Summary of Stock Option Activity (Detail) (Stock Options, USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Oct. 31, 2014	Oct. 31, 2013
Stock Options
Number of shares
Outstanding at beginning of period, Number of shares	1,496,000
Granted, Number of shares	0	179,601
Exercised, Number of Shares	(9,194)	(40,000)
Cancelled/forfeited, Number of shares	(34,000)
Outstanding at end of period, Number of shares	1,453,000
Exercisable at end of period, Number of Shares	918,000
Weighted Average Exercise Price Per Share
Outstanding at beginning of period, Weighted average exercise price per share	$ 24.79
Granted, Weighted average exercise price per share	$ 0.00
Exercised, Weighted average exercise price per share	$ 13.34
Cancelled, Weighted average exercise price per share	$ 29.96
Outstanding at end of period, Weighted average exercise price per share	$ 24.75
Exercisable at end of period, Weighted average exercise price per share	$ 26.85
Weighted average remaining contractual life (in years)
Outstanding at end of period, Weighted average remaining contractual life	6 years 9 months 18 days
Exercisable at end of period, Weighted average remaining contractual life	5 years 9 months 18 days
Aggregate intrinsic value
Outstanding at end of period, Aggregate intrinsic value	$ 14,511
Exercisable at end of period, Aggregate intrinsic value	$ 8,574