Financial Information of L3 and Its Subsidiaries, Condensed Combining Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 662	$ 363	$ 207	$ 442
Billed receivables, net	723	700
Contracts in process	1,933	1,858
Prepaid expenses and other current assets	689	505
Assets held for sale	135	0	0
Assets of discontinued operations	306	481	1,124
Total current assets	4,448	3,907
Goodwill	6,615	6,374	6,095
Other assets	1,666	1,584
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	12,729	11,865	12,069
Current liabilities	2,136	1,959
Liabilities held for sale	17	0
Liabilities of discontinued operations	226	235
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,869	1,722
Long-term debt	3,330	3,325
Total liabilities	7,578	7,241
L3 shareholders' equity	5,083	4,553
Noncontrolling interests	68	71
Total equity	5,151	4,624	4,429	5,360
Total liabilities and equity	12,729	11,865
L-3 Communications Corporation [Member]
Current assets:
Cash and cash equivalents	432	291	141	358
Billed receivables, net	266	261
Contracts in process	706	694
Prepaid expenses and other current assets	330	236
Assets held for sale	0
Assets of discontinued operations	0	0
Total current assets	1,734	1,482
Goodwill	2,248	2,258
Other assets	658	705
Investment in and amounts due from consolidated subsidiaries	5,593	5,721
Total assets	10,233	10,166
Current liabilities	811	789
Liabilities held for sale	0
Liabilities of discontinued operations	0	0
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	1,009	1,499
Long-term debt	3,330	3,325
Total liabilities	5,150	5,613
L3 shareholders' equity	5,083	4,553
Noncontrolling interests	0	0
Total equity	5,083	4,553
Total liabilities and equity	10,233	10,166
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	14	1	0	4
Billed receivables, net	232	254
Contracts in process	891	928
Prepaid expenses and other current assets	231	144
Assets held for sale	118
Assets of discontinued operations	306	481
Total current assets	1,792	1,808
Goodwill	2,652	2,613
Other assets	556	567
Investment in and amounts due from consolidated subsidiaries	5,270	5,272
Total assets	10,270	10,260
Current liabilities	800	846
Liabilities held for sale	16
Liabilities of discontinued operations	226	235
Amounts due to consolidated subsidiaries	0	0
Other long-term liabilities	714	191
Long-term debt	0	0
Total liabilities	1,756	1,272
L3 shareholders' equity	8,514	8,988
Noncontrolling interests	0	0
Total equity	8,514	8,988
Total liabilities and equity	10,270	10,260
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	287	207	165	142
Billed receivables, net	225	185
Contracts in process	336	236
Prepaid expenses and other current assets	128	125
Assets held for sale	17
Assets of discontinued operations	0	0
Total current assets	993	753
Goodwill	1,715	1,503
Other assets	452	312
Investment in and amounts due from consolidated subsidiaries	0	0
Total assets	3,160	2,568
Current liabilities	596	460
Liabilities held for sale	1
Liabilities of discontinued operations	0	0
Amounts due to consolidated subsidiaries	352	763
Other long-term liabilities	146	32
Long-term debt	0	0
Total liabilities	1,095	1,255
L3 shareholders' equity	2,065	1,313
Noncontrolling interests	0	0
Total equity	2,065	1,313
Total liabilities and equity	3,160	2,568
Eliminations [Member]
Current assets:
Cash and cash equivalents	(71)	(136)	$ (99)	$ (62)
Billed receivables, net	0	0
Contracts in process	0	0
Prepaid expenses and other current assets	0	0
Assets held for sale	0
Assets of discontinued operations	0	0
Total current assets	(71)	(136)
Goodwill	0	0
Other assets	0	0
Investment in and amounts due from consolidated subsidiaries	(10,863)	(10,993)
Total assets	(10,934)	(11,129)
Current liabilities	(71)	(136)
Liabilities held for sale	0
Liabilities of discontinued operations	0	0
Amounts due to consolidated subsidiaries	(352)	(763)
Other long-term liabilities	0	0
Long-term debt	0	0
Total liabilities	(423)	(899)
L3 shareholders' equity	(10,579)	(10,301)
Noncontrolling interests	68	71
Total equity	(10,511)	(10,230)
Total liabilities and equity	$ (10,934)	$ (11,129)