Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net (loss) income		$ (2,985)	$ 9,830	$ (1,609)	$ 13,484
Weighted-average number of common shares outstanding-basic		12,418	12,378	12,422	12,393
Effect of dilutive securities:
Stock options and restricted stock units			180		195
Weighted-average number of common shares outstanding-diluted		12,418	12,558	12,422	12,588
Basic net (loss) income per share		$ (0.24)	$ 0.79	$ (0.13)	$ 1.09
Diluted net (loss) income per share		$ (0.24)	$ 0.78	$ (0.13)	$ 1.07
Anti-dilutive shares related to outstanding stock options and unvested restricted stock	[1]	326	194	357	192

[1] These shares related to outstanding stock options and unvested restricted stock were not included in our calculations of diluted earnings per share, as the effect of including them would be anti-dilutive.