Schedule of Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2014
Stockholders' Equity
Outstanding at beginning of year, Shares		5,000	106,313
Exercised, Shares		(5,000)	(101,313)
Forfeited, Shares	0	0	0
Expired, Shares	0	0	0
Granted, Shares	0	0	0
Outstanding at end of year, Shares			5,000
Vested and expected to vest at end of year, Shares			5,000
Exercisable at year-end, Shares			5,000
Outstanding at beginning of year, Weighted-Average Exercise Price		$ 28.23	$ 31.48
Exercised, Weighted-Average Exercise Price		28.23	31.64
Forfeited, Weighted-Average Exercise Price	$ 0	0	0
Expired, Weighted-Average Exercise Price	0	0	0
Granted, Weighted-Average Exercise Price	$ 0	$ 0	0
Outstanding at end of year, Weighted-Average Exercise Price			28.23
Vested and expected to vest at end of year, Weighted-Average Exercise Price			28.23
Exercisable at year-end, Weighted-Average Exercise Price			$ 28.23