Segment Information Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,886	$ 1,783	$ 1,710	$ 1,536	$ 1,801	$ 1,550	$ 1,537	$ 1,517	$ 6,915	$ 6,405	$ 6,516
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 3,481	$ 3,076	$ 3,224
Percentage of Revenues by Geographic Area									50.00%	48.00%	50.00%
Americas (Excluding United States) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 693	$ 631	$ 585
Percentage of Revenues by Geographic Area									10.00%	10.00%	9.00%
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 1,843	$ 1,751	$ 1,786
Percentage of Revenues by Geographic Area									27.00%	27.00%	27.00%
APJ [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 898	$ 947	$ 921
Percentage of Revenues by Geographic Area									13.00%	15.00%	14.00%