Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2018	Apr. 30, 2017
Earnings Per Share [Abstract]
Net income (loss)		$ 7,110	$ (59,664)	$ 19,317	$ (49,618)
Weighted average number of common shares outstanding-basic		12,503	12,486	12,489	12,457
Effect of dilutive securities:
Stock options and restricted stock units		130		128
Weighted average number of common shares outstanding-diluted		12,633	12,486	12,617	12,457
Basic net income (loss) per share		$ 0.57	$ (4.78)	$ 1.55	$ (3.98)
Diluted net income (loss) per share		$ 0.56	$ (4.78)	$ 1.53	$ (3.98)
Anti-dilutive shares related to outstanding stock options and unvested restricted stock	[1]		242	2	228

[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.