Goodwill and Purchased Intangible Assets - Amorization Expense (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 28	$ 57
Amortization expense for the remainder of the year	59	59
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	85	85
2019	75	75
2020	57	57
2021	49	49
2022	$ 45	$ 45