Income Taxes - Differences between income taxes calculated using the federal statutory income tax rate and the provision for income taxes from continuing operations (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Jul. 31, 2019	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Operating Loss Carryforwards [Line Items]
Income before income taxes		$ 1,881	$ 1,566	$ 1,390
U.S. federal statutory rate		21.00%	26.90%	35.00%
Statutory federal income tax		$ 395	$ 420	$ 486
State income tax, net of federal benefit		50	29	24
Federal research and experimentation credits		(48)	(38)	(24)
Domestic production activities deduction		0	(28)	(34)
Share-based compensation		15	11	14
Federal excess tax benefits related to share-based compensation		120	100	72
2017 Tax Act - Deferred tax re-measurement		0	(29)	0
Capital loss on subsidiary reorganization	$ (35)	0	(35)	0
Effects of non-U.S. operations		13	1	6
Other, net		5	0	2
Total provision for income taxes		$ 324	$ 237	$ 405

Effective Income Tax Rate Reconciliation, Capital Loss On Reorganization

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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