RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
U.S. | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	$ 14	$ 41	$ 14
Company contributions expected to be made during the remainder of the year	43
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	0	150	0
Company contributions expected to be made during the remainder of the year	0
Non-U.S. plans | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	34	153	29
Company contributions expected to be made during the remainder of the year	107
Non-U.S. plans | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	3	$ 6	$ 3
Company contributions expected to be made during the remainder of the year	$ 7