Changes in Accumulated Other Comprehensive Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 134,386	$ 157,451	$ 145,208	$ 155,642
Components of Other Comprehensive Income (Loss):
Before Reclassifications			9	(27)
Reclassifications			474	302
Other Comprehensive Gain (Loss), Net of Tax	243	88	483	275
Ending balance	132,038	156,892	132,038	156,892
Related income taxes	165	1,469	(1,591)	4,429
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4,750)	(3,357)	(4,990)	(3,544)
Components of Other Comprehensive Income (Loss):
Other Comprehensive Gain (Loss), Net of Tax	243	88	483	275
Ending balance	(4,507)	(3,269)	(4,507)	(3,269)
Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(142)	(124)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			5	(32)
Reclassifications			0	0
Other Comprehensive Gain (Loss), Net of Tax			5	(32)
Ending balance	(137)	(156)	(137)	(156)
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			(5)	2
Reclassifications			0	0
Other Comprehensive Gain (Loss), Net of Tax			(5)	2
Ending balance	(13)	(8)	(13)	(8)
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			0	(2)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			0	2
Reclassifications			0	0
Other Comprehensive Gain (Loss), Net of Tax			0	2
Ending balance	0	0	0	0
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(4,840)	(3,408)
Components of Other Comprehensive Income (Loss):
Before Reclassifications			9	1
Reclassifications			474	302
Other Comprehensive Gain (Loss), Net of Tax			483	303
Ending balance	$ (4,357)	$ (3,105)	(4,357)	$ (3,105)
Defined Benefit Plans | Reclassification out of Accumulated Other Comprehensive Income
Components of Other Comprehensive Income (Loss):
Employee Benefits for reclassified components			615
Related income taxes			$ 141