RETIREMENT BENEFITS - Defined Contribution Plans and Postemployment Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Postemployment Retirement Benefits
Service-related expense
Interest cost on benefit obligation	$ 1	$ 1	$ 1	$ 1
Expected return on plan assets	(1)	(1)	(1)	(1)
Amortization of unrecognized:
Prior service benefit	0	(7)	0	(15)
Net actuarial loss	0	0	1	1
Total service-related benefit	0	(7)	1	(14)
Non-service-related expense (benefit)	2	(3)	6	3
Total net (benefit) expense	2	(10)	7	(11)
U.S. | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	99	99	198	203
Service-related expense
Interest cost on benefit obligation	6	7	13	13
Expected return on plan assets	(4)	(3)	(9)	(6)
Amortization of unrecognized:
Prior service benefit	0	0	0	0
Total net (benefit) expense	2	4	4	7
Non-U.S. plans | Postretirement Benefit Plans
Defined Contribution Plans
Company's contributions for defined contribution plans	71	72	139	148
Service-related expense
Interest cost on benefit obligation	26	25	52	51
Expected return on plan assets	(21)	(22)	(42)	(45)
Amortization of unrecognized:
Prior service benefit	(3)	(3)	(5)	(5)
Total net (benefit) expense	$ 10	$ 11	$ 20	$ 21