Condensed Combining Financial Information of L3 and Its Subsidiaries- Condensed Combining Balance Sheets (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 24, 2016	Dec. 31, 2015
Current assets [Abstract]
Cash and cash equivalents	$ 385	$ 363	$ 352	$ 207
Billed receivables, net	843	731
Contracts in process	2,200	2,055
Other current assets	593	548
Total current assets	4,021	3,697
Goodwill	6,739	6,560
Other assets	1,672	1,608
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	12,432	11,865
Current liabilities	2,195	2,135
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,863	1,781
Long-term debt	3,327	3,325
Total liabilities	7,385	7,241
L3 shareholders' equity	4,976	4,553
Noncontrolling interests	71	71
Total equity	5,047	4,624	4,559	4,429
Total liabilities and equity	12,432	11,865
L-3 [Member]
Current assets [Abstract]
Cash and cash equivalents	272	291	199	137
Billed receivables, net	237	261
Contracts in process	769	694
Other current assets	241	236
Total current assets	1,519	1,482
Goodwill	2,386	2,380
Other assets	694	705
Investment in and amounts due from consolidated subsidiaries	6,091	5,649
Total assets	10,690	10,216
Current liabilities	757	789
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,630	1,549
Long-term debt	3,327	3,325
Total liabilities	5,714	5,663
L3 shareholders' equity	4,976	4,553
Noncontrolling interests	0	0
Total equity	4,976	4,553
Total liabilities and equity	10,690	10,216
Guarantor Subsidiaries [Member]
Current assets [Abstract]
Cash and cash equivalents	0	1	0	0
Billed receivables, net	377	285
Contracts in process	1,166	1,125
Other current assets	231	187
Total current assets	1,774	1,598
Goodwill	3,099	3,007
Other assets	605	591
Investment in and amounts due from consolidated subsidiaries	4,991	5,650
Total assets	10,469	10,846
Current liabilities	993	1,022
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	204	200
Long-term debt	0	0
Total liabilities	1,197	1,222
L3 shareholders' equity	9,272	9,624
Noncontrolling interests	0	0
Total equity	9,272	9,624
Total liabilities and equity	10,469	10,846
Non-Guarantor Subsidiaries [Member]
Current assets [Abstract]
Cash and cash equivalents	198	207	165	165
Billed receivables, net	229	185
Contracts in process	265	236
Other current assets	121	125
Total current assets	813	753
Goodwill	1,254	1,173
Other assets	373	312
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	2,440	2,238
Current liabilities	530	460
Amounts due to consolidated subsidiaries	303	284
Other long-term liabilities	29	32
Long-term debt	0	0
Total liabilities	862	776
L3 shareholders' equity	1,578	1,462
Noncontrolling interests	0	0
Total equity	1,578	1,462
Total liabilities and equity	2,440	2,238
Eliminations [Member]
Current assets [Abstract]
Cash and cash equivalents	(85)	(136)	$ (12)	$ (95)
Billed receivables, net	0	0
Contracts in process	0	0
Other current assets	0	0
Total current assets	(85)	(136)
Goodwill	0	0
Other assets	0	0
Investment in and amounts due from consolidated subsidiaries	(11,082)	(11,299)
Total assets	(11,167)	(11,435)
Current liabilities	(85)	(136)
Amounts due to consolidated subsidiaries	(303)	(284)
Other long-term liabilities	0	0
Long-term debt	0	0
Total liabilities	(388)	(420)
L3 shareholders' equity	(10,850)	(11,086)
Noncontrolling interests	71	71
Total equity	(10,779)	(11,015)
Total liabilities and equity	$ (11,167)	$ (11,435)