v3.19.3.a.u2
Post-Employment Benefits - Expense (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plans      
Defined benefit plan net periodic benefit cost      
Service cost - benefits earned during the period $ 250 $ 293 $ 283
Interest cost on projected benefit obligations 337 308 287
Expected return on plans assets (710) (680) (613)
Amortization of actuarial losses 132 205 163
Amortization of prior service cost (credits) 1 1 1
Total net cost 10 127 121
Net actuarial losses (gains), net of any prior service credits 944 86 247
Pretax amount included in accumulated other comprehensive income (loss), expected to be recognized in the net period benefit cost in 2020      
Pretax amount of actuarial losses expected to recognized in the net periodic benefit cost in 2020 (253)    
Pretax amount of prior service cost (credits) expected to recognized in the net periodic benefit cost in 2020 1    
Medical and Dental Plans      
Defined benefit plan net periodic benefit cost      
Service cost - benefits earned during the period 23 26 25
Interest cost on projected benefit obligations 52 48 45
Expected return on plans assets (27) (33) (33)
Amortization of actuarial losses 22 33 23
Amortization of prior service cost (credits) (32) (45) (45)
Total net cost 38 29 15
Net actuarial losses (gains), net of any prior service credits (190) $ 53 97
Pretax amount included in accumulated other comprehensive income (loss), expected to be recognized in the net period benefit cost in 2020      
Pretax amount of actuarial losses expected to recognized in the net periodic benefit cost in 2020 32    
Pretax amount of prior service cost (credits) expected to recognized in the net periodic benefit cost in 2020 $ 28    
AMO      
Defined benefit plan net periodic benefit cost      
Curtailment gain related to sale of AMO     $ 10