Segment Information and Concentrations - Revenue by Geography (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,536	$ 1,517
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	920	889
Europe, Middle East and Africa (EMEA)
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	419	408
Asia Pacific (APJ)
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 197	$ 220