Debt - Interest Income and Expense (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Debt Disclosure [Abstract]
Interest expense	[1]	$ 62	$ 74	$ 188	$ 235
Interest income	[2]	$ 75	$ 85	$ 229	$ 253

[1] Includes Cost of financing as well as non-financing interest expense that is included in Other expenses, net in the Condensed Consolidated Statements of Income.

[2] Includes Finance income as well as other interest income that is included in Other expenses, net in the Condensed Consolidated Statements of Income.