Segment and Related Information - Revenue Disaggregated by Type (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,571	$ 1,567
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	343	379
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	1,228	1,188
Subscription
Disaggregation of Revenue [Line Items]
Total revenue	698	637
Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	334	352
Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	343	379
Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	148	136
Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	48	63
Operating Segments | Ratings
Disaggregation of Revenue [Line Items]
Total revenue	696	748
Operating Segments | Ratings | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	331	368
Operating Segments | Ratings | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	365	380
Operating Segments | Ratings | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Ratings | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	365	380
Operating Segments | Ratings | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	331	368
Operating Segments | Ratings | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Ratings | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue	482	439
Operating Segments | Market Intelligence | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	10	9
Operating Segments | Market Intelligence | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	472	430
Operating Segments | Market Intelligence | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	467	425
Operating Segments | Market Intelligence | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Market Intelligence | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	10	9
Operating Segments | Market Intelligence | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	5	5
Operating Segments | Market Intelligence | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Platts
Disaggregation of Revenue [Line Items]
Total revenue	207	196
Operating Segments | Platts | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	2	2
Operating Segments | Platts | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	205	194
Operating Segments | Platts | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	191	181
Operating Segments | Platts | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Platts | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	2	2
Operating Segments | Platts | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Platts | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	14	13
Operating Segments | Indices
Disaggregation of Revenue [Line Items]
Total revenue	217	212
Operating Segments | Indices | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Indices | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	217	212
Operating Segments | Indices | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	40	31
Operating Segments | Indices | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Indices | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Operating Segments | Indices | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	143	131
Operating Segments | Indices | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	34	50
Intersegment Elimination
Disaggregation of Revenue [Line Items]
Total revenue	(31)	(28)
Intersegment Elimination | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Intersegment Elimination | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue	(31)	(28)
Intersegment Elimination | Subscription
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Intersegment Elimination | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue	(31)	(28)
Intersegment Elimination | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Intersegment Elimination | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue	0	0
Intersegment Elimination | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue	$ 0	$ 0