Acquisitions and Divestitures (Acquisitions) (Narrative) (Details) company in Thousands, $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 01, 2015 USD ($) sector	Mar. 31, 2014 country company	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Amortization of intangibles			$ 17	$ 12	$ 40	$ 36
Minimum Number of Companies Represented in Broad Market Indices | company		11
Minimum Number of Countries Represented in Broad Market Indices | country		52
Contingent consideration payment					5	$ 11
SNL Financial LC [Member]
Business Acquisition [Line Items]
Consideration transfered	$ 2,225
Number of sectors in global economy that acquiree serves | sector	5
Acquisition-related expenses			32		32
Amortization of intangibles			$ 4		$ 4
SNL Financial LC [Member] | Minimum [Member]
Business Acquisition [Line Items]
Useful life of intangible assets	10 years
SNL Financial LC [Member] | Maximum [Member]
Business Acquisition [Line Items]
Useful life of intangible assets	18 years
Scenario, Forecast [Member] | SNL Financial LC [Member]
Business Acquisition [Line Items]
Amortization expense, year one							$ 53
Amortization expense, year two							53
Amortization expense, year three							53
Amortization expense, year four							53
Amortization expense, year five							$ 53