Acquisitions and Divestitures - Purchase Price Allocation (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 01, 2015
Business Acquisition [Line Items]
Goodwill	$ 2,989	$ 2,949	$ 2,882
SNL Financial LC
Business Acquisition [Line Items]
Current assets				$ 29
Property, plant and equipment				19
Goodwill				1,574
Other intangible assets, net				772
Other non-current assets				1
Total assets acquired				2,395
Current liabilities				(43)
Unearned revenue				(117)
Other non-current liabilities				(1)
Total liabilities acquired				(161)
Net assets acquired				2,234
SNL Financial LC | Databases and software
Business Acquisition [Line Items]
Other intangible assets, net				421
SNL Financial LC | Customer relationships
Business Acquisition [Line Items]
Other intangible assets, net				162
SNL Financial LC | Tradenames
Business Acquisition [Line Items]
Other intangible assets, net				185
SNL Financial LC | Other intangibles
Business Acquisition [Line Items]
Other intangible assets, net				$ 4