Segment Information (Schedule of Revenues By Geographic Area Based On The Location of Customers) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenue	$ 36,193	$ 30,973	$ 30,561
North America
Segment Reporting Information [Line Items]
Revenue	29,333	24,434	23,869
North America | United States
Segment Reporting Information [Line Items]
Revenue	28,578	23,519	23,160
North America | Other North America
Segment Reporting Information [Line Items]
Revenue	755	915	709
Europe
Segment Reporting Information [Line Items]
Revenue	2,772	2,558	2,152
Asia Pacific
Segment Reporting Information [Line Items]
Revenue	2,252	2,011	1,650
Africa Middle East
Segment Reporting Information [Line Items]
Revenue	1,565	1,655	2,617
South America
Segment Reporting Information [Line Items]
Revenue	$ 271	$ 315	$ 273