Other Balance Sheet Information - Summary of Account Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020
Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable	$ 202,691	$ 195,587
Less allowance for expected credit losses	(5,937)	(7,216)
Accounts receivable, net	196,679	188,291
Allowance for Sales Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Less allowance for sales returns	$ (75)	$ (80)