Derivative Financial Instruments - Additional Information (Details) - USD ($)	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Derivatives, Fair Value [Line Items]
Company's hedged interest rate transactions	4 years
Derivative, notional amount	$ 0	$ 0
Deferred gains (losses) in comprehensive loss related to foreign exchange hedging	0	0
Interest Rate Swap
Derivatives, Fair Value [Line Items]
Derivative, notional amount	820,000,000	820,000,000
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification and tax	(29,000,000)	(8,000,000)
Pre-tax gains (losses) of the company derivative interest rate swaps	(27,000,000)	(11,000,000)
Foreign Exchange Forward
Derivatives, Fair Value [Line Items]
Derivative, gain (loss) on derivative, net	$ (4,000,000)
Pre-tax gains (losses) of the company derivative interest rate swaps		$ 3,000,000

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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-Publisher FASB
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Nominal or face amount used to calculate payment on derivative.

+ References

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Maximum period the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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Deferred gains losses in comprehensive loss related to foreign exchange hedging.

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