Derivative Financial Instruments - Effect of Hedge Activity on Income and Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss)
Cost	$ 9,525	$ 9,649
SG&A expense	5,174	5,955
Other (income) and expense	362	182
Interest expense	280	326
Cost of services
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	14	10
Cost of sales
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(22)	9
Cost of financing
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	2	3
SG&A expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	34	(191)
Other (income) and expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(160)	(101)
Interest expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	5	10
Services
Derivative Instruments, Gain (Loss)
Cost	7,775	7,843
Sales
Derivative Instruments, Gain (Loss)
Cost	1,585	1,624
Financing
Derivative Instruments, Gain (Loss)
Cost	$ 165	$ 181