Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive (Loss) Income, Balance, beginning			$ (10,615)
Other comprehensive loss before reclassifications, net of tax			(7)
Amounts reclassified from accumulated other comprehensive income, net of tax			437
Net current-period other comprehensive income (loss), net of tax	$ (175)	$ (73)	(430)	$ (561)
Accumulated Other Comprehensive (Loss) Income, Balance, ending	(10,185)		(10,185)
Pension and Postretirement Health Benefits
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive (Loss) Income, Balance, beginning			(10,384)
Other comprehensive loss before reclassifications, net of tax			0
Amounts reclassified from accumulated other comprehensive income, net of tax			437
Net current-period other comprehensive income (loss), net of tax			(437)
Accumulated Other Comprehensive (Loss) Income, Balance, ending	(9,947)		(9,947)
Cumulative Translation Adjustment
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive (Loss) Income, Balance, beginning			(231)
Other comprehensive loss before reclassifications, net of tax			(7)
Amounts reclassified from accumulated other comprehensive income, net of tax			0
Net current-period other comprehensive income (loss), net of tax			7
Accumulated Other Comprehensive (Loss) Income, Balance, ending	$ (238)		$ (238)