Revenue recognition - Performance Obligation Narrative (Details) - Extended Service Plans and Lifetime Warranty Agreements - North America - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-02-02	Feb. 01, 2020
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percentage of revenue recognized	55.00%
Expected timing of satisfaction, period	2 years