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Derivative Financial Instruments (Details)
 3 Months Ended
Apr. 30, 2016
USD ($)
bu
Apr. 30, 2015
USD ($)
bu
Disclosure Text Block Supplement [Abstract]    
Derivative, Nonmonetary Notional Amount, Volume | bu 2,500,000 35,000
Quantity of Bushels under Forward Purchase Contract | bu 600,000  
Debt Instrument, Collateral Amount | $ $ 520,000  
Gain on Derivative Instruments, Pretax | $ $ 488,000 $ 0