Segment and Geographic Information - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,867	$ 1,846	$ 1,943	$ 1,786	$ 1,735	$ 1,689	$ 1,704	$ 1,571	$ 7,442	$ 6,699	$ 6,258
Depreciation & Amortization									206	204	206
Capital Expenditures									76	115	113
Total Assets	12,537				11,348				12,537	11,348
Assets held for sale	0				9				0	9
Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									2,039	1,632	1,401
Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									5,403	5,067	4,857
Subscription
Disaggregation of Revenue [Line Items]
Total revenue									3,036	2,843	2,682
Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue									2,039	1,632	1,401
Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue									1,492	1,401	1,408
Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue									648	623	542
Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue									227	200	225
Operating Segments
Disaggregation of Revenue [Line Items]
Depreciation & Amortization									167	162	167
Capital Expenditures									72	103	84
Total Assets	7,206				7,199				7,206	7,199
Operating Segments | Ratings
Disaggregation of Revenue [Line Items]
Total revenue									3,606	3,106	2,883
Depreciation & Amortization									40	34	32
Capital Expenditures									33	41	42
Total Assets	1,088				963				1,088	963
Operating Segments | Ratings | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									1,977	1,577	1,350
Operating Segments | Ratings | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									1,629	1,529	1,533
Operating Segments | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue									2,106	1,959	1,833
Depreciation & Amortization									101	99	99
Capital Expenditures									28	44	30
Total Assets	3,762				3,806				3,762	3,806
Operating Segments | Market Intelligence | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									55	45	40
Operating Segments | Market Intelligence | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									2,051	1,914	1,793
Operating Segments | Platts
Disaggregation of Revenue [Line Items]
Total revenue									878	844	815
Depreciation & Amortization									17	21	27
Capital Expenditures									7	13	9
Total Assets	913				938				913	938
Operating Segments | Platts | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									7	10	11
Operating Segments | Platts | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									871	834	804
Operating Segments | Indices
Disaggregation of Revenue [Line Items]
Total revenue									989	918	837
Depreciation & Amortization									9	8	9
Capital Expenditures									4	5	3
Total Assets	1,443				1,492				1,443	1,492
Operating Segments | Indices | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Indices | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									989	918	837
Operating Segments | Subscription | Ratings
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Subscription | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue									2,050	1,904	1,773
Operating Segments | Subscription | Platts
Disaggregation of Revenue [Line Items]
Total revenue									809	774	750
Operating Segments | Subscription | Indices
Disaggregation of Revenue [Line Items]
Total revenue									177	165	144
Operating Segments | Non-subscription / Transaction | Ratings
Disaggregation of Revenue [Line Items]
Total revenue									1,977	1,577	1,350
Operating Segments | Non-subscription / Transaction | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue									55	45	40
Operating Segments | Non-subscription / Transaction | Platts
Disaggregation of Revenue [Line Items]
Total revenue									7	10	11
Operating Segments | Non-subscription / Transaction | Indices
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Non-transaction | Ratings
Disaggregation of Revenue [Line Items]
Total revenue									1,629	1,529	1,533
Operating Segments | Non-transaction | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Non-transaction | Platts
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Non-transaction | Indices
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Asset-linked fees | Ratings
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Asset-linked fees | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue									1	10	20
Operating Segments | Asset-linked fees | Platts
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Asset-linked fees | Indices
Disaggregation of Revenue [Line Items]
Total revenue									647	613	522
Operating Segments | Sales usage-based royalties | Ratings
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Sales usage-based royalties | Market Intelligence
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Operating Segments | Sales usage-based royalties | Platts
Disaggregation of Revenue [Line Items]
Total revenue									62	60	54
Operating Segments | Sales usage-based royalties | Indices
Disaggregation of Revenue [Line Items]
Total revenue									165	140	171
Corporate
Disaggregation of Revenue [Line Items]
Total revenue									0	0	15
Depreciation & Amortization									39	42	39
Capital Expenditures									4	12	29
Total Assets	$ 5,331				$ 4,140				5,331	4,140
Corporate | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Corporate | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									0	0	15
Corporate | Subscription
Disaggregation of Revenue [Line Items]
Total revenue									0	0	15
Corporate | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Corporate | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Corporate | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Corporate | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Intersegment Elimination
Disaggregation of Revenue [Line Items]
Total revenue									(137)	(128)	(125)
Intersegment Elimination | Services transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Intersegment Elimination | Services transferred over time
Disaggregation of Revenue [Line Items]
Total revenue									(137)	(128)	(125)
Intersegment Elimination | Subscription
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Intersegment Elimination | Non-subscription / Transaction
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Intersegment Elimination | Non-transaction
Disaggregation of Revenue [Line Items]
Total revenue									(137)	(128)	(125)
Intersegment Elimination | Asset-linked fees
Disaggregation of Revenue [Line Items]
Total revenue									0	0	0
Intersegment Elimination | Sales usage-based royalties
Disaggregation of Revenue [Line Items]
Total revenue									$ 0	$ 0	$ 0