CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income		$ 1,026	$ 693	$ 724
Other comprehensive income (loss):
Foreign currency translation adjustments		(82)	124	(77)
Unrealized (losses) gains on hedging instruments(1)	[1]	(19)	3	14
Pension and postretirement benefit plans:
Amortization of net loss and prior service cost previously recognized(2)	[2]	53	45	30
Net gain (loss) arising during the period(3)	[3]	14	(137)	(119)
Net change in pension and postretirement benefit plans		67	(92)	(89)
Total other comprehensive (loss) income		(34)	35	(152)
Comprehensive income		992	728	572
Comprehensive income attributable to noncontrolling interests		(21)	(16)	(14)
Comprehensive income attributable to L3		$ 971	$ 712	$ 558

[1] Net of income tax benefits of $5 million in 2018, net of income taxes of $1 million in 2017 and $5 million in 2016.

[2] Net of income taxes of $15 million in 2018, $14 million in 2017 and $18 million in 2016.

[3] Net of income taxes of $4 million in 2018, net of income tax benefits of $42 million in 2017 and $69 million in 2016.