Segment Information (details) - Enterprise-Wide Disclosures - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues based on location
Benchmark percentage of revenue transactions from a single customer									10.00%	10.00%	10.00%
Total revenues	$ 6,674	$ 6,794	$ 6,706	$ 6,626	$ 6,783	$ 6,886	$ 6,785	$ 6,708	$ 26,800	$ 27,162	$ 26,191
U.S. [Member]
Revenues based on location
Total revenues									25,112	25,091	25,138
Non-U.S. [Member]
Revenues based on location
Total revenues									1,688	2,071	1,053
Canada [Member]
Revenues based on location
Total revenues									1,202	1,474	529
Other Non-U.S. [Member]
Revenues based on location
Total revenues									$ 486	$ 597	$ 524