Inventories - Summary of inventories (Details) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2013	Jan. 31, 2013	Oct. 31, 2012
Inventory Disclosure [Abstract]
Finished goods	$ 314,780	$ 271,155	$ 299,797
Raw materials and work-in-process	8,554	9,774	7,680
Inventories	$ 323,334	$ 280,929	$ 307,477