Goodwill and Intangible Assets (Schedules for Amortization Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Finite Lived Intangible Asset
Amortization expense for acquired intangible assets	$ 51	$ 63	$ 162	$ 195
Expected amortization expense for acquired intangible assets recorded as of balance sheet date
Remainder of 2017	49		49
2018	192		192
2019	183		183
2020	174		174
2021	162		162
2022	148		148
After 2022	$ 602		$ 602