Segment and Related Information - Operating Results by Segment (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 1,689	$ 1,546	$ 4,964	$ 4,721
Operating Profit	891	704	2,408	2,086
Amortization of intangibles from acquisitions	29	33	92	91
Operating Segments
Segment Reporting Information [Line Items]
Operating Profit	936	775	2,558	2,262
Operating Segments \| Ratings
Segment Reporting Information [Line Items]
Revenue	789	700	2,286	2,223
Operating Profit	472	395	1,290	1,173
Employee severance charges			11
Legal settlement expenses		73
Amortization of intangibles from acquisitions		1	2	2
Operating Segments \| Market Intelligence
Segment Reporting Information [Line Items]
Revenue	488	466	1,457	1,355
Operating Profit	171	147	462	384
Employee severance charges			1
Amortization of intangibles from acquisitions	19	19	56	55
Gain (loss) on disposal before tax	22		22
Business disposition and employee severance charges		2		2
Operating Segments \| Platts
Segment Reporting Information [Line Items]
Revenue	212	204	632	604
Operating Profit	132	98	333	285
Employee severance charges			1
Amortization of intangibles from acquisitions	2	4	9	13
Gain (loss) on disposal before tax	27		27
Operating Segments \| Indices
Segment Reporting Information [Line Items]
Revenue	232	203	684	621
Operating Profit	161	135	473	420
Amortization of intangibles from acquisitions	1	1	4	4
Corporate
Segment Reporting Information [Line Items]
Revenue	0	5	0	10
Operating Profit	(45)	(71)	(150)	(176)
Employee severance charges		7	7	7
Amortization of intangibles from acquisitions	7	8	21	17
Retention related expenses	6	11	17	23
Lease impairment		11	5	11
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue	$ (32)	$ (32)	$ (95)	$ (92)

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