Financial Instruments - Effect of Hedge Activity on Income and Expense (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018
Derivative Instruments, Gain (Loss)
Cost	$ 9,692	$ 9,953		$ 29,982		$ 31,582
SG&A expense	5,024	4,363		15,171		14,665
Other (income) and expense	(31)	275		(850)		968
Interest expense	432	191		990		530
Cost of services
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	22	1		52		29
Cost of sales
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	10	8		40		(15)
Cost of financing
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(11)	(3)		(47)		1
SG&A expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	20	47		199		24
Other (income) and expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(561)	(63)		(358)		(449)
Interest expense
Derivative Instruments, Gain (Loss)
Gains/(losses) of total hedge activity	(35)	(3)		(96)		1
Services
Derivative Instruments, Gain (Loss)
Cost	7,840	7,951	[1]	24,293	[1]	25,238	[1]
Sales
Derivative Instruments, Gain (Loss)
Cost	1,635	1,714	[1]	4,979	[1]	5,498	[1]
Financing
Derivative Instruments, Gain (Loss)
Cost	$ 217	$ 287		$ 710		$ 846

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