Share-based compensation - Additional Information about Awards Granted under Omnibus Plan (Details) - USD ($) $ in Millions	12 Months Ended
Feb. 02, 2019	Feb. 03, 2018	Jan. 28, 2017
Omnibus Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of awards vested	$ 6.8	$ 7.1	$ 13.6

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration