Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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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.

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Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount of net unrealized gain (loss) related to the change in fair value of foreign currency exchange rate derivatives designated as cash flow hedging instruments. Recorded in accumulated other comprehensive income to the extent that the cash flow hedge is determined to be effective.

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Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Derivatives Fair Value [Line Items]
Companys hedged interest rate transactions			4 years
Outstanding hedge contracts					$ 0
Unrealized deferred losses in comprehensive income related to foreign exchange hedging			$ 2,000,000
Deferred gains (losses) in comprehensive loss related to foreign exchange hedging					0
Deferred (losses) gains on derivative financial instruments	$ (3,000,000)	$ 1,000,000	(9,000,000)	$ 2,000,000
Unrealized pre-tax (losses) gains of the company foreign exchange forward contracts			(2,000,000)	2,000,000
Unrealized pre-tax (losses) gains of the company derivative interest rate			(9,000,000)	$ (1,000,000)
Interest Rate Swap
Derivatives Fair Value [Line Items]
Outstanding hedge contracts	320,000,000		320,000,000		320,000,000
Deferred (losses) gains on derivative financial instruments			(4,000,000)		$ 3,000,000
Sale
Derivatives Fair Value [Line Items]
Outstanding hedge contracts	272,000,000		272,000,000
Purchase
Derivatives Fair Value [Line Items]
Outstanding hedge contracts	$ 164,000,000		$ 164,000,000