Dispositions and Acquisitions - Statement of Operations Data Classified as Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2013	Jun. 29, 2012	Jun. 28, 2013	Jun. 29, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations, net of income taxes		$ 17		$ 33
Net income from discontinued operations attributable to L-3		14		29
Engility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Product and service revenues		415		843
Operating income from discontinued operations before income taxes		36		68
Interest expense allocated to discontinued operations		(7)		(13)
Income from discontinued operations before income taxes		29		55
Income tax expense		12		22
Income from discontinued operations, net of income taxes		17		33
Less: Net income from discontinued operations attributable to noncontrolling interests		3		4
Net income from discontinued operations attributable to L-3		$ 14		$ 29