XML 51 R32.htm IDEA: XBRL DOCUMENT v3.10.0.1
Summary of significant accounting policies - Textual (Details)
 12 Months Ended
Jul. 19, 2018
Sep. 29, 2018
USD ($)
vendor
operating_segment
Sep. 30, 2017
USD ($)
Oct. 01, 2016
USD ($)
Sep. 28, 2014
USD ($)
Accounting Policies [Abstract]          
Stock split, conversion ratio 2        
Restricted cash   $ 200,000 $ 200,000    
Impairment of long-lived assets   $ 0 0    
Product Warranty Liability [Line Items]          
Product warranty term   1 year      
Foreign currency remeasurement and transaction gain (losses)   $ (941,000) 3,568,000 $ (782,000)  
401(k) plan maximum annual contribution per employee, percent   100.00%      
Cumulative effect, new accounting principle         $ 43,400,000
Number of operating segments | operating_segment   1      
Retained earnings (accumulated deficit)   $ (203,611,000) $ (188,007,000)   $ (110,200,000)
Goodwill   $ 1,000,000      
European Union          
Product Warranty Liability [Line Items]          
Product warranty term   2 years      
Supplier concentration risk          
Product Warranty Liability [Line Items]          
Concentration percentage   98.00% 99.00% 99.00%  
Number of vendors | vendor   1      
Other income (expense)          
Product Warranty Liability [Line Items]          
Foreign currency remeasurement and transaction gain (losses)   $ (1,200,000) $ 3,200,000 $ (2,200,000)  
Sales and marketing          
Product Warranty Liability [Line Items]          
Advertising costs   $ 50,200,000 $ 72,200,000 $ 50,600,000