Revenue Recognition - Schedule of Revenue Recognition (Details) - 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
Disaggregation of Revenue [Line Items]
Total revenues									$ 8,244	$ 6,547	$ 6,276
Transaction-based expenses									2,208	1,345	1,297
Revenues, less transaction-based expenses	$ 1,671	$ 1,411	$ 1,395	$ 1,559	$ 1,298	$ 1,336	$ 1,298	$ 1,270	6,036	5,202	4,979
Exchanges Segment
Disaggregation of Revenue [Line Items]
Total revenues									5,839	4,652	4,573
Transaction-based expenses									2,208	1,345	1,297
Revenues, less transaction-based expenses									3,631	3,307	3,276
Fixed Income and Data Services Segment
Disaggregation of Revenue [Line Items]
Total revenues									1,810	1,756	1,681
Transaction-based expenses									0	0	0
Revenues, less transaction-based expenses									1,810	1,756	1,681
Mortgage Technology
Disaggregation of Revenue [Line Items]
Total revenues									595	139	22
Transaction-based expenses									0	0	0
Revenues, less transaction-based expenses									595	139	22
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									2,733	2,187	2,070
Services transferred at a point in time | Exchanges Segment
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									2,045	1,784	1,806
Services transferred at a point in time | Fixed Income and Data Services Segment
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									249	270	247
Services transferred at a point in time | Mortgage Technology
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									439	133	17
Services transferred over time
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									3,303	3,015	2,909
Services transferred over time | Exchanges Segment
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									1,586	1,523	1,470
Services transferred over time | Fixed Income and Data Services Segment
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									1,561	1,486	1,434
Services transferred over time | Mortgage Technology
Disaggregation of Revenue [Line Items]
Revenues, less transaction-based expenses									156	6	5
Exchanges
Disaggregation of Revenue [Line Items]
Total revenues									5,839	4,652	4,573
Exchanges | Exchanges Segment
Disaggregation of Revenue [Line Items]
Total revenues									5,839	4,652	4,573
Exchanges | Fixed Income and Data Services Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Exchanges | Mortgage Technology
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Fixed income and data services
Disaggregation of Revenue [Line Items]
Total revenues									1,810	1,756	1,681
Fixed income and data services | Exchanges Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Fixed income and data services | Fixed Income and Data Services Segment
Disaggregation of Revenue [Line Items]
Total revenues									1,810	1,756	1,681
Fixed income and data services | Mortgage Technology
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Mortgage Technology
Disaggregation of Revenue [Line Items]
Total revenues									595	139	22
Mortgage Technology | Exchanges Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Mortgage Technology | Fixed Income and Data Services Segment
Disaggregation of Revenue [Line Items]
Total revenues									0	0	0
Mortgage Technology | Mortgage Technology
Disaggregation of Revenue [Line Items]
Total revenues									$ 595	$ 139	$ 22