RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
U.S. | Pension Plans
Service-related expense
Benefits earned during the period	$ 0	$ 1	$ 0	$ 1
Interest cost on benefit obligation	87	112	294	365
Expected return on plan assets	(205)	(208)	(619)	(613)
Amortization of unrecognized:
Prior service cost (benefit)	0	1	1	1
Net actuarial loss	62	52	171	144
Curtailment loss (gain)			0	1
Settlement (gain) loss	0	1	0	0
Total net (benefit) expense	(56)	(41)	(153)	(101)
U.S. | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligation	4	6	14	19
Expected return on plan assets	(4)	(5)	(13)	(14)
Amortization of unrecognized:
Prior service cost (benefit)	0	0	0	0
Net actuarial loss	0	0	0	0
Curtailment loss (gain)			0	0
Settlement (gain) loss	0	0	0	0
Total net (benefit) expense	0	1	1	5
Non-U.S. plans | Pension Plans
Service-related expense
Benefits earned during the period	38	37	109	108
Interest cost on benefit obligation	59	70	184	218
Expected return on plan assets	(62)	(72)	(183)	(208)
Amortization of unrecognized:
Prior service cost (benefit)	(1)	(1)	(4)	(3)
Net actuarial loss	17	15	51	45
Curtailment loss (gain)			0	(5)
Settlement (gain) loss	(6)	(5)	(3)	2
Total net (benefit) expense	45	44	154	157
Non-U.S. plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	2	2	6	6
Interest cost on benefit obligation	22	25	68	77
Expected return on plan assets	(18)	(20)	(56)	(62)
Amortization of unrecognized:
Prior service cost (benefit)	(3)	(2)	(7)	(7)
Net actuarial loss	5	5	15	16
Curtailment loss (gain)			0	0
Settlement (gain) loss	0	0	0	0
Total net (benefit) expense	$ 8	$ 10	$ 26	$ 30