RETIREMENT BENEFITS - Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019
U.S. | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	$ 14	$ 425	$ 14
Company contributions expected to be made during the remainder of the year	43		467
U.S. | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	0		0
Company contributions expected to be made during the remainder of the year	0		4
Non-U.S. plans | Pension Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	37		34
Company contributions expected to be made during the remainder of the year	116		116
Non-U.S. plans | Postretirement Benefit Plans
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]
Company contributions	2	$ 220	3
Company contributions expected to be made during the remainder of the year	$ 6		$ 222