Segment and Related Information - Operating Results by Segment (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Segment	Jun. 30, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment			3
Segment Reporting Information [Line Items]
Revenue	$ 1,509	$ 1,482	$ 2,962	$ 2,823
Operating Profit	677	651	1,324	1,163
Amortization of intangibles	25	23	49	47
Ratings
Segment Reporting Information [Line Items]
Legal settlement			2
Insurance recoveries		34		46
Employee termination charges		6		6
Amortization of intangibles	1	1	2	3
Market and Commodities Intelligence
Segment Reporting Information [Line Items]
Employee termination charges	5		5
Amortization of intangibles	23	21	44	41
Charge to exit a leased facility	6		6
Asset write off	2		2
Non-cash acquisition and disposition-related adjustments			15
Disposition-related gain (loss)		(10)		(12)
Technology-related impairment charge				24
Indices
Segment Reporting Information [Line Items]
Amortization of intangibles	1	1	3	3
Segment reconciling items
Segment Reporting Information [Line Items]
Disposition-related gain (loss)		3		3
Operating segments
Segment Reporting Information [Line Items]
Revenue	1,509	1,482	2,962	2,823
Operating Profit	707	682	1,384	1,227
Operating segments | Ratings
Segment Reporting Information [Line Items]
Revenue	747	682	1,461	1,234
Operating Profit	397	396	773	658
Operating segments | Market and Commodities Intelligence
Segment Reporting Information [Line Items]
Revenue	606	671	1,199	1,333
Operating Profit	191	186	378	369
Operating segments | Indices
Segment Reporting Information [Line Items]
Revenue	184	153	355	304
Operating Profit	119	100	233	200
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	(28)	(24)	(53)	(48)
Operating Profit	0	0	0	0
Segment reconciling items
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Operating Profit	$ (30)	$ (31)	$ (60)	$ (64)