Goodwill and Intangible Assets (Schedules for Amortization Expense) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Finite Lived Intangible Asset
Amortization expense for acquired intangible assets	$ 63	$ 47	$ 127	$ 111
Expected amortization expense for acquired intangible assets recorded as of balance sheet date
Remainder of 2018	123		123
2019	241		241
2020	229		229
2021	220		220
2022	206		206
2023	175		175
After 2023	$ 950		$ 950