PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Changes in Projected Benefit Obligations of Our Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation beginning of year	$ 6,795	$ 6,469
Service cost	37	35	$ 48
Interest cost	236	264	277
Plan participants’ contributions	0	0
Actuarial (gains) losses	(718)	489
Foreign currency translation	(69)	59
Benefits paid (includes lump sum settlements)	(1,024)	(527)
Plan amendments and other	5	3
Plan transfers	1	3
Projected benefit obligation, end of year	5,263	6,795	6,469
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation beginning of year	200	225
Service cost	0	0	0
Interest cost	7	8	8
Plan participants’ contributions	4	6
Actuarial (gains) losses	(18)	(18)
Foreign currency translation	(5)	5
Benefits paid (includes lump sum settlements)	(22)	(26)
Plan amendments and other	0	0
Plan transfers	0	0
Projected benefit obligation, end of year	$ 166	$ 200	$ 225