Segment Information Geographic Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 38,654	$ 35,943	$ 39,485	$ 37,718	$ 40,251	$ 38,144	$ 37,263	$ 33,900	$ 151,800	$ 149,558	$ 144,077
Long-Lived Assets	60,901				57,256				60,901	57,256	53,343
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									93,433	93,142	82,665
Long-Lived Assets	42,946				39,853				42,946	39,853	34,645
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									10,041	11,451	11,742
Long-Lived Assets	1,302				1,490				1,302	1,490	1,491
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									10,028	8,978	9,409
Long-Lived Assets	4,264				3,814				4,264	3,814	4,008
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									7,322	6,950	7,487
Long-Lived Assets	2,254				2,203				2,254	2,203	2,510
Other Geographical [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									30,976	29,037	32,774
Long-Lived Assets	$ 10,135				$ 9,896				$ 10,135	$ 9,896	$ 10,689