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, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 4,853	$ 5,147
Less accumulated amortization		(1,200)	(1,220)
Total finite-lived intangible assets, net		3,653	3,927
Total other indefinite-lived intangible assets		6,616	6,493
Total other intangible assets, net		10,269	10,420	$ 10,758
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 3,923	4,063
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	15 years	3 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	20 years	25 years
Technology
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 461	438
Technology | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		2 years 6 months
Technology | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		11 years
Trading products with finite lives
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 237	237
Finite-lived intangible asset, useful life		20 years
Russell licensing rights
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 0	184
Finite-lived intangible asset, useful life		10 years
Data/databases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 150	145
Data/databases | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		4 years
Data/databases | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		10 years
Market data provider relationships
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 11	11
Finite-lived intangible asset, useful life		20 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 38	38
Non-compete agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		1 year
Non-compete agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		5 years
Other
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross		$ 33	31
Other | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		1 year
Other | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life		5 years
Exchange registrations, licenses and contracts with indefinite lives
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		$ 6,243	6,083
Trade names and trademarks with indefinite lives
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		280	294
In-process research and development
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		85	108
Other
Finite-Lived Intangible Assets [Line Items]
Total other indefinite-lived intangible assets		$ 8	$ 8