Schedule of Stock Award Activity (Detail) (USD $)	12 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2012
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, beginning of year, Shares	17,530	10,041
Granted, Shares		9,498	10,041
Vested, Shares	(3,910)	(2,009)
Nonvested, end of year, Shares	13,620	17,530	10,041
Nonvested, beginning of year, Weighted Average Grant Date Fair Value	$ 31.03	$ 29.46
Granted, Weighted Average Grant Date Fair Value		$ 32.36	$ 29.46
Vested, Weighted Average Grant Date Fair Value	$ 30.87	$ 29.46
Nonvested, end of year, Weighted Average Grant Date Fair Value	$ 31.08	$ 31.03	$ 29.46
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested, beginning of year, Shares	139,275
Granted, Shares	151,168	143,069
Vested, Shares	(63,852)
Forfeited, Shares	(14,518)	(3,794)
Nonvested, end of year, Shares	212,073	139,275
Nonvested, beginning of year, Weighted Average Grant Date Fair Value	$ 38.06
Granted, Weighted Average Grant Date Fair Value	$ 54.26	$ 38.01
Vested, Weighted Average Grant Date Fair Value	$ 38.68
Forfeited, Weighted Average Grant Date Fair Value	$ 47.26	$ 36.32
Nonvested, end of year, Weighted Average Grant Date Fair Value	$ 49.21	$ 38.06