PENSION AND OTHER POSTRETIREMENT BENEFIT PLANS - Changes in Fair Value of Plan Assets (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Adjustment for final fair value of plan assets		$ 44
Pension
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year (estimated)			$ 5,514	$ 5,351
Adjustment for final fair value of plan assets			44	18
Actual return on plan assets			123	553
Foreign currency translation			(73)	59
Employer contributions and benefit payments			345	57
Plan participants’ contributions			0	0
Plan transfers			1	3
Benefits paid (includes lump sum settlements)	$ (664)		(1,024)	(527)
Fair value of plan assets at end of year (estimated)	4,930		4,930	5,514
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year (estimated)			0	0
Adjustment for final fair value of plan assets			0	0
Actual return on plan assets			0	0
Foreign currency translation			0	0
Employer contributions and benefit payments			36	20
Plan participants’ contributions			4	6
Plan transfers			0	0
Benefits paid (includes lump sum settlements)			(22)	(26)
Fair value of plan assets at end of year (estimated)	$ 18		$ 18	$ 0