Revisions to Previously Issued Financial Statements - Condensed Combining Statements of Operations (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 27, 2013	Jun. 28, 2013	Mar. 29, 2013	Dec. 31, 2012	Sep. 28, 2012	Jun. 29, 2012	Mar. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net sales:
Products									$ 7,189	$ 7,586	$ 7,549
Services									5,433	5,521	5,605
Total net sales									12,622	13,107	13,154
Cost of sales:
Products									(6,409)	(6,782)	(6,666)
Services									(5,001)	(5,017)	(5,047)
Total cost of sales									(11,410)	(11,799)	(11,713)
Impairment charge											(43)
Operating income	306	306	290	310	339	319	328	322	1,212	1,308	1,398
Interest expense									(177)	(184)	(204)
Interest and other income, net									20	11	3
Debt retirement charge										(13)	(35)
Income from continuing operations before income taxes									1,055	1,122	1,162
Provision for income taxes									(295)	(360)	(296)
Income from continuing operations	188	204	176	192	199	188	189	186	760	762	866
Income from discontinued operations, net of income tax										32	104
Net income									760	794	970
Net income attributable to noncontrolling interests									(9)	(10)	(12)
Net income attributable to L-3	185	200	175	191	196	185	203	200	751	784	958
Net income allocable to participating securities											(2)
Net income allocable to L-3 Holdings' common shareholders									751	784	956
Basic earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations					$ 2.11	$ 1.94	$ 1.93	$ 1.88	$ 8.40	$ 7.85	$ 8.19
Discontinued operations										$ 0.29	$ 0.97
Basic earnings per share	$ 2.10	$ 2.23	$ 1.95	$ 2.12	$ 2.11	$ 1.93	$ 2.09	$ 2.02	$ 8.40	$ 8.14	$ 9.16
Diluted earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations					$ 2.08	$ 1.91	$ 1.91	$ 1.86	$ 8.24	$ 7.74	$ 8.10
Discontinued operations										$ 0.29	$ 0.95
Diluted earnings per share	$ 2.04	$ 2.19	$ 1.92	$ 2.09	$ 2.08	$ 1.90	$ 2.06	$ 2.00	$ 8.24	$ 8.03	$ 9.05
Cash dividends paid per common share									$ 2.20	$ 2.00	$ 1.80
L-3 Holdings' weighted average common shares outstanding:
Basic									89.4	96.3	104.4
Diluted									91.1	97.6	105.6
Out of Period Amounts [Member]
Net sales:
Total net sales									39	(36)	(3)
Cost of sales:
Operating income									14	(18)	4
As Previously Reported [Member]
Net sales:
Products									7,192	7,535	7,552
Services									5,437	5,611	5,606
Total net sales									12,629	13,146	13,158
Cost of sales:
Products									(6,409)	(6,724)	(6,673)
Services									(4,962)	(5,071)	(5,043)
Total cost of sales									(11,371)	(11,795)	(11,716)
Impairment charge											(43)
Operating income									1,258	1,351	1,399
Interest expense									(177)	(184)	(204)
Interest and other income, net									15	8
Debt retirement charge										(13)	(35)
Income from continuing operations before income taxes									1,096	1,162	1,160
Provision for income taxes									(309)	(374)	(296)
Income from continuing operations									787	788	864
Income from discontinued operations, net of income tax										32	104
Net income									787	820	968
Net income attributable to noncontrolling interests									(9)	(10)	(12)
Net income attributable to L-3									778	810	956
Net income allocable to participating securities											(2)
Net income allocable to L-3 Holdings' common shareholders									778	810	954
Basic earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ 8.70	$ 8.12	$ 8.17
Discontinued operations										$ 0.29	$ 0.97
Basic earnings per share									$ 8.70	$ 8.41	$ 9.14
Diluted earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ 8.54	$ 8.01	$ 8.08
Discontinued operations										$ 0.29	$ 0.95
Diluted earnings per share									$ 8.54	$ 8.30	$ 9.03
Cash dividends paid per common share									$ 2.20	$ 2.00	$ 1.80
L-3 Holdings' weighted average common shares outstanding:
Basic									89.4	96.3	104.4
Diluted									91.1	97.6	105.6
Restatement Adjustments [Member]
Cost of sales:
Impairment charge
Income from continuing operations									(27)	(26)	2
Income from discontinued operations, net of income tax
Net income									(27)	(26)	2
Restatement Adjustments [Member] | Aerospace Systems Segment Internal Review [Member ]
Net sales:
Products									(11)	64
Services									(28)	(66)	(1)
Total net sales									(39)	(2)	(1)
Cost of sales:
Products									(3)	(57)
Services									(18)	34	(4)
Total cost of sales									(21)	(23)	(4)
Impairment charge
Operating income									(60)	(25)	(5)
Interest expense
Interest and other income, net
Debt retirement charge
Income from continuing operations before income taxes									(60)	(25)	(5)
Provision for income taxes									21	9	2
Income from continuing operations									(39)	(16)	(3)
Income from discontinued operations, net of income tax
Net income									(39)	(16)	(3)
Net income attributable to noncontrolling interests
Net income attributable to L-3									(39)	(16)	(3)
Net income allocable to participating securities
Net income allocable to L-3 Holdings' common shareholders									(39)	(16)	(3)
Basic earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ (0.43)	$ (0.17)	$ (0.03)
Discontinued operations
Basic earnings per share									$ (0.43)	$ (0.17)	$ (0.03)
Diluted earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ (0.43)	$ (0.17)	$ (0.03)
Discontinued operations
Diluted earnings per share									$ (0.43)	$ (0.17)	$ (0.03)
Cash dividends paid per common share
L-3 Holdings' weighted average common shares outstanding:
Basic
Diluted
Restatement Adjustments [Member] | Sales-Type Lease Transaction [Member]
Net sales:
Products									(7)
Services
Total net sales									(7)
Cost of sales:
Products									7
Services
Total cost of sales									7
Impairment charge
Operating income
Interest expense
Interest and other income, net									5	3	3
Debt retirement charge
Income from continuing operations before income taxes									5	3	3
Provision for income taxes									(2)	(1)	(1)
Income from continuing operations									3	2	2
Income from discontinued operations, net of income tax
Net income									3	2	2
Net income attributable to noncontrolling interests
Net income attributable to L-3									3	2	2
Net income allocable to participating securities
Net income allocable to L-3 Holdings' common shareholders									3	2	2
Basic earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ 0.03	$ 0.02	$ 0.02
Discontinued operations
Basic earnings per share									$ 0.03	$ 0.02	$ 0.02
Diluted earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ 0.03	$ 0.02	$ 0.02
Discontinued operations
Diluted earnings per share									$ 0.03	$ 0.02	$ 0.02
Cash dividends paid per common share
L-3 Holdings' weighted average common shares outstanding:
Basic
Diluted
Restatement Adjustments [Member] | Out of Period Amounts [Member]
Net sales:
Products									15	(13)	(3)
Services									24	(24)
Total net sales									39	(37)	(3)
Cost of sales:
Products									(4)	(1)	7
Services									(21)	20
Total cost of sales									(25)	19	7
Impairment charge
Operating income									14	(18)	4
Interest expense
Interest and other income, net
Debt retirement charge
Income from continuing operations before income taxes									14	(18)	4
Provision for income taxes									(5)	6	(1)
Income from continuing operations									9	(12)	3
Income from discontinued operations, net of income tax
Net income									9	(12)	3
Net income attributable to noncontrolling interests
Net income attributable to L-3									9	(12)	3
Net income allocable to participating securities
Net income allocable to L-3 Holdings' common shareholders									$ 9	$ (12)	$ 3
Basic earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ 0.10	$ (0.12)	$ 0.03
Discontinued operations
Basic earnings per share									$ 0.10	$ (0.12)	$ 0.03
Diluted earnings per share allocable to L-3 Holdings' common shareholders:
Continuing operations									$ 0.10	$ (0.12)	$ 0.03
Discontinued operations
Diluted earnings per share									$ 0.10	$ (0.12)	$ 0.03
Cash dividends paid per common share
L-3 Holdings' weighted average common shares outstanding:
Basic
Diluted