Derivative Instruments and Hedging Activities - Effect of Derivative Instruments Designated as Fair Value and Cash Flow Hedges and Not Designated as Hedges on Consolidated Statement of Income (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivatives not designated as hedges | Foreign exchange contracts | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	$ (14)	$ 4	$ (8)	$ 32
Fair Value Hedging | Derivatives designated as hedges | Cross currency swaps | Interest expense
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income		(39)		(12)
Cash Flow Hedging | Derivatives designated as hedges
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	(24)	37	(42)	60
Cash Flow Hedging | Derivatives designated as hedges | Cross currency swaps | Interest expense
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	(22)	36	(38)	55
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)	$ 1	$ (4)	$ 5