Deferred revenue - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 29, 2017	Jul. 30, 2016	Jul. 29, 2017	Jul. 30, 2016
Sterling Jewelers
Deferred Revenue Warranty [Roll Forward]
ESP deferred revenue, beginning of period	$ 736.0	$ 723.8	$ 737.4	$ 715.1
Plans sold	63.5	61.6	128.8	137.6
Revenue recognized	(66.8)	(65.1)	(133.5)	(132.4)
ESP deferred revenue, end of period	732.7	720.3	732.7	720.3
Zale
Deferred Revenue Warranty [Roll Forward]
ESP deferred revenue, beginning of period	167.7	155.1	168.2	146.1
Plans sold	33.3	31.9	64.6	72.5
Revenue recognized	(31.5)	(30.8)	(63.3)	(62.4)
ESP deferred revenue, end of period	$ 169.5	$ 156.2	$ 169.5	$ 156.2