Financial Instruments and Hedging Activities (Additional Information) (Detail) - Derivatives Not Designated as Hedges - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2020	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Derivative, Notional Amount	$ 54.5	$ 189.6
Maximum
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Term of foreign currency forward contracts	90 days

Nominal or face amount used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant