Supplementary Balance Sheet Information - Summary of Account Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Oct. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts receivable	$ 169,317		$ 126,350
Less allowance for doubtful accounts	(3,644)		(1,113)
Accounts receivable, net	165,602	$ 125,200	125,192
Allowance for Sales Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Less allowance for sales returns	$ (71)		$ (45)	$ (81)	$ (101)