Segment And Geographic Information (Geographic Information) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Information
Revenues	$ 17,978	$ 15,126	$ 16,281	$ 14,970	$ 16,329	$ 16,726	$ 16,297	$ 15,304	$ 64,355	$ 64,656	$ 64,341
Long-Lived Assets	9,951				10,106				9,951	10,106
UNITED STATES
Segment Information
Revenues									25,986	27,509	28,726
Long-Lived Assets	6,329				6,488				6,329	6,488
Switzerland [Member]
Segment Information
Revenues									13,819	13,016	12,911
CAYMAN ISLANDS
Segment Information
Revenues									3,958	4,374	5,724
GERMANY
Segment Information
Revenues									1,979	2,026	2,179
BRAZIL
Segment Information
Revenues									2,357	2,381	1,702
Long-Lived Assets	781				869				781	869
Other Foreign [Member]
Segment Information
Revenues									14,012	13,282	11,472
Long-Lived Assets	$ 2,841				$ 2,749				2,841	2,749
MEXICO
Segment Information
Revenues									$ 2,244	$ 2,068	$ 1,627