Accumulated Other Comprehensive Loss - Schedule of AOCL Components (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2020
Jun. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Components of accumulated other comprehensive loss          
Beginning balance $ 8,690 $ 14,309 $ 13,958 $ 15,358 $ 13,687
Changes in value (net of tax effect)       (85) (8)
Changes in value, tax effect       31 2
Reclassifications into earnings (net of tax effect)       135 188
Reclassifications into earnings, tax effect       149 57
Ending balance 3,357 8,690 15,068 3,357 15,068
Tax benefit 1,480   (452) 2,849 (1,131)
Accumulated Other Comprehensive Income          
Components of accumulated other comprehensive loss          
Beginning balance (7,937) (7,898) (7,694) (7,989) (7,825)
Beginning balance, tax effect       1,549 1,492
Ending balance (7,939) (7,937) (7,645) (7,939) (7,645)
Ending balance, tax effect 1,431   1,437 1,431 1,437
Pension and Other Benefit Liabilities          
Components of accumulated other comprehensive loss          
Beginning balance       (8,095) (7,925)
Changes in value (net of tax effect)       (102) (12)
Reclassifications into earnings (net of tax effect)       218 189
Ending balance (7,979)   (7,748) (7,979) (7,748)
Deferred income tax expense in that will not be recognized until obligation is fully extinguished 755   755 755 755
Other          
Components of accumulated other comprehensive loss          
Beginning balance       106 100
Changes in value (net of tax effect)       17 4
Reclassifications into earnings (net of tax effect)       (83) (1)
Ending balance $ 40   $ 103 $ 40 $ 103
Foreign currency hedges | Released from AOCI          
Components of accumulated other comprehensive loss          
Tax benefit   $ 83