Segment Information and Concentrations Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,517	$ 1,478
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	889	847
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	408	422
APJ [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 220	$ 209