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Fair Value of Financial Instruments - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Oct. 31, 2012
Oct. 31, 2011
Sep. 30, 2012
Fair Value Measurements [Line Items]      
Net unrealized gain on foreign currency forward contracts $ 3.3 $ 8.6  
Net unrealized loss on foreign currency forward contracts 4.4 11.9  
Fair value of the Company's nonqualified deferred compensation plan investments 33.9    
Fair value of the Company's nonqualified deferred compensation plan related liability 31.6    
Senior Notes carried at cost 350   350
Estimated fair value of the Senior Notes $ 356.7