Condensed Combining Financial Information of L3 and Its Subsidiaries- Condensed Combining Balance Sheets (Details) - USD ($) $ in Millions	Sep. 29, 2017	Dec. 31, 2016	Sep. 23, 2016	Dec. 31, 2015
Current assets [Abstract]
Cash and cash equivalents	$ 439	$ 363	$ 411	$ 207
Billed receivables, net	776	731
Contracts in process	2,273	2,055
Other current assets	611	548
Total current assets	4,099	3,697
Goodwill	6,652	6,560
Other assets	1,717	1,608
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	12,468	11,865
Current liabilities	2,283	2,135
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,787	1,781
Long-term debt	3,329	3,325
Total liabilities	7,399	7,241
L3 shareholders' equity	4,999	4,553
Noncontrolling interests	70	71
Total equity	5,069	4,624	4,640	4,429
Total liabilities and equity	12,468	11,865
Eliminations [Member]
Current assets [Abstract]
Cash and cash equivalents	(23)	(136)	(16)	(95)
Billed receivables, net	0	0
Contracts in process	0	0
Other current assets	0	0
Total current assets	(23)	(136)
Goodwill	0	0
Other assets	0	0
Investment in and amounts due from consolidated subsidiaries	(11,366)	(11,134)
Total assets	(11,389)	(11,270)
Current liabilities	(23)	(136)
Amounts due to consolidated subsidiaries	(416)	(119)
Other long-term liabilities	0	0
Long-term debt	0	0
Total liabilities	(439)	(255)
L3 shareholders' equity	(11,020)	(11,086)
Noncontrolling interests	70	71
Total equity	(10,950)	(11,015)
Total liabilities and equity	(11,389)	(11,270)
L-3 [Member]
Current assets [Abstract]
Cash and cash equivalents	197	291	188	137
Billed receivables, net	249	261
Contracts in process	768	694
Other current assets	263	236
Total current assets	1,477	1,482
Goodwill	2,221	2,231
Other assets	695	705
Investment in and amounts due from consolidated subsidiaries	6,279	5,798
Total assets	10,672	10,216
Current liabilities	788	789
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,556	1,549
Long-term debt	3,329	3,325
Total liabilities	5,673	5,663
L3 shareholders' equity	4,999	4,553
Noncontrolling interests	0	0
Total equity	4,999	4,553
Total liabilities and equity	10,672	10,216
Guarantor Subsidiaries [Member]
Current assets [Abstract]
Cash and cash equivalents	11	1	0	0
Billed receivables, net	337	285
Contracts in process	1,182	1,125
Other current assets	227	187
Total current assets	1,757	1,598
Goodwill	3,225	3,321
Other assets	605	591
Investment in and amounts due from consolidated subsidiaries	5,087	5,336
Total assets	10,674	10,846
Current liabilities	953	1,022
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	203	200
Long-term debt	0	0
Total liabilities	1,156	1,222
L3 shareholders' equity	9,518	9,624
Noncontrolling interests	0	0
Total equity	9,518	9,624
Total liabilities and equity	10,674	10,846
Non-Guarantor Subsidiaries [Member]
Current assets [Abstract]
Cash and cash equivalents	254	207	$ 239	$ 165
Billed receivables, net	190	185
Contracts in process	323	236
Other current assets	121	125
Total current assets	888	753
Goodwill	1,206	1,008
Other assets	417	312
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	2,511	2,073
Current liabilities	565	460
Amounts due to consolidated subsidiaries	416	119
Other long-term liabilities	28	32
Long-term debt	0	0
Total liabilities	1,009	611
L3 shareholders' equity	1,502	1,462
Noncontrolling interests	0	0
Total equity	1,502	1,462
Total liabilities and equity	$ 2,511	$ 2,073