Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2013		Jul. 31, 2012		Jul. 31, 2011
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Income from continuing operations	$ 11,707	$ 5,224	$ 9,809	$ 4,381	$ 12,100	$ 7,330	$ 19,615	$ 4,026	$ 31,121		$ 43,071		$ 16,620
Income from discontinued operations, net of tax													289
Gain on disposal of discontinued operations, net of tax													924
Net income									$ 31,121		$ 43,071		$ 17,833
Weighted average number of common shares outstanding-basic									12,247		12,265		12,491
Effect of dilutive securities:
Stock options and RSUs									322		311		81
Weighted average number of common shares outstanding-diluted									12,569		12,576		12,572
Basic net income per share:
Income from continuing operations	$ 0.96	$ 0.42	$ 0.80	$ 0.36	$ 0.99	$ 0.60	$ 1.61	$ 0.32	$ 2.54		$ 3.51		$ 1.33
Income from discontinued operations, net of tax													$ 0.02
Gain on disposal of discontinued operations, net of tax													$ 0.08
Basic net income per share									$ 2.54		$ 3.51		$ 1.43
Diluted net income per share:
Income from continuing operations	$ 0.93	$ 0.41	$ 0.78	$ 0.35	$ 0.96	$ 0.59	$ 1.59	$ 0.32	$ 2.48		$ 3.42		$ 1.33
Income from discontinued operations, net of tax													$ 0.02
Gain on disposal of discontinued operations, net of tax													$ 0.07
Diluted net income per share									$ 2.48		$ 3.42		$ 1.42
Anti-dilutive shares related to outstanding stock options and unvested restricted stock									105	[1]	212	[1]	204	[1]

[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.