Derivative Instruments and Hedging Activities - Effect of Derivative Instruments Designated as Cash Flow Hedges and Not Designated as Hedges on Consolidated Statement of Income (Loss) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivatives not designated as hedges | Foreign exchange contracts | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	$ (14)		$ (12)	$ (8)
Cash Flow Hedging | Derivatives designated as hedges
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	190	$ (5)	335	(47)
Cash Flow Hedging | Derivatives designated as hedges | Foreign exchange contracts | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	(7)	(3)	(12)	(7)
Cash Flow Hedging | Derivatives designated as hedges | Cross currency swaps | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	$ 197	$ (2)	$ 347	$ (40)