Revenue recognition - Performance Obligation Narrative (Details) - North America	9 Months Ended
	Oct. 31, 2020
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
Extended Service Plans and Lifetime Warranty Agreements | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognized, percentage	55.00%
Revenue, performance obligation, expected timing of satisfaction	2 years
Jewelry Replacement Plan
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation, description of timing	three years