Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,930	$ 1,663	$ 6,011	$ 4,880
Interest rates and other financial futures and options contracts
Disaggregation of Revenue [Line Items]
Total revenues	1,155	929	3,726	2,698
Trading and Clearing Segment
Disaggregation of Revenue [Line Items]
Total revenues	1,230	996	3,950	2,892
Trading and Clearing Segment | Interest rates and other financial futures and options contracts
Disaggregation of Revenue [Line Items]
Total revenues	1,155	929	3,726	2,698
Trading and Clearing Segment | Interest rates and other financial futures and options contracts | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	$ 57	$ 66	$ 209	$ 188