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