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Net Income Per Common Share (Narrative) (Details) (USD $)
 3 Months Ended 9 Months Ended
Oct. 31, 2011
Oct. 31, 2010
Oct. 31, 2011
Oct. 31, 2010
Net Income Per Common Share [Abstract]        
Anti-dilutive common shares 4,688,250 1,917,100 3,490,017 1,366,633
Anti-dilutive common shares exercise price, minimum $ 27.45 $ 32.89 $ 27.45 $ 32.89
Anti-dilutive common shares exercise price, maximum $ 39.58 $ 39.58 $ 39.58 $ 39.58