RETIREMENT BENEFITS - Defined Contribution Plans and Postemployment Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Postemployment Retirement Benefits
Service-related expense
Interest cost on benefit obligation	$ 0	$ 0
Expected return on plan assets	0	0
Amortization of unrecognized:
Prior service benefit	0	(8)
Net actuarial loss	1	1
Total service-related benefit	1	(7)
Non-service-related expense	4	6
Total net (benefit) expense	5	(1)
U.S. | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	99	104
Service-related expense
Interest cost on benefit obligation	7	6
Expected return on plan assets	(5)	(3)
Amortization of unrecognized:
Prior service benefit	0	0
Total net (benefit) expense	2	3
Non-U.S. plans | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	68	76
Service-related expense
Interest cost on benefit obligation	26	26
Expected return on plan assets	(21)	(23)
Amortization of unrecognized:
Prior service benefit	(2)	(2)
Total net (benefit) expense	$ 10	$ 10