Segment Information (Details) - Enterprise-Wide Disclosures - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues based on location
Benchmark percentage of revenue transactions from a single customer									10.00%	10.00%	10.00%
Total revenues	$ 8,063	$ 8,013	$ 7,834	$ 7,671	$ 7,796	$ 7,723	$ 7,477	$ 7,286	$ 31,581	$ 30,282	$ 28,902
United States [Member]
Revenues based on location
Total revenues									29,638	28,418	27,253
Non-U.S. [Member]
Revenues based on location
Total revenues									1,943	1,864	1,649
Canada [Member]
Revenues based on location
Total revenues									1,371	1,293	1,232
Other Non-U.S. [Member]
Revenues based on location
Total revenues									$ 572	$ 571	$ 417