Summary of significant accounting policies - Fiscal year (Details)	3 Months Ended								12 Months Ended
	Feb. 01, 2020	Nov. 02, 2019	Aug. 03, 2019	May 04, 2019	Feb. 02, 2019	Nov. 03, 2018	Aug. 04, 2018	May 05, 2018	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Summary of significant accounting policies
Fiscal period	91 days	91 days	91 days	91 days	91 days	91 days	91 days	91 days	364 days	364 days	371 days
Minimum
Summary of significant accounting policies
Fiscal period									364 days
Maximum
Summary of significant accounting policies
Fiscal period									371 days