Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Dec. 29, 2017
Income Tax [Line Items]
Federal statutory tax rate	24.50%	35.00%	35.00%
EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRateNew	21.00%
Other Tax Expense (Benefit)	$ 640
ExpectedDeferredTaxAssetLiabilityReversalRate	21.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 182
OtherTaxExpenseBenefitTransitionTax	$ 822
TransitionTaxPayableAcquiree				$ 175
Transition Tax, Annual Percentage Payable	8.00%
TransitionTaxEstimatedToBePayable	$ 1,000
OtherTaxExpenseBenefitRelatedtoHistoricUnremittedForeignEarnings	134
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	632	$ 415	$ 478
Unrecognized tax benefits interest and penalties reflected in current year	20	57	(38)
Tax reductions related to tax holidays	$ 101	$ 144	$ 121
Income Tax Holiday, Income Tax Benefits Per Share	$ 0.38	$ 0.64	$ 0.56
Income taxes paid, net	$ 235	$ 265	$ 218
Deferred Income Taxes and Other
Income Tax [Line Items]
Indemnification liability, non-current	$ 140

The annual statutory tax rate effective upon new U.S. tax legislation.

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Tax rate expected to apply to the reversal of certain deferred tax assets and liabilities,

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Income Tax.

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Indemnification Liability, Non-current

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OtherTaxExpenseBenefitRelatedtoHistoricUnremittedForeignEarnings

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Amount of other income tax expense attributable to one-time transition tax.

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Transition Tax, Annual Percentage Payable

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The amount of one-time transition tax that is currently estimated to be payable.

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Income tax payable attributable to acquiree's one-time transition tax.

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

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Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

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The amount of income taxes from which a reporting entity is exempt or for which it will receive a reduction in income taxes as a result of the income tax holiday granted by the taxing jurisdiction.

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Per share amount effect of the income tax benefit resulting from the income tax holidays granted by taxing jurisdictions.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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Amount of other income tax expense (benefit).

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Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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