v3.19.3.a.u2
Pension And Postretirement Benefits (Net Periodic Benefit Cost) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]      
Net periodic benefit (credit) cost $ 2,762 $ (4,251) $ 155
Pension Benefit [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost - benefits earned during the period 1,019 1,116 1,128
Interest cost on projected benefit obligation 1,960 2,092 1,936
Expected return on assets (3,561) (3,190) (3,134)
Amortization of prior service cost (credit) (113) (115) (123)
Actuarial (gain) loss 3,088 (812) 844
Net periodic benefit (credit) cost 2,393 (909) 651
Postretirement Benefit [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost - benefits earned during the period 71 109 138
Interest cost on projected benefit obligation 675 778 809
Expected return on assets (227) (304) (319)
Amortization of prior service cost (credit) (1,820) (1,635) (1,466)
Actuarial (gain) loss 1,670 (2,290) 342
Net periodic benefit (credit) cost $ 369 $ (3,342) $ (496)