v3.20.4
Post-Employment Benefits - Net Periodic Benefit Cost (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined benefit plans      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Service cost $ 370 $ 269 $ 285
Interest cost 264 259 227
Expected return on plan assets (575) (474) (439)
Amortization of prior service cost 2 0 0
Amortization of actuarial loss (227) (109) (140)
Net periodic benefit cost 288 163 213
Other post-employment plans      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Service cost 42 25 26
Interest cost 34 29 25
Amortization of prior service cost (4) 0 0
Amortization of actuarial loss (26) (1) (1)
Net periodic benefit cost $ 98 $ 55 $ 52