Provision For Income Taxes - Additional information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Income Taxes [Line Items]
Maximum percentage of tax benefits realized upon ultimate settlement			50.00%
Gross uncertain tax benefit reserve and related interest and penalties	$ 334		$ 697
Accrued an additional uncertain tax benefit related to prior tax periods	222		222
Decreases in unrecognized tax benefits resulting from effective settlement	4,567		4,814
Income tax benefit, net	1,675		1,814
Effective income tax rate	22.10%	36.40%	30.40%	35.80%
Anticipated decrease in unrecognized tax benefits			3,500
Accrued interest and penalties related to unrecognized tax benefits	800		800
Minimum
Income Taxes [Line Items]
Anticipated decrease in unrecognized tax benefits possible range			3,200
Accrued interest and penalties related to unrecognized tax benefits possible range	1,800		1,800
Maximum
Income Taxes [Line Items]
Anticipated decrease in unrecognized tax benefits possible range			9,400
Accrued interest and penalties related to unrecognized tax benefits possible range	$ 4,800		$ 4,800