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Pension and Other Postretirement Healthcare Benefits, Defined Contribution Plans (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2013
Dec. 31, 2006
Qualified Plan | U.S. Savings Investment Plan          
Defined Contribution Plans [Abstract]          
Employer matching contribution percentage, first portion 100.00%        
Employee contribution percentage, first portion 6.00%        
Discretionary contribution percentage 6.00% 6.00% 6.00% 6.00%  
Discretionary contribution vesting period 3 years        
Compensation expenses associated with matching contribution $ 4 $ 4 $ 4    
Compensation expense associated with discretionary contribution 4 5 5    
Nonqualified Plan | U.S. Benefit Restoration Plan          
Defined Contribution Plans [Abstract]          
Compensation expenses associated with matching contribution $ 2 $ 1 $ 1    
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent         20.00%