Schedule - Valuation and Qualifying Accounts (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Valuation allowances on deferred tax assets written off against the deferred tax assets		$ 2,416	$ 9,231
Accounts receivable allowances written off against related accounts receivables	$ 6,659	3,008	$ 12,727
Accounts receivable allowances were netted against deferred revenue		$ 5,291

Amount of direct write-downs of accounts receivable charged against the allowance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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