PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS (Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3,307	$ 3,097
Defined Contribution Plan, Cost	$ 21	$ 17	$ 16
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Concentration Risk, Percentage	99.00%	99.00%	99.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	23.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	45.00%
Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	27.00%
Other Pension Plan Asset Category [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	5.00%
Defined Benefit Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3,307	$ 3,097	$ 3,173
Defined Benefit Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	846	547
Defined Benefit Pension Plan [Member] | Alternative Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 863	$ 873
Defined Benefit Plan Liability, Annuity Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Concentration Risk, Percentage	35.00%