RETIREMENT BENEFITS - Post Employment and Defined Contribution Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Funded status	$ (32,000,000)	$ (46,000,000)
Amount recognized in accumulated other comprehensive income (loss)	(15,000,000)	3,000,000
Service-related expense
Interest cost on benefit obligation	2,000,000	2,000,000	$ 3,000,000
Expected return on plan assets	(1,000,000)	0	0
Amortization of unrecognized
Prior service cost (benefit)	(23,000,000)	(31,000,000)	(31,000,000)
Net actuarial loss	2,000,000	2,000,000	5,000,000
Total service-related benefit	(20,000,000)	(27,000,000)	(23,000,000)
Non-service-related (benefit) expense	2,000,000	30,000,000	21,000,000
Total net expense	$ (18,000,000)	$ 3,000,000	(2,000,000)
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Discount rate (as a percent)	3.95%	3.20%
Expected return on assets (as a percent)	3.00%	3.00%
Health care cost increase following year (as a percent)	7.00%	6.50%
Ultimate rate to which cost increase is assumed to decline (as a percent)	5.00%	5.00%
Year in which the ultimate rate is reached	2027	2023
Defined Contribution Plans
Maximum percentage contribution by employer of employees eligible pay	6.00%	6.00%
Maximum compensation to be eligible for fixed contribution from employer	$ 100,000
Percentage of fixed contribution by employer, for eligible employees whose compensation is $100,000 or less	2.00%
VEBA Trust
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Expected return on assets (as a percent)		3.00%
U.S.
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Health care cost increase following year (as a percent)	7.00%	6.50%
Ultimate rate to which cost increase is assumed to decline (as a percent)	5.00%	5.00%
Year in which the ultimate rate is reached	2027	2023
Defined Contribution Plans
Company contributions	$ 396,000,000	$ 383,000,000	371,000,000
Non-U.S.
Defined Benefit Plan, Assumptions Used in Calculations [Abstract]
Health care cost increase following year (as a percent)	6.90%	6.87%
Ultimate rate to which cost increase is assumed to decline (as a percent)	6.90%	6.87%
Year in which the ultimate rate is reached	2019
Defined Contribution Plans
Company contributions	$ 283,000,000	$ 270,000,000	$ 268,000,000