Segment And Geographic Information (Geographic Information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 15,947	$ 15,800	$ 17,068	$ 15,526	$ 16,070	$ 14,827	$ 14,943	$ 14,988	$ 64,341	$ 60,828	$ 62,346
Long-Lived Assets	9,953				10,138				9,953	10,138
UNITED STATES
Segment Reporting Information [Line Items]
Revenues									28,726	27,894	29,419
Long-Lived Assets	6,615				6,767				6,615	6,767
BRAZIL
Segment Reporting Information [Line Items]
Long-Lived Assets	802				731				802	731
Switzerland [Member]
Segment Reporting Information [Line Items]
Revenues									12,911	14,095	13,413
CAYMAN ISLANDS
Segment Reporting Information [Line Items]
Revenues									5,724	4,189	3,617
GERMANY
Segment Reporting Information [Line Items]
Revenues									2,179	2,090	2,341
Other Foreign [Member]
Segment Reporting Information [Line Items]
Revenues									14,801	12,560	$ 13,556
Long-Lived Assets	$ 2,536				$ 2,640				$ 2,536	$ 2,640