Revenues - Schedule of Changes in the Deferred Revenue Balances (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Change in Contract with Customer, Liability [Abstract]
Beginning Balance	$ 1,105	$ 1,071	$ 1,162	$ 1,076
Revenue recognized that was included in the deferred revenue balance at the beginning of the period	(465)	(455)	(988)	(878)
Increases due to amounts billable excluding amounts recognized as revenue during the period	356	372	826	788
Increases due to RDC acquisition during the period			20
Amount included in liabilities reclassified as held for sale				(3)
Effect of exchange rate changes	24	(17)	0	(12)
Total changes in deferred revenue	(85)	(100)	(142)	(105)
Ending Balance	1,020	971	1,020	971
Deferred revenue - current	918	856	918	856	$ 1,050
Deferred revenue - noncurrent	102	115	102	115	$ 112
MIS
Change in Contract with Customer, Liability [Abstract]
Beginning Balance	365	376	322	326
Revenue recognized that was included in the deferred revenue balance at the beginning of the period	(118)	(111)	(207)	(191)
Increases due to amounts billable excluding amounts recognized as revenue during the period	83	82	219	212
Increases due to RDC acquisition during the period			0
Amount included in liabilities reclassified as held for sale				0
Effect of exchange rate changes	5	(3)	1	(3)
Total changes in deferred revenue	(30)	(32)	13	18
Ending Balance	335	344	335	344
Deferred revenue - current	237	234	237	234
Deferred revenue - noncurrent	98	110	98	110
MA
Change in Contract with Customer, Liability [Abstract]
Beginning Balance	740	695	840	750
Revenue recognized that was included in the deferred revenue balance at the beginning of the period	(347)	(344)	(781)	(687)
Increases due to amounts billable excluding amounts recognized as revenue during the period	273	290	607	576
Increases due to RDC acquisition during the period			20
Amount included in liabilities reclassified as held for sale				(3)
Effect of exchange rate changes	19	(14)	(1)	(9)
Total changes in deferred revenue	(55)	(68)	(155)	(123)
Ending Balance	685	627	685	627
Deferred revenue - current	681	622	681	622
Deferred revenue - noncurrent	$ 4	$ 5	$ 4	$ 5