Segment Information and Concentrations Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,537	$ 1,593	$ 3,054	$ 3,071
Americas [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	875	915	1,764	1,762
EMEA [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	418	454	826	876
APJ [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 244	$ 224	$ 464	$ 433