Segment and Related Information - Operating Results by Segment (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 1,546	$ 1,513	$ 4,721	$ 4,475
Operating Profit	704	649	2,086	1,956
Amortization of intangibles	33	24	91	73
Ratings
Segment Reporting Information [Line Items]
Legal settlement			73	2
Employee severance charges		15		15
Amortization of intangibles	1	1	2	3
Market Intelligence
Segment Reporting Information [Line Items]
Employee severance charges			2	4
Amortization of intangibles	18	17	54	52
Business disposition and employee severance charges	2
Non-cash acquisition and retention related adjustments				4
Platts
Segment Reporting Information [Line Items]
Employee severance charges				1
Amortization of intangibles	4	5	13	13
Non-cash acquisition and retention related adjustments				11
Business exit costs				6
Asset impairment charges				2
Indices
Segment Reporting Information [Line Items]
Amortization of intangibles	2	1	5	4
Operating Segments
Segment Reporting Information [Line Items]
Operating Profit	775	701	2,262	2,080
Operating Segments \| Ratings
Segment Reporting Information [Line Items]
Revenue	700	739	2,223	2,199
Operating Profit	395	375	1,173	1,144
Operating Segments \| Market Intelligence
Segment Reporting Information [Line Items]
Revenue	464	422	1,349	1,238
Operating Profit	148	123	388	339
Operating Segments \| Platts
Segment Reporting Information [Line Items]
Revenue	204	193	604	577
Operating Profit	98	84	285	245
Operating Segments \| Indices
Segment Reporting Information [Line Items]
Revenue	205	187	627	542
Operating Profit	134	119	416	352
Corporate
Segment Reporting Information [Line Items]
Revenue	5	0	10	0
Operating Profit	(71)	(52)	(176)	(124)
Amortization of intangibles	8		17
Non-cash acquisition and retention related adjustments	11		23
Asset impairment charges	11		11
Restructuring charges	7	4	7	4
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue	$ (32)	$ (28)	$ (92)	$ (81)

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