Revenues - Consolidated Revenue Information by Geographic Area (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenue	$ 1,553	$ 1,435	$ 3,153	$ 2,725
MIS
Segment Reporting Information [Line Items]
Revenue	980	938	2,016	1,732
MA
Segment Reporting Information [Line Items]
Revenue	573	497	1,137	993
United States
Segment Reporting Information [Line Items]
Revenue	831	837	1,716	1,551
United States | MIS
Segment Reporting Information [Line Items]
Revenue	582	616	1,229	1,119
United States | MA
Segment Reporting Information [Line Items]
Revenue	249	221	487	432
Non-U.S.
Segment Reporting Information [Line Items]
Revenue	722	598	1,437	1,174
Non-U.S. | MIS
Segment Reporting Information [Line Items]
Revenue	398	322	787	613
Non-U.S. | MA
Segment Reporting Information [Line Items]
Revenue	324	276	650	561
EMEA
Segment Reporting Information [Line Items]
Revenue	481	373	959	736
EMEA | MIS
Segment Reporting Information [Line Items]
Revenue	248	183	496	354
EMEA | MA
Segment Reporting Information [Line Items]
Revenue	233	190	463	382
Asia-Pacific
Segment Reporting Information [Line Items]
Revenue	155	144	311	280
Asia-Pacific | MIS
Segment Reporting Information [Line Items]
Revenue	100	90	197	171
Asia-Pacific | MA
Segment Reporting Information [Line Items]
Revenue	55	54	114	109
Americas
Segment Reporting Information [Line Items]
Revenue	86	81	167	158
Americas | MIS
Segment Reporting Information [Line Items]
Revenue	50	49	94	88
Americas | MA
Segment Reporting Information [Line Items]
Revenue	$ 36	$ 32	$ 73	$ 70