Revenues - Schedule of Changes in the Deferred Revenue Balances (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Change in Contract with Customer, Liability [Abstract]
Beginning Balance	$ 1,328	$ 1,222	$ 1,187	$ 1,162
Revenue recognized that was included in the deferred revenue balance at the beginning of the period	(457)	(456)	(727)	(745)
Increases due to amounts billable excluding amounts recognized as revenue during the period	360	334	774	691
Increases due to acquisitions during the period			4	20
Effect of exchange rate changes	4	5	(3)	(23)
Total changes in deferred revenue	(93)	(117)	48	(57)
Ending Balance	1,235	1,105	1,235	1,105
Deferred revenue - current	1,142	1,001	1,142	1,001	$ 1,089
Deferred revenue - noncurrent	93	104	93	104	$ 98
MIS
Change in Contract with Customer, Liability [Abstract]
Beginning Balance	388	379	313	322
Revenue recognized that was included in the deferred revenue balance at the beginning of the period	(119)	(115)	(162)	(167)
Increases due to amounts billable excluding amounts recognized as revenue during the period	98	100	219	213
Increases due to acquisitions during the period			0	0
Effect of exchange rate changes	1	1	(2)	(3)
Total changes in deferred revenue	(20)	(14)	55	43
Ending Balance	368	365	368	365
Deferred revenue - current	279	265	279	265
Deferred revenue - noncurrent	89	100	89	100
Decrease due to change in recognition of contract renewals				99
MA
Change in Contract with Customer, Liability [Abstract]
Beginning Balance	940	843	874	840
Revenue recognized that was included in the deferred revenue balance at the beginning of the period	(338)	(341)	(565)	(578)
Increases due to amounts billable excluding amounts recognized as revenue during the period	262	234	555	478
Increases due to acquisitions during the period			4	20
Effect of exchange rate changes	3	4	(1)	(20)
Total changes in deferred revenue	(73)	(103)	(7)	(100)
Ending Balance	867	740	867	740
Deferred revenue - current	863	736	863	736
Deferred revenue - noncurrent	$ 4	$ 4	$ 4	4
Decrease due to change in recognition of contract renewals				$ 99