Goodwill and intangibles - Summary of Goodwill (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jul. 30, 2016	Jan. 30, 2016
Goodwill [Roll Forward]
Beginning Balance	$ 515.5	$ 519.2
Impact of foreign exchange	2.6	(3.7)
Ending Balance	518.1	515.5
Sterling Jewelers
Goodwill [Roll Forward]
Beginning Balance	23.2	23.2
Impact of foreign exchange	0.0	0.0
Ending Balance	23.2	23.2
Zale Jewelry
Goodwill [Roll Forward]
Beginning Balance	488.7	492.4
Impact of foreign exchange	2.6	(3.7)
Ending Balance	491.3	488.7
Piercing Pagoda
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Impact of foreign exchange	0.0	0.0
Ending Balance	0.0	0.0
UK Jewelry
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Impact of foreign exchange	0.0	0.0
Ending Balance	0.0	0.0
Other
Goodwill [Roll Forward]
Beginning Balance	3.6	3.6
Impact of foreign exchange	0.0	0.0
Ending Balance	$ 3.6	$ 3.6