Other Balance Sheet Information - Summary of Account Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable	$ 116,740	$ 108,713
Accounts receivable, net	114,429	106,372
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Less allowances	(2,209)	(2,241)
Allowance for Sales Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Less allowances	$ (102)	$ (100)