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Hedging Instruments - Additional Information (Details)
oz in Thousands, $ in Millions
12 Months Ended
Jan. 31, 2020
USD ($)
oz
Jul. 31, 2012
USD ($)
Derivative [Line Items]    
Expected approximate amount of net pre-tax derivative gains included in accumulated other comprehensive loss that will be reclassified into earnings within the next 12 months $ (6.7)  
2012 4.40% Series B Notes, Due July 2012    
Derivative [Line Items]    
Debt, face amount   $ 250.0
Interest Rate Swap | 2012 Debt Issuance    
Derivative [Line Items]    
Unrealized loss on interest rate swaps 16.1  
Interest Rate Swap | 2014 Debt Issuance    
Derivative [Line Items]    
Unrealized loss on interest rate swaps $ 3.3  
Foreign Exchange Forward | Maximum    
Derivative [Line Items]    
Derivative, term of contract 12 months  
Precious Metal Forward Contracts | Maximum    
Derivative [Line Items]    
Derivative, term of contract 18 months  
Platinum    
Derivative [Line Items]    
Notional amount of precious metal hedge (in ounces) | oz 29  
Silver    
Derivative [Line Items]    
Notional amount of precious metal hedge (in ounces) | oz 557  
Gold    
Derivative [Line Items]    
Notional amount of precious metal hedge (in ounces) | oz 84