Revenue recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Aug. 04, 2018	Jul. 29, 2017	Aug. 04, 2018	Jul. 29, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 1,420.1	$ 1,399.6	$ 2,900.7	$ 2,803.0
North America
Disaggregation of Revenue [Line Items]
Revenue	1,286.7	1,262.2	2,634.5	2,536.6
International
Disaggregation of Revenue [Line Items]
Revenue	131.5	131.9	260.2	254.4
Other
Disaggregation of Revenue [Line Items]
Revenue	1.9	5.5	6.0	12.0
Bridal
Disaggregation of Revenue [Line Items]
Revenue	636.9	571.2	1,310.4	1,187.2
Bridal | North America
Disaggregation of Revenue [Line Items]
Revenue	585.1	518.6	1,203.0	1,081.5
Bridal | International
Disaggregation of Revenue [Line Items]
Revenue	51.8	52.6	107.4	105.7
Bridal | Other
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Fashion
Disaggregation of Revenue [Line Items]
Revenue	447.7	430.0	934.7	906.7
Fashion | North America
Disaggregation of Revenue [Line Items]
Revenue	420.5	400.8	881.6	851.7
Fashion | International
Disaggregation of Revenue [Line Items]
Revenue	27.2	29.2	53.1	55.0
Fashion | Other
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Watches
Disaggregation of Revenue [Line Items]
Revenue	104.8	99.1	196.1	187.1
Watches | North America
Disaggregation of Revenue [Line Items]
Revenue	58.0	55.1	110.2	106.6
Watches | International
Disaggregation of Revenue [Line Items]
Revenue	46.8	44.0	85.9	80.5
Watches | Other
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Other
Disaggregation of Revenue [Line Items]
Revenue	230.7	299.3	459.5	522.0
Other | North America
Disaggregation of Revenue [Line Items]
Revenue	223.1	287.7	439.7	496.8
Other | International
Disaggregation of Revenue [Line Items]
Revenue	5.7	6.1	13.8	13.2
Other | Other
Disaggregation of Revenue [Line Items]
Revenue	1.9	5.5	6.0	12.0
Store
Disaggregation of Revenue [Line Items]
Revenue	1,267.9	1,311.9	2,597.9	2,627.8
Store | North America
Disaggregation of Revenue [Line Items]
Revenue	1,150.2	1,191.5	2,363.9	2,394.8
Store | International
Disaggregation of Revenue [Line Items]
Revenue	117.7	120.4	234.0	233.0
Store | Other
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
E-commerce
Disaggregation of Revenue [Line Items]
Revenue	150.3	82.2	296.8	163.2
E-commerce | North America
Disaggregation of Revenue [Line Items]
Revenue	136.5	70.7	270.6	141.8
E-commerce | International
Disaggregation of Revenue [Line Items]
Revenue	13.8	11.5	26.2	21.4
E-commerce | Other
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Other
Disaggregation of Revenue [Line Items]
Revenue	1.9	5.5	6.0	12.0
Other | North America
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Other | International
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0	0.0	0.0
Other | Other
Disaggregation of Revenue [Line Items]
Revenue	1.9	$ 5.5	6.0	$ 12.0
James Allen | E-commerce | North America
Disaggregation of Revenue [Line Items]
Revenue	$ 54.4		$ 107.7