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Post Retirement Benefit Plans - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Nov. 30, 2016
Jan. 31, 2017
Jan. 31, 2016
Oct. 31, 2016
Postemployment Benefits [Abstract]        
Annuity contract   $ 49.2    
Lump sum payments made to participants   35.1    
Decrease in projected benefit obligation   84.3    
Pension settlement charge   23.5 $ 0.0  
Reduction in projected benefit obligation $ 21.3      
Discount rate 4.20%     3.82%
Company's pension contributions   $ 3.8 $ 3.1