Segment and Related Information - Operating Results by Segment (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) Segment	Sep. 30, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment			3
Segment Reporting Information [Line Items]
Revenue	$ 1,513	$ 1,439	$ 4,475	$ 4,262
Operating Profit	658	1,348	1,982	2,512
Amortization of intangibles	24	23	73	71
Gain on sale of business	0	722	0	722
Ratings
Segment Reporting Information [Line Items]
Employee termination charges	15		15	6
Legal settlement			2
Insurance recoveries		17		63
Amortization of intangibles	1	1	3	4
Market and Commodities Intelligence
Segment Reporting Information [Line Items]
Employee termination charges			5
Amortization of intangibles	22	21	66	63
Charge to exit a leased facility			6
Asset write off			2
Non-cash acquisition and disposition-related adjustments			15
Disposition-related gain (loss)		(6)		(17)
Acquisition related costs		1		1
Gain on sale of business		722		722
Technology-related impairment charge				24
Indices
Segment Reporting Information [Line Items]
Amortization of intangibles	1	1	4	4
Operating segments
Segment Reporting Information [Line Items]
Revenue	1,513	1,439	4,475	4,262
Operating Profit	703	1,377	2,087	2,605
Operating segments | Ratings
Segment Reporting Information [Line Items]
Revenue	739	642	2,199	1,877
Operating Profit	376	346	1,149	1,004
Operating segments | Market and Commodities Intelligence
Segment Reporting Information [Line Items]
Revenue	615	658	1,815	1,990
Operating Profit	208	924	586	1,293
Operating segments | Indices
Segment Reporting Information [Line Items]
Revenue	187	164	542	468
Operating Profit	119	107	352	308
Intersegment eliminations
Segment Reporting Information [Line Items]
Revenue	(28)	(25)	(81)	(73)
Operating Profit	0	0	0	0
Segment reconciling items
Segment Reporting Information [Line Items]
Revenue	0	0	0	0
Operating Profit	(45)	(29)	(105)	$ (93)
Employee termination charges	$ 4		$ 4
Disposition-related gain (loss)		$ 3