Debt - Interest Income and Expense (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Debt Disclosure [Abstract]
Interest expense	[1]	$ 65	$ 69
Interest income	[2]	$ 74	$ 78

[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.