Balance sheet components - Accrued expenses (Details) - USD ($) $ in Thousands	Jun. 29, 2019	Sep. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued advertising and marketing	$ 17,707	$ 11,613
Accrued taxes	4,999	4,175
Accrued inventory	1,723	4,179
Accrued manufacturing, logistics and product development	9,348	8,290
Accrued general and administrative expenses	7,413	3,322
Other accrued payables	5,372	7,108
Total accrued expenses	$ 46,562	$ 38,687