RETIREMENT BENEFITS - Defined Contribution Plans and Postemployment Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Postemployment Retirement Benefits
Service-related expense
Interest cost on benefit obligation	$ 1	$ 1	$ 1	$ 1
Expected return on plan assets	(1)	0	(1)	0
Amortization of unrecognized
Prior service benefit	(7)	(7)	(15)	(15)
Net actuarial loss	0	0	1	1
Total service-related benefit	(7)	(6)	(14)	(13)
Non-service-related expense (benefit)	(3)	4	3	12
Total net (benefit) expense	(10)	(2)	(11)	(1)
U.S. | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	99	100	203	198
Service-related expense
Interest cost on benefit obligation	7	8	13	14
Expected return on plan assets	(3)	(2)	(6)	(3)
Amortization of unrecognized
Prior service benefit	0	0	0	0
Total net (benefit) expense	4	7	7	11
Non-U.S. plans | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	72	66	148	135
Service-related expense
Interest cost on benefit obligation	25	25	51	49
Expected return on plan assets	(22)	(22)	(45)	(43)
Amortization of unrecognized
Prior service benefit	(3)	(3)	(5)	(5)
Total net (benefit) expense	$ 11	$ 11	$ 21	$ 22