Business Group Information (Schedule of Revenues By Geographic Area Based On The Location of Customers) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 30,973	$ 30,561	$ 31,781
North America
Segment Reporting Information [Line Items]
Revenue	24,434	23,869	24,601
North America | United States
Segment Reporting Information [Line Items]
Revenue	23,519	23,160	23,480
North America | Other North America
Segment Reporting Information [Line Items]
Revenue	915	709	1,121
Europe
Segment Reporting Information [Line Items]
Revenue	2,558	2,152	2,760
Asia Pacific
Segment Reporting Information [Line Items]
Revenue	2,011	1,650	1,589
Africa Middle East
Segment Reporting Information [Line Items]
Revenue	1,655	2,617	2,426
South America
Segment Reporting Information [Line Items]
Revenue	$ 315	$ 273	$ 405