Debt - Components of Notes Payable (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Principal amount		$ 572	$ 438	[1]
U.S. commercial paper
Short-term Debt [Line Items]
Principal amount		$ 285	$ 80
Effective interest rate (a)		1.29%	0.61%
Europe commercial paper
Short-term Debt [Line Items]
Principal amount		$ 201	$ 306
Effective interest rate (a)	[2]	(0.26%)	(0.18%)
Bank borrowings
Short-term Debt [Line Items]
Principal amount		$ 86	$ 52

[1] Condensed from audited financial statements.

[2] Negative effective interest rates on certain borrowings in Europe are the result of efforts by the European Central Bank to stimulate the economy in the eurozone.