Derivative Instruments (Effect of Derivative Instruments Designated as Cash Flow Hedges on Other Comprehensive Income and Consolidated Statements of Operations Summary) (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 27, 2018	Oct. 28, 2017
Derivatives designated as cash flow hedging instruments:
Derivative [Line Items]
GAINS (LOSSES) RECOGNIZED IN OCI ON DERIVATIVES (EFFECTIVE PORTION)	$ (4)	$ 8
GAINS (LOSSES) RECLASSIFIED FROM AOCI INTO INCOME (EFFECTIVE PORTION)	0	13
Derivatives designated as cash flow hedging instruments: | Foreign currency derivatives
Derivative [Line Items]
GAINS (LOSSES) RECOGNIZED IN OCI ON DERIVATIVES (EFFECTIVE PORTION)	(4)	8
Derivatives designated as cash flow hedging instruments: | Foreign currency derivatives | Revenue — service | Service
Derivative [Line Items]
GAINS (LOSSES) RECLASSIFIED FROM AOCI INTO INCOME (EFFECTIVE PORTION)	1	0
Derivatives designated as cash flow hedging instruments: | Foreign currency derivatives | Operating expenses
Derivative [Line Items]
GAINS (LOSSES) RECLASSIFIED FROM AOCI INTO INCOME (EFFECTIVE PORTION)	(1)	10
Derivatives designated as cash flow hedging instruments: | Foreign currency derivatives | Cost of sales | Service
Derivative [Line Items]
GAINS (LOSSES) RECLASSIFIED FROM AOCI INTO INCOME (EFFECTIVE PORTION)	0	3
Derivatives designated as net investment hedging instruments: | Foreign currency derivatives
Derivative [Line Items]
GAINS (LOSSES) RECOGNIZED IN OCI ON DERIVATIVES (EFFECTIVE PORTION)	4	(5)
Derivatives designated as net investment hedging instruments: | Foreign currency derivatives | Other income (loss), net
Derivative [Line Items]
GAINS (LOSSES) RECLASSIFIED FROM AOCI INTO INCOME (EFFECTIVE PORTION)	$ 0	$ 0