Inventories, net - Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2011
Inventories [Line Items]
Raw materials	$ 6,736				$ 9,130
Work in process	1,969				2,647
Finished goods	336,041				335,980
Inventories	$ 344,746	$ 391,052	$ 358,915	$ 412,291	$ 347,757	$ 364,833	$ 289,538	$ 309,561