Goodwill and Purchased Intangible Assets - Schedule of Acquired Intangibles (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,215	$ 1,210
Accumulated Amortization	(624)	(538)
Reseller & customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	659	656
Accumulated Amortization	(159)	(128)
Intellectual property
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	394	392
Accumulated Amortization	$ (339)	(302)
Customer Contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	8 years
Gross Carrying Amount	$ 89	89
Accumulated Amortization	(77)	(66)
Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	73	73
Accumulated Amortization	$ (49)	$ (42)
Minimum [Member] | Reseller & customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	1 year
Minimum [Member] | Intellectual property
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	2 years
Minimum [Member] | Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	2 years
Maximum [Member] | Reseller & customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	20 years
Maximum [Member] | Intellectual property
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	8 years
Maximum [Member] | Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	10 years