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Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Jan. 31, 2012
Jan. 31, 2011
Jan. 31, 2010
Summary Of Significant Accounting Policies [Line Items]      
Minimum percentage rate of par value, guarantee of agencies to auction rate securities 97.00%    
Fair value of Company's ARS $ 216,767 $ 468,408  
Interest rate intervals of auction process 7, 28, 35 or 90 days    
Advertising costs reported as prepaid expenses 3,586 3,323  
Advertising expense 71,684 58,336 46,827
Auction Rate Securities [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Minimum percentage rate of par value, guarantee of agencies to auction rate securities 97.00%    
Fair value of Company's ARS 20,197 29,462  
Temporary impairment of auction rate securities 2,778 3,788  
Accumulated Other Comprehensive Loss [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Foreign currency translation losses 10,037 7,752  
Unrealized loss on marketable securities, net of tax $ 1,475 $ 2,510  
Furniture And Fixtures [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Average useful life (in years) 5    
Leasehold Improvements [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Depreciable life (in years) lesser of the lease term or useful life for leasehold improvements    
Other Operating Equipment [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Useful life, minimum (in years) 3    
Useful life, maximum (in years) 10    
Buildings [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Average useful life (in years) 39