Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Earnings Per Share [Abstract]
Net (loss) income		$ (74,237)	$ 12,127	$ 33,481
Weighted average number of common shares outstanding-basic		12,456	12,402	12,407
Effect of dilutive securities:
Stock options and restricted stock units			213	199
Weighted average number of common shares outstanding-diluted		12,456	12,615	12,606
Basic net (loss) income per share		$ (5.96)	$ 0.98	$ 2.70
Diluted net (loss) income per share		$ (5.96)	$ 0.96	$ 2.66
Anti-dilutive shares related to outstanding stock options and unvested restricted stock	[1]	143	5	176

[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.