v3.19.3.a.u2
Post-Employment Benefits - Assumptions (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
A one percentage point increase / (decrease) in the assumed health care cost      
Increase in accumulated post employment benefit obligations due to a one percentage point increase in the assumed health care cost $ 221    
Decrease in accumulated post employment benefit obligations due to a one percentage point decrease in the assumed health care cost (179)    
Increase in the total of service and interest cost components of net post employment health care cost due to a one percentage point increase in the assumed health care cost 12    
Decrease in the total of service and interest cost components of net post employment health care cost due to a one percentage point decrease in the assumed health care cost $ (9)    
Defined benefit plans and medical and dental plans      
Weighted average assumptions used to determine benefit obligations      
Discount rate (as a percent) 3.00% 4.00% 3.40%
Expected aggregate average long-term change in compensation (as a percent) 4.30% 4.30% 4.40%
Weighted average assumptions used to determine the net cost      
Discount rate (as a percent) 4.00% 3.40% 3.90%
Expected return on plan assets (as a percent) 7.50% 7.70% 7.60%
Expected aggregate average long-term change in compensation (as a percent) 4.30% 4.40% 4.30%
Medical and Dental Plans      
Assumed health care cost trend rates      
Health care cost trend rate assumed for the next year (as a percent) 9.00% 9.00% 9.00%
Rate that the cost trend rate gradually declines to (as a percent) 5.00% 5.00% 5.00%
Year that rate reaches the assumed ultimate rate 2025 2025 2027