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Reconciliation of Beginning and Ending Auction Rate Securities Balances (Detail) (Fair Value, Inputs, Level 3, Auction Rate Securities, USD $)
In Thousands, unless otherwise specified
12 Months Ended
Jan. 31, 2013
Jan. 31, 2012
Fair Value, Inputs, Level 3 | Auction Rate Securities
   
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Balance at beginning of period $ 20,197 $ 29,462
Total gains realized/unrealized, Included in earnings      
Total gains realized/unrealized, Included in other comprehensive income 2,183 1,010
Settlements (18,050) (10,275)
Transfers in and/or out of Level 3      
Balance at end of period 4,330 20,197
Unrealized losses included in accumulated other comprehensive loss related to assets still held at reporting date (595) (2,778)
Total gains for the period included in earnings attributable to the change in unrealized gains or losses related to assets still held at reporting date