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RETIREMENT BENEFITS Retirement Benefits - Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure    
Defined Contribution Plan Employers Matching Contribution Percentage to Participants Percentage Conribution 100.00%  
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year $ 8  
Defined Contribution Plan, Employer Matching Contribution, Percent 5.00%  
Other Postretirement Benefits Plan [Member]    
Defined Benefit Plan Disclosure    
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Arising During Period, before Tax $ 18  
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate 2.92% 3.44%
Other Postretirement Benefits Plan [Member] | Fixed Income Securities    
Defined Benefit Plan Disclosure    
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 75.00%  
Other Postretirement Benefits Plan [Member] | Market index fund [Member]    
Defined Benefit Plan Disclosure    
Large Cap US Equitiies   100.00%
Other Postretirement Benefits Plan [Member] | International index fund [Member]    
Defined Benefit Plan Disclosure    
Large Cap US Equitiies   5.00%
International Securities Funds   95.00%
Other Postretirement Benefits Plan [Member] | U.S. bond index fund [Member]    
Defined Benefit Plan Disclosure    
Large Cap US Equitiies   23.00%
Other securities   7.00%
Fixed Income Securities   44.00%
Mortgage-backed securities   26.00%
Savings Plan [Member]    
Defined Benefit Plan Disclosure    
Defined Contribution Plan, Cost $ 2  
Supplemental Employee Retirement Plan [Member]    
Defined Benefit Plan Disclosure    
Defined Contribution Plan, Employer Matching Contribution, Percent 3.00%  
Company Contributions Vested 100.00%  
Company Contributions Years five  
Defined Contribution Plan, Cost $ 1  
Minimum [Member] | Other Postretirement Benefits Plan [Member] | Equity Securities    
Defined Benefit Plan Disclosure    
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 25.00%  
Minimum [Member] | Other Postretirement Benefits Plan [Member] | Fixed Income Securities    
Defined Benefit Plan Disclosure    
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 65.00%  
Maximum [Member] | Other Postretirement Benefits Plan [Member] | Equity Securities    
Defined Benefit Plan Disclosure    
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage 35.00%