Segment Information, Products and Services (Details) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2016 USD ($)	Sep. 23, 2016 USD ($)	Jun. 24, 2016 USD ($)	Mar. 25, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 25, 2015 USD ($)	Jun. 26, 2015 USD ($)	Mar. 27, 2015 USD ($)	Dec. 31, 2016 USD ($) Segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Information [Abstract]
Number of reportable segments | Segment										3
Corporate expenses											$ 15	$ 16
Net Sales [Abstract]
Products										$ 6,442	6,589	6,839
Services										4,069	3,877	4,147
Total net sales		$ 2,989	$ 2,505	$ 2,664	$ 2,353	$ 2,871	$ 2,564	$ 2,543	$ 2,488	10,511	10,466	10,986
Operating income [Abstract]
Operating income		294	$ 215	$ 247	$ 252	(96)	$ 231	$ 153	$ 187	1,008	475	1,012
Loss related to business divestitures	[1]									0	(31)	0
Goodwill impairment charges	[2]									0	(384)	0
Depreciation and amortization [Abstract]
Depreciation and amortization										206	210	214
Capital Expenditures [Abstract]
Capital Expenditures										216	197	174
Total Assets [Abstract]
Total Assets		11,865				12,069				11,865	12,069	13,692
Assets held for sale		0				0				0	0	547
Assets of discontinued operations		0				664				0	664	1,262
Continuing Operations [Member]
Operating income [Abstract]
Goodwill impairment charges											(384)
NSS Including Business Retained [Member] | Continuing Operations [Member]
Operating income [Abstract]
Goodwill impairment charges											(46)
NSS [Member]
Operating income [Abstract]
Goodwill impairment charges											(608)
NSS [Member] | Continuing Operations [Member]
Operating income [Abstract]
Goodwill impairment charges											(37)
Business Retained from NSS [Member] | Continuing Operations [Member]
Operating income [Abstract]
Goodwill impairment charges											(9)
Vertex Aerospace [Member]
Operating income [Abstract]
Goodwill impairment charges											(338)
Vertex Aerospace [Member] | Continuing Operations [Member]
Operating income [Abstract]
Goodwill impairment charges											(338)
Electronic Systems [Member]
Operating income [Abstract]
Goodwill impairment charges											(26)
Aerospace Systems [Member]
Operating income [Abstract]
Goodwill impairment charges											(338)
Communication Systems [Member]
Operating income [Abstract]
Goodwill impairment charges											(20)
Operating Segments [Member]
Operating income [Abstract]
Operating income										1,008	890	1,012
Operating Segments [Member] | Electronic Systems [Member]
Net Sales [Abstract]
Products										3,293	3,390	3,685
Services										1,042	999	1,057
Operating income [Abstract]
Operating income										518	489	533
Depreciation and amortization [Abstract]
Depreciation and amortization										105	110	123
Capital Expenditures [Abstract]
Capital Expenditures										113	99	80
Total Assets [Abstract]
Total Assets		6,802				6,426				6,802	6,426	6,281
Operating Segments [Member] | Aerospace Systems [Member]
Net Sales [Abstract]
Products										1,662	1,661	1,722
Services										2,580	2,503	2,604
Operating income [Abstract]
Operating income										289	205	283
Depreciation and amortization [Abstract]
Depreciation and amortization										54	50	40
Capital Expenditures [Abstract]
Capital Expenditures										56	55	59
Total Assets [Abstract]
Total Assets		2,535				2,630				2,535	2,630	3,011
Operating Segments [Member] | Communication Systems [Member]
Net Sales [Abstract]
Products										1,585	1,648	1,546
Services										488	441	539
Operating income [Abstract]
Operating income										201	196	196
Depreciation and amortization [Abstract]
Depreciation and amortization										47	50	51
Capital Expenditures [Abstract]
Capital Expenditures										37	37	29
Total Assets [Abstract]
Total Assets		2,031				1,984				2,031	1,984	2,025
Corporate [Member]
Capital Expenditures [Abstract]
Capital Expenditures										10	6	6
Total Assets [Abstract]
Total Assets		$ 497				$ 365				497	365	566
Elimination of Intercompany Sales [Member]
Net Sales [Abstract]
Products										(98)	(110)	(114)
Services										$ (41)	$ (66)	$ (53)

[1] See Note 3 for information regarding the Company's business divestitures.

[2] Represents non-cash goodwill impairment charges recorded during 2015, including (i) $338 million related to a decline in the estimated fair value of the Vertex Aerospace reporting unit, and (ii) $46 million related to a business retained by L3 in connection with the sale of the NSS business, comprised of (i) $37 million related to the re-allocation of impairment charges recorded for the NSS reporting unit in 2015, and (ii) $9 million related to the re-allocation of goodwill. See Note 6 for additional information.