Disposition of Business (Details) - USD ($)
3 Months Ended 6 Months Ended
Apr. 07, 2015
Jan. 31, 2016
Apr. 30, 2015
Jan. 31, 2015
Jan. 31, 2016
Jan. 31, 2015
Disposition of Business            
Diluted earnings per share (in dollars per share)   $ 0.37   $ 0.27 $ 0.71 $ 0.54
Specialty Packaging business | Other. | Disposal Group, Disposed of by Sale, Not Discontinued Operations            
Disposition of Business            
Proceeds from sale of business, net of cash retained and disposal costs $ 7,531,000          
Amount held in escrow $ 660,000          
Loss on sale of business     $ 2,206,000      
Diluted earnings per share (in dollars per share)     $ (0.04)