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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivatives not designated as hedges | Foreign exchange contracts | Cost of services/sales
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income (Loss)	$ 4	$ 1	$ 32	$ 7
Fair Value Hedging | Derivatives designated as hedges | Cross currency swap | Interest expense
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income (Loss)	(39)	$ 29	(12)	$ 47
Cash Flow Hedging | Derivatives designated as hedges
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income (Loss)	37		60
Cash Flow Hedging | Derivatives designated as hedges | Cross currency swap | Interest expense
Derivative Instruments Gain Loss [Line Items]
Gain (Loss) Recognized in Income (Loss)	36		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 (Loss)	$ 1		$ 5