Goodwill and Purchased Intangible Assets - Schedule of Acquired Intangibles (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,212	$ 1,210
Accumulated Amortization	(567)	(538)
Reseller & customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	657	656
Accumulated Amortization	(139)	(128)
Intellectual property
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	393	392
Accumulated Amortization	$ (314)	(302)
Customer Contracts [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization Period (in Years)	8 years
Gross Carrying Amount	$ 89	89
Accumulated Amortization	(70)	(66)
Tradenames
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	73	73
Accumulated Amortization	$ (44)	$ (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