Segment and Related Information - Operating Results by Segment (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 1,609	$ 1,509	$ 3,176	$ 2,962
Operating Profit	672	668	1,383	1,306
Amortization of intangibles	33	25	57	49
Ratings
Segment Reporting Information [Line Items]
Legal settlement	73		73	2
Amortization of intangibles	1	1	1	2
Market Intelligence
Segment Reporting Information [Line Items]
Amortization of intangibles	18	18	36	35
Employee severance charges		4		4
Non-cash acquisition and disposition-related adjustments				4
Platts
Segment Reporting Information [Line Items]
Amortization of intangibles	4	5	9	9
Business exit costs		6		6
Asset impairment charges		2		2
Employee severance charges		1		1
Non-cash acquisition and disposition-related adjustments				11
Indices
Segment Reporting Information [Line Items]
Amortization of intangibles	2	1	3	3
Operating Segments
Segment Reporting Information [Line Items]
Operating Profit	731	704	1,488	1,378
Operating Segments \| Ratings
Segment Reporting Information [Line Items]
Revenue	775	747	1,523	1,461
Operating Profit	369	395	777	769
Operating Segments \| Market Intelligence
Segment Reporting Information [Line Items]
Revenue	447	414	884	816
Operating Profit	128	112	240	216
Operating Segments \| Platts
Segment Reporting Information [Line Items]
Revenue	205	192	401	383
Operating Profit	98	78	188	160
Operating Segments \| Indices
Segment Reporting Information [Line Items]
Revenue	209	184	423	355
Operating Profit	136	119	283	233
Corporate
Segment Reporting Information [Line Items]
Revenue	5	0	5	0
Operating Profit	(59)	(36)	(105)	(72)
Amortization of intangibles	8		8
Non-cash acquisition and disposition-related adjustments	12		12
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue	$ (32)	$ (28)	$ (60)	$ (53)

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