Derivative Financial Instruments - Gains Losses on Derivative Financial Instruments Recorded in Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Foreign currency forward contracts
Derivative [Line Items]
Gain (loss) on foreign currency forward contracts	$ (62)	$ 256	$ 25

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959

Name:	us-gaap_GainLossOnDerivativeInstrumentsNetPretax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration