PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Change in Projected Benefit Obligations, Plan Assets and Funded Status of All Significant Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	$ 3,097
Fair Value of Plan Assets, Ending	3,307	$ 3,097
Defined Benefit Pension Plans [Member]
Defined Benefit Plan, Change in Benefit Obligations [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning	4,025	3,993
Service cost	38	39	$ 44
Interest cost	129	131	164
Actuarial changes in assumptions and experience	241	155
Benefits Paid	(281)	(285)
Defined Benefit Plan, Other Cost (Credit)	(2)	(8)
Defined Benefit Plan, Benefit Obligation, end	4,150	4,025	3,993
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	3,097	3,173
Actual return on plan assets	331	165
Employer contributions	162	52
Asset transfers (1)	(2)	(8)
Defined Benefit Plan, Plan Assets, Benefits Paid	(281)	(285)
Fair Value of Plan Assets, Ending	3,307	3,097	3,173
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(843)	(928)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(2)	(2)
Noncurrent liabilities	(841)	(926)
Net amounts recognized in the consolidated balance sheets	(843)	(928)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Net loss (gain)	2,083	2,035
Prior service credit	(12)	(13)
Pretax balance in AOCI at end of year	2,071	2,022
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligations [Roll Forward]
Defined Benefit Plan, Benefit Obligation, beginning	264	276
Service cost	1	1	1
Interest cost	8	8	10
Actuarial changes in assumptions and experience	(23)	4
Benefits Paid	(26)	(25)
Defined Benefit Plan, Other Cost (Credit)	0	0
Defined Benefit Plan, Benefit Obligation, end	224	264	276
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair Value of Plan Assets, Beginning	0	0
Actual return on plan assets	0	0
Employer contributions	0	0
Asset transfers (1)	0	0
Defined Benefit Plan, Plan Assets, Benefits Paid	0	0
Fair Value of Plan Assets, Ending	0	0	$ 0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	(224)	(264)
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Current liabilities	(15)	(24)
Noncurrent liabilities	(209)	(240)
Net amounts recognized in the consolidated balance sheets	(224)	(264)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax [Abstract]
Net loss (gain)	(86)	(69)
Prior service credit	0	0
Pretax balance in AOCI at end of year	$ (86)	$ (69)