Income Taxes Deferred Taxes Classified in Consolidated Statements of Financial Position (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Deferred Taxes [Line Items]
Deferred Tax Assets, Net of Valuation Allowance	$ 1,768	$ 2,245
Deferred Tax Liabilities, Gross	1,456	1,768
Net deferred tax asset	312	477
Other noncurrent assets
Deferred Taxes [Line Items]
Deferred Tax Assets, Net of Valuation Allowance	755	862
Other Noncurrent Liabilities
Deferred Taxes [Line Items]
Deferred Tax Liabilities, Gross	$ 443	$ 385