Segment Information - Net Income Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment profit	$ 42,518	$ 41,143	$ 89,621	$ 83,425
Unallocated amounts:
Administrative costs	(6,488)	(6,347)	(12,969)	(13,218)
Investment and other income	1,377	1,056	1,360	1,272
Interest expense	(717)	(829)	(1,429)	(1,692)
Earnings before income taxes	$ 36,690	$ 35,023	$ 76,583	$ 69,787