Information about Segments and Geographic Areas (Revenues by Geographic Area) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 17,258	$ 15,420
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	7,388	6,656
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	1,675	1,583
Rest of the world
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 8,195	$ 7,181