Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Target Allocation and Actual Asset Allocations for Pension and VEBA Plan Assets) (Details)

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PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Target Allocation and Actual Asset Allocations for Pension and VEBA Plan Assets) (Details)
Dec. 31, 2017
Dec. 31, 2016
Pension Benefits [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 100.00% 100.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 100.00%  
Pension Benefits [Member] | Equity Securities [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 43.60% 43.20%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 45.00%  
Pension Benefits [Member] | Fixed Income Investments [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 27.00% 26.40%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 28.00%  
Pension Benefits [Member] | Hedge Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 5.00% 5.90%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 5.00%  
Pension Benefits [Member] | Private Equity Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 5.30% 5.30%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 7.00%  
Pension Benefits [Member] | Structured Finance [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 9.70% 9.30%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 7.50%  
Pension Benefits [Member] | Real Estate [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 8.70% 9.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 7.50%  
Pension Benefits [Member] | Cash [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 0.70% 0.90%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 0.00%  
Other Benefits [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 100.00% 100.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 100.00%  
Other Benefits [Member] | Equity Securities [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 8.70% 8.40%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 8.00%  
Other Benefits [Member] | Fixed Income Investments [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 77.70% 78.30%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 80.00%  
Other Benefits [Member] | Hedge Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 4.40% 4.40%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 4.00%  
Other Benefits [Member] | Private Equity Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 1.50% 1.70%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 3.00%  
Other Benefits [Member] | Structured Finance [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 3.00% 2.70%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 2.00%  
Other Benefits [Member] | Real Estate [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 4.60% 4.40%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 3.00%  
Other Benefits [Member] | Cash [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Weighted-average asset allocation 0.10% 0.10%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 0.00%