Dispositions and Acquisitions - Statement of Operations Data Classified as Discontinued Operations (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 30, 2012
Acquisitions And Discontinued Operations [Line Items]
Income from discontinued operations, net of income tax	$ 16
Net income from discontinued operations attributable to L-3	15
Engility [Member]
Acquisitions And Discontinued Operations [Line Items]
Product and service revenues	428
Operating income from discontinued operations before income taxes	32
Interest expense allocated to discontinued operations	(6)
Income from discontinued operations before income taxes	26
Income tax expense	10
Income from discontinued operations, net of income tax	16
Less: Net income from discontinued operations attributable to noncontrolling interests	1
Net income from discontinued operations attributable to L-3	$ 15