Information about Segments and Geographic Areas (Revenues by Geographic Area) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 18,675	$ 16,523	$ 53,660	$ 47,898
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	8,748	7,324	24,517	21,177
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	1,792	1,627	5,145	4,826
Rest of the world
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 8,135	$ 7,572	$ 23,998	$ 21,895