Revenues - Consolidated Revenue Information by Geographic Area (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 1,435	$ 1,214	$ 2,725	$ 2,356
MIS
Segment Reporting Information [Line Items]
Revenue	938	739	1,732	1,409
MA
Segment Reporting Information [Line Items]
Revenue	497	475	993	947
United States
Segment Reporting Information [Line Items]
Revenue	837	638	1,551	1,250
United States | MIS
Segment Reporting Information [Line Items]
Revenue	616	436	1,119	847
United States | MA
Segment Reporting Information [Line Items]
Revenue	221	202	432	403
EMEA
Segment Reporting Information [Line Items]
Revenue	373	362	736	695
EMEA | MIS
Segment Reporting Information [Line Items]
Revenue	183	178	354	327
EMEA | MA
Segment Reporting Information [Line Items]
Revenue	190	184	382	368
Asia-Pacific
Segment Reporting Information [Line Items]
Revenue	144	141	280	273
Asia-Pacific | MIS
Segment Reporting Information [Line Items]
Revenue	90	84	171	163
Asia-Pacific | MA
Segment Reporting Information [Line Items]
Revenue	54	57	109	110
Americas
Segment Reporting Information [Line Items]
Revenue	81	73	158	138
Americas | MIS
Segment Reporting Information [Line Items]
Revenue	49	41	88	72
Americas | MA
Segment Reporting Information [Line Items]
Revenue	32	32	70	66
Non-U.S.
Segment Reporting Information [Line Items]
Revenue	598	576	1,174	1,106
Non-U.S. | MIS
Segment Reporting Information [Line Items]
Revenue	322	303	613	562
Non-U.S. | MA
Segment Reporting Information [Line Items]
Revenue	$ 276	$ 273	$ 561	$ 544