Debt, Outstanding Senior Subordinated Notes (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 02, 2017
Outstanding Senior Note Terms [Abstract]
Net Cash Proceeds		$ 547	$ 0	$ 996
Net cash proceeds from senior unsecured notes		$ 988
Senior Notes Redemption [Abstract]
Tender date		Dec. 22, 2015
Debt Retirement Charge		$ (7)	(1)	0
Cash payments of senior notes		856	297	0
Repayments under the credit facility		$ 819	1,194	1,367
Conversion of converted securities				161
CODES Due 2035 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.00%
Senior Notes Redemption [Abstract]
Redemption Date	[1]	Jun. 20, 2014
Redemption amount	[1]	$ 700
Debt Retirement Charge	[1]	0
Redemption cash payments	[1]	$ 935
Interest rate on senior notes		3.00%
Sale of 3% Convertible Contingent Debt Securities by L-3 Holdings		$ 700
Conversion of converted securities		935
Excess of conversion value over fair value of the debt component		$ 161
Interest expense recognized				2
CODES Due 2035 [Member] | Subsequent Event [Member]
Senior Notes Redemption [Abstract]
Debt repurchased					$ 11
3.95% Senior Notes due 2016 [Member]
Outstanding Senior Note Terms [Abstract]
Redemption price as percentage of principal amount		101.475%
Senior Notes due		Nov. 15, 2016
Senior Notes Redemption [Abstract]
Redemption Date	[2]	May 20, 2016
Maturity date		Nov. 15, 2016
Redemption amount	[2]	$ 300
Principal Amount		200
Debt Retirement Charge	[2]	5
Redemption cash payments	[2]	305
Cash payments of senior notes		$ 200
1.50% Senior Notes due 2017 [Member]
Outstanding Senior Note Terms [Abstract]
Redemption price as percentage of principal amount		100.323%
Senior Notes Redemption [Abstract]
Redemption Date	[3]	Dec. 30, 2016
Redemption amount	[3]	$ 350
Debt Retirement Charge	[3]	2
Redemption cash payments	[3]	$ 351
5.20% Senior Notes due 2019 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		Oct. 02, 2009
Amount Issued		$ 1,000
Discount	[4]	4
Net Cash Proceeds		$ 987
Effective Interest Rate		5.25%
Redemption at Treasury Rate	[5],[6]	30.00%
4.75% Senior Notes due 2020 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		May 21, 2010
Amount Issued		$ 800
Discount	[4]	3
Net Cash Proceeds		$ 790
Effective Interest Rate		4.79%
Redemption at Treasury Rate	[5],[6]	25.00%
4.95% Senior Notes due 2021 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		Feb. 07, 2011
Amount Issued		$ 650
Discount	[4]	4
Net Cash Proceeds		$ 639
Effective Interest Rate		5.02%
Redemption at Treasury Rate	[5],[6]	25.00%
3.95% Senior Notes due 2024 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		May 28, 2014
Amount Issued		$ 650
Discount	[4]	3
Net Cash Proceeds	[7]	$ 641
Effective Interest Rate		4.02%
Redemption at Treasury Rate	[5],[6]	20.00%
Senior Notes Redemption [Abstract]
Tender amount		$ 300
Debt Retirement Charge		1
Tender cash payments		$ 297
3.85% Senior Notes due 2026 [Member]
Outstanding Senior Note Terms [Abstract]
Date of Issuance		Dec. 05, 2016
Amount Issued		$ 550
Discount	[4]	3
Net Cash Proceeds		$ 542
Effective Interest Rate		3.91%
Redemption at Treasury Rate	[5],[6]	25.00%
L3 Technologies [Member]
Outstanding Senior Note Terms [Abstract]
Discount		$ 8	8
Net Cash Proceeds		$ 547		$ 996
Redemption price as percentage of principal amount		101.00%
Senior Notes Redemption [Abstract]
Principal Amount		$ 3,350	3,650
Debt Retirement Charge		(7)	(1)
Cash payments of senior notes		$ 856	$ 297
L3 Technologies [Member] | Minimum [Member]
Outstanding Senior Note Terms [Abstract]
Redemption price as percentage of principal amount		100.00%
L3 Technologies [Member] | 3.95% Senior Notes due 2016 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.95%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		3.95%
L3 Technologies [Member] | 1.50% Senior Notes due 2017 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		1.50%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		1.50%
L3 Technologies [Member] | 5.20% Senior Notes due 2019 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		5.20%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		5.20%
L3 Technologies [Member] | 4.75% Senior Notes due 2020 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		4.75%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		4.75%
L3 Technologies [Member] | 4.95% Senior Notes due 2021 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		4.95%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		4.95%
L3 Technologies [Member] | 3.95% Senior Notes due 2024 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.95%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		3.95%
L3 Technologies [Member] | 3.95% Senior Notes due 2024 [Member] | Minimum [Member]
Outstanding Senior Note Terms [Abstract]
Senior Notes due		Feb. 28, 2024
Senior Notes Redemption [Abstract]
Maturity date		Feb. 28, 2024
L3 Technologies [Member] | 3.85% Senior Notes due 2026 [Member]
Outstanding Senior Note Terms [Abstract]
Interest rate on senior notes		3.85%
Senior Notes Redemption [Abstract]
Interest rate on senior notes		3.85%
L3 Technologies [Member] | 3.85% Senior Notes due 2026 [Member] | Minimum [Member]
Outstanding Senior Note Terms [Abstract]
Senior Notes due		Sep. 15, 2026
Senior Notes Redemption [Abstract]
Maturity date		Sep. 15, 2026

[1] In 2005, L3 sold $700 million of 3% Convertible Contingent Debt Securities (CODES) due August 1, 2035. On February 2, 2011, L3 repurchased approximately $11 million of the CODES. The conversion value of CODES of $935 million was calculated in accordance with the indenture governing the CODES. L3 settled the entire conversion value with respect to converted CODES in cash. As a result of the conversion, the Company recorded a reduction to shareholders' equity of $161 million, related to the excess conversion value over the fair value of the debt component of the CODES, net of deferred tax liability. Interest expense recognized for the CODES was $2 million for the year ended December 31, 2014.

[2] The redemption price was determined on May 17, 2016 at 101.475% of the principal amount. Interest ceased to accrue on and after May 20, 2016 and the only remaining right of holders of such Notes was to receive payment of the Redemption Price and accrued interest.

[3] The Notes were redeemed at a price equal to 100.323%, plus accrued and unpaid interest, if any, to the redemption date. Interest ceased to accrue on and after the redemption date.

[4] Bond discounts are recorded as a reduction to the principal amount of the notes and are amortized as interest expense over the term of the notes.

[5] The Senior Notes maturing in 2019, 2020 and 2021 may be redeemed at any time prior to their maturity and the Senior Notes maturing in 2024 and 2026 may be redeemed at any time prior to February 28, 2024 and September 15, 2026, respectively, (three months prior to their maturity) at the option of L3, in whole or in part, at a redemption price equal to the greater of: (1) 100% of the principal amount, or (2) the present value of the remaining principal and interest payments discounted to the date of redemption, on a semi-annual basis, at the Treasury Rate (as defined in the indentures governing the Senior Notes), plus the spread indicated in the table above. In addition, if the Senior Notes maturing in 2024 and 2026 are redeemed at any time on or after February 28, 2024 and September 15, 2026, respectively, the redemption price would be equal to 100% of the principal amount.

[6] Upon the occurrence of a change in control (as defined in the indentures governing the Senior Notes), each holder of the notes will have the right to require L3 to repurchase all or any part of such holder's notes at an offer price in cash equal to 101% of the aggregate principal amount plus accrued and unpaid interest, if any, to the date of purchase.

[7] The net cash proceeds of $988 million (after deduction of the bond discount, underwriting expenses and commissions and other related expenses) were used primarily to fund the CODES retirement as discussed below. The remaining net proceeds were used for general corporate purposes.