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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivatives not designated as hedges | Foreign exchange contracts | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	$ (45)	$ (14)	$ (19)	$ (12)
Cash Flow Hedging | Derivatives designated as hedges
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	(87)	190	(260)	335
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	(89)	197	(267)	347
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	$ 2	$ (7)	$ 7	$ (12)