Segment Information - Net Income Reconciliation (Detail) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2016	Oct. 31, 2015
Segment Reconciliation [Abstract]
Total profit from reportable segments	$ 39,518	$ 34,813
Unallocated amounts:
Administrative costs	(6,310)	(4,711)
Investment and other income	(489)	(759)
Interest expense	(1,732)	(2,151)
Earnings before income taxes	$ 30,987	$ 27,192