Derivative Financial Instruments - Effect of Hedge Activity on Income and Expense (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss)
Cost		$ 9,649	$ 10,139
SG&A expense		5,955	4,691
Other (income) and expense		182	(73)
Interest expense		326	210
Cost of services
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity		10	10
Cost of sales
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity		9	18
Cost of financing
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity		3	(18)
SG&A expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity		(191)	141
Other (income) and expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity		(101)	(69)
Interest expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity		10	(20)
Services
Derivative Instruments, Gain (Loss)
Cost	[1]	7,843	8,272
Sales
Derivative Instruments, Gain (Loss)
Cost	[1]	1,624	1,603
Financing
Derivative Instruments, Gain (Loss)
Cost		$ 181	$ 264

[1] Reclassified to conform to current period presentation. Refer to note 1, “Basis of Presentation,” for additional information.