Condensed Combining Financial Information of L-3 Communications and Its Subsidiaries - Condensed Combining Balance Sheets (Detail) - USD ($) $ in Millions	Sep. 25, 2015	Dec. 31, 2014	Sep. 26, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 323	$ 442	$ 508	$ 500
Billed receivables, net	796	852
Contracts in process	2,483	2,295
Other current assets	693	601
Assets held for sale		547
Total current assets	4,295	4,737
Goodwill	7,112	7,501
Other assets	$ 1,629	$ 1,598
Investment in and amounts due from consolidated subsidiaries
Total assets	$ 13,036	$ 13,836
Current liabilities	$ 2,464	2,288
Liabilities held for sale		$ 237
Amounts due to consolidated subsidiaries
Other long-term liabilities	$ 1,973	$ 2,012
Long-term debt	3,940	3,939
Total liabilities	8,377	8,476
L-3 shareholders' equity	4,584	5,285
Noncontrolling interests	75	75
Total equity	4,659	5,360	$ 5,979	$ 6,056
Total liabilities and equity	13,036	13,836
L-3 Communications Holdings, Inc. [Member]
Current assets:
Cash and cash equivalents
Investment in and amounts due from consolidated subsidiaries	4,584	5,285
Total assets	4,584	5,285
Long-term debt	3,940	3,939
L-3 shareholders' equity	4,584	5,285
Total equity	4,584	5,285
Total liabilities and equity	4,584	5,285
L-3 Communications Corporation [Member]
Current assets:
Cash and cash equivalents	170	361	$ 330	$ 258
Billed receivables, net	260	320
Contracts in process	938	867
Other current assets	413	$ 365
Assets held for sale
Total current assets	1,781	$ 1,913
Goodwill	2,317	2,308
Other assets	800	817
Investment in and amounts due from consolidated subsidiaries	6,294	6,855
Total assets	11,192	11,893
Current liabilities	$ 931	$ 878
Liabilities held for sale
Amounts due to consolidated subsidiaries
Other long-term liabilities	$ 1,737	$ 1,791
Long-term debt	3,940	3,939
Total liabilities	6,608	6,608
L-3 shareholders' equity	$ 4,584	$ 5,285
Noncontrolling interests
Total equity	$ 4,584	$ 5,285
Total liabilities and equity	11,192	11,893
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	1	1	1
Billed receivables, net	318	329
Contracts in process	1,197	1,144
Other current assets	163	141
Assets held for sale		52
Total current assets	1,679	1,667
Goodwill	3,777	4,280
Other assets	552	576
Investment in and amounts due from consolidated subsidiaries	4,475	4,157
Total assets	10,483	10,680
Current liabilities	$ 1,044	1,017
Liabilities held for sale		$ 10
Amounts due to consolidated subsidiaries
Other long-term liabilities	$ 203	$ 190
Long-term debt
Total liabilities	$ 1,247	$ 1,217
L-3 shareholders' equity	$ 9,236	$ 9,463
Noncontrolling interests
Total equity	$ 9,236	$ 9,463
Total liabilities and equity	10,483	10,680
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	167	142	239	$ 261
Billed receivables, net	218	203
Contracts in process	348	284
Other current assets	117	95
Assets held for sale		495
Total current assets	850	1,219
Goodwill	1,018	913
Other assets	$ 277	$ 205
Investment in and amounts due from consolidated subsidiaries
Total assets	$ 2,145	$ 2,337
Current liabilities	504	455
Liabilities held for sale		227
Amounts due to consolidated subsidiaries	16	333
Other long-term liabilities	$ 33	$ 31
Long-term debt
Total liabilities	$ 553	$ 1,046
L-3 shareholders' equity	$ 1,592	$ 1,291
Noncontrolling interests
Total equity	$ 1,592	$ 1,291
Total liabilities and equity	2,145	2,337
Eliminations [Member]
Current assets:
Cash and cash equivalents	$ (15)	$ (62)	$ (62)	$ (19)
Billed receivables, net
Contracts in process
Other current assets
Assets held for sale
Total current assets	$ (15)	$ (62)
Goodwill
Other assets
Investment in and amounts due from consolidated subsidiaries	$ (15,353)	$ (16,297)
Total assets	(15,368)	(16,359)
Current liabilities	(15)	$ (62)
Liabilities held for sale
Amounts due to consolidated subsidiaries	$ (16)	$ (333)
Other long-term liabilities
Long-term debt
Total liabilities	$ (31)	$ (395)
L-3 shareholders' equity	(15,412)	(16,039)
Noncontrolling interests	75	75
Total equity	(15,337)	(15,964)
Total liabilities and equity	$ (15,368)	$ (16,359)