Goodwill and Identifiable Intangible Assets, Allocated by Reportable Segment (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($) Employee	Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)
Goodwill [Line Items]
Approximate number of employees | Employee		38,000
Goodwill [Roll Forward]
Goodwill		$ 7,002	$ 6,723		$ 6,570
Accumulated impairment losses		(442)	(442)	[1]	(58)
Balance, Beginning		6,281	6,512
Business acquisitions	[2]	335	244
Business divestitures	[3]		(20)
Business retained from NSS divestiture			28
Goodwill impairment charges	[4]	0	(384)		0
Foreign currency translation adjustments	[5]	(56)	(99)
Balance, Ending		6,560	6,281		6,512
Vertex Aerospace [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(338)
Continuing Operations [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(384)
Continuing Operations [Member] | Vertex Aerospace [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(338)
Discontinued Operations [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(571)
Discontinued Operations [Member] | Vertex Aerospace [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			0
NSS [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(608)
NSS [Member] | Continuing Operations [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(37)
NSS [Member] | Discontinued Operations [Member]
Goodwill [Roll Forward]
Goodwill impairment charges			(571)
Electronic Systems [Member]
Goodwill [Roll Forward]
Goodwill		4,246	3,994		3,816
Accumulated impairment losses		(69)	(69)	[1]	(43)
Balance, Beginning		3,925	3,773
Business acquisitions	[2]	315	233
Business divestitures	[3]		(20)
Business retained from NSS divestiture			26
Goodwill impairment charges			(26)
Foreign currency translation adjustments	[5]	(63)	(61)
Balance, Ending		4,177	3,925		3,773
Aerospace Systems [Member]
Goodwill [Roll Forward]
Goodwill		1,698	1,691		1,730
Accumulated impairment losses		(338)	(338)	[1]	0
Balance, Beginning		1,353	1,730
Business acquisitions	[2]	0	0
Business divestitures	[3]		0
Business retained from NSS divestiture			0
Goodwill impairment charges			(338)
Foreign currency translation adjustments	[5]	7	(39)
Balance, Ending		1,360	1,353		1,730
Communication Systems [Member]
Goodwill [Roll Forward]
Goodwill		1,058	1,038		1,024
Accumulated impairment losses		(35)	(35)	[1]	(15)
Balance, Beginning		1,003	1,009
Business acquisitions	[2]	20	11
Business divestitures	[3]		0
Business retained from NSS divestiture			2
Goodwill impairment charges			(20)
Foreign currency translation adjustments	[5]	0	1
Balance, Ending		$ 1,023	$ 1,003		$ 1,009

[1] The accumulated impairment losses at December 31, 2015 exclude $571 million of impairment charges recorded during 2015 relating to the NSS reporting unit, which is reported in discontinued operations.

[2] For the year ended December 31, 2016, the net increase in goodwill for the Electronic Systems segment was due to the L3 MacDonald Humfrey, Aeroism and Micreo business acquisitions, as well as the final purchase price allocations for the L3 ForceX and L3 CTC business acquisitions. The increase in goodwill for the Communication Systems segment was due to the ATM business acquisition. For the year ended December 31, 2015, the net increase in goodwill for the Electronic Systems segment was due to the L3 CTC and L3 ForceX business acquisitions. The increase in goodwill for the Communication Systems segment was due to the Miteq business acquisition.

[3] For the year ended December 31, 2015, the decrease in goodwill for the Electronic Systems segment was due to the divestitures of BSI, the Tinsley Product Line and Klein.

[4] 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.

[5] During 2016, the decrease in goodwill presented in the Electronic Systems segment was due to the strengthening of the U.S. dollar against the British pound, the Euro and the Australian dollar, offset by the weakening of the U.S. dollar against the Canadian dollar. The increase in goodwill presented in the Aerospace Systems segment was due to the weakening of the U.S. dollar against the Canadian dollar. During 2015, the decrease in goodwil presented in the Electronic Systems segment was primarily due to the strengthening of the U.S. dollar against the Canadian dollar, the British pound and the Euro. The decrease in goodwill presented in the Aerospace Systems segment was due to the strengthening of the U.S. dollar against the Canadian dollar.