Changes in Accumulated Other Comprehensive Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 145,208	$ 155,642
Components of Other Comprehensive Income (Loss):
Before Reclassifications	(20)	(9)
Reclassifications	126	94
Other Comprehensive Gain (Loss), Net of Tax	106	85
Ending balance	144,914	156,118
Related income taxes	564	1,315
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4,990)	(3,544)
Components of Other Comprehensive Income (Loss):
Other Comprehensive Gain (Loss), Net of Tax	106	85
Ending balance	(4,884)	(3,459)
Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(142)	(124)
Components of Other Comprehensive Income (Loss):
Before Reclassifications	(19)	(4)
Reclassifications	0	0
Other Comprehensive Gain (Loss), Net of Tax	(19)	(4)
Ending balance	(161)	(128)
Unrealized Holding Gains (Losses) on Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(8)	(10)
Components of Other Comprehensive Income (Loss):
Before Reclassifications	(3)	(1)
Reclassifications	0	0
Other Comprehensive Gain (Loss), Net of Tax	(3)	(1)
Ending balance	(11)	(11)
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	0	(2)
Components of Other Comprehensive Income (Loss):
Before Reclassifications	0	0
Reclassifications	0	0
Other Comprehensive Gain (Loss), Net of Tax	0	0
Ending balance	0	(2)
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4,840)	(3,408)
Components of Other Comprehensive Income (Loss):
Before Reclassifications	2	(4)
Reclassifications	126	94
Other Comprehensive Gain (Loss), Net of Tax	128	90
Ending balance	(4,712)	$ (3,318)
Defined Benefit Plans | Reclassification out of Accumulated Other Comprehensive Income
Components of Other Comprehensive Income (Loss):
Employee Benefits for reclassified components	163
Related income taxes	$ 37