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, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Earnings Per Share [Abstract]
Net income		$ 6,549	$ 7,510	$ 12,207	$ 10,046
Weighted average number of common shares outstanding-basic		12,490	12,466	12,482	12,442
Effect of dilutive securities:
Stock options and restricted stock units		111	214	124	270
Weighted average number of common shares outstanding-diluted		12,601	12,680	12,606	12,712
Basic net income per share		$ 0.52	$ 0.60	$ 0.98	$ 0.81
Diluted net income per share		$ 0.52	$ 0.59	$ 0.97	$ 0.79
Anti-dilutive shares related to outstanding stock options and unvested restricted stock	[1]		372		372

[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.