Balance sheet components - Accounts receivable, net of allowances (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Sep. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accounts receivable	$ 110,507	$ 85,840
Allowance for doubtful accounts	(1,069)	(872)
Allowance for sales incentives	(18,105)	(11,754)
Accounts receivable, net of allowances	$ 91,333	$ 73,214

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant