Deferred revenue - Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 29, 2017	Apr. 30, 2016
Sterling Jewelers
Deferred Revenue Warranty [Roll Forward]
ESP deferred revenue, beginning of period	$ 737.4	$ 715.1
Plans sold	65.3	76.0
Revenue recognized	(66.7)	(67.3)
ESP deferred revenue, end of period	736.0	723.8
Zale
Deferred Revenue Warranty [Roll Forward]
ESP deferred revenue, beginning of period	168.2	146.1
Plans sold	31.3	40.6
Revenue recognized	(31.8)	(31.6)
ESP deferred revenue, end of period	$ 167.7	$ 155.1