RETIREMENT BENEFITS - Defined Contribution Plans and Postemployment Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Postemployment Retirement Benefits
Service-related expense
Interest cost on benefit obligation	$ 0	$ 0	$ 1	$ 1
Expected return on plan assets	0	0	(1)	0
Amortization of unrecognized:
Prior service benefit	(8)	(8)	(23)	(23)
Net actuarial loss	1	1	2	2
Total service-related benefit	(7)	(7)	(21)	(20)
Non-service-related expense (benefit)	4	9	7	21
Total net (benefit) expense	(3)	2	(14)	1
U.S. | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	90	95	293	293
Service-related expense
Interest cost on benefit obligation	6	9	19	20
Expected return on plan assets	(4)	(2)	(10)	(5)
Amortization of unrecognized:
Prior service benefit	0	0	0	0
Total net (benefit) expense	2	7	9	15
Non-U.S. plans | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	68	68	216	203
Service-related expense
Interest cost on benefit obligation	26	27	77	76
Expected return on plan assets	(22)	(24)	(67)	(67)
Amortization of unrecognized:
Prior service benefit	(2)	(2)	(7)	(7)
Total net (benefit) expense	$ 11	$ 12	$ 32	$ 34