RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
U.S. | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	$ 14	$ 13
Company contributions made or expected to be made during the remainder of the year	45	92
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	0	12
Company contributions made or expected to be made during the remainder of the year	0	164
Non-U.S. plans | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the three months ended March 31	29	34
Company contributions made or expected to be made during the remainder of the year	99	101
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	2
Company contributions made or expected to be made during the remainder of the year	$ 8	$ 7