Other Balance Sheet Information - Summary of Account Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable	$ 168,851	$ 169,317
Less allowance for doubtful accounts	(3,592)	(3,644)
Accounts receivable, net	165,176	165,602
Allowance for Sales Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Less allowance for sales returns	$ (83)	$ (71)