Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive (Loss) Income, Balance, beginning			$ (10,292)
Other comprehensive income before reclassifications, net of tax			70
Amounts reclassified from accumulated other comprehensive income, net of tax			418
Net current-period other comprehensive income, net of tax	$ 381	$ 372	488	$ 627
Accumulated Other Comprehensive (Loss) Income, Balance, ending	(9,804)		(9,804)
Pension and Postretirement Health Benefits
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive (Loss) Income, Balance, beginning			(10,327)
Other comprehensive income before reclassifications, net of tax			0
Amounts reclassified from accumulated other comprehensive income, net of tax			418
Net current-period other comprehensive income, net of tax			418
Accumulated Other Comprehensive (Loss) Income, Balance, ending	(9,909)		(9,909)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive (Loss) Income, Balance, beginning			35
Other comprehensive income before reclassifications, net of tax			70
Amounts reclassified from accumulated other comprehensive income, net of tax			0
Net current-period other comprehensive income, net of tax			70
Accumulated Other Comprehensive (Loss) Income, Balance, ending	$ 105		$ 105