Fair value measurement - Outstanding Debt (Details) - USD ($) $ in Millions	Jan. 30, 2021	Feb. 01, 2020
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding debt	$ 146.7	$ 245.9
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding debt	145.1	244.8
Senior Notes | Level 2 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding debt	146.7	146.4
Senior Notes | Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding debt	145.1	144.8
Term Loan | Level 2 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding debt	0.0	99.5
Term Loan | Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Outstanding debt	$ 0.0	$ 100.0