Inventories (Details) - USD ($) $ in Thousands	Jul. 31, 2015	Jan. 31, 2015	Jul. 31, 2014
Inventory Disclosure [Abstract]
Finished goods	$ 600,529	$ 417,332	$ 524,350
Raw materials and work-in-process	4,685	8,848	9,836
Inventories	$ 605,214	$ 426,180	$ 534,186