RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
U.S. | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	$ 425	$ 463	$ 27	$ 28
Company contributions expected to be made during the remainder of the year	30	30
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions		0	143	7
Company contributions expected to be made during the remainder of the year	2	2
Non-U.S. plans | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions		64	70	112
Company contributions expected to be made during the remainder of the year	70	70
Non-U.S. plans | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	220	223	$ 4	$ 5
Company contributions expected to be made during the remainder of the year	$ 5	$ 5