RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
U.S. | Pension Plans
Service-related expense
Benefits earned during the period	$ 0	$ 0	$ 0	$ 0
Interest cost on benefit obligation	95	101	177	207
Expected return on plan assets	(174)	(206)	(356)	(414)
Amortization of unrecognized:
Prior service cost (benefit)	0	0	1	1
Net actuarial loss	54	53	116	109
Settlement loss	0	0	0	0
Total net expense	(25)	(52)	(62)	(97)
U.S. | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligation	3	5	6	10
Expected return on plan assets	(3)	(4)	(7)	(9)
Amortization of unrecognized:
Prior service cost (benefit)	(2)	0	(4)	0
Net actuarial loss	(1)	0	(1)	0
Settlement loss	0	0	0	0
Total net expense	(3)	1	(6)	1
Non-U.S. plans | Pension Plans
Service-related expense
Benefits earned during the period	38	34	77	71
Interest cost on benefit obligation	70	61	132	125
Expected return on plan assets	(63)	(56)	(124)	(121)
Amortization of unrecognized:
Prior service cost (benefit)	(2)	(2)	(3)	(3)
Net actuarial loss	14	17	32	34
Settlement loss	4	3	4	3
Total net expense	61	57	118	109
Non-U.S. plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	2	2	4	4
Interest cost on benefit obligation	24	22	49	46
Expected return on plan assets	(21)	(18)	(43)	(38)
Amortization of unrecognized:
Prior service cost (benefit)	(3)	(2)	(5)	(4)
Net actuarial loss	3	5	8	10
Settlement loss	0	0	0	0
Total net expense	$ 5	$ 9	$ 13	$ 18