Segment Information (details) - Enterprise-Wide Disclosures (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues based on location
Total revenues	$ 6,783	$ 6,886	$ 6,785	$ 6,708	$ 6,737	$ 6,452	$ 6,674	$ 6,328	$ 27,162	$ 26,191	$ 25,740
Customer Concentration Risk [Member] | Total Revenues [Member] | Minimum [Member]
Revenues based on location
Benchmark percentage of revenue transactions from a single customer									10.00%	10.00%	10.00%
U.S. [Member]
Revenues based on location
Total revenues									25,091	25,138	24,827
Non-U.S. [Member]
Revenues based on location
Total revenues									2,071	1,053	913
Canada [Member]
Revenues based on location
Total revenues									1,474	529	349
Other Non-U.S. [Member]
Revenues based on location
Total revenues									$ 597	$ 524	$ 564