Nature of Operations and Basis of Presentation - Revenue Disaggregated by Revenue Type (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 1,567	$ 1,453
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	(28)	(25)
Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	748	714
Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	437	402
Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	196	191
Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	214	171
Subscription
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	638	588
Subscription | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Subscription | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Subscription | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	424	385
Subscription | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	181	172
Subscription | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	33	31
Non-transaction
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	352	316
Non-transaction | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	(28)	(25)
Non-transaction | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	380	341
Non-transaction | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Non-transaction | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Non-transaction | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Non-subscription / Transaction
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	378	387
Non-subscription / Transaction | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Non-subscription / Transaction | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	368	373
Non-subscription / Transaction | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	8	11
Non-subscription / Transaction | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	2	3
Non-subscription / Transaction | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Asset-linked fees
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	136	114
Asset-linked fees | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Asset-linked fees | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Asset-linked fees | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	5	6
Asset-linked fees | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Asset-linked fees | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	131	108
Sales usage-based royalties
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	63	48
Sales usage-based royalties | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Sales usage-based royalties | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Sales usage-based royalties | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Sales usage-based royalties | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	13	16
Sales usage-based royalties | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	50	32
Transferred at Point in Time
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	378	387
Transferred at Point in Time | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Transferred at Point in Time | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	368	373
Transferred at Point in Time | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	8	11
Transferred at Point in Time | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	2	3
Transferred at Point in Time | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	0	0
Transferred over Time
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	1,189	1,066
Transferred over Time | Intersegment Elimination
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	(28)	(25)
Transferred over Time | Ratings | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	380	341
Transferred over Time | Market Intelligence | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	429	391
Transferred over Time | Platts | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	194	188
Transferred over Time | Indices | Operating Segments
Segment Reporting Information [Line Items]
Revenue from contract with customer, excluding assessed tax	$ 214	$ 171