'	1	'	1
(Loss) income before income taxes	126	189	373	507
Benefit (Provision) for income taxes	-34	-45	-110	-139
Equity in net income of consolidated subsidiaries	'	'	'	'
Net income	92	144	263	368
Net income attributable to noncontrolling interests	'	'	'	'
Net income attributable to L-3	92	144	263	368
Comprehensive income attributable to L-3	89	145	264	369
Non-Guarantor Subsidiaries [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Total net sales	525	543	1,623	1,705
Total cost of sales	-469	-483	-1,468	-1,527
Operating (loss) income	56	60	155	178
Interest expense	1	-1	'	-1
Interest and other income, net	1	'	2	4
(Loss) income before income taxes	58	59	157	181
Benefit (Provision) for income taxes	-16	-14	-46	-50
Equity in net income of consolidated subsidiaries	'	'	'	'
Net income	42	45	111	131
Net income attributable to noncontrolling interests	'	'	'	'
Net income attributable to L-3	42	45	111	131
Comprehensive income attributable to L-3	-22	77	53	108
Eliminations [Member]	'	'	'	'
Condensed Financial Statements, Captions [Line Items]	'	'	'	'
Total net sales	-73	-99	-221	-268
Total cost of sales	83	113	260	310
Operating (loss) income	10	14	39	42
Interest expense	'	5	2	15
Interest and other income, net	'	'	'	'
(Loss) income before income taxes	10	19	41	57
Benefit (Provision) for income taxes	-3	-5	-12	-16
Equity in net income of consolidated subsidiaries	-292	-399	-855	-1,100
Net income	-285	-385	-826	-1,059
Net income attributable to noncontrolling interests	-3	-4	-9	-6
Net income attributable to L-3	-288	-389	-835	-1,065
Comprehensive income attributable to L-3	($157)	($472)	($728)	($1,064)

Condensed_Combining_Financial_5

Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Statements of Cash Flows (Detail) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 26, 2014	Sep. 27, 2013
Operating activities:	'	'
Net cash from operating activities	$605	$617
Investing activities:	'	'
Business acquisitions, net of cash acquired	-57	-2
Investments in L-3 Communications	'	'
Other investing activities	-105	-139
Net cash used in investing activities	-162	-141
Financing activities:	'	'
Proceeds from sale of senior notes	996	'
Retirement of CODES	-935	'
Common stock repurchased	-413	-404
Dividends paid on L-3 Holdings common stock	-158	-151
Dividends paid to L-3 Holdings	'	'
Investments from L-3 Holdings	'	'
Other financing activities	84	109
Net cash used in financing activities	-426	-446
Effect of foreign currency exchange rate changes on cash	-9	-2
Net increase (decrease) in cash	8	28
Cash and cash equivalents, beginning of the period	500	349
Cash and cash equivalents, end of the period	508	377
L-3 Communications Holdings, Inc. [Member]	'	'
Operating activities:	'	'
Net cash from operating activities	1,506	555
Investing activities:	'	'
Business acquisitions, net of cash acquired	'	'
Investments in L-3 Communications	-87	-104
Other investing activities	'	'
Net cash used in investing activities	-87	-104
Financing activities:	'	'
Proceeds from sale of senior notes	'	'
Retirement of CODES	-935	'
Common stock repurchased	-413	-404
Dividends paid on L-3 Holdings common stock	-158	-151
Dividends paid to L-3 Holdings	'	'
Investments from L-3 Holdings	'	'
Other financing activities	87	104
Net cash used in financing activities	-1,419	-451
Effect of foreign currency exchange rate changes on cash	'	'
Net increase (decrease) in cash	'	'
Cash and cash equivalents, beginning of the period	'	'
Cash and cash equivalents, end of the period	'	'
L-3 Communications Corporation [Member]	'	'
Operating activities:	'	'
Net cash from operating activities	201	86
Investing activities:	'	'
Business acquisitions, net of cash acquired	-57	-2
Investments in L-3 Communications	'	'
Other investing activities	-37	-70
Net cash used in investing activities	-94	-72
Financing activities:	'	'
Proceeds from sale of senior notes	996	'
Retirement of CODES	'	'
Common stock repurchased	'	'
Dividends paid on L-3 Holdings common stock	'	'
Dividends paid to L-3 Holdings	-1,506	-555
Investments from L-3 Holdings	87	104
Other financing activities	388	345
Net cash used in financing activities	-35	-106
Effect of foreign currency exchange rate changes on cash	'	'
Net increase (decrease) in cash	72	-92
Cash and cash equivalents, beginning of the period	258	246
Cash and cash equivalents, end of the period	330	154
Guarantor Subsidiaries [Member]	'	'
Operating activities:	'	'
Net cash from operating activities	382	523
Investing activities:	'	'
Business acquisitions, net of cash acquired	'	'
Investments in L-3 Communications	'	'
Other investing activities	-52	-53
Net cash used in investing activities	-52	-53
Financing activities:	'	'
Proceeds from sale of senior notes	'	'
Retirement 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	-329	-469
Net cash used in financing activities	-329	-469
Effect of foreign currency exchange rate changes on cash	'	'
Net increase (decrease) in cash	1	1
Cash and cash equivalents, beginning of the period	'	'
Cash and cash equivalents, end of the period	1	1
Non-Guarantor Subsidiaries [Member]	'	'
Operating activities:	'	'
Net cash from operating activities	69	101
Investing activities:	'	'
Business acquisitions, net of cash acquired	'	'
Investments in L-3 Communications	'	'
Other investing activities	-16	-16
Net cash used in investing activities	-16	-16
Financing activities:	'	'
Proceeds from sale of senior notes	'	'
Retirement 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	-66	-81
Net cash used in financing activities	-66	-81
Effect of foreign currency exchange rate changes on cash	-9	-2
Net increase (decrease) in cash	-22	2
Cash and cash equivalents, beginning of the period	261	242
Cash and cash equivalents, end of the period	239	244
Eliminations [Member]	'	'
Operating activities:	'	'
Net cash from operating activities	-1,553	-648
Investing activities:	'	'
Business acquisitions, net of cash acquired	'	'
Investments in L-3 Communications	87	104
Other investing activities	'	'
Net cash used in investing activities	87	104
Financing activities:	'	'
Proceeds from sale of senior notes	'	'
Retirement of CODES	'	'
Common stock repurchased	'	'
Dividends paid on L-3 Holdings common stock	'	'
Dividends paid to L-3 Holdings	1,506	555
Investments from L-3 Holdings	-87	-104
Other financing activities	4	210
Net cash used in financing activities	1,423	661
Effect of foreign currency exchange rate changes on cash	'	'
Net increase (decrease) in cash	-43	117
Cash and cash equivalents, beginning of the period	-19	-139
Cash and cash equivalents, end of the period	($62)	($22)