Organization and principal accounting policies - Additional information (Details)	9 Months Ended
	Nov. 03, 2018 segment
Property, Plant and Equipment [Line Items]
Current Fiscal Year End Date	--02-02
Number of reportable segments	3
Minimum
Property, Plant and Equipment [Line Items]
Seasonal revenues, fourth quarter sales, percent	3500.00%
Maximum
Property, Plant and Equipment [Line Items]
Seasonal revenues, fourth quarter sales, percent	40.00%