Revenue recognition - Narrative (Details) - USD ($) $ in Millions		12 Months Ended
		Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Disaggregation of Revenue [Line Items]
Impact from adoption of new accounting pronouncements	[1]			$ 16.5
Extended Service Plans and Lifetime Warranty Agreements
Disaggregation of Revenue [Line Items]
Capitalized contract cost, amortization		$ 29.5	$ 52.4
North America | Extended Service Plans and Lifetime Warranty Agreements
Disaggregation of Revenue [Line Items]
Revenue, performance obligation, description of timing		17 years
North America | Jewelry Replacement Plan
Disaggregation of Revenue [Line Items]
Revenue, performance obligation, description of timing		three years
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Revenue recognized			$ 111.2
Capitalized contract cost				16.5
Retained earnings
Disaggregation of Revenue [Line Items]
Impact from adoption of new accounting pronouncements	[1]			15.7
Retained earnings | Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Impact from adoption of new accounting pronouncements				$ 16.5

[1] Reflects reclassifications to retained earnings related to 1) unrealized gains related to the Company’s equity security investments as of February 3, 2018 from AOCI associated with the adoption of ASU 2016-01 and 2) deferred costs associated with the sale of extended service plans due to the adoption of ASU 2014-09.