Segment and Related Information - Revenue Disaggregated by Type (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,846	$ 1,689	$ 5,575	$ 4,964
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	505	414	1,589	1,187
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	1,341	1,275	3,986	3,777
Subscription
Disaggregation of Revenue [Line Items]
Total revenue	765	713	2,260	2,117
Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	505	414	1,589	1,187
Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	370	355	1,077	1,043
Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	156	153	469	464
Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	50	54	180	153
Operating Segments | Ratings
Disaggregation of Revenue [Line Items]
Total revenue	894	789	2,725	2,286
Operating Segments | Ratings | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	490	402	1,546	1,148
Operating Segments | Ratings | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	404	387	1,179	1,138
Operating Segments | Ratings | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Ratings | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	490	402	1,546	1,148
Operating Segments | Ratings | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	404	387	1,179	1,138
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	530	488	1,565	1,457
Operating Segments | Market Intelligence | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	13	10	39	31
Operating Segments | Market Intelligence | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	517	478	1,526	1,426
Operating Segments | Market Intelligence | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	517	477	1,525	1,416
Operating Segments | Market Intelligence | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	13	10	39	31
Operating Segments | Market Intelligence | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Market Intelligence | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	1	1	10
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	222	212	654	632
Operating Segments | Platts | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	2	2	4	8
Operating Segments | Platts | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	220	210	650	624
Operating Segments | Platts | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	205	194	603	579
Operating Segments | Platts | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	2	2	4	8
Operating Segments | Platts | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
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	15	16	47	45
Operating Segments | Indices
Disaggregation of Revenue [Line Items]
Total revenue	234	232	733	684
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	234	232	733	684
Operating Segments | Indices | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	43	42	132	122
Operating Segments | Indices | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Operating Segments | Indices | Non-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	156	152	468	454
Operating Segments | Indices | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	35	38	133	108
Intersegment Elimination
Disaggregation of Revenue [Line Items]
Total revenue	(34)	(32)	(102)	(95)
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	(34)	(32)	(102)	(95)
Intersegment Elimination | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0	0	0
Intersegment Elimination | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	(34)	(32)	(102)	(95)
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