Accumulated Other Comprehensive Income (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Apr. 30, 2016
Apr. 30, 2015
Apr. 30, 2016
Apr. 30, 2015
Accumulated Other Comprehensive Income        
Accumulated Other Comprehensive (Loss) Income, Balance, beginning     $ (9,245)  
Other comprehensive income, before reclassifications, net of tax     142  
Amounts reclassified from accumulated other comprehensive income, net of tax     457  
Net current-period other comprehensive income, net of tax $ 441 $ 230 599 $ (129)
Accumulated Other Comprehensive (Loss) Income, Balance, ending (8,646)   (8,646)  
Pension and Postretirement Health Benefits        
Accumulated Other Comprehensive Income        
Accumulated Other Comprehensive (Loss) Income, Balance, beginning     (8,975)  
Other comprehensive income, before reclassifications, net of tax     0  
Amounts reclassified from accumulated other comprehensive income, net of tax     457  
Net current-period other comprehensive income, net of tax     457  
Accumulated Other Comprehensive (Loss) Income, Balance, ending (8,518)   (8,518)  
Cumulative Translation Adjustment        
Accumulated Other Comprehensive Income        
Accumulated Other Comprehensive (Loss) Income, Balance, beginning     (270)  
Other comprehensive income, before reclassifications, net of tax     142  
Amounts reclassified from accumulated other comprehensive income, net of tax     0  
Net current-period other comprehensive income, net of tax     142  
Accumulated Other Comprehensive (Loss) Income, Balance, ending $ (128)   $ (128)