RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
U.S. | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	$ 425	$ 42	$ 467
Company contributions expected to be made during the remainder of the year		16	14
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions		0	4
Company contributions expected to be made during the remainder of the year		0	0
Non-U.S. plans | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions		111	98
Company contributions expected to be made during the remainder of the year		37	52
Non-U.S. plans | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	$ 220	6	225
Company contributions expected to be made during the remainder of the year		$ 3	$ 0