For defined benefit pension plans, the actuarial present value of benefits (whether vested or nonvested) attributed by the pension benefit formula to employee service rendered before a specified date and based on employee service and compensation (if applicable) before that date. The accumulated benefit obligation differs from the projected benefit obligation in that it includes no assumption about future compensation levels. For plans with flat-benefit or nonpay-related pension benefit formulas, the accumulated benefit obligation and the projected benefit obligation are the same.

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The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status.

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Pensions and Other Employee Benefits - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Health care cost trend in 2013	8.50%
Health care cost trend in 2021 and thereafter	5.00%
Continuing Operations [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Company's matching contributions in L-3 Holdings' common stock and cash	$ 126	$ 113	$ 120
Discontinued Operations [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Company's matching contributions in L-3 Holdings' common stock and cash	8	24	27
Pension Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Aggregate accumulated benefit obligation (ABO)	2,783	2,298
Expected contributions to plans	165
Voluntary contributions	95
Postretirement Benefit Plans [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Expected contributions to plans	$ 11