v3.19.3.a.u2
Post-Employment Benefits - Benefit Obligation (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Plan assets at fair value:      
Plan assets at fair value, balance at the beginning of the year $ 8,904    
Plan assets at fair value, balance at the end of the year 10,637 $ 8,904  
Projected benefit obligations greater than plan assets      
Long-term liabilities (2,817) (2,040)  
Amounts Recognized in Accumulated Other Comprehensive Income (loss):      
Projected benefit obligations 3,300 2,700  
Accumulated benefit obligations 10,200 8,300  
The aggregate accumulated benefit obligations, the projected benefit obligations and the aggregate plan assets      
Accumulated benefit obligation 1,985 1,265  
Projected benefit obligation 2,266 1,362  
Fair value of plan assets 821 375  
Defined Benefit Plans      
Projected benefit obligations:      
Projected benefit obligations, balance at the beginning of the year 9,093 9,953  
Service cost - benefits earned during the period 250 293 $ 283
Interest cost on projected benefit obligations 337 308 287
(Gains) losses, primarily changes in discount rates, plan design changes, law changes and differences between actual and estimated health care costs 1,856 (1,044)  
Benefits paid (302) (295)  
Other, including foreign currency translation 4 (122)  
Projected benefit obligations, balance at the end of the year 11,238 9,093 9,953
Plan assets at fair value:      
Plan assets at fair value, balance at the beginning of the year 8,553 9,298  
Actual return (loss) on plans' assets 1,622 (450)  
Company contributions 382 114  
Benefits paid (302) (295)  
Other, including foreign currency translation 22 (114)  
Plan assets at fair value, balance at the end of the year 10,277 8,553 9,298
Projected benefit obligations greater than plan assets      
Projected benefit obligations greater than plan assets, December 31 (961) (540)  
Long-term assets 687 583  
Short-term liabilities (26) (23)  
Long-term liabilities (1,622) (1,100)  
Net liability (961) (540)  
Amounts Recognized in Accumulated Other Comprehensive Income (loss):      
Actuarial losses, net 4,131 3,326  
Prior service cost (credits) (2) (2)  
Total 4,129 3,324  
Medical and Dental Plans      
Projected benefit obligations:      
Projected benefit obligations, balance at the beginning of the year 1,292 1,393  
Service cost - benefits earned during the period 23 26 25
Interest cost on projected benefit obligations 52 48 45
(Gains) losses, primarily changes in discount rates, plan design changes, law changes and differences between actual and estimated health care costs 228 (106)  
Benefits paid (76) (68)  
Other, including foreign currency translation 37 (1)  
Projected benefit obligations, balance at the end of the year 1,556 1,292 1,393
Plan assets at fair value:      
Plan assets at fair value, balance at the beginning of the year 351 419  
Actual return (loss) on plans' assets 65 (20)  
Company contributions 12 12  
Benefits paid (68) (60)  
Plan assets at fair value, balance at the end of the year 360 351 $ 419
Projected benefit obligations greater than plan assets      
Projected benefit obligations greater than plan assets, December 31 (1,196) (941)  
Short-term liabilities (1) (1)  
Long-term liabilities (1,195) (940)  
Net liability (1,196) (941)  
Amounts Recognized in Accumulated Other Comprehensive Income (loss):      
Actuarial losses, net 529 361  
Prior service cost (credits) (95) (163)  
Total $ 434 $ 198