Segment and Related Information - Revenue Disaggregated by Type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,689	$ 1,546	$ 4,964	$ 4,721
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	414	331	1,187	1,112
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	1,275	1,215	3,777	3,609
Subscription
Disaggregation of Revenue [Line Items]
Total revenue	713	685	2,117	1,978
Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	355	347	1,043	1,058
Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	414	331	1,187	1,112
Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	153	136	464	411
Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	54	47	153	162
Operating Segments | Ratings
Disaggregation of Revenue [Line Items]
Total revenue	789	700	2,286	2,223
Operating Segments | Ratings | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	402	321	1,148	1,073
Operating Segments | Ratings | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	387	379	1,138	1,150
Operating Segments | Ratings | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Ratings | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	387	379	1,138	1,150
Operating Segments | Ratings | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	402	321	1,148	1,073
Operating Segments | Ratings | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Ratings | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue	488	466	1,457	1,355
Operating Segments | Market Intelligence | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	10	8	31	31
Operating Segments | Market Intelligence | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	478	458	1,426	1,324
Operating Segments | Market Intelligence | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	477	453	1,416	1,309
Operating Segments | Market Intelligence | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Market Intelligence | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	10	8	31	31
Operating Segments | Market Intelligence | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	1	5	10	15
Operating Segments | Market Intelligence | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Platts
Disaggregation of Revenue [Line Items]
Total revenue	212	204	632	604
Operating Segments | Platts | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	2	2	8	8
Operating Segments | Platts | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	210	202	624	596
Operating Segments | Platts | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	194	188	579	556
Operating Segments | Platts | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Platts | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	2	2	8	8
Operating Segments | Platts | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Platts | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	16	14	45	40
Operating Segments | Indices
Disaggregation of Revenue [Line Items]
Total revenue	232	203	684	621
Operating Segments | Indices | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Indices | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	232	203	684	621
Operating Segments | Indices | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	42	39	122	103
Operating Segments | Indices | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Indices | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Indices | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	152	131	454	396
Operating Segments | Indices | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	38	33	108	122
Corporate
Disaggregation of Revenue [Line Items]
Total revenue	0	5	0	10
Corporate | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Corporate | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	0	5	0	10
Corporate | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	5		10
Corporate | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Corporate | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Corporate | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Corporate | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination
Disaggregation of Revenue [Line Items]
Total revenue	(32)	(32)	(95)	(92)
Intersegment Elimination | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	(32)	(32)	(95)	(92)
Intersegment Elimination | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	(32)	(32)	(95)	(92)
Intersegment Elimination | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	$ 0	$ 0	$ 0	$ 0