Property, Plant and Equipment, Net of Accumulated Depreciation (Property, Plant and Equipment, Net of Accumulated Depreciation) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 29,405	$ 28,332
Accumulated depreciation	(13,663)	(12,995)
Property and equipment, net	15,742	15,337
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	471	452
Building [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	6,453	6,023
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	20,563	19,100
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 1,918	$ 2,757