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
	Mar. 31, 2019	Mar. 31, 2018
Derivatives not designated as hedges | Foreign exchange contracts | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	$ 6	$ 28
Fair Value Hedging | Derivatives designated as hedges | Cross currency swaps | Interest expense
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income		27
Cash Flow Hedging | Derivatives designated as hedges
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	(18)	23
Cash Flow Hedging | Derivatives designated as hedges | Cross currency swaps | Interest expense
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income	(16)	19
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)	$ 4