Goodwill and intangibles - Summary of Goodwill (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 31, 2015	Jan. 31, 2015
Goodwill [Roll Forward]
Beginning Balance	$ 519.2	$ 26.8
Acquisitions		499.4
Impact of foreign exchange	(1.6)	(7.0)
Ending Balance	517.6	519.2
Sterling Jewelers
Goodwill [Roll Forward]
Beginning Balance	23.2	23.2
Acquisitions		0.0
Impact of foreign exchange	0.0	0.0
Ending Balance	23.2	23.2
Zale Jewelry
Goodwill [Roll Forward]
Beginning Balance	492.4	0.0
Acquisitions		499.4
Impact of foreign exchange	(1.6)	(7.0)
Ending Balance	490.8	492.4
Piercing Pagoda
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Acquisitions		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
Acquisitions		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
Acquisitions		0.0
Impact of foreign exchange	0.0	0.0
Ending Balance	$ 3.6	$ 3.6