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Stock-based Compensation Expense Additional Information (Details)
$ / shares in Units, $ in Millions
3 Months Ended
Apr. 30, 2016
USD ($)
period
$ / shares
shares
Apr. 30, 2015
USD ($)
$ / shares
shares
Jan. 31, 2016
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated share-based compensation expense | $ $ 56.9 $ 50.2  
Restricted Stock Units (RSUs) and Performance Shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Awards granted in period, weighted average grant date fair value (in usd per share) | $ / shares $ 57.68    
Awards vested in period, fair value | $ $ 49.1 59.0  
Awards granted in period 1,015,900    
Awards, nonvested, number 7,550,700   7,739,600
Restricted Stock Units (RSUs)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Awards granted in period 600,000    
Allocated share-based compensation expense | $ $ 41.7 37.8  
Performance Stock Unit      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
Awards granted in period 400,000    
Allocated share-based compensation expense | $ $ 8.1 $ 5.6  
Employee Qualified Stock Purchase Plan 1998 ESP Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Employee stock purchase plan maximum percentage of compensation to purchase shares by eligible participants 15.00%    
Employee stock purchase plan minimum percentage of common stock fair value defined to purchase shares by eligible participants 85.00%    
Employee stock purchase plan, number of exercise periods | period 4    
Employee stock purchase plan, term of exercise period 6 months    
Employee stock purchase plan, term of offering period 24 months    
Shares issued under employee stock purchase plans (shares) 1,200,000 1,100,000  
Awards issued, share average price (in usd per share) | $ / shares $ 36.67 $ 36.91  
Weighted average grant date fair value per share of stock options granted (in dollars per share) | $ / shares $ 17.88 $ 15.99  
Share-based Compensation Award, Tranche One | Performance Stock Unit      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
PSU Annual Vesting Percentage 33.33%    
Share-based Compensation Award, Tranche Two | Performance Stock Unit      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
PSU Annual Vesting Percentage 33.33%    
Share-based Compensation Award, Tranche Three | Performance Stock Unit      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
PSU Annual Vesting Percentage 33.33%