Revenue Recognition - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) obligation	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Number of performance obligations | obligation	2
Number of performance obligations related to trade execution | obligation	1
Rebates	$ 860	$ 844	$ 749
Total revenues	6,547	6,276	5,843
Transaction and clearing, net
Disaggregation of Revenue [Line Items]
Total revenues	3,627	3,483	3,131
Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	3,887	3,717	3,333
Services transferred over time | Trading and Clearing Segment | Transaction and clearing, net
Disaggregation of Revenue [Line Items]
Total revenues	$ 247	$ 248	$ 226