Segment Information Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 1,802	$ 1,677	$ 1,620	$ 1,444	$ 1,680	$ 1,613	$ 1,604	$ 1,476	$ 6,543	$ 6,373	$ 6,591
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 3,106	$ 2,909	$ 2,723
Percentage of Revenues by Geographic Area									47.00%	46.00%	41.00%
Americas (Excluding United States) [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 637	$ 590	$ 634
Percentage of Revenues by Geographic Area									10.00%	9.00%	10.00%
EMEA
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 1,896	$ 1,964	$ 2,184
Percentage of Revenues by Geographic Area									29.00%	31.00%	33.00%
APJ [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 904	$ 910	$ 1,050
Percentage of Revenues by Geographic Area									0.00%	14.00%	16.00%