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Activity of Sales Return Reserve (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Jan. 31, 2013
Jan. 31, 2012
Jan. 31, 2011
Revenue Recognition, Allowances [Line Items]      
Balance at beginning of year $ 10,967 $ 11,367 $ 9,912
Additions 49,412 41,034 41,692
Deductions (45,931) (41,434) (40,237)
Balance at end of year $ 14,448 $ 10,967 $ 11,367