Segment Information (Details) - Enterprise-Wide Disclosures - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues based on location
Benchmark percentage of revenue transactions from a single customer									10.00%	10.00%	10.00%
Total revenues	$ 8,397	$ 8,275	$ 7,401	$ 7,908	$ 8,063	$ 8,013	$ 7,834	$ 7,671	$ 31,981	$ 31,581	$ 30,282
United States [Member]
Revenues based on location
Total revenues									30,123	29,638	28,418
Non-U.S. [Member]
Revenues based on location
Total revenues									1,858	1,943	1,864
Canada [Member]
Revenues based on location
Total revenues									1,278	1,371	1,293
Other Non-U.S. [Member]
Revenues based on location
Total revenues									$ 580	$ 572	$ 571