Revenues - Transaction and Relationship Revenue (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 1,522	$ 1,600
Percentage of Revenues	100.00%	100.00%
MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 827	$ 1,036
Percentage of Revenues	100.00%	100.00%
MA
Disaggregation of Revenue [Line Items]
Revenue	$ 695	$ 564
Percentage of Revenues	100.00%	100.00%
Corporate Finance (CFG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 417	$ 605
Percentage of Revenues	100.00%	100.00%
Structured Finance (SFG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 144	$ 116
Percentage of Revenues	100.00%	100.00%
Financial Institutions (FIG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 131	$ 162
Percentage of Revenues	100.00%	100.00%
Public, Project And Infrastructure Finance (PPIF) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 123	$ 143
Percentage of Revenues	100.00%	100.00%
MIS Other | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 12	$ 10
Percentage of Revenues	100.00%	100.00%
Decision Solutions | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 334	$ 225
Percentage of Revenues	100.00%	100.00%
Research and Insights | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 183	$ 171
Percentage of Revenues	100.00%	100.00%
Data and Information | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 178	$ 168
Percentage of Revenues	100.00%	100.00%
Transaction Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 573	$ 788
Percentage of Revenues	38.00%	49.00%
Transaction Revenue | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 529	$ 745
Percentage of Revenues	64.00%	72.00%
Transaction Revenue | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 44	$ 43
Percentage of Revenues	6.00%	8.00%
Transaction Revenue | Corporate Finance (CFG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 293	$ 487
Percentage of Revenues	70.00%	80.00%
Transaction Revenue | Structured Finance (SFG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 93	$ 66
Percentage of Revenues	65.00%	57.00%
Transaction Revenue | Financial Institutions (FIG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 61	$ 90
Percentage of Revenues	47.00%	56.00%
Transaction Revenue | Public, Project And Infrastructure Finance (PPIF) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 79	$ 100
Percentage of Revenues	64.00%	70.00%
Transaction Revenue | MIS Other | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 3	$ 2
Percentage of Revenues	25.00%	20.00%
Transaction Revenue | Decision Solutions | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 43	$ 41
Percentage of Revenues	13.00%	18.00%
Transaction Revenue | Research and Insights | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 1	$ 1
Percentage of Revenues	1.00%	1.00%
Transaction Revenue | Data and Information | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 1
Percentage of Revenues	0.00%	1.00%
Recurring Revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 949	$ 812
Percentage of Revenues	62.00%	51.00%
Recurring Revenue | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 298	$ 291
Percentage of Revenues	36.00%	28.00%
Recurring Revenue | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 651	$ 521
Percentage of Revenues	94.00%	92.00%
Recurring Revenue | Corporate Finance (CFG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 124	$ 118
Percentage of Revenues	30.00%	20.00%
Recurring Revenue | Structured Finance (SFG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 51	$ 50
Percentage of Revenues	35.00%	43.00%
Recurring Revenue | Financial Institutions (FIG) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 70	$ 72
Percentage of Revenues	53.00%	44.00%
Recurring Revenue | Public, Project And Infrastructure Finance (PPIF) | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 44	$ 43
Percentage of Revenues	36.00%	30.00%
Recurring Revenue | MIS Other | MIS
Disaggregation of Revenue [Line Items]
Revenue	$ 9	$ 8
Percentage of Revenues	75.00%	80.00%
Recurring Revenue | Decision Solutions | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 291	$ 184
Percentage of Revenues	87.00%	82.00%
Recurring Revenue | Research and Insights | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 182	$ 170
Percentage of Revenues	99.00%	99.00%
Recurring Revenue | Data and Information | MA
Disaggregation of Revenue [Line Items]
Revenue	$ 178	$ 167
Percentage of Revenues	100.00%	99.00%