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Fair Value Of Financial Assets And Financial Liabilities (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
 9 Months Ended 12 Months Ended
Oct. 31, 2011
Oct. 31, 2010
Jan. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Transfers of assets between levels $ 0 $ 0  
Auction Rate Securities [Member]
      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Temporary impairment of auction rate securities $ 2,694 $ 3,707 $ 3,788