Income Taxes - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Tax Credit Carryforward [Line Items]
US income before taxes		$ 11,051	$ 11,002	$ 9,178
Deferred tax assets, net	$ 1,167	$ 1,167	$ 1,046
Effective income tax rate		18.00%	23.00%	21.00%
Recognized tax benefit	176
Non-recurring, non-cash tax expense related to the remeasurement of UK deferred tax liabilities		$ 1,000		$ 329
Effective income tax rate reconciliation, recognized tax benefit		0	$ 255	0
Income taxes receivable included in prepaid and other current assets	190	190	83
Income taxes payable included in accrued taxes as part of accrued liabilities	365	365	325
Accrued income taxes included in other long-term liabilities	2,300	2,300	2,400
Increase (decrease) in Singapore tax as a result of the tax incentive agreement		$ (362)	$ (273)	$ (280)
Benefit of the tax incentive agreement on diluted net income per share (in dollars per share)		$ 0.17	$ 0.12	$ 0.13
Total unrecognized tax benefits exclusive of interest and penalties	2,683	$ 2,683	$ 2,488	$ 2,579	$ 2,234
Unrecognized tax benefits, if recognized, would reduce the effective tax rate in a future period	1,300	1,300	1,300	1,600
Interest expense included in interest expense and administrative and other		15	1	68
Accrued penalties related to uncertain tax positions	31	31	3	4
Accrued interest related to uncertain tax positions in other long term liabilities	238	238	233
Accrued penalties related to uncertain tax positions in other long term liabilities	3	3	34
Foreign Country
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	517	517
Other Assets
Tax Credit Carryforward [Line Items]
Deferred tax assets, net	87	87	80
Non-current income tax receivable	$ 1,000	1,000	974
Non United States Customers
Tax Credit Carryforward [Line Items]
US income before taxes		$ 3,600	$ 3,100	$ 3,000