RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
U.S. | Pension Plans
Service-related expense
Benefits earned during the period	$ 0	$ 0	$ 0	$ 0
Interest cost on benefit obligation	87	87	264	294
Expected return on plan assets	(173)	(205)	(529)	(619)
Amortization of unrecognized:
Prior service cost (benefit)	0	0	1	1
Net actuarial loss (gain)	57	62	173	171
Settlement loss (gain)	0	0	0	0
Total net (benefit) expense	(29)	(56)	(91)	(153)
U.S. | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligation	3	4	9	14
Expected return on plan assets	(3)	(4)	(10)	(13)
Amortization of unrecognized:
Prior service cost (benefit)	(3)	0	(7)	0
Net actuarial loss (gain)	0	0	(1)	0
Settlement loss (gain)	0	0	0	0
Total net (benefit) expense	(3)	0	(9)	1
Non-U.S. plans | Pension Plans
Service-related expense
Benefits earned during the period	36	38	113	109
Interest cost on benefit obligation	67	59	199	184
Expected return on plan assets	(65)	(62)	(189)	(183)
Amortization of unrecognized:
Prior service cost (benefit)	(1)	(1)	(4)	(4)
Net actuarial loss (gain)	16	17	48	51
Settlement loss (gain)	1	(6)	5	(3)
Total net (benefit) expense	54	45	172	154
Non-U.S. plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	2	2	6	6
Interest cost on benefit obligation	25	22	74	68
Expected return on plan assets	(22)	(18)	(65)	(56)
Amortization of unrecognized:
Prior service cost (benefit)	(2)	(3)	(7)	(7)
Net actuarial loss (gain)	4	5	12	15
Settlement loss (gain)	0	0	0	0
Total net (benefit) expense	$ 7	$ 8	$ 20	$ 26