L-3 Holdings' Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 29, 2013	Mar. 30, 2012
Reconciliation of net income:
Net income	$ 194	$ 203
Net income from continuing operations attributable to noncontrolling interests	(1)	(1)
Net income from discontinued operations attributable to noncontrolling interests		(1)
Net income attributable to L-3 Holdings' common shareholders	193	201
Earnings attributable to L-3 Holdings' common shareholders:
Continuing operations	193	186
Discontinued operations, net of income tax		15
Net income attributable to L-3 Holdings' common shareholders	$ 193	$ 201
Basic:
Weighted average common shares outstanding	90.3	99.0
Basic earnings per share attributable to L-3 Holdings' common shareholders:
Continuing operations	$ 2.14	$ 1.88
Discontinued operations, net of income tax		$ 0.15
Basic earnings per share	$ 2.14	$ 2.03
Common and potential common shares:
Weighted average common shares outstanding	90.3	99.0
Assumed purchase of common shares for treasury	(4.2)	(2.4)
Assumed conversion of the CODES
Common and potential common shares	91.5	100.2
Continuing operations	$ 2.11	$ 1.86
Discontinued operations, net of income tax		$ 0.15
Diluted earnings per share	$ 2.11	$ 2.01
Assumed exercise of stock options [Member]
Common and potential common shares:
Common and potential common shares	3.4	1.2
Unvested restricted stock awards [Member]
Common and potential common shares:
Common and potential common shares	1.7	2.0
Employee stock purchase plan contributions [Member]
Common and potential common shares:
Common and potential common shares	0.2	0.3
Performance unit awards [Member]
Common and potential common shares:
Common and potential common shares	0.1	0.1