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Summary of Fair Value and Carrying Value of Notes Payable (Detail) (USD $)
In Thousands, unless otherwise specified
Jul. 31, 2012
Jan. 31, 2012
Disclosure Summary Of Fair Value And Carrying Value Of Notes Payable [Abstract]    
Fair value of notes payable $ 278,844 $ 259,821
Carrying value of notes payable $ 217,206 $ 214,573