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Amount, before tax and reclassification, of gain (loss) from derivative designated and qualifying as net investment hedge.

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Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Pre-tax gains (losses) in other comprehensive income (loss) related to net investment hedges	$ 20	$ (318)	$ 234
Earnings related to forward points and interest differentials from forward contracts and swap agreements	156	150	$ 95
Accrued liabilities
Derivative [Line Items]
Collateral received with counterparties	35
Other Assets
Derivative [Line Items]
Posted collateral	9
Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	11,200	10,700
Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	$ 800	$ 1,600