PENSION AND OTHER POSTRETIREMENT BENEFITS - WEIGHTED-AVERAGE ASSUMPTIONS (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount Rate	3.73%	4.30%
Rate of Compensation Increase	3.50%	3.50%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount Rate	4.30%	4.83%	4.25%
Expected Long-Term Return on Plan Assets	7.25%	7.50%	7.75%
Rate of Compensation Increase	3.50%	3.50%	3.50%
Other Postretirement Benefits
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount Rate	3.63%	4.13%
Rate of Compensation Increase	3.50%	3.50%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount Rate	4.13%	4.73%	4.20%
Expected Long-Term Return on Plan Assets	6.50%	6.50%	6.25%
Rate of Compensation Increase	3.50%	3.50%	3.50%