Goodwill and Other Intangible Assets - Schedule of Intangible Assets and Related Accumulated Amortization (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 03, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 5,403	$ 4,853
Less accumulated amortization		(1,532)	(1,200)
Total finite-lived intangible assets, net		3,871	3,653
Total other indefinite-lived intangible assets		6,591	6,616
Total other intangible assets, net		10,462	10,269	$ 10,420
Exchange registrations, licenses and contracts with indefinite lives
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		6,253	6,243
Trade names and trademarks with indefinite lives
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		280	280
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		49	85
Other
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		9	8
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 4,406	3,923
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	15 years	3 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)	20 years	25 years
Technology
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 524	461
Technology | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		2 years 6 months
Technology | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		11 years
Trading products with finite lives
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 237	237
Useful Life (Years)		20 years
Data/databases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 150	150
Data/databases | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		4 years
Data/databases | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		10 years
Market data provider relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 11	11
Useful Life (Years)		20 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 39	38
Non-compete agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		1 year
Non-compete agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		5 years
Other
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 36	$ 33
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		1 year
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life (Years)		5 years