Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended
Dec. 31, 2017	Sep. 30, 2017
Derivatives Fair Value [Line Items]
Outstanding hedge contracts		$ 0
Unrealized deferred income in comprehensive income related to foreign exchange hedging	$ 1,000,000
Deferred gains (losses) in comprehensive loss related to foreign exchange hedging		$ 0
Sale
Derivatives Fair Value [Line Items]
Outstanding hedge contracts	220,000,000
Purchase
Derivatives Fair Value [Line Items]
Outstanding hedge contracts	$ 131,000,000

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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- Definition

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

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