Derivative Financial Instruments - Effect of Hedge Activity on Income and Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss)
Cost	$ 9,447	$ 9,130	$ 28,714	$ 28,202
SG&A expense	4,860	4,647	15,368	15,849
Other (income) and expense	234	253	911	614
Interest expense	291	323	852	971
Cost of services
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	12	10	33	18
Cost of sales
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	1	(4)	(30)	14
Cost of financing
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(1)	3	1	9
SG&A expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(14)	58	88	24
Other (income) and expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(7)	101	(246)	92
Interest expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(2)	8	3	24
Services
Derivative Instruments, Gain (Loss)
Cost	7,770	7,357	23,416	22,720
Sales
Derivative Instruments, Gain (Loss)
Cost	1,513	1,601	4,792	4,964
Financing
Derivative Instruments, Gain (Loss)
Cost	$ 165	$ 172	$ 506	$ 517