Financial Instruments - Effect of Hedge Activity on Income and Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	$ (2,996)	$ (3,065)	$ (6,908)	$ (6,931)
Cost of Services
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	8,040		25,519
Gains/(losses) of total hedge activity	1		29
Cost of Sales
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	1,625		5,216
Gains/(losses) of total hedge activity	8		(15)
Cost of financing
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	287		846
Gains/(losses) of total hedge activity	15		56
SG&A Expense
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	4,363		14,665
Gains/(losses) of total hedge activity	47		24
Other (Income) and Expense
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	275		968
Gains/(losses) of total hedge activity	(63)		(449)
Interest expense
Derivative Instruments, Gain (Loss)
Loss (income) from continuing operations before income taxes	191		530
Gains/(losses) of total hedge activity	$ (21)		$ (53)