RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
U.S. | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the six months ended June 30	$ 28	$ 26
Company contributions made or expected to be made during the remainder of the year	29	79
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the six months ended June 30	7	19
Company contributions made or expected to be made during the remainder of the year	2	157
Non-U.S. plans | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the six months ended June 30	112	58
Company contributions made or expected to be made during the remainder of the year	67	68
Non-U.S. plans | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions for the six months ended June 30	5	3
Company contributions made or expected to be made during the remainder of the year	$ 5	$ 6