RETIREMENT BENEFITS - Net (Benefit) Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
U.S. | Pension Plans
Service-related expense
Benefits earned during the period	$ 0	$ 0	$ 0	$ 1
Interest cost on benefit obligation	123	126	253	249
Expected return on plan assets	(202)	(211)	(405)	(424)
Amortization of unrecognized:
Prior service cost (benefit)	(1)	0	0	0
Net actuarial loss	48	42	92	89
Curtailment loss	0	1	0	1
Settlement loss	0	0	0	0
Total net (benefit) expense	(32)	(42)	(60)	(84)
U.S. | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	0	0	0	0
Interest cost on benefit obligation	6	7	13	13
Expected return on plan assets	(4)	(3)	(9)	(6)
Amortization of unrecognized:
Prior service cost (benefit)	0	0	0	0
Net actuarial loss	0	0	0	0
Curtailment loss	0	0	0	0
Settlement loss	0	0	0	0
Total net (benefit) expense	2	4	4	7
Non-U.S. plans | Pension Plans
Service-related expense
Benefits earned during the period	35	38	71	76
Interest cost on benefit obligation	73	72	148	147
Expected return on plan assets	(68)	(72)	(136)	(150)
Amortization of unrecognized:
Prior service cost (benefit)	(1)	(1)	(2)	(2)
Net actuarial loss	15	14	30	27
Curtailment loss	0	0	0	0
Settlement loss	2	1	2	5
Total net (benefit) expense	56	52	113	103
Non-U.S. plans | Postretirement Benefit Plans
Service-related expense
Benefits earned during the period	2	3	4	5
Interest cost on benefit obligation	26	25	52	51
Expected return on plan assets	(21)	(22)	(42)	(45)
Amortization of unrecognized:
Prior service cost (benefit)	(3)	(3)	(5)	(5)
Net actuarial loss	6	8	11	15
Curtailment loss	0	0	0	0
Settlement loss	0	0	0	0
Total net (benefit) expense	$ 10	$ 11	$ 20	$ 21