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Stock-based compensation - Additional Information (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Dec. 28, 2019
Sep. 28, 2019
Dec. 28, 2019
Jun. 27, 2020
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period       48 months
Cliff vesting period       1 year
Unrecognized stock-based compensation expense   $ 43.9   $ 23.5
Unrecognized stock-based compensation expense, period of recognition     2 years 1 year 7 months 6 days
Restricted Stock Units        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Cliff vesting period       4 years
Unrecognized stock-based compensation expense   $ 55.6   $ 106.2
Unrecognized stock-based compensation expense, period of recognition 3 years 3 months 18 days 3 years 4 months 24 days    
2003 Stock Plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Exercisable period       10 years