RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
U.S. | Pension Plans
Service-related expense
Benefits earned during the period	$ 0	$ 0	$ 0	$ 0
Interest cost on benefit obligation	101	123	207	253
Expected return on plan assets	(206)	(202)	(414)	(405)
Amortization of unrecognized:
Prior service cost (benefit)	0	(1)	1	0
Net actuarial loss	53	48	109	92
Settlement loss	0	0	0	0
Total net (benefit) expense	(52)	(32)	(97)	(60)
U.S. | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligation	5	6	10	13
Expected return on plan assets	(4)	(4)	(9)	(9)
Amortization of unrecognized:
Prior service cost (benefit)	0	0	0	0
Net actuarial loss	0	0	0	0
Settlement loss	0	0	0	0
Total net (benefit) expense	1	2	1	4
Non-U.S. plans | Pension Plans
Service-related expense
Benefits earned during the period	34	35	71	71
Interest cost on benefit obligation	61	73	125	148
Expected return on plan assets	(56)	(68)	(121)	(136)
Amortization of unrecognized:
Prior service cost (benefit)	(2)	(1)	(3)	(2)
Net actuarial loss	17	15	34	30
Settlement loss	3	2	3	2
Total net (benefit) expense	57	56	109	113
Non-U.S. plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	2	2	4	4
Interest cost on benefit obligation	22	26	46	52
Expected return on plan assets	(18)	(21)	(38)	(42)
Amortization of unrecognized:
Prior service cost (benefit)	(2)	(3)	(4)	(5)
Net actuarial loss	5	6	10	11
Settlement loss	0	0	0	0
Total net (benefit) expense	$ 9	$ 10	$ 18	$ 20