Revenue recognition - Narrative (Details) - North America	3 Months Ended
	May 04, 2019	May 05, 2018
Extended Service Plans and Lifetime Warranty Agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation, description of timing	17 years
Jewelry Replacement Plan
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation, description of timing		three years
Revenue recognized, percentage	55.00%