Accounting Changes And Error Corrections [Text Block] New Accounting Standards Accounts Payable Current Accounts payable, trade Accounts Receivable Net Current Billed receivables, net Billed receivables, net of allowances of $27 in 2012 and $25 in 2011 Accrued Income Taxes Current Income taxes Accrued Liabilities And Deferred Credits [Line Items] Accrued Liabilities And Deferred Credits [Line Items] Accrued Liabilities And Deferred Credits [Line Items] Accrued Liabilities Current Accrued expenses Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated other comprehensive loss Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Loss Acquired Finite Lived Intangible Assets Weighted Average Useful Life Weighted average useful life for identifiable intangible assets, years Acquisitions And Discontinued Operations [Line Items] Acquisitions And Discontinued Operations [Line Items] Acquisitions And Discontinued Operations [Line Items] Acquisitions And Discontinued Operations [Table] Acquisitions And Discontinued Operations [Table] Acquisitions And Discontinued Operations [Table] The entire disclosure for business combinations and divestitures. This may include a description of a business combination or divestiture (or series of individually immaterial business combinations or divestitures) completed during the period, including background, timing, and assets and liabilities recognized and reclassified or sold. Also, includes acquisition pro forma information and financial information related to acquisitions and dispositions. Acquisitions And Dispositions Disclosure [Text Block] Dispositions and Acquisitions Additional amount of shares authorized to be repurchased. Additional Amount Of Shares Authorized To Be Repurchased Additional amount of shares authorized to be repurchased Additional Paid In Capital [Member] Additional Paid-in Capital Adjustments To Additional Paid In Capital Tax Effect From Share Based Compensation Stock-based compensation expense The current portion, due within one year or one operating cycle, if longer, of aggregate prepayments received from customers for goods or services to be provided in the future, as well as the current portion of money or property received from customers that are to be returned upon satisfactory contract completion or as partial prepayment for goods or services to be provided in the future and also includes liabilities due to billings on long term contracts that exceed the income recorded under the percentage of completion contract accounting method, or that exceed the accumulated costs under the completed contract accounting method. Advance Payments And Billings In Excess Of Costs Incurred Advance payments and billings in excess of costs incurred The current portion, due within one year or one operating cycle, if longer, of aggregate prepayments received from customers for goods or services to be provided in the future, as well as the current portion of money or property received from customers that are to be returned upon satisfactory contract completion or as partial prepayment for goods or services to be provided in the future and also includes liabilities due to billings on long term contracts that exceed the income recorded under the percentage of completion contract accounting method, or that exceed the accumulated costs under the completed contract accounting method. Advance Payments Billings In Excess Costs Incurred Advance payments and billings in excess of costs incurred Aircraft Modernization and Maintenance. Aircraft Modernization And Maintenance [Member] AM&M [Member] Allowance For Doubtful Accounts Receivable Current Net allowances for billed receivables Amendment Flag Amendment Flag Amortization expense. Amortization Expense Table [Text Block] Amortization Expense Amortization Of Debt Discount Premium Amortization of bond discounts and deferred debt issue costs (included in interest expense) Amortization Of Intangible Assets Amortization Expense The aggregate expense charged against earnings to allocate the cost of intangible assets and other assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. Amortization Of Intangible Assets And Other Assets Amortization of intangibles and other assets Amounts charged to cost of sales. Amounts Charged To Cost Of Sales Less: Amounts charged to cost of sales Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Shares excluded from computation of diluted earnings per share Assets Total Assets Total assets Assets [Abstract] ASSETS Assets Current Total current assets Assets Current [Abstract] Current assets: Assets Fair Value Disclosure Total Assets Assets Fair Value Disclosure [Abstract] Assets Assets Of Disposal Group Including Discontinued Operation Assets of discontinued operations Total assets of discontinued operations Assets Of Disposal Group Including Discontinued Operation [Abstract] Assets Assets Of Disposal Group Including Discontinued Operation Current Current assets Assets reclassified from segment one to segment four as result of business unit re-alignments. Assets Reclassified From Segment One To Segment Four As Result Of Business Unit Realignments Assets reclassified from C3ISR segment to Electronic Systems segment as a result of business unit re-alignments Assumed purchase of common shares for treasury. Assumed Purchase Of Common Shares For Treasury Assumed purchase of common shares for treasury Award Type [Axis] Award Type [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Balance sheets. Balance Sheets Table [Text Block] Condensed Combining Balance Sheets Basis Of Presentation [Line Items] Basis Of Presentation [Line Items] Basis Of Presentation [Line Items] Basis Of Presentation [Table] Basis Of Presentation [Table] Basis Of Presentation [Table] Basis of Presentation. Basis Of Presentation [Text Block] Basis of Presentation British Pound [Member] British Pound [Member] British pound [Member] Business Acquisition Contingent Consideration At Fair Value Estimated contingent purchase price payable for acquired businesses Business Acquisition Cost Of Acquired Entity Purchase Price Aggregate purchase price of acquisition Business Acquisition [Line Items] Business Acquisition [Line Items] Business Acquisition Pro Forma Earnings Per Share Diluted Pro forma diluted earnings per share Business Acquisition Pro Forma Information [Text Block] Unaudited Pro Forma Statements of Operations Data Business Acquisition Purchase Price Allocation Assets Acquired Liabilities Assumed Net Acquisition of assets and liabilities Business Acquisition Purchase Price Allocation Goodwill Amount Amount of goodwill recognized Business Acquisition Purchase Price Allocation Goodwill Expected Tax Deductible Amount Goodwill deductible for income tax purposes Business Acquisitions Pro Forma Income Loss From Continuing Operations Before Changes In Accounting And Extraordinary Items Net Of Tax Pro forma income from continuing operations Business Acquisitions Pro Forma Net Income Loss Pro forma net income attributable to L-3 Business Acquisitions Pro Forma Revenue Pro forma net sales Business Acquisition [Table] Business Acquisition [Table] Business Acquisition [Table] Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Intangibles Identifiable intangible assets recognized Canadian Dollar [Member] Canadian Dollar [Member] Canadian dollar [Member] Carrying amounts and estimated fair values of the Company's financial instruments. Carrying Amounts And Estimated Fair Values Of Financial Instruments Table [Text Block] Carrying Amounts and Estimated Fair Values of Company's Long-term Debt and Foreign Currency Forward Contracts Carrying Reported Amount Fair Value Disclosure [Member] Carrying Amount [Member] Cash And Cash Equivalents At Carrying Value Cash and cash equivalents, end of the period Cash and cash equivalents, beginning of the period Cash and cash equivalents Cash And Cash Equivalents Fair Value Disclosure Cash equivalents Cash And Cash Equivalents Period Increase Decrease Net (decrease) increase in cash Net decrease in cash and cash equivalents Cash Dividends Paid To Parent Company Dividends paid to L-3 Holdings Supplemental Cash Flow Information. Cash Flow Supplemental Disclosures Table [Text Block] Supplemental Cash Flow Information Cash Flow Supplemental Disclosures [Text Block] Supplemental Cash Flow Information Cash Provided By Used In Financing Activities Discontinued Operations Financing activities Cash Provided By Used In Investing Activities Discontinued Operations Investing activities Cash Provided By Used In Operating Activities Discontinued Operations Operating activities Cash Transferred With Spin Off Transaction Cash Transferred With Spin Off Transaction Contribution received from the spin-off of Engility The net change during the reporting period in the aggregate value of inventory held by the reporting entity, associated with underlying transactions that are classified as operating activities. Excludes inventoried contract costs already included in CIP. Change In Inventories Inventories Closing stock price. Closing Stock Price Closing stock price Combining statements of cash flows. Combining Statements Of Cash Flows Table [Text Block] Condensed Combining Statements of Cash Flows Command, Control, Communications, Intelligence, Surveillance and Reconnaissance (C3ISR) systems. Command Control Communications Intelligence Surveillance And Reconnaissance Systems [Member] C3ISR [Member] Commitments And Contingencies Commitments and contingencies (see Note 16) Equity: Commitments And Contingencies Disclosure [Text Block] Commitments and Contingencies Common Stock Dividends Per Share Cash Paid Cash dividends paid on common stock, per share Cash dividends paid per common share Common Stock Dividends Per Share Declared Cash dividend, declared per share Common Stock [Member] L-3 Holdings Common Stock Common Stock Par Or Stated Value Per Share Common stock, par value Common Stock Shares Authorized Common stock, shares authorized Common Stock Shares Issued Common stock, shares issued Common Stock Shares Outstanding Common stock, shares outstanding Common Stock Value L-3 Communications Holdings, Inc.'s common stock: $.01 par value; 300,000,000 shares authorized, 94,802,315 shares outstanding at September 28, 2012 and 98,979,411 shares outstanding at December 31, 2011 (L-3 Communications Corporation's common stock: $.01 par value, 100 shares authorized, issued and outstanding) Compensatory damages awarded by trial court. Compensatory Damages Awarded By Trial Court Compensatory damages Components Of Contracts In Process. Components Of Contracts In Process [Abstract] Components of contracts in process Components of contracts in process. Components Of Contracts In Process Table [Text Block] Components of Contracts in Process Components of debt and reconciliation to carrying amount. Components Of Debt And Reconciliation To Carrying Amount Table [Text Block] Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt Components of net periodic benefit cost. Components Of Net Periodic Benefit Cost Table [Text Block] Components of Net Periodic Benefit Cost Comprehensive Income Net Of Tax Comprehensive income attributable to L-3 Comprehensive income attributable to L-3 Comprehensive Income Net Of Tax Attributable To Noncontrolling Interest Less: Comprehensive income attributable to noncontrolling interests Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest Comprehensive income Comprehensive Income. Comprehensive Income Policy [Text Block] Comprehensive Income Condensed Financial Statements Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Consolidation Eliminations [Member] Eliminations [Member] Contingencies And Commitments [Line Items] Contingencies And Commitments [Line Items] Contingencies And Commitments [Line Items] Contingencies And Commitments [Table] Contingencies And Commitments [Table] Contingencies And Commitments [Table] Contract costs incurred. Contract Costs Incurred Total contract costs incurred Net unbilled contract receivables and net inventoried contract costs. Contracts In Process Contracts in process Total contracts in process Inventoried contract costs, Unbilled receivables, and Unliquidated progress payments. Contracts In Process Operating Activities Contracts in process Includes inventoried contract costs, unbilled receivables, and unliquidated progress payment amounts capitalized and descriptions for long-term contracts. Separately, includes Selling, General, and Administrative costs and Research and Development costs related to commercial businesses incurred and expensed during the period. Contracts In Process [Text Block] Contracts in Process Contributions To Employee Savings Plans In Company's Common Stock. Contributions To Employee Savings Plans In Companys Common Stock Contributions to employee savings plans in L-3 Holdings' common stock Principal amount of convertible debt as of the balance sheet date, which can be converted into cash under certain circumstances, at the option of the issuer, and if the settlement amount exceeds the principal amount, the excess will be settled in cash or stock or a combination thereof, at the Company's option. Convertible Debt Principal Amount 3% Convertible Contingent Debt Securities due 2035 Convertible Debt Securities [Member] CODES due 2035 [Member] Convertible Subordinated Debt CODES Including the current and noncurrent portions, the fair value of convertible subordinated debt, as of the balance sheet date, initially scheduled to be repaid after one year or beyond the normal operating cycle if longer. This form of debt can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder, and places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets. Convertible Subordinated Debt Estimated Fair Value CODES Corporate [Member] Corporate [Member] Cost Of Goods And Services Sold Total cost of sales Total cost of sales Cost Of Goods And Services Sold [Abstract] Cost of sales: Cost Of Goods Sold Products Cost Of Services Services Current convertible common stock price, which is 120% of the current conversion price. Used for calculating the conversion of its convertible debt as contained in the provisions of the Convertible Contingent Debt Securities, which is used under certain conditions to settle the principal in cash based on a 120% of the conversion price, and if the settlement amount exceeds the principal amount, the excess will be settled in cash or stock or a combination thereof, at the Company's option. Current Convertible Common Stock Price Current convertible common stock price Current Fiscal Year End Date Current Fiscal Year End Date Current liabilities excluding liabilities of discontinued operations. Current Liabilities Current liabilities Customer Relationships [Member] Customer Contractual Relationships [Member] Damages sought net. Damages Sought Net Total damages sought Debt Disclosure [Text Block] Debt Debt Instrument Carrying Amount Principal amount of long-term debt Debt Instrument Convertible Carrying Amount Of The Equity Component Carrying amount of the equity component (conversion feature) Debt Instrument Convertible Conversion Price 1 Conversion price of L-3 Holdings' CODES Debt instrument convertible number of shares. Debt Instrument Convertible Number Of Shares Common stock, shares Debt Instrument Interest Rate Effective Percentage Effective interest rate Debt Instrument Interest Rate Stated Percentage Interest rate on debt instruments Interest rate on senior notes Debt Instrument [Line Items] Debt Instrument [Line Items] Debt Instrument [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument Unamortized Discount Less: Unamortized discounts The aggregate costs related to the retirement of debt, including call premium and the write-off of deferred debt issuance costs. Debt Retirement Charge Debt retirement charge Deferred Compensation Liability Classified Noncurrent Deferred compensation Deferred Finance Costs Noncurrent Net Deferred debt issue costs Deferred Income Tax Expense Benefit Deferred income tax provision Deferred Revenue Current Deferred revenues Deferred Tax Assets Net Current Deferred income taxes Deferred Tax Liabilities Noncurrent Deferred income taxes Defined Benefit Plan Amortization Of Gains Losses Amortization of net loss (gain) Defined Benefit Plan Amortization Of Prior Service Cost Credit Amortization of prior service credits Defined Benefit Plan Contributions By Employer Employer contributions Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year Expected contributions to plans Defined Benefit Plan Expected Return On Plan Assets Expected return on plan assets Defined Benefit Plan Interest Cost Interest cost Defined Benefit Plan Net Periodic Benefit Cost Net periodic benefit cost Defined Benefit Plan Net Periodic Benefit Cost [Abstract] Components of net periodic benefit cost: Defined Benefit Plan Recognized Net Gain Loss Due To Curtailments Curtailment loss (gain) Defined Benefit Plans Disclosures Defined Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans [Domain] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan Service Cost Service cost Depreciation Depreciation of property, plant and equipment Depreciation And Amortization [Abstract] Depreciation and amortization: Depreciation Depletion And Amortization Depreciation and amortization Derivative By Nature [Axis] Derivative, by Nature [Axis] Derivative Contract Type [Domain] Derivative Contract Type [Domain] Derivative Fair Value Of Derivative Asset Embedded derivative related to the CODES Derivative Instrument Risk [Axis] Derivative Instrument Risk [Axis] Derivative Instruments And Hedging Activities Disclosure [Text Block] Derivative Financial Instruments Derivative [Line Items] Derivative [Line Items] Derivative Name [Domain] Derivative, Name [Domain] Derivative [Table] Derivative [Table] Description Of Business [Line Items] Description Of Business [Line Items] Description Of Business [Line Items] Description Of Business [Table] Description Of Business [Table] Description Of Business [Table] Designated As Hedging Instrument [Member] Designated as Hedging Instrument [Member] Diluted Earnings Per Share Pro Forma Pro forma diluted earnings per share from continuing operations Dilutive Securities Included In Computation Of Earnings Per Share [Axis] Dilutive Securities Included In Computation Of Earnings Per Share [Axis] Dilutive Securities Included In Computation Of Earnings Per Share [Axis] Dilutive Securities Included In Computation Of Earnings Per Share [Domain] Dilutive Securities Included In Computation Of Earnings Per Share [Domain] Dilutive Securities Included In Computation Of Earnings Per Share [Domain] Dilutive Securities Included In Computation Of Earnings Per Share [Line Items] Dilutive Securities Included In Computation Of Earnings Per Share [Line Items] Dilutive Securities Included In Computation Of Earnings Per Share [Line Items] Dilutive Securities Included In Computation Of Earnings Per Share [Table] Dilutive Securities Included In Computation Of Earnings Per Share [Table] Dilutive Securities Included In Computation Of Earnings Per Share [Table] Disclosure - Accrued Product Warranty Costs [Abstract] Disclosure Accrued Product Warranty Costs [Abstract] Disclosure - Accrued Product Warranty Costs [Abstract] Disclosure - Amortization Expense [Abstract] Disclosure Amortization Expense [Abstract] Disclosure - Amortization Expense [Abstract] Disclosure Basis Of Presentation Additional Information [Abstract] Disclosure Basis Of Presentation Additional Information [Abstract] Disclosure Basis Of Presentation Additional Information [Abstract] Disclosure - Carrying Amounts and Estimated Fair Values of Company's Long-term Debt and Foreign Currency Forward Contracts [Abstract] Disclosure Carrying Amounts And Estimated Fair Values Of Companys Longterm Debt And Foreign Currency Forward Contracts [Abstract] Disclosure - Carrying Amounts and Estimated Fair Values of Company's Long-term Debt and Foreign Currency Forward Contracts [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure Commitments And Contingencies Additional Information [Abstract] Disclosure - Company's Assets and Liabilities at Fair Value on Recurring Basis [Abstract] Disclosure Companys Assets And Liabilities At Fair Value On Recurring Basis [Abstract] Disclosure - Company's Assets and Liabilities at Fair Value on Recurring Basis [Abstract] Disclosure - Components of Contracts in Progress [Abstract] Disclosure Components Of Contracts In Progress [Abstract] Disclosure - Components of Contracts in Progress [Abstract] Disclosure - Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt [Abstract] Disclosure Components Of Debt And Reconciliation To Carrying Amount Of Long Term Debt [Abstract] Disclosure - Components of Debt and Reconciliation to Carrying Amount of Long-Term Debt [Abstract] Disclosure Components Of Net Periodic Benefit Cost [Abstract] Disclosure Components Of Net Periodic Benefit Cost [Abstract] Disclosure Components Of Net Periodic Benefit Cost [Abstract] Disclosure - Condensed Combining Balance Sheets [Abstract] Disclosure Condensed Combining Balance Sheets [Abstract] Disclosure - Condensed Combining Balance Sheets [Abstract] Disclosure - Condensed Combining Statements of Cash Flows [Abstract] Disclosure Condensed Combining Statements Of Cash Flows [Abstract] Disclosure - Condensed Combining Statements of Cash Flows [Abstract] Disclosure - Condensed Combining Statements of Operations [Abstract] Disclosure Condensed Combining Statements Of Operations [Abstract] Disclosure - Condensed Combining Statements of Operations [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure Debt Additional Information [Abstract] Disclosure Derivative Financial Instruments Additional Information [Abstract] Disclosure Derivative Financial Instruments Additional Information [Abstract] Disclosure Derivative Financial Instruments Additional Information [Abstract] Disclosure - Description of Business - Additional Information [Abstract] Disclosure Description Of Business Additional Information [Abstract] Disclosure - Description of Business - Additional Information [Abstract] Disclosure - Dispositions and Acquisitions - Additional Information [Abstract] Disclosure Dispositions And Acquisitions Additional Information [Abstract] Disclosure - Dispositions and Acquisitions - Additional Information [Abstract] Disclosure - Earnings Classified within Discontinued Operations [Abstract] Disclosure Earnings Classified Within Discontinued Operations [Abstract] Disclosure - Earnings Classified within Discontinued Operations [Abstract] Disclosure Earnings Per Share Additional Information [Abstract] Disclosure Earnings Per Share Additional Information [Abstract] Disclosure Earnings Per Share Additional Information [Abstract] Disclosure - Employee Severance and Other Termination Costs Incurred by Reportable Segment [Abstract] Disclosure Employee Severance And Other Termination Costs Incurred By Reportable Segment [Abstract] Disclosure - Employee Severance and Other Termination Costs Incurred by Reportable Segment [Abstract] Disclosure - Employee Severance and Termination Costs - Additional Information [Abstract] Disclosure Employee Severance And Termination Costs Additional Information [Abstract] Disclosure - Employee Severance and Termination Costs - Additional Information [Abstract] Disclosure - Employee Stock-Based Compensation - Additional Information [Abstract] Disclosure Employee Stock Based Compensation Additional Information [Abstract] Disclosure - Employee Stock-Based Compensation - Additional Information [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure Equity Additional Information [Abstract] Disclosure - Estimated Amortization Expense [Abstract] Disclosure Estimated Amortization Expense [Abstract] Disclosure - Estimated Amortization Expense [Abstract] Disclosure - Fair Values and Location of Company's Derivative Instruments in Condensed Consolidated Balance Sheets [Abstract] Disclosure Fair Values And Location Of Companys Derivative Instruments In Condensed Consolidated Balance Sheets [Abstract] Disclosure - Fair Values and Location of Company's Derivative Instruments in Condensed Consolidated Balance Sheets [Abstract] Disclosure - General & Administrative, Independent Research & Development and Bid and Proposal Costs [Abstract] Disclosure General Administrative Independent Research Development And Bid And Proposal Costs [Abstract] Disclosure - General & Administrative, Independent Research & Development and Bid and Proposal Costs [Abstract] Disclosure - Goodwill And Identifiable Intangible Assets [Abstract] Disclosure Goodwill And Identifiable Intangible Assets [Abstract] Disclosure - Goodwill And Identifiable Intangible Assets [Abstract] Disclosure Identifiable Intangible Assets [Abstract] Disclosure Identifiable Intangible Assets [Abstract] Disclosure Identifiable Intangible Assets [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure Income Taxes Additional Information [Abstract] Disclosure - Inventories at Lower of Cost or Market [Abstract] Disclosure Inventories At Lower Of Cost Or Market [Abstract] Disclosure - Inventories at Lower of Cost or Market [Abstract] Disclosure - Major Classes of Assets and Liabilities Included in Discontinued Operations [Abstract] Disclosure Major Classes Of Assets And Liabilities Included In Discontinued Operations [Abstract] Disclosure - Major Classes of Assets and Liabilities Included in Discontinued Operations [Abstract] Disclosure - Notional Amounts of Company's Outstanding Foreign Currency Forward Contracts by Currency [Abstract] Disclosure Notional Amounts Of Companys Outstanding Foreign Currency Forward Contracts By Currency [Abstract] Disclosure - Notional Amounts of Company's Outstanding Foreign Currency Forward Contracts by Currency [Abstract] Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Employee Stock-Based Compensation