Business Segments - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	3
Cash and cash equivalents	$ 1,043	$ 1,132	$ 1,476
Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 355	$ 310
Concentrations of cash and cash equivalents	34.00%	27.00%
Asia Pacific
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 344	$ 427
Concentrations of cash and cash equivalents	33.00%	38.00%
Americas
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 169	$ 203
Concentrations of cash and cash equivalents	16.00%	18.00%